UNIT VI
Chapter – 1: - REPRODUCTION IN ORGANISMS
A.Importantterms& Definitions:
1.
Vegetative propagules: The vegetative parts of plants which are used to raise new
plants e.g. Rhizome, Bulb, tuber etc.,
2.Juvenile phase: The period of growth of an organism from birth to reproductive
maturity. In plants this phase is called vegetative phase.
3.Oestrus Cycle: The reproductive cycle of non- primate mammals is called oestrus cycle
which consists of a few days of oestrus or heat. The female shows strong urge and allows
male to copulate. Ex. Cow, Sheep, Tiger.
4.Menstrual Cycle: The reproductive cycle of primate mammals such as Monkeys, Apes
and humans is called menstrual cycle in which monthly flow of blood and dead tissues
takes place through genital organs.
5. Gametogenesis: The process of formation of gametes.
6.Homogametes or Isogametes: When gametes are similar in shape and size e.g Algae.
7.Heterogametes: In majority of organisms, two distinct types of gametes are produced.
The male gametes is called antherozoid or sperm while female gamete is called egg or
ovem.
8.Homothallic and Monoecious: When an organism has both male and female
reproductive organs. E.g Fungi, maize plants, Coconut plant.
9.Heterothallic and Dioecious: When male and female reproductive organs are found on
two separate organism. Such organisms are called Unisexual.. E.g Date palm tree, Palm
tree and cockroach.
10.Hermophrodite or Bisexual: When an organism has both male and female sex
organs.e.g earthworm, Leech etc. A majority of flowers are hermaphrodites.
11.Meiocytes: Specialised cells which undergo meiosis found in Diploid organisms.
12.Pistillate: When a flower has only female sex organ (carpel or pistil)
13.Staminate: When a flower has only male sex organ i.e stamens
14.Pollination: The transfer of pollen grains from anther to stigma.
15.Syngamy: The fusion of male and female gametes.
16.Fertilization: The process of fusion of male and female gametes
17.Parthenogenesis: The development of egg to new form without fertilization. E.g
Rotifers, Honey bees, Turkey birds etc.
18.External fertilization: When fertilization takes place outside the body of organisms.
E.g Frog and Bony Fishes.
19.Internal Fertilization: When fertilization takes place inside the body of female
organisms. E.g Female human.
20.Zygote: The product of fusion of male and female gametes.
21.Embryogenesis: The development of embryo from the zygote.
22.Oviparous: Egg laying animals e.g Fishes, Reptiles, Amphibians and Birds.
23.Viviparous: The organism which gives birth of young one. E.g Mammals excepting
Echidra ( oviparous mammals)
24.Pericarp: Protective wall of fruit, sometimes pericarp is differentiated into mesocarp
and Endocarp.
25.Clone: Organisms which are morphologically and Genetically identical with eah other.
B. Important Notes:
1.Life Span
 Period from birth till natural death.Every organism lives only for certain period of
time Eg Elephant 60 -90 years, Fruit fly 4-5 weeks.
 Life span of mayfly is one day.Life span of Man is 100 years.Life span of parrot is
140 years
 Life span of a banyan tree is 200 yearsLife span of Tortoises is 100- 150 years
PHASES OF LIFE SPAN.
 Juvenile phase: The phase of growth before reproductive maturity.
 Reproductive phase: Reproductive maturity.
 Senescent phase: Phase between reproductive maturity and death.

2.Reproduction: The biological process by which an organism produces its own kind to
maintain the race. Reproduction enables the continuity of species generation after
generation.
Types of Reproduction:
(a) Asexual reproduction
(b) Sexual reproduction
a.Asexual reproduction:- When single parent produces offspring without the involvement
of gamete formation . Such offspring is morphologically and genetically similar to the
parent.
Types of asexual reproduction:
a.Binary fission: In Monerans and protists the single celled organisms divide equally to
form two daughter cells. e.g., Amoeba , Paramoecium
b.Multiple fission : When an organism divides to form many daughter organisms . e.g.,
Plasmodium.
c.Budding : When parent organism gives rise to a small projection called the bud. The bud
increases in size and gets detached from parent organism and matures into new organism.
e.g., Yeast & Hydra.
d.Gemmule formation : In sponges a large number of buds are formed inside the body
which are called gemmules . Gemmules are small bodies which consist of a mass of
undifferentiated cells surrounded by protective covering of spicules and sycon.
e.Fragmentation : When parent body breaks into two or more pieces due to water current.
Each piece or fragment develops to form new parent. e.g., spirogyra ,sponges, flatworms.
f.Vegetative propagules : In higher plants the vegetative parts are used to raise new
plants.These vegetative parts are called propagules , these are as below
(i) Runner in Oxalis ad Marsilea
(ii) Rhizome in ginger and turmeric
(iii)Sucker in banana, pineapple,mint,etc
(iv)Tuber in Potato(EYES)
(v) Offset in water hyacinth and pistia
(vi) Bulb in onion and Garlic.
(vii Leaf buds in bryophyllum
(viii)Bulbil in Agave.
g.Zoospores and conidia formation: In certain algae and fungi, asexual reproduction
takes place by specialized reproduction structures called zoospores. Zoospores are
flagellated oval structures. e.g., Chlamydomonas.
In Aspergillus and penicillium a chain of non motile small spores are formed on fungal
hyphae – Conidiophores. These small spores are called conidia which on return of
favourable conditions germinate to form new plant body.
b.Sexual reproduction :
Sexual reproduction involves the formation of male and female gametes either
by the
same parent or by different parents of opposite sex.The events of sexual reproduction can
be dealt under three stages.
(a)Pre –fertilization events
(b)Syngamy and fertilization
(c)Post-fertilization events
(a)Pre fertilization events: These are (i) Gametogenesis (ii)Gametic transfer
(i)Gametogenesis :
1. The formation of gametes.
2. Gametes are generally haploid.
3. Gametes are called homogametes or isogametes when they are similar in
structures.
4. Gametes are called heterogametes when they are dissimilar in structures. The male
gamete is called antherozoid or sperm while female gamete is called ovum.
5. An individual organism
heterothallic/dioecious.
may
be
either
homothallic/monoecious
or
6.Cucurbits and coconuts are monoecious plants, where as papaya and date palm are
dioecious plants.
7. When parent body is haploid, the gametes are formed by mitosis and when parent body
is diploid the gametes are formed by meiosis.
(ii)Gametic transfer:
1.In some algae and fungi both male and female gametes are motile.
2. In majority of organisms ,the male gametes are motile whereas female gametes are
stationary.
3.In algae, bryophytes and pteridophytes , water is the medium for gametic transfer.
4. Since large number of male gametes fail to reach the female gametes, the number of
male gametes produced is several thousand times more than those of female gametes.
5. Pollination is the method of gamete transfer in higher plants , so pollen grains are the
carriers of male gametes
(b)Syngamy and Fertilization:
1.. Syngamy results in the formation of a diploid zygote.
2. In certain animals such as rotifers, honeybees, some lizards and birds(Turkey), the
female gamete develops into an adult without fertilization which is called
parthenogenesis.
3. Fertilization may be external or internal.
Fertilization
Two types- external and internal .
п‚· External fertilisation- outside the body of organism in external- medium (water) eg.
majority of algae, fishes, amphibians.
 Advantage- show great synchrony between the sexes –
1. Release of large number of gametes into surrounding medium
2. Large number of offsprings produced.
п‚· Disadvantage- offspring vulnerable to predators, natural disasters.
п‚· Internal fertilisation- fusion occurs inside female body eg. majority of plants and
animals. Egg non-motile and formed inside female body. Male gamete motile, produced
in large numbers to reach egg and fuse with it. In seed plants, non- motile male gamete
carried to female gamete by pollen-tube.
C.Post -fertilisation events- formation of zygote.
a. Zygote. One celled , diploid, vital link between two generations.
 External fertilization –zygote formed in external medium water eg. Frog,
 Internal fertilization –zygote formed inside the body eg. Humanbeings. Development
of zygote depends on type of life cycle and environment. Some develop thick wall (
prevent damage and desiccation) & undergo period of rest eg. Algae, fungi.
п‚· Haplontic life cycle- zygote (2n) divides by meiosis to form haploid (n) spores.
п‚· Diplontic life-cycle- zygote (2n) divides mitotically, develops into embryo (2n).
п‚· Oviparous animals lay eggs out-side the female body.Eggs can be fertilized/
unfertilized. Fertilized eggs covered which hard calcareous shell, laid in safe place in
the environment. Unfertilised eggs laid in water. Example- fishes, frogs, reptiles, birds
п‚· Viviparous animals bear and rear the embryo inside female body, give birth to youngones.Advantage- proper embryonic care, protection, survival chances of young-ones
greater. Example- cows, whales, humanbeings
п‚· Embryogenesis: development of embryo from zygote by cell division (mitosis) and cell
differentiation.
пѓ� Cell- division increases the number of cells in the developing embryo
Cell differentiation - groups of cells undergo certain modifications for the formation of
different kinds of tissues and organs.
п‚· In flowering plants- zygote formed inside ovule
пЃ¶ Changes occur in flowering plants:
Sepal
Fall off
Petal
Fall off
Stamen
Fall off
Zygote
Embryo
Primary endosperm nucleus
Endosperm (3 N)
Synergid
Disintegrate
Antipodals
Disintegrate
Ovary
Fruit
Ovule
Seed
Pericarp (epicarp + mesocarp +
Ovary wall
endocarp)
Integument
Seed coat (testa + tegmen)
IMPORTANT QUESTIONS
Q) What is meiocyte?
Ans) It is the gamete mother cell which undergoes meiosis.
Q) Why is date palm referred to as dioecious?
Ans) In date palm the male and female flowers are present in different plants.
Q) What is special in flowering in bamboo?
Ans) Bamboo flowers only once in their life time generally after 50-100 years .
Q) Define clone?
Ans) It is a group of individual of the same species that are morphologically and
genetically similar.
Q) What is vegetative propagule?
Ans) The units of vegetative propargations that gives rise to a new plant is called vegetative
propagule. Examples: Runner and rhizome.
Q) Cucur bit are called monoecious. Justify?
Ans) They have male and female reproductive structures in different flowers.
Q) If chromosomes number in meiocyte in rat, elephant and rice is 42,56,24 what will be
the chromosomes number in their gamete?
Ans) Rat 21, elephant 28,rice 12
Q) Why higher organisms have resorted to sexual reproduction in spite of its complexcity?
Ans) 1. It brings about variations.
2. Variation helps in better adaptation in nature.
3. Variation is the basis of evolution.
Q) What is parthenogenesis. Give Example?
Ans) Development of a new individual from an unfertilized egg is called parthenogenesis.
It is simpler easier and rapid mode of replication. But there is no chance of any variation.
So it does not play any role in evolution. Eg.- Honey bee and some lizards
Q Mention the reason for difference in ploidy of zygote and primary endosperm nucleus in
angiosperm
Ans Zygote is formed by fusion of haploid male gamete and haploid egg so it is diploid.
Whereas the PEN is formed by fusion of haploid male gamete with two haploid polar
nuclei so it is triploid.
Q) What are vegetative propagules. Name any four of them and give example?
Definition:Vegetative propagules: The vegetative parts of plants which are used to raise
new plants e.g. Rhizome, Bulb, tuber etc.,
Rhizome of ginger, leaf bud of bryophyllum, bulb of onion, offset of pistia.
HOTS.
Q)Amoeba is immortal. Explain?
Ans) Amobea has no natural death. It undergoes binary fission and forms two new daughter
cells.
Q) Which is the first diploid single cell which begins life?
Ans) Zygote.
Q What is the fate of zygote in organism which show
1 Haplontic life cycle
2Diplontic life cycle
Ans In haplontic life cycle zygote undergoes meiosis during its generation
In diplontic life cycle zygote divides mitotically during embryogenesis
Q) What type gametes are formed in staminate and pistillate flowers?
Ans) Pollen grains and egg cell respectively.
Q) Name the organisms with respect to their sexuality?
i) Monoecious animal
ii) Dioecious animal
iii) Monoecious plant
iv) Dioecious plant
Ans :- i) Earthworm ii) Cockroach iii) Chara iv) Marchantia.
Q.Is marchantia monoecious or dioecious?what are the sex organs borne in this plant?
Marchantia is dioecious. The male sex organs are borne on antheridiophores and female
sexorgansareborne on archegoniophores.
Fertilization of gametes is the critical event in sexual reproduction
Q.Which is the most critical event in sexal reproduction?
Fertilization of gametes is the critical event in sexual reproduction
Q.How does new organism develop in rotifers, turkey, honey bee and lizards?
The female gamete undergoes development without process of fertilization and form new
organisms
VALUE BASED QUESTIONS.
Q1 Raju observed colony of Honey bees in his field..He does not want to disturb it and he
wants to protect the bee colony .When he observed the bees,he found both haploid and
diploid individuals, considering the above views answer the following questions.
A).What value showed by the Raju?
(1)
B)Name the haploid and diploid organisms.
(1)
C)Analyze the reasons behind their formations.
(3)
Ans 1(A) Sense of responsibility towards nature.
B.Queen and workers are diploid but male(drones) are haploid.
(C) Drones develop parthenogentically. Since female gametes form new individuals
without fertilization in honey bees therefore they are haploid and grow into males.
Q2 Reproduction is a Biological process that evaluates the continuity of species generation
after generation. Each species have evolved its own mode of producing organisms. The
farmers want to cultivate different varieties of crops alternatively in the same land. The
farmer cultivate different plants to get different products for their use.
A) What kind of value shown by the farmer?
(1)
B) Name two types of reproductions found in organisms.
(1)
C) Out of two which is better mode of reproduction, Why?
(3)
Ans2(A) conservation of land.
B Asexual and sexual reproduction.
Ans2(C) sexual is better method of reproduction because it ensures recombination and
variations among the progeny essential for survival.
Q3 A student visited a botanical garden and spent lot of time by observing different flowers
He found thatt some trees in an area flower during same month year after year, some other
flower throughout the year, whereas some other plants show seasonal flowering.He spent
Plants are mostly of 3 types—annual, biennial, perennial type. Some plant show unusual
flowering.
Answer the following with respect to the statement
(A) What are 3 clear cut phases in the life of annual and biennial type of plants? (1)
(B) Why is it difficult to define these phases in perennial species of plants?
(2)
(C) Name one plant that flower only once in its life time.
(1)
(D) What kind of value made him to sit in the garden?
(1)
Ans 3 (A)
(1) Juvenile phase/ vegetative phase
(2) Reproductive phase
(3) Senescent phase
Ans 3(B) Since the entire life cycle of perennial plants has to be completed in one growing
season , their senescent phase is very short, it is directly related to their reproductive phase.
Ans 3 (C) bamboo species D,Aesthetic value.
CHAPTER- 2 Sexual Reproduction in flowering plants
IMPORTANT TERMS :-
1.Stamen: Male sex organ of a flower.
2. Microsporangium: 4-Microscopic chambers found in anther.
3. Dithecous anther (Bilobed anther) : When anther consists of two lobes
4.Tapetum: The innermost wall layer of a microsporangium having multinucleated cells. It
provides nourishment to developing pollen grains
5.Sporogenous tissue: A group of homogenous cells found in the centre of each
microsporangium
6. Microsporogenesis: The process of formation of microspores (pollens) from pollen
mother cells by meiosis inside each microsporangium
7.Exine: The hard outer layer of pollen grains made up of sporopollenin. Sporopollenin can
tolerate high temperature and strong acids and alkali.
8. Intine:Inner wall of pollen grain.
9. Germ pore: Microscopic pore present in exine.
10. Megasporangium (Ovule): It is ovule found inside ovary.
11. Megasporogenesis: The process of formation of megaspores from Megaspore mother
cells.
12. Placenta: Placenta is a tissue on which ovules are attached to the ovary wall
13. Pollination: The transfer of pollen grains from anther to the stigma.
14. Autogamy: The transfer of pollen grains from the anther to the stigma of the same
flower.
15. Chasmogamous flowers: These flowers are open flowers with exposed anther and
stigma. They lie close to each other to ensure autogamy. e.g., Oxalis, Commelina.
16.Cliestogamousflowers: These flowers are closed flowers which do not bloom but
ensure autogamy. e.g., Balsam, Oxalis, Viola. Balsam, Oxalis ,Viola plants possess both
chasmogamous and cleistogamous flowers.
17. Geitonogamy: The transfer of pollen grains from the anther to the stigma of another
flower of the same plant.
18. Xenogamy or Allogamy or Cross pollination: The transfer of pollen grains from the
anther of one flower to the stigma of a genetically different flower.
19. Anemophily: When cross pollination is brought about by the agency of wind. e.g.,
Maize, Cannabis, Coconut plant, palm tree, Date palm and many grasses.
20.Hydrophily: When cross pollination is brought about by the agency of water. e.g.,
Vallisneria , Zostera, Ceratophyllum, Hydrilla, etc.
21. Entomophily: When cross pollination is brought about by the agency of insects. e.g.,
Bougainvellia , Jasmine, Euphorbia .
22.Hybridization: Artificial cross between two plants.
23.Emasculation: The removal of anthers from a bisexual flower before its maturation.
24. Non albuminous seed: Seed without endosperm. e.g., Pea , Groundnut.
25.Albuminous seeds: Seeds with endosperm. e.g., Wheat, Maize ,Castor.
26. Perisperm: The residual and persistent nucellus present in the seed.
27.True fruits: The fruits which develop from ovary. e.g., Mango.
28.False fruits: The fruits which develop from other floral parts such as thalamus. e.g.,
Apple , Pear ,Strawberry.
29.Parthenocarpic fruits: The fruits which develop without fertilization. Such fruits do
not have viable seeds.
30.Apomixis or Agamospermy : Apomixis is a mode of asexual reproduction which
mimics sexual reproduction but produces seed without fertilization.
31.Parthenocarpy: The process of formation of fruits without fertilization.
32.Polyembryony: The presence of more than one embryo in a seed.
33.Monosporic: The development of embryo sac from single megaspore.
Important Notes:
Flowers( A fascinating organ of Angiosperms)
1, A flower is a modified shoot meant for reproduction
2, Flower bears the reproductive organs where gametes
are produced.
3,Androecium is a male reproductive organ which consists
of stamens
4,Gynoecium is thefemale reproductive organ which consists of carpels.
Male Reproductive OrganStamen consists of a filament and an anther.
Anther may be one lobed called monthecous or bilobed called Dithecous.
An anther is tetragonal in structure having four microsporangia two in each lobe.
Microsporangia of each lobe fused to form pollen sacs.
Structure of Microsporangium:
Each microsporangium consists of four parts
viz .
a. Outermost layer of epidermis
b. Second layer of endothecium
c. Middle layer of 2-4 layers of cell and
d. Innermost layer of Tapetum.
Tapetum provides nourishment to the developing pollen grains whereas other
three layers provide protection and help in dehiscence of anther to release the
pollen grains.
Microsporogenesis
1.Tapetum consists of sporogenous tissue which consists of potential pollen mother cells
(PMC) or Microspore mother cells.
2. Microspore mother cells undergo meiosis to produce pollen grains by
microsporogenesis. Pollen grains are haploid microspores. Pollen grains are haploid
microspores.
Microspore mother cell (2n)
Meiosis
Microspore (n)
Mitosis
Pollen grains (n)
Structure of pollen grain:
1. A pollen grain consists of two layers viz. outer layer is exine made up of
sporopollenin which can tolerate to high temperature, strong acids and alkali.
Innerlayer is intine made up of cellulose and pectin.
2. Exine has microspores at certain places called germpores.
3. A mature pollen grain has two cells. viz.
a) Vegetative cells and
b) Generative cells.
4. Generative cell divides mitotically to give rise two male gametes.
Female Reproductive organ
Gynoecium / carpel
Each Carpel consists of ovary, style &stigma.
Ovules are attached to ovary by placenta.
Funicle – stalk of ovule
Hilum, a region where funicle is attached
Integuments –cover embryo sac.
Micropyle – a pore for entry of pollen tube &to imbibe
water.
(Structure of anatropous ovule-Megasporangium)
Structure of an Ovule ( Megasporangium)
1. The ovule is a small structure attached to the placenta by a stalk called funicle. The
body of ovule fuses with funicle at Hilium.
2. Each ovule consists of one or two protective envelopes called integuments. Enclosed
within the integuments a mass of cells called Nucellus which have abundant reserve
food materials and provide nourishment to embryo sac.
3. Inside Nucellus a sac like structure is present which is called embryo sac.
4. The ovule has a minute aperture called micropyle.
5. The basal part of ovule opposite to micropyle is called chalaza.
6. A matured embryosac has * cell, 3 at micropylar end, 2 in the middle and 3 at
chalazal end.
7. The middle two cells are called central cells (polar nuclei)
8. The three cells at micropylar end constitute egg apparatus which has two synergids
and one egg cell.
9. The three cells at chalazal end are antipodal cells.Fig 2.7(d) Page No. 25 NCERT
Book
Megasporogenesis
Megaspore mother cell (2n)
Meiosis
4 Megaspores (n)
(3 megaspores degenerate, 1 remains functional)
Funtional Megaspore (n) (Divides 3times by mitosis)
8 Nucleated Embryo Sac formed
3 cells group at micropylar end -the egg cell(n) & 2 synergids(n)
Embryo sac
3 cells at chalazal end called antipodals(n)
2 polar nuclei at center(n each )
Development of Megaspore(Megasporogenesis)
пѓ� Embryo sac develops from a single large cell called megaspore mother cell which
has dense cytoplasm and a prominent nucleus.
пѓ� MM cell undergoes meiosis to form four megaspores.
пѓ� Three megaspores degenerate while one remain functional.
пѓ� The nucleus of functional megaspore divides mitotically to form two nuclei which
move to the opposite poles resulting into the formation of 2 nucleate embryosac.
пѓ� Both two nuclei undergo two successive mitotic division forming 8 nucleate stage.
пѓ� After that cell wall formation starts which result the formation of female
gametophyte or embryo sac.
пѓ� Three cells are grouped at micropylar end to constitute egg apparatus.
пѓ� Three cells are grouped at chalazal end called antipodals.
пѓ� The remaining two nuclei moves to centre of embryo sac and are called polar nuclei
which fuse to form diploid secondary nucleus.
пѓ� Fig 2.8(a) to (c) Page No. 28 NCERT Book Class XII
POLLINATION– transfer of pollen from anther to stigma. Agents of pollination –air,
water,insect.bat,bird,man.
Transfer of
pollen to
stigma
Self pollination (Autogamy)
Cross pollination
(Allogamy)
Xenogamy
(different
flowers on different plants
of the same species)
Geitenogamy
Auto gamy
(Same
flower)
Different
flowers same
plant
Adaptations in Flowers for Pollination
Wind Pollination:
п‚· The pollen grains of wid pollinated flowers are lighter, non sticky, dry and
sometimes winged.
п‚· The anthers are well exposed for easy disposal of pollen grains.
п‚· Stigma is large and feathery. E.g Maize , grams etc.
п‚· Wind pollinated flowers are not very colourful and do not produce nectar.
Water Pollination:
п‚· Water pollinated flowers are not very colorful and do not produce nectar.
п‚· In Vallisneria, the male flowers are released on water surface where as female
flowers with long coiled stalk reaches the surface of water for pollination.
п‚· In Hyacinth and Waterlilly flowers , flowers emerge above the level of water and are
pollinated by insects or wind.
п‚· In sea grasses, the female flowers remain submerged and pollen grains are released
inside the water.
п‚· In many acquatic species pollen grains are long, ribbon like and sticky.
Insect Pollination:
п‚· Insect pollinated flowers are large brightly coloured , fragnant and rich in nectar.
п‚· The flowers pollinated by flies and beetles secrete foul odours to attract them. E.g
Amorphophallus, Lotus.etc.
Pollen- Pistil Interaction:
1. A compatible pollen grain starts its germination on stigma.
2. The intine grows out through germ pore to form pollen tube.
3. The contents of the pollen move into the pollen tube.
4. The tube nucleus and generative nucleus reaches at the tip of pollen tube.
5. Pollen tube grows in length by utilizing the tissues of style and finally reaches
to embryo sac through micropyle.
6. Generative nucleus divides to form two male gametes.
7. The pollen tube releases two male gametes into the cytoplasm of synergid.
8. One male gamete moves to egg cell and fuses to form diploid zygote which
later on forms embryo of seed.
9. Another male gamete fuses polar nuclei (secondary nucleus) to form triploid
primary endosperm nucleus (PEN) which later on form endosperm of seed.
Double fertilization: i)Fusion of male gamete with egg – First fertilization ,SYNGAMY
ii)Fusion of fusion product of polar nuclei with male gamete – Second fertilization
.TRIPLE FUSION
Post fertilisation changes:
Stages of embryo development after fertilization:
1. Zygote divides by mitosis into suspensor &
embryo cells
2. Suspensor cell forms a globular basal cell which
remains embedded in the endosperm & a
multicellular suspensor bearing the embryo
3.Globular embryo becomes heart-shaped & then
mature embryo with radicle, plumule&Cotyledons
– divides repeatedly
to form endosperm, food for theembryo.
True Fruit develops only from the ovary, e.g.
mango, tomato
False Fruit develops from parts of the
flowerother than the ovary e.g. apple, peach etc.
Seeds two types: i) Albuminous (with Endosperm)
ii) Non albuminous(without Endosperm)
Special mechanism of reproduction:I) Apomixis- Production of seeds without fertilisation e.g. species of Astereceae and
grasses.
ii) Polyembryony- Occurrence of more than one embryo in a seed e.g.Orange.
Outbreeding devices:
Continued self-pollination result in breeding depression. Flowering plants have developed
many
devices to discourage self-pollination & encourage cross-pollination such as
Bearing unisexual flowers Unisexuality
Anther & stigma mature at different times Dichogamy
Anther & stigma placed at different positions Heterostyly
Pollen grains of a flower do not germinate on the stigma of the same flower Self
incompatibility
Types of cross-pollination performed by man for cropimprovement. Achieved by
i) Emasculation i.e. removal of anthers from the flower bud of a bisexual flower before the
anther dehisces using a pair of forceps and
ii) Bagging i.e. covering the emasculated flowers with a bag of suitable size to protect them
from contamination with unwanted pollen.
Important Questions.
1.Define microsporogenesis?
A. . Microsporogenesis: The process of formation of microspores (pollens) from pollen
mother cells by meiosis inside each microsporangium.
2. What do you mean by Parthenocarpy?
A.The process of formation of fruits without fertilization.
3. What is emasculation? Explain its importance in Hybridization.
A. The removal of anthers from a bisexual flower before its maturation.It prevents self
pollination.
4. Name the inner most layer of microsporangium that nourishes the developing
pollengrains?
A. Tapetum
5. Draw a well labeled diagram of an ovule and label its six parts?
A.
6.Write any three characteristics of wind pollinated flowers.
п‚·
The pollen grains of wid pollinated flowers are lighter, non sticky, dry and
sometimes winged.
п‚· The anthers are well exposed for easy disposal of pollen grains.
п‚· Stigma is large and feathery. E.g Maize , grams etc.
п‚· Wind pollinated flowers are not very colourful and do not produce nectar
7. How do the false fruit differ from true fruit ?
A.True Fruit develops only from the ovary, e.g. mango,
False Fruit develops from parts of the flowerother than the ovary e.g. apple,
8. Describe the process of development of female gametophyte up to the 7 celled and 8
nucleated stage .
пѓ� A. Embryo sac develops from a single large cell called megaspore mother cell which
has dense cytoplasm and a prominent nucleus.
пѓ� MM cell undergoes meiosis to form four megaspores.
пѓ� Three megaspores degenerate while one remain functional.
пѓ� The nucleus of functional megaspore divides mitotically to form two nuclei which
move to the opposite poles resulting into the formation of 2 nucleate embryosac.
пѓ� Both two nuclei undergo two successive mitotic division forming 8 nucleate stage.
пѓ� After that cell wall formation starts which result the formation of female
gametophyte or embryo sac.
пѓ� Three cells are grouped at micropylar end to constitute egg apparatus.
пѓ� Three cells are grouped at chalazal end called antipodals.
пѓ� The remaining two nuclei moves to centre of embryo sac and are called polar nuclei
which fuse to form diploid secondary nucleus enveloped by single cell wall.
пѓ� Fig 2.8(a) to (c) Page No. 26 NCERT Book Class XII
9. Flowering plants have developed many devices to discourage self-pollination &
encourage cross-pollination. Explain any three.
п‚· Bearing unisexual flowers Unisexuality
п‚· Anther & stigma mature at different times Dichogamy
п‚· Anther & stigma placed at different positions Heterostyly
п‚· Pollen grains of a flower do not germinate on the stigma of the same flower Self
incompatibility
HIGHER ORDER THINKING SKILLS QUESTIONS
1. Name the type of pollination that ensures genetic variation?
A.Xenogamy.
2. The plant yucca and moth cannot complete their life cycle without each other. Why?
A.The moth deposits its eggs in the locule of ovary and flower, in turn gets pollinated by
the moth. The larvae of the moth come out of eggs as the seeds start developing.
3. Cliestogamy can favour only autogamy. Justify
A.In cliesgamy, flowers never open at all. Hence foreign pollen will not land on stigma of
such flowers. So cliestogamy will only favourself pollination or autogamy.
4. Can an unfertilized, apomictic embryosac give rise to a diploid embryo? If yes how?
A. Yes, if embryo develops from the cells of nucellus or integuments, it will be diploid.
5. Name the plants in which chasmogamous and cliestogamous both types of flowers are
formed?
A.Oxalis and commilina.
VALUE BASED QUESTIONS
Q1. Ravi is suffering from Asthma. Whenever he comes out of the home ,he feels
suffocated and breathlessness. When Ramu visited Ravi�s house , he observed that weeds
were overgrown around the house of Ravi. He told Ramu to clear the weeds grown around
his house . Some exotic species in plants have invaded India as a contaminant with
imported wheat. Some of them have become ubiquitous in occurrence. The pollen grains
cause harm to us.
(A) Name the grass whose pollens grains cause allergy and bronchial disorder in some
persons (2)
(B) Can pollens be useful to us? How?
(C) Why did Ravi tell Ravi to clear the weeds?(1)
Ans 1 (A) Carrot grass—Parthenium
Ans 1(B) Pollen tablet and syrups are consumed by athletes and race horses.
(c ) Sense of responsibility.
Q2 Now a days the human population is rapidly increasing to meet the nutritional demand
of people, farmers are cultivating hybrid variety of food and vegetable crops extensively.
One farmer adopted the technique of apomixes .
(A) Explain One problem of hybrids. (3)
(2B)What is importance of apomixes in seed industry? Why did farmer adopt this
technique?
Ans2(A) Hybrids change the basic nature of the organisms, hence may cause gene
pollution and affect biodiversity.
Ans2 (B) Formation of seed without fertilization is apomixes. It maintains the hybrid
vigour in crop plants. Therefore they can be stored and preserved for longer time.
Apomictic seeds are cheaper than hybrid seed.
Q 3 Artificial hybridization is popular among plant breeders. They produce commercially
better varieties of desirable traits. Referring to this programe explain.
(A) What is meant by artificial hybridization?
(2)
(B) How can it be achieved by farmers.
Ans 3(A) The different species / genera are crossed artificially for combination of desired
traits to get commercially superior varieties of organisms is called artificial hybridization.
Ans3 (B) Anthers are removed from the bisexual flower before dehiscence(emasculation)
and bagging is done to prevent contamination from unwanted pollen. On attaining maturity
mature pollens from desirable plant are dusted on stigma of bagged flowers and rebagged
for fruit development to have desired quality of fruits and seed.
CHAPTER-3 HUMAN REPRODUCTION
IMPORTANT TERMS:
1.Gametogenesis: The process of formation of gametes for sexual reproduction.
2.Spermatogenesis: The process of formation of spermatozoa in the seminiferous
tubules of testes.
3.Spermiogenesis: The process of transformation of spermatid into spermatozoa.
4.Spermiation: The process of release of spermatozoa from seminiferous tubules.
5.Semen: The seminal plasma with sperms constitutes semen.
6.Acrosome: The cap like structure which covers the head of the sperm. Acrosome
contains sperm Lysins.
7.Oogenesis: The process of formation of ova.
8.Ovulation: The release of ovum from the ovaries of the female human.
9.Antrum: The fluid filled cavity of graffian follicle.
10.Menarche: The beginning of first menstruation at puberty in female primates.
11.Menstrual cycle: The reproductive cycle in the female primates i.e. Monkey,
Apes and Human beings.
12.Corpus luteum: Corpus luteum is a temporary endocrine gland formed by
ruptured follicle and blood clot. It releases progesterone which maintains pregnancy.
13.Fertilization: The process of fusion of a sperm with ovum.
14. LH-surge: The maximum level of LH during middle of menstrual cycle. LHsurge induces rupture of graffian follicle releasing ovum.
15.Follicular Atresia: In human female, a large number of primary follicles
degenerate in the ovaries from birth to puberty.
16.Menopause: Stoppage of menstruation in human female at the age of 45-50
years.
17. Insemination: The deposition of sperms into the female genital tract during a
coitus. The human male ejaculates about 200-300 million sperms during a coitus.
18. Implantation: The attachment of developing embryo to the uterine wall of
human female.
19. Umbilical Cord: The cord which connects the placenta with the developing
embryo. Umbilical cord helps in the transport of substances from uterine wall to
embryo and vice- versa.
20. Parturition: The process of delivery of foetus or birth of child.
21.Foetal ejection reflex: The signals for parturition originate from fully developed
foetus which induces uterine contractions triggered by oxytocin.
22. Lactation: The process of release of milk from mammary glands after
parturition.
23.Colostrum: The first milk which comes out of mammary glands for few days
contain anti-bodies which develops resistance in newly born baby.
Important Notes:
1. Human male reproductive system:
a. A pair of testes
b. Duct system
c. Accessary glands
d. External genitilia(Penis)
a. Testes:
1. Testes are located in pouch of skin called scrotum whichj lie outside the
abdominal cavity.
2. Each testis is oval in shape consists of 250 testicular lobules.
3. Each testicular lobule contains three highly coiled seminiferous tubules.
4. Each seminiferous tubule is lined by two types of cells viz. male germ cells and
sertoli cells.
5. Male germ cells undergo meiosis to form haploid spermatozoa.
6. Sertoli cells provides nutrition to developing spermatozoa.
7. In between the seminiferous tubules, connective tissue blood vessels and leydig
cells are present.
8. Leydig cells secrete male sex hormone called androgens. E.g Testosterone.
b. Duct system: Includes
1. Rete testis- seminiferous tubules open into very finer ducts called rete testis.
2. Vasa efferntia: Vasa efferntia receives the opening of rete testis and open into
epididymis which is located in the posterior part of testis.
3. Epididymis leads to vas deferens which ascends into abdominal cavity.
4. Vas deferens receive the ducts from seminal vesical and opens into urethra which
acts as ejaculatory duct. These ducts store and transport spermatozoa from tyestes
to urethra.
5. Urethra: It comes out from urinary bladder and runs inside the penis and opens
outside by an aperture called urethral meatus.
c. Accessory Glands:
1. Seminal vesicles
2. Prostrate gland
3. Bulbourethral glands.
The secretions of these glands constitute semen. The secretion of Bulbourethral
glands help in the lubrication of the penis.
Fig 3.1(b) Page No. 43, NCERT Book Class XII
Fig 3.2 Page No. 44 ,NCERT Book Class XII
d. External Genetalia:
Penis is the external genitilia which is made up of special tissue which helps in
erection of penis to facilitate insemination. The enlarged tip of penis is called glans
penis which is covered by a loose fold of skin called foreskin.
2. Human Female Reproductive system:
It consists of the following organs like
a. A pair of ovaries.
b. A pair of Oviduct ( Fallopian tubes)
c. Uterus
d. Vagina
e. Mammary glands.
a. Ovaries:
1. Ovaries are located in the abdominal cavity one on each side near the kidneys.
2. Each ovary is almond shaped covered by a thin epithelium.
3. Inside ovary, ovarian follicles are found in various stages of development.
b. Fallopian Tube:
1. Each fallopian tube is 10 to 12 cm long which extends from the periphery of
ovary to uterus.
2. The fallopian tube near the ovary is funnel shaped called infundibulum.
3. The edges of infundibulum possess finger like projections called fimbriae.
4. Fimbriae help in collection of ovum after ovulation.
5. Infundibulum leads to a wider part of oviduct called ampulla.
6. The last part of oviduct is isthmus which opens into uterus.
Fig 3.3 (b) Page No. 45 ,NCERT Book Class XII
c. Uterus (Womb):
1. It is pear shaped muscular structure.
2. It consists of three layer of tissue viz.
a. Perimetrium- the outer thin membranous layer.
b. Myometrium- the middle thick layer of smooth muscles.
c. Endometrium- Inner glandular layer.
3. Myometrium contracts during delivary of baby.
4. Endometrium undergoes cyclic changes during menstrual cycle.
5. Uterus opens into vagina by a narrow cervix, the cavity of which is called
cervical canal.
d.Vagina :
1. Vagina is a muscular tube covered by a hymen membrane and guarded by two large
folds of skin and two small folds of skin which are called labia majora and labia minora
respectively.
2. At the upper junction of labia minota, a tiny finger like projection is present which is
called clitoris.
e. Mammary Glands
1. Mammary gland consists of glandular tissues and fats.
2. Glandular tissue of each mammary gland consists of 15-20 mamary lobes.
3. each mammary gland hasa nipple, areola, lactiferous duct, ampulla, mammary alveolus
and fat.
Fig 3.4 Page No. 46 ,NCERT Book Class XII
3.Gametogenesis: Formation of gametes.
A. Spermatogenesis:
1. Phase of multiplication: Sperm mother cells of tests undergo rapid mitotic division
to
produce large number of diploid cells called spermatogonia.
2.Phase of Growth: and3. Phase of maturation:
a. Each spermatogonium increases in size by accumulating food materials and is
called
primary spermatocyte.
b. Each primary spermatocyte undergoes firstmeiotic division or reduction to form
two
haploid secondary spermatocytes.
c.Each secondary spermatocyte undergoes secong meiotic division to produce
spermatids.
d. Each spermatid transformed into spermatozoa.
B. Hormonal Control of Spermatogenesis:
1. Spermatogenesis begins at puberty by gonadotropin releasing hormone released
by Hypothalamus.
2. LH ( Lutinising hormone) released by pituitary acts on Leydig cells, which
secretes androgens. Androgens stimulate spermatogenesis.
3. Follicle stimulating Hormone(FHS) acts on sertoli cells which secretes some
factors necessary for spermiogenesis..
c. Structure of Human spermatozoan:
1. A human spermatozoan consists of four parts- head, neck, middle piece and tail.
2. Head contains chromosomal material (DNA) and a cap like structure called
acrosoe which contains enzymes that help in dissolving egg membrane during
fertilization.
3. Middle piece contains numerous mitochondria which provide energy for the
movement of the sperm.
4.Neck contains two centrioles, the proximal centriole which is necessary for first
cleavage in zygote. The distal centriole is connected with tail.
5. Tail – It consists of axial filament surrounded by the plasma membrane. Tail helps
in the movement of sperm.
B. Oogenesis : Formation of Ova.
(a)Stage of Oogenesis:
(i) Egg mother cells : (Germ cells) of ovaries undergo rapid mitotic division to form a
large
number of diploid cells called oogonia.
(ii) Phase of growth : Each oogonium increases in size by accumulating reserve food
materials and is called primary oocyte.
(iii)Phase maturity :
1. Each primary oocyte undergoes first meiotic division to produce two haploid cells.
2. The division is unequal, so a large cell called secondary oocyte and small cell
called polocyte( polar body) are formed.
3. Both secondary oocyte and polar body undergo second meiotic division to form
one large haploid egg and three polar bodies.
(
b)Structure of graffian follicle:
1. A mature graffian follicle consists two membranes and follicular cells.
2. Follicular cells enclose a ovum in the centre.
3. The central fluid cavity of graffian follicle is called antrum.
(c)Menstrual cycle: The discharge of blood and dead tissues from the vagina of female in
each month is called menstruation. It repeats after 28 days. It consists of four phases viz..
1. Menstrual Phase: It lasts for 3-5 days in which dead cells and blood (broken tissues of
endometrium) are discharged from the vagina.
2.Proliferative Phase:
(i) In this phase the graffian follicle becomes matured due to increased level of FSH and
LH.
(ii)endometrium of Uterus is regenerated by its proliferation.
(iii)It lasts for about 12 days.
3.Ovulatory Phase: On 14th day of menstrual cycle ovulation takes place, and ovum is
released fromgraffian follicle due to peak level of LH called LH-surge.
4.Secreatory Phase (Luteal phase):
(i)In this phase ruptured graffian follicle is transformed into corpus lutuem and
progesterone is released.
(ii) The endometrium thickens and its glands secrete a fluid into uterus.
(d)Fertilization,Implantation and Parturition:
1. The fertilization takes place in the fallopian tube of human female.
2. The sperms released in the vagina of female reach into the fallopian tube where they
come in contact with the zona pellucida layer of the ovum.
3. The sperm lysine present in the acrosome of sperm dissolves zona pellucida and plasma
membrane of the ovum, and sperm enters into the ovum and fuses to form the zygote.
4. The zygote undergoes repeated mitotic cell divisions to form a solid ball of cells called
morula.
5. Morula consists of 16 cells. The cells of morula rearrange themselves to form an inner
mass of cells and a cavity called blastocoel. The embryo at this stage is called
blastocyst(Blastula).
6. The outer layer of morula form small projections called Trophoblast.
7. Now the blastocyst descends down the fallopian tube and attaches to the endometrium
of uterus of female human.
8. The trophobalst differentiates into two layers. The outer layers secrete enzyme which
dissolve the endometrium. The inner layer forms finger like projections called chorionic
villi which enter into uterine stroma.
9. The chorionic villi and uterine tissue unite to form placenta which secretes four
hormones viz.. hCG, hPL, oestrogens and progesterone. These hormones maintain
pregnancy.
10. The umbilical cord which connects the placenta with foetus is formed.
11.The inner mass of blastocyst undergoes differentiation to form outer ectoderm, middle
mesoderm and inner endoderm.
12. After the formation of three primary germ layers the gastrula undergoes morphogenesis
and organogenesis to form well developed child.
13. After that oxytocin is released from posterior pituitary which causes parturition(birth of
child).
Differentiate between: Spermatogenesis and Oogenesis :
Spermatogenesis
Oogenesis
Produces male gametes (sperm)
produces female gametes (oocytes)
–occurs in the seminiferous tubules
(in testes)
–occurs in the ovaries
–involves meiosis
–occurs throughout life after puberty
– involves meiosis
occurs after puberty until menopause
may produce 400,000,000 per day
–humans normally produce one oocyte
during each ovarian cycle
Primary spermatocyte divide equally
to form two similar secondary
spermatocytes
Primary otocyte divide unequally to
form one large secondary oocyte and a
small polar body
One spermatogonium produces 4
functional spermatozoa
An oogonium produces one functional
ovum and 3 non functional polar
bodies
SH and LH from the pituitary:
Hormone
FSH Controls пѓ LH Controls пѓ FUNCTION
/ PRODUCTION
In Females
In Males
Eggs +
Spermatogenesis
Estrogen
Ovulation +
Testosterone
Corpus
Luteum
From Primordial Follicle to Tertiary Follicle
Primordial follicle:The surviving primary oocytes, at birth, are surrounded by thin, single
layers cells of so-called follicular epithelial cells.
Primary follicle
The primordial follicles while developing into primary follicles the follicular epithelium
that surrounds the oocyte becomes iso- to highly prismatic
Secondary follicle
Secondary follicles with follicular epitheliums encompassing multiple rows are formed
called the stratum granulosum. Pellucid zone, between the oocyte and follicular
epithelium becomes visible.
Tertiary follicle
A well-developed net of capillaries in the theca interna.
Antrum – a fluid filled cavity develops
The theca layer organized into Theca internal & Theca external
EMBRYONIC DEVELOPMENT
Transport of ovum,fertilization and passage of growing embryo through fallopian tube.-Fig
No:3.11 page No:52
Fate of three germ layers
Ectoderm
Mesoderm
Endoderm
Nervous system
Skeleton
Digestive tract
Epidermis of skin
Muscles
Respiratory system
Circulatory system
Liver, pancreas
Gonads
Bladder
IMPORTANT QUESTIONS
1.. Name the important mammary gland secretions that help developing resistance in the
new born baby?
A.Colostrum.
2. What are sertoli cells?
A. Cells of seminiferous epithelium –provide nutrition to developing germ cells.
3.At what stage is the mammalian embryo implanted in the uterus?
A. Blastula
4. What is spermiogenesis?
A. The spermatids are transformed into spermatozoa .
5.. At what stage is meiosis I suspended in primary oocyte?
A.Prophase I
6. When is meiosis II completed in the oogenesis of human female?
A. When the sperm comes into contact with the secondary oocyte.
6. Define foetal ejection reflex?
A. The signals for parturition originate from fully developed foetus which induces uterine
contractions triggered by oxytocin.
7.Zygote undergoes mitosis to form 16 celled stage of embryo. What is it known as?
A.Morula
8.. Fill in the boxes
. Spermatogonia- --------Secondary spermatocytes -------Spermatozoa
A. Primary spermatocytes, spermatids.
9.How do hormones secreted from anterior pituitary gland control and regulate the male
reproductive system?
A.Ant.Pituitary Gland --- 1. LH – Leydig cells – testosterone 2. FSH – sertoli cells factors –spermiogenesis.
10.Draw and label the main parts of the human spermatozoa. Why is the middle piece
considered as power house of the human sperm?
A. Diagram. It contains mitochondria
11.What is acrosome? What is its significance?
A. The anterior end of head of the sperm has a cap like structure called acrosome.It
contains enzymes like sperm lysine help in dissolving memberanes.
12. Faillure of fertilization leads to menstruation. Explain.
A. Degeneration of corpus luteum decreases progesterone levels,this causes degeneration
of endomtrium leading to menstruation.
13.What is the role of pituitary hormone in the regulation of menstrual cycle?
A.It secrets FSH and LH. FSH- development of ovarian follicles LH- LH surge leads
to rupture of mature graffian follicle and release of ovum
14. Name the hormones secreted by placenta that play significant role in maintaining
pregnancy?
A.hCG, hPL, estrogens and progesterone
15.. State any two differences between Spermatogenesis and oogenesis.
A.
Spermatogenesis
Oogenesis
Produces male gametes (sperm)
produces female gametes (oocytes)
–occurs in the seminiferous tubules
(in testes)
–occurs in the ovaries
–involves meiosis
–occurs throughout life after puberty
– involves meiosis
occurs after puberty until menopause
may produce 400,000,000 per day
–humans normally produce one oocyte
during each ovarian cycle
Primary spermatocyte divide equally
to form two similar secondary
spermatocytes
Primary otocyte divide unequally to
form one large secondary oocyte and a
small polar body
One spermatogonium produces 4
functional spermatozoa
An oogonium produces one functional
ovum and 3 non functional polar
bodies
16.. What is pregnancy hormone? Why it is so called? Name the sources of this hormone in
a human female?
A.Progesterone –maintains endometrium- corpous luteum.
17.What is the fate of inner cell mass in the blastocyst? Mention their significance.
A. Inner cell mass acts as stem cells and help in the development of proper embryo .
18.
Study the graph given above.Showing the levels of ovarian hormones during menstruation
and
correlate the uterine events that take place according to the hormonal levels.
1. 6-15 days
2. 16-25 days
3. 26-28 days ( if the ovum is not fertilized)
A.i.)Regeneration of endometrium
ii).Uterus gets highly vascularised ready for embryo implantation
iii) Disintegration of endometrium leading to menstruation
HIGHER ORDER THINKING SKILLS
1. Placenta is called an endocrine gland. Why? Give reasons to support your answer?
A. Placenta produces various hormones. It is called an endocrine gland. As an endocrine
gland placenta produces various hormones—estrogen, progesterone, hPL- human placental
lactogen, HCGX—human chorionic gonadotropin
2. Enlist the chromosome no. in ovum, first polar body and second polar body of human
body.
a.Ovum-----------23
b.-1stpolar body------------23
c. 2nd-polar body-----------23
3. Why does corpous luteum secrete large amount of progesterone during leutal /secretory
phase of menstrual cycle?
A.Progesterone hormone is essential for maintenance of endometrium of uterus, so that
foetus may get implanted here.
4. Name two hormones that can only be found in the blood of pregnant women. Mention the
source that secretes each of them.
A.Human chorionic gonadotropin. Human placental lactogen. The source that secretes
them is placenta
5. What name is given to the cells of inner cell mass, that have the potential to give rise to all
tissues and organs in a human being.
A. Stem cells.
VALUE BASED QUESTIONS
1.Rita and her parents were watching a TV serial in the evening. During a commercial
break,an advertisement flashed on the screen which was promoting use of sanitary napkins.
Ritawas still watching the TV. The parents got embarrassed and changed the channel.
Ritaobjected to her parents� behaviour and explained the need for these advertisements.
a) What values did the parents show?
b) Briefly describe the phases of a menstrual cycle.
Ans-a) The parents were traditional but understood the need for such advertisements.
They showed maturity and openness later.
b). Phases:To write details of thedifferent phases describing thediagram
i) Menstrual phaseii) Proliferative phaseiii) Secretory phase.
CHAPTER-4
REPRODUCTIVE HEALTH
A. IMPORTANT TERMS:
1. Amniocentesis: Amniocentesis is a technique by which amniotic fluid containing
foetal cells are taken out from mother�s womb by special surgical needle to
examine the sex and chromosomal disorder of the foetus.
2. Population Explosion: A tremendous increase of human population in a short
span of time.
3. Periodic Abstinence: Periodic abstinence is a method in which couples avoid
cointus from day 10th to 17th of menstrual cycle.
4. Lactational Amenorrhea: Absence of menstruation during lactation period.
5. Tubectomy: Removal of fallopian tubes in female human.
6. Vasectomy: Removal of vas deferens in male human.
7. Sterilization: The ligation of vas deferens in males and fallopian tubes in female
human.
8. Medical termination of Pregnancy(MTP): Voluntary termination of pregnancy
in the first three months either mechanically or by using infanticides.
9. Sexually Transmitted Diseases (STDs): The transmission of diseases through
sexual intercourse E.g. Gonorrhoea, Syphilis and AIDS.
10.Infertility: Inability of a couple to produce children in spite of unprotected sexual
cohabitation.
11.Artificial insemination or Intra Uterine Insemination (IUI): It is a technique
in which semen is collected either from the husband or from a healthy donor and
is inserted either in Vagina or into the uterus.
B. Important Abbreviations:
1. IUD: Intra Uterine Device.
2. MTP: Medical Termination of Pregnancy.
3. STD: Sexually transmitted disease.
4. ART: Assisted reproductive technology
5. IVF: In vitro fertilization
6. ET: embryo transfer.
7. ZIFT: Zygote intra fallopian transfer
8. IUT: Intra unterine transfer
9. GIFT: Gamete Intra fallopian transfer
10.ICSI: Intra cytoplasmic sperm injection
11.AI: Artificial insemination
12.IUI: Intra uterine Insemination
13.IMR: Infant mortality rate
14.MMR: Maternal Mortality rate.
15.RCH: Reproductive and child health care programmes
16.PID: Pelvic Inflammatory diseases.
17.HIV: Human Immunodeficiency Virus
18.RTI: Reproductive tract infections
C. Important notes:
1. Amniocentesis
2. Population explosion
3. Birth control
4. Medical Termination of pregnancy
5. Sexually transmitted diseases
6. Infertility
1. Amniocentesis
A particular technique which helps to diagnose sex and chromosomal
disorders in an unborn foetus is called Amniocentesis.
Steps of Amniocentesis:
a. Amniotic fluid containing foetal cells are taken out from mother�s womb by a
special surgical needle without damaging the foetus.
b. Now the foetal cells are cultured to examine sex and chromosomal disorders of
the foetus.
Advantages of Amniocentesis:
1. It helps in finding out the sex of the foetus.
2. It is useful in finding out any metabolic disorders of the foetus at a very early
stage.
3. By this method serious incurable congenital defects in foetus can be detected by
MTP.
Disadvantages of Amniocentesis:
1. It has been that not only fathers, even mothers also do not want female child and
they get it aborted out. This will be a serious menace to eliminate human race
from the earth. So, this technique has now been banned.
2. For amniocentesis an experience and expert doctor is required otherwise the
syringe may damage the developing foetus leading to abortion.
Causes of population explosion:
1. Decline in death rate
2. Decline in maternal mortality rate
3. Decline in infant mortality rate
4. Increase in the number of people in the reproductive age.
5. Increased health facilities with better living conditions
6. Greater medical attention
Measures to control overpopulation:
1. Raising the age of marriage is a most effective means to control population. Now
marriageable age of female is 18 years and that of male is 21 years.
2. Knowledge of sex education should be given at adolescence age.
3. Couples with small families or who adopted ―One child norm‖ should be given
incentives.
4. Family planning methods should be adopted by all couples of different religion.
5. Mass media such as Radio, Television, News[papers, magazines and posters are
employed to spread the advantages of small family( i.e Hum Do Hamare Do) and
evils of large family.
2. Birth Control:
a. Natural methods:
1. Periodic abstinence: In this method, the couple abstain or avoid coitus
between 10th to 17th day of menstrual cycle when ovulation is expected and
chances of fertilization is very high.
2. Coitus interruptus: In this method, the male partner withdraws his penis
from vagina just before ejaculation so as to avoid insemination.
3. Lactational amenorrhea: It is the absence of menstruation during the
period of intense lactation. In this period ovulation does not occur as a
result the chances of conception is almost nil.
b. Barrier methods:
In this method ovum and sperms are prevented to meet together.
1. Condoms are barriers made up of thin rubber latex sheath which covers
the penis in males and vagina and cervix in female. E.g Nirodh.
2. Diaphragms cervical caps and vaults- They are made up of rubber and
used by female during coitus.
3. Spermicidal creams, Jellies and foams are used as barriers to prevent
fertilization of ovum with sperm.
c. Intra uterine devices:
The most popular and effective devices are IUDs. IUDs are introduced
into the vagina of female to prevent fertilization.
Types of IUDs
1. Non medicated IUDs e.g – Lippes loop
2. Copper releasing IUDs e.g Cu T, Cu 7, Multiload- 375
3. Hormone releasing IUDs e.g progestasert, LNG- 20
IUDs prevents contraception in the following ways.
1.
2.
3.
4.
5.
They increase phagocytosis of sperms within the uterus.
They release Cu ++ ions which suppresses sperm motility
They reduce fertilizing capacity of sperms
They release hormones which makes the uterus unsuitable for implantation
They make cervix hostile to sperms.
Oral contraceptives (oral pills)
Oral contraceptives are hormonal preparation in the form of pills or tablets which alter
ovulatory cycle.
Oral administration of small doses of either progestogen or progestogen- oestrogen
combination.
Oral pills have to be taken daily for a period of 21 days starting from first five days of
menstruation.
After a gap of 7 days during menstruation oral pills may again be taken.
Oral pills inhibit ovulation and implantation
They alter the quality of cervical mucus to prevent the entry of sperm. E.g Mala D, Mala N,
saheli.
Saheli is most effective contraceptive pills made up of non steroidal preparation taken once
in a week.
Emergency contraceptives: Administration of progestogens or progestogen- oestrofgen
combination or IUDs within 72 hours of coitus have been found very effectiveas
emergency contraceptives.
Injection or Implants: Progestones alone or in combination of oestrogen can be used by
females as injections or implants under skin.
Surgical methods: (Sterilisation)
Surgical methods block the transport of gametes thereby preventing conception. This
method is advised to those couple who do not want more children.
1. Vasectomy: Removal of small part of vas deferens or ligation of vas
deferens in male.
2. Tubectomy: Removal of small part of fallopian tube or ligation of
fallopian tubules in females.
Medical Termination of Pregnancy:
1. MTP has been legalized by the Government of India in 1971 with strict
conditions to avoid its misuse to prevent female foeticde.
2.MTP is essential to get rid of unwanted pregnancies either due to
unprotected
coitus or due to rape.
3.MTP is safe during the first transfer (i.e up to 3 months or 12 weeks )
where as
MTP is riskier in second trimester.
4.MTP is essential where pregnancy is harmful or fatal either to mother or
foetus or both.
.Sexually Transmitted Diseases (STDs) or Veneral Diseases (VD)
The diseases which are transmitted through sexual intercourse are called STDs or VD.
Diseases
Causative Agents
Syphilis
Treponema pallidum
(Bacterium)
Gonorrhoea
Neisseria gonorhoeae
(Bacterium)
Chlamydiasis
Trichomoniasis
AIDS
Hepatitis-B
Genital Herpes
Chlamydia trachomatis
(Bacterium)
Trichomonas vaginalis
(Protozoa)
Human Immuno deficiency
Virus
Hepatitis virus
Herpex simplex virus or
Human papilloma virus
AIDS, genital herpes and Hepatitis B cannot be cured where as other STDs are
curable.
Symptoms of STDs
1. Itching
2. Fluid discharge
3. Swelling and
4. Mild pain
Preventions:
1. Avoid sex with unknown partners or multiple partners
2. Use condom during coitus every time
3. Seek medical help in case of doubt.
Mode of Transmissions:
1. Sharing of injection needles, surgical instruments with infected persons
2. By blood transfusion
3. By sexual intercourse with infected persons
4. By infected mother to her foetus.
Infertility:
Inability of a couple to produce children in spite of unprotected sexual cohabitation.
Reasons for infertility
1. Physical
2. Congenital diseases
3. Use of certain drugs
4. Immunological reactions
5. Psychological
Special Health care units or infertility clinics have diagnosed the problems of
infertility and given corrective treatments called Assisted reproductive technology
(ART).
Test tube Baby programme (invitro fertilization)
Step of Test tube baby programme:
a. The ovum is taken out from the reproductive tract or ovaries of female.
b. Now the ovum is kept in liquid nitrogen in aseptic conditions in a test tube
c. The ovum is fertilized by the sperm of her husband or Nobel laureate
(Sperm bank) into the test tube(in vitro) to obtain zygote.
d. The zygote is developed up to 32 celled stage.
e. Now 32 celled embryo is transformed into fallopian tube of the female to
grw under natural conditions till the birth.
E.T (Embryo transfer): The transfer of zygote or early embryo into the fallopian tube or
uterus for further development is called Embryo transfer. It can be done in two ways.
a. ZIFT: The transfer of embryo up to 8- blastomeres in fallopian tube is
called zygote Intra fallopian transfer.
b. IUT: The transfer of embryo with more than 8-blastomeres into the uterus is
called intra uterine transfer.
Gamete Intra Falopian transfer (GIFT): The transfer of an ovum collected from a donor
female into another female who cannot produce ova but can provide suitable conditions for
fertilization and development of the foetus up to parturition.
Intra Cytoplasmic sperm injection(ICSI) The method in which a sperm is directly
injected into ovum to form an embryo in the laboratory is called ICSI.
Artificial insemination: The process by which semen collected from the husband or
healthy donor is artificially introduced into the vagina or uterus is called intra uterine
insemination(IUI). The method is used in cases where infertility is due to the inability of
male partner to inseminate the female or in case of aspermia.
IMPORTANT QUESTIONS.
Q1) Table of certain terms associated with ART. Fill in the spaces a,b,c,d.(1X4 )
IVF&ET
a
b
Introduction of zygote/embryo with 8 blastomeres into fallopian tube.
c
Introduction of ova of a donor into the fallopian tube
d
Introduction of semen from the husband or healthy donor into the
uterus.
Ans.( a) test tube baby programme
.( b) ZIFT (zygote intra fallopian transfer )
.( c) GIFT (gamete intra fallopian transfer )
(d ) IUI (intra uterine insemination )
Q2) Name 3 incurable sexually transmitted diseases and their causative
organisms ( 3)
1. Hepatitis-B ----- Hepatitis-B virus
2.Genital herpes-------Herpes simplex virus
3. AIDS---------HIV (Human Immunodeficiency virus)
Q3)Why is the term test tube baby a misnomer.(3)
Baby not developed in test tube. Only fertilization carried out in test tube in lab conditions.
The fertile egg is then transferred into the fallopian tube or uterus where it develops and
grows into a normal baby is born.
Q4. Why do intensely lactating mothers do not generally conceive?
Due to suppression of gonadotropins�
Q5 Name 2 sexually transmitted diseases caused by bacteria.
Syphilis and gonorrhea.
HIGHER ORDER THINKING SKILLS
1. How can pregnancy due to unprotected sex be prevented?
A.Progesteron-estrogen combination and IUD administered within 72 hrs of intercourse.
2. Classify the following contraceptive measures in to different methods of birth control {1}
Saheli {2} Tubectomy {3} Vasectomy {4} Condoms {5} Diaphragms {6} Cervical caps
{1} Oral pills{2} Surgical methods{3}
Barrier methods{6} Barrier methods
Surgical methods{4} Barrier methods{5}
3. When and why is MTP necessary?
MTP is carried out to get rid of unwanted pregnancies. It is also essential when the foetus is
suffering from an incurable disease or when continuation of pregnancy could be harmful or
even fatal to the mother and or foetus.
4. An ideal contraceptive must be user friendly and effective. Why? State two reasons?
{1}It should have no side effects
{2} It should be easily available.
VALUE BASED QUESTIONS
Q. Women are often blamed for producing female children. Consequently, they are ill
treated and ostracized. How will you address this issue scientifically if you were to conduct
an awareness programme to highlight the values involved?
Ans. – Male produces two types of sperms ( X & Y type in the ratio 1 : 1) , Female
produces only
one type of ovum (X type) , hence the sex of baby is determined by the type of sperm
fertilising
the ovum therefore women should not be blamed // A genetic cross showing sex
determination
in human beings covering above value points can be considered in lieu of the above
explanation
=ВЅГ—3
– Sensitivity towards community / Social awareness / Self discipline / Responsible
behaviour /
Leadership quality / Caring attitude / Responsible attitude towards society / Concern for
others
/ Sharing of knowledge or information / Presence of mind /Being proactive / any other
relevant
value.
(Any three values) = ВЅ Г— 3
[
Q. A person in your colony has recently been diagnosed with AIDS. People/ residents in
the colony want him to leave the colony for the fear of spread of AIDS.
a)Write your view on the situation, giving reasons.
b) list the possible preventive measures that you would suggest to the residents of your
locality in a meeting organized by you so that they understand the situation.
c) Write the symptoms and the causative agent of AIDS.
Ans –
a. The colony people thought that AIDS is a communicable disease but it is a STD.
b. 1.Avoid sex with unknown partners or multiple partners
2.Use condom during coitus every time
3.Avoid Sharing of injection needles, surgical instruments with infected persons
4.Avoid contaminated blood transfusion
c. Syptoms: Loss of weight, persistent fever for prolonged period , persistent cough,
respiratory problems,
weakness etc. Causative agent- HIV
Q. Joy loves to play football and was selected as captain of the school team for the district
level tournament. He also does social work. He attended a blood donation camp to donate
blood and came to know that he was HIV positive. He lost interest in games and refused to
play or study. He started counting his days. He remained absent from school for a long
time. The Biology teacher visited his house and counselled him. Joy was back at school and
also played the tournament.
a) What sense of responsibility did the Biology teacher exhibit?
b) A person detected to be HIV positive should be isolated in the society? Do you agree?
Why/ Why not?
c) How is AIDS not spread
Ans-a) The teacher shows social and moral responsibility along with his commitment to
service as a professional teacher.
Ans-b) No.
AIDS is not a contagious disease and does not spread until a blood/ body fluid
contact is established.
Ans-c) AIDS is not spread by: body contact in crowded place, hand shaking, sharing
telephone, meal, utensil or clothings, light kissing, using same toilet seat or even
swimming pool. It is not transmitted by blood sucking vectors or by coughing and
sneezing.
Q. During a visit to Kedarnath, Mohun came across a young couple staying in the adjacent
room in the hotel. He learnt that the couple had been visiting different temples and
performing rituals to get a child. Mohun was astonished and explained to them about ART
which he had recently studied in Biology. The couple were happy and understood their
wrong approach and thanked Mohun.
a) Identify the values which Mohun has shown.
b) What is ART? What are the various method included in ART?
c) What are the limitations for which ART is not commonly accepted?
Ans-a) Sympathetic attitude with alertness and practical approach.
Ans-b) Assisted Reproductive Technology
Methods are: i) test tube baby programme which includes IVF and Zygote or
embryo transfer b) gamete intra fallopian transfer iii) Intra cytoplasmic sperm
injection iv) artificial insemination methods
C.)1. These techniques require extremely high precision handling by
specialized professionals and expensive instrumentation. Therefore,
these facilities are presently available only in a very few centres in the
country.
2. Emotional, religious and social factors are also deterrents in the adoption
of these methods.
Q. Mrs. Kavita was eager to know the sex of the foetus which her daughter- in- law was
carrying. She was so anxious that she could pay any amount for that. The doctor refused to
disclose the result of the test.
a) What value do you learn from the doctor�s act?
b) How can one know the sex of the foetus? How is it done?
c) Why is disclosing the sex of the foetus banned in our country?
Ans-a) The doctor is devoted to his duties and has professional ethics.
Ans-b) By amniocentesisAns-c) In the past there have been numerous cases where the
female foetus has beenaborted. This anti -feeling for the girl child is considered a crime.
The number offemales to males is thereby reduced.
UNIT -VII
CHAPTER – 5
PRINCIPLES OF INHERITANCE AND VARIATION
Important terms:
1. Genetics: Branch of Science which deals with the inheritance and variation.
2. Inheritance/ Heredity: The process by which characters are passed on from
parents to progeny.
3. Variation: Is the degree by which progeny differ from their parents.
4. Gene/Factor: Determines a biological character of an organism.
5. Alleles: Alternative forms of the same gene i.e.. T and t.
6. Phenotype: The observable character of an organism. i.e.. Tall or Dwarf.
7. Genotype: The genetic constituent of an organism i.e. TT, Ti or tt.
8. Homozygous: An individual with two identical alleles i.e. TT or tt.
9. Heterozygous: : An individual with two different alleles i.e. Tt or Rr.
10.Monohybrid Cross: When only one allelic pair is considered in cross i.e TT (
tall x tt(dwarf).
11.Dihybrid cross: When two allelic pairs are used for crossing i.e. RRYY( Round
yellow) x rryy( Green Wrinkled).
12.Test cross: In a test cross an organism showing a dominant phenotype is crossed
with the recessive parent to know the genotype of an organism i.e. Cross between
tall (TT or tt) with dwarf (tt) plant.
13.Multiple allelism: When a gene exists in more than two allelic form. Example:
Three alleles Ia , Ib, Io determine the blood group.
14.Aneuploidy:Addition or loss of one or more chromosomes in the complete
diploid chromosomal complements of an organism.
15.Polyploidy: Increase in a whole set of chromosomes in a organism.
16.Linked Genes: The genes present on the same chromosome in an organism
17.Linkage: Phenomenon where linked genes inherited together.
18.Punnet Square: A checker board used to show the result of a cross between two
organisms.
19.Dominant gene: A gene that is capable of expressing itself in the presence of
contrasting gene.
20.Recessive gene: A gene which is unable to express itself in the presence of
contrasting gene.
Important Notes
1. MENDEL’S EXPERIMENT :
(i) Gregor Mendel was born in 1822 in sillsian, a village in Heizendorf .He
conducted hybridization experiments on garden pea for seven years.
(ii)Material of the experiment: Mendel selected garden pea for his experiments due
to following reasons:
(a) Pea plants are generally self pollinated.
(b) It can be easily cross pollinated.
(c) Many varieties were available.
(d) Life cycle of plants is short.
(iii)Steps of the experiment : Mendel performed his experiments in three stages.
Stage I – Selection of true breeding plant, as parents (For seven pairs of contrasting
characters)
Stage II – Hybridization of parents with contrasting character to obtain plants of first
hybrid generation (F1 generation)
Stage III – Self pollination of F1 plants to produce F2 generation and selfing of F2
plants to produce F3 generation.
2. Results of Mendel’s experiment:
1.Only one type of parental character appeared in F1 generation.
2. Both parental characters appeared in F2 generation in the ratio of 3:1 in case of
monohybrid cross.
3. In dihybrid cross two parental and two new combinations of plants appeared in
the ratio of 9:3:3:1.
3. MENDEL’S LAWS OF INHERITANCE:
Based on monohybrid crosses mendel proposed law of dominance and law of
segregation.
(i)Law of Dominance:
(a) Characters are controlled by discrete units called factors.
(b) Factors occur in pair.
(c) In a dissimilar pair of factors, one member of the pair dominates(Dominant)
the
other (Recessive).
(ii) Law of segregation: Allele pairs separate or segregate during gamete
formation and the paired condition is restored by random fusion of gametes during
fertilization.
Fig.
(iii) Law of independent assortment: Based on dihybrid crosses,Mendel proposed
law of independent assortment. This law states that, when two pairs of traits are
combined in a hybrid, segregation of one pair of character is independent of the
other pair of character.
(iv)Law ofIncomplete dominance: When F1 individual has a phenotype that does not
resemble either of two parents and intermediate between the two parents, here one allele is
incompletely dominant over another.
EXAMPLE: Cross between red flowers plant and white flowers plant in snapdragon.
5. Co – Dominance: When two alleles of a gene are equally dominant and express
themselves when they are together.
Example blood group AB
Dominant Allele IA produces glycoprotein A
Dominant Allele IB produces glycoprotein B
When IA and IB remain together they produce both glycoprotein A and B as in case of blood
group AB (Genotype IA IB )
Co Dominance and multiple allelisim
Blood group
Possible genotype
A
IAIA OR IAi
B
IBIB OR IBi
AB
IAIB
O
ii
Crosses of blood group (CO DOMINANCE)
Blood group
Possible genotype
AXA
IAIA X IAIA
IAIA X IAi
IAi X IAi
BXB
IBIB X IBIB
IBIB X IBi
IBi X IBi
AB X AB
IAIB XIAIB
OXO
ii X ii
Possible phenotype
A
A
A;O
B
B
B; O
AB: A; B
O
6.Chromosomal Theory of Inheritance:
Walter Sutton and Theodore Boveri noted that the behavior of chromosome was
parallel to behavior of gene.
1.Both genes and chromosome occur in pair
2. Both of them segregated during gamete formation.
On the basis of above observation Sutton and Boverui proposed chromosomal
theory of inheritance which state that Mendelian factors (gene) are located on the
chromosome and separation of the homologous chromosome lead to the segregation of a
pair of factor they carried.
7.Linkage and Recombination:
Linkage: The genes located on same chromosome remain linked together in passing from
one generation to other generation due to the phenomenon of linkage.
Example: Morgan conducted several dihybrid crosses in Drosophilla and observed that the
two genes located on the same chromosome did not segregate independently of each other
and F2 ratio deviated very significantly from the 9:3:3:1.
A cross between yellow body white eyed female Drososphilla to brown body red eyed male
resulted following ratio.
Parental Type – 97.7%
Recombinant type – 1.3%
The greater percentage of parental type is due to the phenomenon of Linkage.
Fig: 5.11 Page No;84 NCERT Book, Class XII
8.Sex determination:
The mechanism of sex determination are following types.
1. XO type of sex determination
a. A large number of insects show this type of sex determination.
b. Females have a pair of X chromosomes and produce only one type of
gamete(egg)
c. Male have only one X chromosome and produce two types of gametes
d. Sex of the offspring determine by the type of male gamete.
2. XY types of sex determination
a. A number of insects and mammals including man show this type of mechanism
b. Females have two X chromosomes nd produce only one type of egg
c. Males have one X and one Y chromosome and produce two types of sperm.
d. The sex of offspring depends on the type of male gamete.(sperm)
3. ZW type of sex determination:
a. Females have ZW sex chromosomes (Female heterogamaety)
b. Males have ZZ sex chromosomes
c. Females produce two types of gametes
d. Sex of the individual is determined by the type of ovum.
Pedigree Analysis
Pedigree is a chart of graphic representation of record of inheritance of a trait through
several generations in a family
Symbols used:- refer NCERT Text Book
AUTOSOMAL DOMINANT
AUTOSOMAL RECESSIVE
1. Traits are controlled by dominant
1. Traits controlled by recessive
genes
genes and appear only when
2. Both males and females are equally
homozygous
affected
2. Both male and female equally
3. traits do not skip generations
affected
4. e.g. polydactyly, tongue rolling ability
3. Traits may skip generations
etc
4. 3:1ratio between normal and
affected.
5. Appearance of affected children
from normal parents
(heterozygous)
6. All children of affected parents
are also affected.
7. e.g.- Albinism, sickle cell
anaemia etc
A 'typical' autosomal dominant pedigree
x-chromosome linked pedigree
10.Genetic Disorders:
Genetic disorders can be grouped in two categories
A. Mendelian disorder
B. Chromosomal disorder
A. Mendelian disorder
1. Mainly due to alternation or mutation in a single gene
2. May be dominant or recessive
3. May be autosomal or sex linked
Example
a. Haemophilia
1. Sex linked recessive disorder
2. Clotting of blood is abnormally delayed
3. More male than female suffer from this disorder as the defective gene located on X
chromosome.
b.
1.
2.
3.
Sickle cell Anaemia:
An autosomal linked recessive disorder
The disease is controlled by a single pair of allele HbA and HbS
The defect is caused by substitution of glutamic acid by valine at sixth position of
the beta globin chain of the haemoglobin molecule.
4. The shape of RBC change to elongated sickle like structure.
c. Phenylketonuria:
1. Caused by recessive mutant allele located on autosome
2. The affected individuals lack an enzyme that catalyses the conversion of the amino
acids Phenylalanine into lyrosine
3. Accumulation of these chemicals in the brain results in mental retardation.
B. Chromosomal disorder
These are caused due to absence or excess or abnormal arrangement of one or
more chromosomes
Example.
a. Down’s Syndrome
1. Caused due to the presence of an extra copy of chromosome number 21
(Trisomy)
2. Affected individual is short statured with small round head, furrowed tongue and
partially open mouth.
3. Palm is broad with characteristic Palm crease
4. Mentally retarded
b.
1.
2.
3.
Klinefelter’s Syndrome:
Caused by an additional copy of X chromosome in male (XXY)
Individual is male with feminine character (Development of breast)
Individuals are sterile
c. Turner’s Syndrome:
1. Caused due to the absence of one of the X chromosome XO
Such females are sterile as ovaries are rudimentary
IMPORTANT QUESTIONS
Q.What is the phenotypic and genotypic ratio of incomplete dominance?
A.1:2:1
Q. How many genotypes are possible for 4 phenotypes of blood groups?
A. 6
Q. What is the mechanism of sex –determination in alarge no. of insects.?
A. XO
Q. AaBb was crossed with aabb.What would be the phenotypic ratio of progeny? Mention
the term todenote this kind of cross.
A.
AaBb X aabb
↓
↓
AB,Ab,aB,ab
ab
↓
↓
AaBb, Aabb, aBab, aabb
1
: 1
; 1 : 1
Cross : Test cross.
Q. Define female heterogametophyte.
A. Two different types of gametes produced by female. –ZW - Birds.
Q.Name the disorders caused by
1. Trisomy- 21
2. Presence of additional copy of X chromosome in males.
A. 1. Down�s
Syndrome: 2. Klinefelter�s Syndrome:
Q. Name the disorder caused by substitution of glutamic acid by valine at sixth position of
the beta globin chain of the haemoglobin molecule.
A.Sickle cell Anaemia:
Q. A dihybrid heterozygous round, yellow seeded garden pea was crossed with a double
recessive plant.
(i)
What type of cross is this ?
(ii) Work out the genotype & phenotype of the progeny.
(iii) What principle of Mendel is illustrated by it ?
Ans . Test Cross
(1)
Working out
(3)
Principle of segregation
(1)
Q. Describe the nature of inheritance of the ABO blood group in humans. In which ways
does this inheritance differ from that of height of the plant in garden pea?
Ans17. Refer Pg 77 NCERT Book
(3)
Co Dominance & multiple allelism where as height shows dominance
(2)
Q. State the law of independent assortment. Illustrate with the help of suitable cross.
A. Law:
(1)
Dihybrid cross with suitable example
3
Punnet square
1
HIGHER ORDER THINKING SKILLS
1. Which cross is the example of deviation from first rule of inheritance proposed by Mendel?
Explain with example.
A.Incomplete dominance, In Snapdragon plant, Punnett square showing cross, phenotype
and genotype
2. Observation from which cross shows deviation from third law of inheritance proposed by
Mendel? Explain with an example.
A.Linkage, cross between Drosophila, % of parental and recombination in F2 generation.
3. What can be possible blood groups in children of the couple who are heterozygous A and
heterozygous B for blood group?
A. All possible Blood groups – A, B, AB, O
Father A
IAo x Mother IB o
Children- IA o (blood group A) , IB o (blood group B) , IA IB (blood group AB), ii (blood
group O)
4. Why males in humans and females in fowl (hen) said to be heterogametic?
A.Human Males produce two types of gametes 50 % sperms with X chromosomes, 50 %
sperms with Y chromosomes
Female fowl produces two types of eggs 50 % with Z and 50 %b with W chromosomes
5.
a.
b.
c.
What can be the disorders caused by the following type of aneuploidy –
47 chromosomes with an extra copy of 21st chromosome
47 chromosomes with an extra copy of X chromosome
45 chromosomes with only one X chromosome
A. a. Down�s Syndrome b. Klinefelter�s Syndrome
c. Turner�s syndrome
VALUE BASED QUESTIONS
Q1. Ravi was rushed to a nearby hospital after an accident which caused a lot of blood loss.
The hospital failed to supply O negative blood for transfusion. Rahman who was attending
a patient learned about the situation and agreed to donate blood being of the same blood
group. Ravi�s mother initially refused but was later convinced by her daughter.
a) What values do you find in Ravi�s sister and Rahman?
b) Why can�t O positive blood be transfused into Ravi�s body?
c) What is the genetic basis of blood group inheritance?
Ans. 1.a.Humanity is above all religion. Ravi�s sister shows understanding of science.
Rahman believes in helping a person in need without thinking about which religion or caste
he belongs to.
b)O+ blood group contains antigen for Rh factor. Rh negative blood lacks the antigen. So if
the two bloods mix it shall cause clotting resulting in death of the patient.
c )Human blood groups are A, B, AB and O. The four phenotypes are expressed by paired
combination of three alleles (IA, IB and i). IA and IB are dominant alleles for blood groups
A and B respectively. O blood group is due to lack of any dominant gene. Its genotype is ii.
Alleles IAIB expresses both dominant traits and the blood group is AB.
Q2. Sonam is a bright, fair girl. Her parents are dark complexioned. Her friends in college
regularly passed remarks asking her how she was so fair or what treatment she had
undergone to become fair. Sonam got irritated at their repeated embarrassing questions.
Her friend Srijita came to her support and invited the friends to the Biology lab where she
explained the inheritance of body colour. The friends realised their mistake and stopped
teasingSonam.
1. What are the values observed in Srijita.
2. Name the pattern of inheritance involving in inheritance of color.
3. Give other examples about the same pattern of inheritance.
Ans2-a)Humanity and responsibility towards a friend. She also used her knowledge to
educate her friends.
Ans-b)Polygenic inheritance or quantitative inheritance
Ans-c)Height, weight, skin colour, hair colour, size of some organs, face form, intelligence
etc of human beings are examples of quantitative inheritance.
. Brijmohan angrily says to his daughter not to marry Rajiv since their family is known to
inherit Haemophilia. The daughter objected to her father�s order. Brijmohan was adamant
and threatened Rajiv also. Brijmohan�s daughter explained the biological interpretation of
his fear and convinced her father.
a) Rajiv was not haemophilic. Why was Brijmohan so worried? 1
b) What values do you identify from the role played by Brijmohan�s daughter? 1
c) What explanation must have convinced Brijmohan? 2
d) Is there any fear of haemophilia if Brijmohan�s daughter marries Rajiv? 1
Ans-a) Brijmohan was not aware of the inheritance pattern for haemophilia. He thought
that the disease shall be expressed among his grandchildren.
Ans-b) Scientific attitude, deep understanding and practical application of the subject. She
was focussed having convincing ability.
Ans-c) Haemophilia is a sex linked recessive inherited disease. The gene is located on the
X
chromosome. Human male has only one sex chromosome (44A + XY). Rajiv is not
haemophilic since he does not have the gene on his X chromosome. There remains
no chance for him to pass on any haemophilic gene to the next generation.
Ans-d) No there remains no fear if they are married, provided the girl is not a carrier of
haemophilia. If the girl is a carrier, then the chance for the son to be haemophilic is
50%.
UNIT VII
CHAPTER 6
MOLECULAR BASIS OF INHERITANCE
GIST:
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п‚·
п‚·
п‚·
п‚·
Chromosomes are the carriers of genetic material.
Chromosome contains proteins, DNA or RNA.
It is universally accepted that DNA is the genetic material in most of the organisms.
In most of the plants viruses, RNA is the genetic material.
There are many direct evidences for DNA being the genetic material.
These genetic materials contain the information for cell structure, function and
rep0roduction in stable form.
п‚· DNA can also replicate the same information in the descendent cells and in
successive generations.
п‚· Information coded in the genetic material could be decoded to produce molecules
essential for structure and functions of cell.
п‚· Genetic material must be capable of frequent variation that could be stably inherited.
IMPORTANT TERMS AND DEFINITIONS
cistron
Coding strand
exon
Frame shift mutations
intron
monocistronic
Operon
promoter
polycistronic
euchromatin
Aminoacylation of tRNA
Repetitive DNA
Satellite DNA
splicing
Structural genes
A segment of DNA coding for a polypeptide
The strand that is displaced during
transcription.
The coding sequence present in the mRNA
of a eukaryotic organism
A mutation that chanfes the reading frame of
an mRNA , either by inserting or deleting
nucleotides.
The non coding sequence present in the
mRNA of an eukaryotic organism
An mRNA with only one cistron
The basic unit of regulation consists of
polycistronic structural gene regulated by a
common promote and regulator gene
It is a DNAsequence located towards 5� end
of the structural gene that provides binding
site for RNA polymerase
mRNA with more than one cistron
The loosely packed region of chromatin
which stains light. It is transcriptionally
active chromatin.
Charging of tRNA with syuitable amino
acid
Do not code for protein
The portion of DNA that consist of highly
repetitive sequences
The process that eliminated intervening
intron sequences .
A DNA sequence that forms the blueprint
for the synthesis of a polypeptide.
IMPORTANT QUESTIONS
ONE MARK QUESTIONS:
1. Name the factors for RNA polymerase enzyme which recognises the start and
termination
Signals on DNA for transcription process in Bacteria.
2. Mention the function of non-histone protein.
3. During translation what role is performed by tRNA
4. RNA viruses mutate and evolve faster than other viruses. Why?
5.
How many bases will there be in three codons? How many aminoacids will this
number of bases code far?
ANSWERS
1. Sigma ( ) factor and Rho( ) factor)
2. Packaging of chromatin
3. (i) Structural role
(ii) Transfer of amino acid.
4.–OH group is present on RNA, which is a reactive group so it is unstable and
mutate faster.
5. In three codons– 9 bases, which code far 3 amino-acids.
Two marks questions
1. complete the blanks a, b, c and d on the basis of Frederick Griffith Experiment.
S Strain inject into mice _______
(a) R strain ------- inject into mice --------(b)S strain (heat killed) ---------inject into mice ---------(c) S strain (heat killed) + R strain (live) ------------inject into mice ---------------------(d)
2.If the length of E.Coli DNA is 1.36 mm, Calculate the number of base pairs it contains.
3. DNA is unzipped twice in a cell. Name the two different events which can occur and the
enzymes responsible for it.
Answers:
a) mice dies
b) mice lives
c) mice dies
2. The distance between two adjacent bp = 0.34 × 10–9 m length = Total no. of bp ×
distance
between two bp.
No. of bp. = 1.36 × 10–3/0.34× 10–9 = 4 × 106 bp
3 (i) during DNA replication i.e., in the S-phase of interphase enzyme-DNA polymerase.
(ii) During transcription for protein synthesis-enzyme-DNA dependent RNA polymerase.
THREE MARKS QUESTIONS:
1. Name the three major types of RNAs, specifying the function of each in the
synthesis of
Polypeptide.
2 . Why is Human Genome Project called a Mega Project?
3. Enlist the goals of Human genome project.
ANSWERS:
1. (i) mRNA-(Messenger RNA) : decides the sequence of amino acids.
(ii) tRNA-(Transfer RNA) : (a) Recognises the codon on mRNA (b) transport the
aminoacid
to the site of protein synthesis.
(iii) rRNA (Ribosomal RNA) : Plays the structural and catalytic role during translation.
2. . Refer page 118, NCERT Biology XII.
3. . Refer points given on page 118, NCERT Biology XII.
FIVE MARKS QUESTIONS
1. What is meant by semi conservative replication? How did Meselson and Stahl prove
it experimentally?
2. . What does the lac operon consist of? How is the operator switch turned on and off
in the expression of genes in this operon? Explain.
ANSWERS:
1.Meselson and Stahl, performed an experiment using E.Coli to prove that DNA replication
is semi conservative.
– They grew E. Coli in a medium containing 15NH4Cl.
– Then separated heavy DNA from normal (14N) by centrifugation in CsCl density
gradient.
– The DNA extracted, after one generation of transfer from 15N medium to 14N medium,
had
an intermediate density.
– The DNA extracted after two generations consisted of equal amounts of light and hybrid
DNA.
– They proved that DNA replicates in a semiconservative manner. (Refer figure 6.7, page
105, NCERT Biology XII)
2. Lac Operon consists of the following :
– Structural genes : z, y, a which transcribe a polycistronic mRNA.
– gene ‗z� codes for -galactosidase
– gene ‗y� codes for permease.
– gene ‗a� codes for transacetylase.
– Promotor : The site where RNA polymerase binds for transcription.
– Operator : acts as a switch for the operon
– Repressor : It binds to the operator and prevents the RNA Polymerase from transcribing.
– Inducer : Lactose is the inducer that inactivates the repressor by binding to it.
– Allows an access for the RNA polymerase to the structural gene and transcription.
– Refer figure 6.14, page 117, NCERT, Biology XI.
HIGHER ORDER THINKING SKILLS
1. DNA polymerase plays a dual function during DNA replication‖ comment on statement?
Ans: It not only catalyses the polymerization reaction fast but also catalyses the reaction
accurately.
2. Give two reasons why both the strands of DNA are not copied during DNA
transcription?
Ans: a) If both the strands act as template, they would code for RNA molecule with
different sequences, and in turn they code for different proteins. B) the two RNA
molecules if produced simultaneously would be complementary to each other , hence
would for a double stranded RNA.
3. The base sequence on one strand of DNA is ATGTCTATA
i) Give the base sequence of its complementary strand.
ii) If an RNA strand is transcribed from this strand what would be the
base sequence of RNA?
iii) What holds these base pairs together?
Ans: i) TACAGATAT ii) UACAGAUAU iii) Hydrogen bonds
4.Two claimant fathers filed a case against a lady claiming to be the father of
her only daughter. How could this case be settled identifying the real
biological father?
Ans: DNA fingerprinting.
5.Why is it essential that tRNA binds to both amino acids & mRNA codon
during protein synthesis?
Ans: tRNA binds to aminoacid and mRNA to decode the information on mRNA is in the
form of sequence of amino acid in a polypeptide .
VALUE BASED QUESTIONS
1.Swati is dark skinned and children of her class tease her. Renu tries to help and explains
her classmates that skin color is an inherited character, so they should stop teasing Swati.
Name the type of inheritance involved in skin coloration of humans.
Ans. Polygenic inheritance
2. Alok was rejected for driving license as it was found that he could not distinguish
between red and green color. What would be the impact of his color blindness on his
driving on road?
Ans: He will not be able to distinguish between red and green signal on road. This may
lead to an accident
3. Ratan was a known sportsman in his school. While returning home he found some
unknown miscreants beating a young fellow. He tried to drive them off but by that time the
fellow died of injury. The police arrested Ratan and he was put on trial. The judge being
convinced by Ratan�s plea, ordered for DNA finger printing reports.
a) Ratan�s fingerprints on the dead body were sufficient to convict him but the judge asked
for authentic proof? What values can be observed?
b) What is the basis of DNA finger printing?
c) Explain the steps in DNA finger printing.
Ans-a) The judge showed wisdom and intention to search for the truth.
Ans-b) 1. DNA fingerprinting involves identifying differences in some specific regions
in DNA sequence called as repetitive DNA.
2. Depending on base composition (A: T rich or G:C rich), length of segment,
and number of repetitive units, the satellite DNA is classified into many
categories,(Micro-satellites, mini-satellites etc).
3. These sequences normally do not code for any proteins, but they form a
large portion of human genome. These sequence show high degree of
polymorphism and form the basis of DNA fingerprinting.
Ans-c) (i) isolation of DNA,
(ii) digestion of DNA by restriction endonucleases,
(iii) separation of DNA fragments by electrophoresis,
(iv) transferring (blotting) of separated DNA fragments to synthetic membranes,
such as nitrocellulose or nylon,
(v) hybridisation using labelled VNTR probe, and
(vi) detection of hybridised DNA fragments by autoradiography.
3.A couple fights frequently for the paternity of their child. The husband thinks that he is
not the father of this child. Name the technique you will suggest to solve the problem of
paternity.
Ans: DNA Fingerprinting
UNIT VII
CHAPTER 7
EVOLUTION
GIST:
 Evolution may be briefly defined as ―descent with modification‖ - Charles Darwin.
п‚· Modification occurs by interaction of genes and environment.
п‚· The term evolution literally means unroll or unfold. It refers to a change from one
form to another. Change in elements with time is called inorganic evolution.
Change in leaving organisms with time is called organic or biological evolution.
Organic evolution has produced a variety of organism. The doctrine or theory of
organic evolutionstates that the present complex organisms have evolved by
gradually change in the earlier simpler forms of life over the ages.
п‚· All organisms on earth have similar living materials, genetic code, life processes, the
same principles of heredity and evolution. These similarities prove that all
organisms evolved from a common primitive ancestor. Evolutionary biology is the
study of history of life forms on earth.
IMPORTANT TERMS AND DEFINITIONS
Adaptive radiation
The process of evolution in a given
geographical area starting from a point and
radiating to different geographical
conditions
Analogous organs
Organs which are different in structure and
origin but similar in functions.
Convergent evolution
Evolution of similar features independently
in different evolutionary lineages, usually
from different antecedent features or by
Founder effect
Homologous organs
Natural selection
saltation
different developmental pathways.
When a small group of individuals breaks
off from a larger population and established
a new population, chance plays a large role
in determining which alleles are represented
in the new population
Organs which are similar in structure and
origin but different in functions.
The differential survival and reproduction of
organisms because of differences in
characteristics that affect their ability to
utilize environmental resources
An evolutionary hypothesis emphasizing
sudeen and drastic change.
ONE MARKS QUESTIONS
1. What were the first mammals like?
2. Name one fish like reptile that evolved from land reptile about 200 million years
ago?
3. For a long time, it was believed that life originated from decaying matter. What is
this theory known as? Name the scientist who experimentally disproved this theory.
4. In a particular habitat under natural conditions, only those organisms which are
better adapted could reproduce more, outnumbering others who are less adapted.
What is this phenomenon known as?
5. If abiotic origin of life is in progress on a planet other than earth, what should be the
conditions there?
ANSWERS
1. Shrews.
2. Ichthyosaurus
3. Theory of Spontaneous generation; Louis Posteur.
4. Differential reproduction.
5. Very high temperature, volcanic storms, Reducing atmosphere containing CH4,
NH3, H2
and water vapours.
TWO MARKS QUESTION
6. (a) Name the most acceptable theory about origin of universe.
(b) How was water formed initially?
7. Give two examples of impact of continental drift on the evolution of mammals.
8.Explain Oparin-Haldane theory of chemical evolution of life.
9.. Mention the three connotations of the theory of special creation.
10.. Distinguish between convergent and divergent evolution giving one example of each
ANSWERS
6.(a) Big bang theory
(b) Oxygen combined with ammonia and methane to form water.
7. (i) When South America joined North America, the mammals like horse, rabbit etc. who
lived
in South America were over-ridden by the mammals of North America.
(ii) The pouched mammals of Australia fluorished due to lack of competition from any
othermammals.
8. The first life form could have come from the pre-existing, non-living organic molecules
(like
RNA, Proteins, etc.) and the formation of life was preceded by chemical evolution.
9. (i) All the organisms that we see today were created as such.
(ii) The diversity was always the same since creation and will be same in future.
(iii) Earth is about 4000 years old.
.
10..Refer page 130, 131, NCERT book, Biology - XII
THREE MARKS QUESTIONS
11. (i) State the Hardy-Weinberg principle.
(ii) When there is a disturbance in the Hardy-Weinberg equilibrium, what would it
result
in?
(iii) According to t principle, what is the sum total of all allelic frequencies?
12. Classify the following as examples of homology and analogy–
(i) Hearts of fish and crocodile
(ii) Wings of butterfly and birds
(iii) Eyes of Octopus and Mammals
(iv) Tubers of Potato and sweet potato
(v) Thorns of Bougainvillea and spines of Opuntia
(vi) Thorn of Bougainvillea and tendrils of cucurbits.
13. Stanley Miller and Harold Urey performed an experiment by recreating in the
laboratory the
probable conditions of the atmosphere of the primitive earth.
(i) What was the aim of the experiment?
(ii) In what forms was the energy supplied for chemical reactions to occur?
ANSWERS
11.i) The allele frequency in a population are stable and constant from generation to
generation.
(ii) Evolution.
(iii) One.
12. (i) Homology (ii) Analogy (iii) Analogy (iv) Analogy
(v) Analogy (vi) Homology
13. (i) To prove Oparin�s theory of origin of life.
(ii) Electric discharge using electrodes.
(iii) One week; Amino acids and Sugar.
FIVE MARKS QUESTIONS
14. (a) Is evolution a ‗process� or the end result of a ‗process�? Discuss.
b) Describe various factors that effect Hardy-Weinberg equilibrium.
15. Trace the origin and evaluation of man in terms of Brain size, skeletal structure and
dietary
preferences.
16. Natural selection is an agent of evolution due to which population adapt to their
immediate
environment. Explain the three type of natural selection along with their diagrammatic
representation.
ANSWERS
14. Refer Page 136 NCERT book.
15. (a) Inheritance of Acquired characters.
(b) Biochemical similarities in biomolecules of different organisms point to the
same/common
ancestry of diverse organisms.
(c) Variations which are inheritable and which make resource utilisation better for few
Better adapted, will enables only those to reproduce and leave more progeny.
Accumulation of variations in these will result in formation of a new species.
HIGHER ORDER THINKING SKILLS
1. If you discovered a fossil bird with scales on the body & teeth in the beak.
What would you conclude about its position in the animal kingdom?
Ans: It is considered as a connecting link between reptilia and aves.
2. A chimpanzee can hold objects by its hand & an elephant by trunk. Are these
organs Analogous or homologous?
Ans: Analogous. Because their origin is different but function is same.
3. Indiscriminate use of antibiotics will jeopardize your future battle against bacteria.
Justify.
Ans. Every time we use antibiotics er are applying selection pressure killing off any
non-resistant bacteria , thereby, we are actually helping to speed the evolution of
resistace to antibiotics.
4. In terms of evolution the fittest does not necessarily means strongest.Explain.
Ans. The fittest are not necessarily the strongest individuals , but those individuals
who are the bearers of advantageous inherited traits that allow them to survive and
reproduce more than others natural selection.
5. The foot print of evolutionary change can be found throughout the nature.
Substantiate the stamen highlighting predator-prey relationship in terms of natural
selection.
Ans: Natural selection favours individuals whose characteristics improve either their
ability to consume others or their ability to avoid being consumed.
VALUE BASED QUESTIONS
1. A snake charmer came to the house and smelled the presence of a cobra which the
residents had never seen in the last 10 years. The landlord agreed to allow the man to
search, catch and take away with him the snake. Little Jazman disagreed and drove the man
away.
a) Did Jazman do the right thing? What values did he show?
b) What importance do snakes have in nature?
c) Draw a food web showing the place of snakes.
Ans-a) Scientific attitude, obligation to maintain the biodiversity of nature.
Ans-b) Important member in food chain (web), see picture below.
2. Seeing a crowd of students in one corner of the school, the Principal rushed to see
the matter and found some children beating and chasing a small monitor lizard. On
seeing the Principal, all the children fled to their classes except Alok who requested
the Principal to arrange for some medical assistance for the injured animal. The
Principal rewarded the student.
a) Was Alok an indisciplined boy who did not run to the class on seeing the Principal?
What
values does the act promote?
b) How do endangered species differ from vulnerable species?
c) Mention the factors resulting in loss of biodiversity / extinction.
Ans-a) No. Alok was a brave and courteous boy. He expressed his love for animals,
commitment towards natural resource conservation.
Ans-b) Endangered species (when population of a species reduces to a level which poses
immediate danger of extinction, e.g. one horn rhinoceros, great Indian bustard,
musk deer etc)
Vulnerable species (species whose population have greatly reduced and may be
endangered species in future if the causative factors continue to operate. E.g
Asiatic wild ass, black buck, spotted deer, golden langur etc)
Ans-c) (i) Habitat loss and fragmentation
(ii) Over exploitation
(iii) Alien species invasion
(iv) Co-extinction
3.. The day next to heavy rains, many insects/moths can be seen near light sources. Some
people believe that these insects develop from mud. Do you agree with this belief? What is
theory of origin of life known as? How will you explain the development of these insects
from mud?
Ans: No, Spontaneous generation theory
4. Mohit had severe pain in his last molar tooth. Doctor advised the tooth to be removed.
Mohit�s sister objected saying that this was ‗wisdom tooth� and is responsible for his IQ.
Mohit followed doctor�s advice and got his tooth extracted. Do you think Mohit will fail in
his final examinations? Justify your answer by naming the type of structures the ‗wisdom
tooth‖ is?
Ans: No. ―Wisdom tooth‖ Has nothing to do with IQ or performance of any person. It is
vestigial organ which can be removed
UNIT-VIII
CHAPTER -8
HUMAN HEALTH AND DISEASE
GIST:
п‚·
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п‚·
п‚·
п‚·
п‚·
п‚·
п‚·
п‚·
п‚·
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Criteria for health.
Factors affecting health.
Common diseases in man and pathogen causing diseases.
Typhoid – widal test.
Pneumonia.
Common cold.
Malaria – Life cycle of Plasmodium vivax.
Amoebiasis.
Ascariasis.
Elephantiasis/Filariasis.
Ring Worms.
Types of immunity – Innate immunity, Acquired immunity-auto immunity, Active
immunity, Passive immunity and Lymphoid organs.
 AIDS – Causative organism, Replication of retro virus, Mode of transmission and
prevention of AIDS.
 CANCER – Types and causes of cancer.
 DRUGS AND ALCOHOL ABUSE – Opioids, Cannabinoids, Cocaine/coke
п‚· Effects of drugs and alcohols abuse,
п‚· Prevention and control.
IMPORTANT TERMS AND DEFINITIONS
Acquired immunity
Active immnuty
autoimmunity
Benign tumor
Contact inhibition
Innate immunity
interferon
Malignant tumor
Oncogenic virus
Passive immunity
Immunity which develops in response to
foreign antigens in the body involving either
the production of antibodies or activated T
cells which react specifically with the
foreign antigen.
Usually long lasting immunity that is
acquired through the production of
antibodies and memory T cells wihin the
organism in response to the presence of
antigens
Autoimmunity is the failure of an organism
to recognize its own constituent parts as self,
which allows an immune response against
its own cells and tissues.
It is tumor that lacks all three of the
malignant properties of a cancer. A benign
tumor does not invade surrounding tissues
and does not metastatise.
It is a natural process of arresting cell
growth when two or more cells come into
contact with each other.
The innate immunity comprises of cells and
mechanisms that defend the host in a nonspecific manner
Thes are proteins made and released by the
cells of most vertebrates in response to the
presence of pathogens or tumor cells. They
allow communication between cells to
trigger the protective defences of the
immune system that eradicate pathogens.
A group of cells which display uncontrolled
growth , invasion and sometimes metastasis.
An oncovirus is a virus that can cause cancer
The immunity that is developed due to the
transfer of ready made antibodies.
Withdrawl syndrome
A group of symptoms that occurs upon the
abrupt discontinuation of dosage of drug or
alcohol.
ONE MARK QUESTIONS
1. Name the diagnostic test which confirms typhoid.
2. Name the two major groups of cells required to attain specific immunity.
3. Infectious diseases are more common than non-infectious diseases. Give reasoS
4. Do you agree with the statement that Auto-immunity causes some diseases? If so, name
the
diseases.
5. Breast fed babies are more immune to diseases than the bottle fed babies. Why?
ANSWERS
1. Widal test
2. B-lymphocytes and T-lymphocytes.
3. Infectious diseases spread from an infected person to a healthy person through many
ways.While, non-infectious diseases remain confined to the affected person.
4.Rheumatoid arthritis, multiple sclerosis. Insulin dependent diabetes
5.The mother�s milk consists of antibodies (IgA) such antibodies are not available to
bottle fed.
TWO MARKS QUESTIONS
6. Where are B-cells and T-cells formed? How do they differ from each other?
7. Modern life style leads us towards lethargic, unhealthy body. Suggest four ways to attain
good physical and mental health.
8. Write the principle of Vaccination on which active immunity works.
9. Pathogens are tissue/organ specific. Justify with suitable examples.
10. Given below are the pathogens and the diseases caused by them. Which out of these
pairs is not correct matching pair and why?
(a) Wuchereria – Filariasis
(b) Microsporum – Ringworm
(c) Salmonella – Common Cold
(d) Plasmodium – Malaria
ANWERS
11. B-cells and T-cells are formed in bone marrow. B-cells produce antibodies but T-cells
do not produce antibodies but help B-cells produce them.
12. (i) Balanced diet (ii) Proper personal hygiene
(iii) Regular exercise (iv) Yoga
(v) Proper rest/sleep.
13. Weakened/inactivated pathogens or antigens are inoculated in the body. Body develops
immunity against antigen. Antigens are destroyed by primary response and memory cells
remain there to act during secondary response.
14. The pathogens enter the body through different means. Specific organ/ Tissue provides
the suitable environment to the specific pathogen for growth development and
multiplication. For example Bacteria causing tuberoculosis effects the lungs but not other
organ.
15. Salmonella : Common cold is not a matching pair.
Salmonella causes typhoid.
THREE MARKS QUESTIONS
11. What are Cannabinoids? From which plant Cannabinoids are obtained? Which part of
the body is effected by consuming these substances?
12. Name two diseases each which are transmited in the following ways.
(i) Through contaminated food and water
(ii) Through insect Vectors
(iii) Through air/droplet inhaled.
13. Mention any three causes of drug abuse. Suggest some measures for the prevention and
control of drug abuse
ANSWERS
11.Cannabinoids are a group of chemicals which interact with Cannabinoid receptors
present
Principally in the brain Cannabinoids are obtained from the inflorescences of the plant
Cannabis Sativa.
The substances effect the cardiovascular system adversely.
12.. (i) Typhoid, Polio, Amoebiasis
(ii) Filariasis, Malaria
(iii) Pnenmonia, Common cold
13.Reasons to attract towards drug abuse : Curiosity, peer pressure, escape from frustation
and failure, family problems, false belief of enhanced performance.
Preventive measurs :.
пѓ�
пѓ�
пѓ�
пѓ�
пѓ�
Avoid undue peer pressure
Education and Counselling
Seeking help from parents and peers.
Looking for danger signs
Seeking professional and medical help
FIVE MARKS QUESTIONS
14. Answer th following with respect to Cancer.
(a) How does a cancerous cell differ from a normal cell?
(b) Benign tumor is less dangerous than malignant tumor. Why?
(c) Describe causes of cancer.
(d) Mention two methods of treatment of the disease.
15.. The pathogen of a disease depends on RBCs of human for growth and reproduction.
The person with this pathogen suffers with chill and high fever.
(a) Identify the disease.
(b) Name the pathogen.
(c) What is the cause of fever?
ANSWERS
14.(a) In normal cells, growth and differentiation is highly controlled and regulated
(contact
inhibition). The cancerous cells have lost the property of contact inhibition, hence continue
to divide giving rise to masses of cells (tumors).
(b) The benign tumor remains confined in the organ affected as it is enclosed in a
connective
tissue sheath and does not enter the metastatic stage.
(c) Cancer may be caused due to carcinogens which are physical (radiations), chemicals
(Nicotine, Aflatoxin, Cadmium oxide, Asbestos) and biological (viral oncogens).
(d) Surgery, radiotherapy, Chemotherapy
15. (a) Malaria
(b) Different species of Plasmodium viz P. vivax, P. Malariae and P. falciparum.
(c) Malaria is caused by the toxins (haemozoin) produced in the human body by the
malarial
parasite. This toxin is released by the rupturing of RBCs.
(d) Life cycle of Plasmodium : Fig. 8.1 Page 148, NCERT book, Biology – xii
HIGHER ORDER THINKING SKILLS
1. Why do children of metro cities of India suffer from allergies and asthma?
Ans:Children of metro cities of India suffer from allergies and asthma because of
their sensitivity to the environment. This may be due to the protected
environment provided early in life.
2. A patient has lost his immunity.
i) Name the diseases associated with it.
ii) Name the confirmatory test to diagnose the disease.
iii) Why did he lost his immunity?
Ans: i) AIDS
ii) ELISA
iii)Because HIV attacks Helper T- Lymphocytes and progressively
decrease
their number leading to immune deficiency.
3. A person shows unwelcome immunogenic reactions while exposed to
certain substances.
(a) Name this condition.
(b) What common term is given to the substances responsible for this
condition?
(c) Name the cells and the chemical substances released which cause
such reactions.
Ans. a) Allergy
b) Allergins
c)Mast cells. Histamins and serotonins.
VALUE BASED QUESTIONS
1. Kavita�s parents suffer from high blood pressure and are obese. Kavita is also
worried about her health. Do you think kavita can inherit these characteristic from
parent. Suggest two measures kavita can adopt to avoid high blood pressure and
obesity.
Ans: . 1)No, these are life style related diseases
2) Any two measures- changing in food habits, exercises, leading active life,
meditation.
2. During a visit to a government office with his father, young Pratap saw dirty
spittoons in
every corner of the building. Some people were spitting paan and gutka through the
window grills. As soon as he objected to their action, Pratap was scolded by some persons
and the quarrel between the two parties became a matter of concern. The very next week
Pratap was amazed to see the walls cleaned, no spittoons and a notification hung to
maintain cleanliness and hygiene inside the office. The officer appreciated Pratap.
a) What values are promoted through the incident?
b) Which diseases are transmitted through droplets and air?
c) How does chewing paan or gutka cause health hazard?
Ans-a) Self Awareness, boldness, insight and commitment towards community health
b) Diphtheria, scarlet fever, Influenza, common cold, measles,mumps, tuberculosis
Ans-c) Gutka contains heavy amounts of magnesium as well as calcium carbonate which
are very toxic chemicals. High amounts of magnesium carbonate in the human body can
cause respiratory and cardiac dysfunction , while calcium carbonate or limedamages the
mucosa, causing chronic mucosal injuries and ulcers in the mouth.
Apart from this, gutka can also cause hypertension and cause reproductive health
dysfunction. Possible problems: Hypertension and cardiovascular diseases, nervous system
disorders, liver and kidney diseases, reproductive health dysfunctions, oro-dental
problems, metabolic disorders including diabetes and obesity, and psychological
disorders including addiction, can be caused by excessive consumption of gutka.
3. One Sunday morning Ratan and his friend emptied all the overhead tanks belonging
to flat owners who were not residing in their apartments for the last few months. On
their return, the owners complained about their empty tanks and created unrest in the
campus. Some elderly people spoke against Ratan and his friends. Ratan humbly
apologized for theinconvenience caused but explained why they had done so. The
people were happy and appreciated the boys.
a) What was the objective behind Ratan�s act? 1
b) What values did he promote? 1
c) Explain in brief the stages of life cycle of a malarial parasite in human body.
Ans.a) The water in the tanks had become stagnant and become a breeding
ground for mosquitoes.
Ans-b) Social responsibility, commitment towards community health and respect towards
Elders
4. Delhi govt. has recently decided to ban the sale of Gutka (this fetches them a lot of
monetary gain) in the state. Do you support the decision and Why?
Ans: Yes, Gutka increases the changes of cancer
5. 8. Anand a 14yr old boy thinks smoking makes him more energetic and feel like
adult and thus more responsible citizen. He tries to smoke when he is with his peer
group. As a friend you have to educate him
• Why he feels more energetic while smoking?
• Effects of CO in smoke
• Other ill effects on body
Ans: i) He feels energetic because nicotine raises blood pressure and increases heart
beat.This is not good for his health.
ii) CO binds to hemoglobin and reduces concentration of oxygen
iv) Any one effort cancer of lung, throat, emphysema.
UNIT VIII
CHAPTER 9
STRATEGIES FOR ENHANCEMENT IN FOOD PRODUCTION
GIST:
п‚· Demand of food is met by agricultural practice of breeding.
п‚· Raising livestock such as buffaloes, cows, pigs, horses, cattle, sheep etc., to produce
milk, egg, meat, honey etc.
п‚· Animal husbandry and plant breeding.
п‚· Animal Husbandry includes management of farm and farm animals through
1. Poultry farming
2. Dairy farming – Animal breeding
3. Fisheries – Aquaculture and Pisciculture – Blue revolution
п‚· Plant breeding.
п‚· Techniques of tissues culture and somatic hybridization.
п‚· Manipulation of plants in vitro to produce new varieties.
IMPORTANT TERMS AND DEFINITIONS
Inbreeding
Outbreeding
Inbreeding depression
Out crossing
Reproduction as a result of mating of two animals which
are genetically related to each other.
The breeding of stocks or individuals that are not closely
related.
Reduced fitness in a given population as a result of
breeding of related individuals
Introduction of unrelated genentic material into
Germplasm
Tissue culture
micropropagation
Somatic hybridisation
Single cell protein
Mutation breeding
breedingline.
Collection of genetic resources for an organism.For plants
the germplasm may be stored as a seed collection.
It is a technique of developing new plants from explants of
any plant.
It is a practice of rapidly multiplying stock of plant
material to produce a large4 number of progeny
plants,using modern plant tissue culture methods.
Asexual fusion of protoplastsfrom somatic cells of
genetically somatic plants
Typically refers to sources of mixed protein extracted from
pure or mixed culture of algae, yeasts, fungi or bacteria
used as a substitute for protein rich foods in human and
animal feeds.
Chemicals or radiation applied to whole plants to change
DNA. Such changes are evaluated for the beneficial
effects.
ONE MARK QUESTIONS
1. How is inbreeding depression got rid off?
2. Name the scientist who developed semi-dwarf varieties of wheat in Mexico.
3. Give an example of freshwater fish and marine water fish.
4. Why is inbreeding necessary in animal husbandary?
5. Name two fungal diseases of Crop plants.
ANSWERS
1. By mating the selected animals from one population with unrelated superior animals
of the same breed.
2. Nroman. E. Borlaug
3. Fresh water fishes : Rohu, Catla, Corps. Marine Water Fishes: Hilsa, Sardine,
Pomfret
4. Inbreeding increases homozyosity.
5. Brown rust of wheat, Smut of wheat, red rot of Sugar cane, Late blight of potato.
TWO MARKS QUESTIONS
6. A new breed of sheep was developed in Punjab by crossing two different breeds of
Sheep. Name the two breeds which were crossed and the new breed developed.
7. In animal husbandary, if two closely related animals are mated for a few generation, it
results in loss of fertility amd vigour, why is it so? What term is given for this
phenomenon?
8.Why are plants obtained by protoplast culture called Somatic hybrids? State any one
disadvantage of Somatic hybridisation.
9. Why are proteins synthesized from Spirulina called Single called Proteins? What is the
significance of such a protein?
10.Differentiate between inbreeding and outbreeding in animals.
ANSWERS
6.By crossing Bikaneri ewes and Marino rams, the new breed Hisardale was developed.
7. This happens because the recessive alleles get together and express harmful effects in the
progeny. This phenomenon is referred to as, inbreeding Depression� and results in loss of
fertility and vigour
8.Somatic hybrids are obtained by the fusion of isolated protoplasts from two different
varieties of
plants having desirable characters. The plants (Somatic hybrids) may not always give the
desired result.
9. The protein rich food produced by microbes is called as single called protein (SCP)
Spirulina is a microorganisms which has more protein. It is a quick method of protein
production because the growth rate of microbes is enormous. Hence, it provides a protein
rich diet for human beings
.
10. When breeding is between animals of the same breed, it is called inbreeding, while
cross between different breeds in called out breeding.
Three marks questions
11. What is micropropagation? Why are plants produced by this technique called
somaclones? Name any two food plants which are produced on commercial scale using this
method.
12. Suggest any three features of Crop plants that will prevent insect and pest infestations.
13. What is mutation? Explain the significance of mutation in plant breeding. Give an
example of a disease resistant variety of cultivated plant induced by mutation.
ANSWERS
11The method of producing many plants through tissue culture is called micropropagation.
original
plant from which they were grown, hence are called somaclones.
12. 1. Rendering the flowers nectarless.
2. Increasing the hairs on aerial parts of the plant.
3. Enabiling plants to secrete insect killing chemicals (toxins).
13. Mutation : Sudden inheritable change in the characters of an organism due to change in
the sequence of bases in the gene(s).
Mutation results in a new character or trait, not found in the parental type
It can also be induced by using mutagens like gamma radiations.
Such plant materials are used as such or used for breeding new variaties.
Mung bean resistance to yellow mosaic virus and powdery mildew.
FIVE MARKS QUESTIONS
14.You are a scientist working in the area of plant breeding. Describe the various steps that
you willundertake to release a new variety of wheat.
15. ‗If you want to survive then you need to sustain. Every little effort makes a change.�
Explain it in reference to strategies for food production.
ANSWERS
14.The main steps in breeding a new genetic variety of a crop are :
(a) Collection of variability : It forms the raw material for breeding experiments. It includes
thegenomes of the domesticated varieties in use, domesticated varieties not in use
presently,wild varieties of the same species, wild relatives, all the hybrids available.
(b) Evaluation and selection of parents.
(i) Identification of the parental plants with desired characters
(ii) Selected plants are multiplied.
(c) Cross hybridisation of selected parents.
(d) Selected and testing of superior recombinants.
(e) Testing, release and commercialisation of new cultivars.
26. Adopt sustainable agriculture, animal husbandry, Multiple ovulation embryo transfer
technology(MOET), Plant breeding, Poultry, fisheries.
These little small efforts will lead to increased profits and hence, present and future will be
secured.
(Elaborate these points to justify).
HIGHER ORDER THINKING SKILLS
1. A new breed of sheep was developed in Punjab by crossing two differentbreeds of
Sheep. Name the two breeds which were crossed and the newbreed developed.
Ans: By crossing Bikaneri ewes and Marino rams, the new breed Hisardale was dveloped.
2. How can we improve the success rate of fertilisation during artificialinsemination in
aminal husbandary programmes?
Ans. Multiple ovulation embryo transfer technology(MOET)
3. Why are proteins synthesized from Spirulina called Single celled Proteins?
What is the significance of such a protein?
Ans: The protein rich food produced by microbes is called as single calledprotein (SCP)
Spirulina is a microorganisms which has more protein. It isa quick method of protein
production because the growth rate of microbesis enormous. Hence, it provides a protein
rich diet for human beings.
4. To which product, following products are related (a) Blue revolution (b)white
revolution (c) Green revolution
Ans: a) Fish production b) milk production c) food production
VALUE BASED QUESTIONS
1. Samir planned to introduce MOET in his farm. He purchased one high milk yielding
exotic breed of cow. Within a few years he earned lot of money by selling calves but
the mother cow met with a premature death. Raghavan objected to Samir earning
money by this way.
a) What values in life did Raghavan possess?
b) Expand MOET.
c) Briefly describe the process.
Ans-a) Raghavan was bold, having love for animals. He had ethics and prudence.
Ans-b) Multiple Ovulation Embryo Transfer Technology
Ans-c) The cow is administered hormones, with FSH-like activity, to induce
Follicular maturation and super ovulation (instead of one egg, which theynormally yield per
cycle, they produce 6-8 eggs).
The animal is either mated with an elite bull or artificially inseminated.
The fertilised eggs at 8–32 cells stages, are recovered non-surgically andtransferred to
surrogate mothers.
The genetic mother is available for another round of super ovulation.
This technology has been demonstrated for cattle, sheep, rabbits,buffaloes, mares, etc. High
milk-yielding breeds of females and high quality(lean meat with less lipid) meat-yield.
2.Ram is managing a dairy firm. He has been advised to use artificial insemination to
overcome several problems in developing better breeds of cow. Govind has advised him
MOET for herd improvement. Ram is ignorant and is not able to decide. How will you help
Ram regarding
• Which technique should he adopt?
• Procedure of new technique
• What is advantage of this technique?
Ans: I)MOET as success rate of this technique is more
II) Cow is administered hormones, with FSH like activity, to induce follicular maturation
and super ovulation-(6-8 eggs). The animal is mated. Fertilized eggs are recovered and
transferred to surrogate mother.
III) Herd size is increased in short time.
Genetic mother is available for another round of super ovulation.
UNIT VIII
CHAPTER 10
MICROBES IN HUMAN WELFARE
GIST:
 Microbes in house hold products – curd and dough used for baking and preparing
idlis dosas made soft
 Microbes in industrial products – Alcoholic.
 Microbes in sewage treatment – Aerobic and anaerobic bacteria.
 Microbes in production of bio-gas – mehanobacteria.
 Microbes as Bio control Agents – Bacillus thuringiensis
 Microbes as Bio Fertilizers – Rhizobium, Mycorrhizae.
IMPORTANT TERMS AND DEFINITIONS
mycorrhiza
It is a symbiotic association between a
fungus and the roots of a plant
methanogens
statins
Organisc farming
cyclosporin
biofertiliser
antibiotic
Microorganisms that produce methane gas
A class of drugs that lower blood cholesterol
levels in people.
it is form of agriculture that relies on crop
rotation, green manure ,compost , biological
pest control and mechanical cultivation to
maintain soil fproductivity and control pests
An immunosuppressant drug widely used in
post allogenic organ transplant to reduce the
activity of the patients immune system and
so the risk of organ rejection
Microorganisms that increase the amount of
nutrients available to the plants.
A chemical substance that kills or inhibits
the growth of living organisms
ONE MARK QUESTIONS:
. 1. Why there are big holes in Swiss cheese?
Answer: The large holes in ―Swiss cheese‖ are due to production of a large amount of
CO2 by a bacterium.
3. Write the name of micro-organism responsible for production of citric Acid and Butyric
acid
Answer: i) Aspergillus niger (Fungus) – Citric Acid.
ii) Clostridium butylicum (a bacterium) – butyric Acid
4. Name the fungus which is very commonly found in the root ecosystem used in treatment
of plant diseases.
Answer: Trichoderma.
5. Which fungus is effective bio control agents of several Plants Pathogens?.
Answer: Trichoderma
TWO MARKS QUESTIONS
1. Define ―bioactive molecules‖. Name two such molecules and give their sources.
Answer: Bioactive molecules are those organic compounds which are produced on
commercial scale by the microbes and are useful in the human welfare.
Cyclosporin A - produced by fungus
Statins - produced by yeast.
2. What is activated sludge?
Answer: It is a measure for secondary treatment of sewage water. In this measure sludge is
used which contain bacteria & algae.
3. Name a bioactive molecule used as an immunosuppressive agent in organ transplant
patients also mention its source.
Answer: Bioactive molecule – Cyclosporin A
Source – Trichoderma polysporum(Fungus)
4. What is mycorrhiza? How is it useful to some plants?
Answer: Fungal association with the roots of some higher plants are known as mycorrhiza.
It increase phosphorous absorption from the soil.
THREE MARKS QUESTIONS
1. What are antibiotics? Give two examples. What is their significance?
Answer: Antibiotics : - are the chemical substances produced by certain microbes, that can
kill or retard the growth of other disease causing microbes.
e.g – Penicillin, Streptomycin
Significance: Antibiotics are used in the treatment of many human, animal and plant diseases.
2. Give the name of the microbes from which cyclosporine A and statins are obtained.
How cyclosporine A and status are useful to man?
Answer: Cyclosporin A is produced by the fungus Trichoderma polysporum
Statins are produced by a yeast, Monascus purpureus.
Uses – Cyclosporin A is used as an immuno suppressive agent during organ
transplantation. Statins are used for lowering the levels of blood cholesterols, as it acts as a
competitive
inhibitor of the enzyme involved in cholesterol synthesis.
3. Name any three organic acids and the bacteria that produce them.
Answer: Organic Acids Bacteria
i) Acetic Acid Acetobacter aceti
ii) Butyric acid Clostridium butylicum
iii) Lactic acid Lactobacillus
FIVE MARKS QUESTIONS
1. How do biofertilisers enrich the fertility of the soil?
Answer: Biofertilizers are the organisms that enrich the nutrient quality of soil.
Bacteria, cyanobacteria and fungi are the three groups of organisms used as biofertilizers.
i) Bacteria
a) symbiotic bacteria Rhizobium.
b) Free living bacteria Azospirillum & Azotobactor.
c) They fix the atmospheric nitrogen and enrich soil nutrients.
ii) Cyanobacteria
Cyanobacteria are autotrophic microbes widely distributed in aquatic and terrestrial
environment. Many of them can fix atmospheric nitrogen and increase the organic matter
of the soil through their photosynthetic activity.
In paddy field cyanobacteria serves as important biofertilizers. Commercially farmers use
these cyanobacteria in their fields to replenish soil nutrients and to reduce dependency on
chemical fertilizers.
Important examples are Anabaena, Nostoc and Oscillatoria.
iii) Fungi/ Mycorrhiza
Fungi are also known to develop symbiotic relationship with plant roots. Such a
relationship is called mycorrhiza. Many members of the genus Glomus form mycorrhizae.
The fungus absorbs
phosphorus from the soil and passes it to the plant.
Plants having such association show other benefits alsoa)
Resistance to root borne pathogens
b) Tolerance to salinity.
c) Tolerance to drought
d) Overall increase in the plant growth and development.
HIGHER ORDER THINKING SKILLS
1. An antibiotic called ‗Wonder Drug� was used to treat the wounded soldiersof
America during World War-II. Name the drug and the scientist whodiscovered it.
Ans: Penicillin, Alexander Fleming
2. Cyanobacteria (Nostoc, Anabaena) are used as biofertilisers in certain cropfields.
Name such one crop. Also, mention the names of two othermicroorganisms which
perform the same function.
Ans: Paddy (Rice Crop), Rhizobium and Azotobacter
3. BOD level of three samples of water labelled as A, B and C are 30 mg/L, 10mg/L
and 500 mg/L respectively. Which sample of water is mostpolluted?
Ans: Sample ‗C� is most polluted because it has highest BOD level among the three
samples of water.
4. You have observed that fruit juice in bottles bought from the market areclearer as
compared to those made at home. Give reason.
Ans: Bottle juices are clarified by the use of pectinase and proteases.
VALUE BASED QUESTIONS
1. After a rainy day Rahul found many dragon flies flying over stagnant water. He
thinks these flies come to drink water. Is Rahul�s explanation correct? Give your
views.
Ans: • No, dragon flies eat mosquito larva and act as bio control agents.
2. Nowadays capsules of Spirulina are used as food supplements. Do you recommend
the use of these capsules? Why?
Ans: Yes. Any one reason –these are rich in proteins andcan be produced in large
quantities in less time.
3. One is organically grown and second is conventionally grown. The organically
grown crops are costlier so your mother does not want to purchase it. Convince your
mother by telling her the advantages of organic foods
.
Ans: Advantages of organic farming like – biofertilisers and
bio pesticides are used inorganic farming which is not
harmful to health.
UNIT IX
CHAPTER 11
BIOTECHNOLOGY- PRINCIPLES AND PROCESSES
IMPORTANT TERMS AND DEFINITIONS
Bacteriophage : A virus that infects bacteria.
Bioreactor : A large vessel in which raw materials are biologically convertedinto specific
products under optimal conditions such as temperature, pH, substrate, salts, vitamins,
oxygen. Stirring type bioreactors are commonly used.
Biotechnology : It deals with techniques of using live organisms (Microbes,plants animals)
or components for benefit to humans.
According to EFB (European Federation of Biotechnology) :
Biotechnology in the integration of natural science and organisms, cells, parts thereof and
molecular analogues for products and services.
Cloning Vectors : A small, self-replicating DNA molecule into which foreign DNAis
inserted. It replicates inside the host cell. The vectors that may be used in genetic
engineering are plasmids, bacteriophages, animal, plant, virus, YACS and BACs and
insome yeasts.
Features of cloning vector: Origin of replication (Ori), selectable marker andcloning sites
are the features that are required to facilitate cloning into a vector.
вќ‘ Origin of Replication (Ori) : This is a sequence from where replicationstarts and any
piece of DNA when linked to this sequence can be made to replicate within the host cells.
This sequence is also responsible for controlling the copy number of the linked DNA.
вќ‘ Selectable Marker : It is a gene which helps in identifying and eliminatingnontransformants from transformants (having recombinant DNA) by selectively permitting the
growth of transformants. The process through which a piece of DNA is introduced in a host
bacterium is called transformation. The genes encooling resistance to antibiotics are
considered useful selectable marker for E.coli
(c) Cloning Sites : A location on a cloning vector into where a foreign gene can be
introduced is called a cloning site. The vector must have very few (preferably single)
recognition sites. The presence of more than one recognition sites within the vector will
produce several fragments which will make the process of gene cloning more complicated.
Therefore, the foreign DNA is ligated at a restriction site present in one of the two
antibiotic resistance gene.
Complementary DNA (cDNA) : A DNA strand formed from mRNA by using theenzyme
reverse transcriptase.
Plasmid : Extra chromosomal, self replicating circular DNA molecule found incertain
bacteria and in some yeasts. It has a few genes. Plasmids are used as cloning vectrors in
genetic engineering.
Genetic Engineering : The techniques to alter the chemistry of geneticmaterial and
introduction of it into organisms to change its phenotype.
Ligase : An enzyme used by a genetic engineer to join the cut ends of thedouble stranded
DNA.
Palindromic Sequence : Complementary DNA sequences that are the samewhen each
restriction endonucleases.
5� – GAATTC – 3�
3� – CTTAAG – 5�
Restriction Enzymes : The enzyme that cuts out a piece of DNA at a specificsite. These
are of two types : exonucleases and endonucleases.
Sticky ends : Single stranded portions of DNA which can form hydrogen bondswith their
complementary cut DNA segments. These ends can be joined by enzyme ligase.
Taq polymerase : A heat stable DNA polymerase isolated from a thermophilicbacterium
Thermus aquaticus and is used in PCR.
Ti Plasmid : An extrachromosomal, double stranded and self replicating DNAmolecule
found in Agrobacterium tumefaciens that causes tumor in plants.
Tools of Recombinant DNA Technology : Restriction enzymes, polymeraseenzymes,
ligases, vectors, and host organisms.
Steps in Formation of rDNA by action of EcoRI : EcoRI cuts the DNAbetween bases G
Recombinant DNA is formed.
Recombinant DNA (rDNA) : The hybrid DNA formed by combining DNAsegment of
two different organisms.
Process of Recombinant DNA Technology :
nstream
processing.
вќ‘ Isolation of Genetic Material (DNA) :
DNA can be obtained from the cell by treating with enzymes like, Lysozyme for
bacteria, Cellulase for plant cell, Chitinase for fungus.
Histone protein and RNA can be removed by treating with proteases and
ribonuclease
Purified DNA ultimately precipitated by the addition of chilled ethanol. Fine
threads of DNA are obtained in the suspension.
вќ‘ Cutting of DNA at specific location : The purified DNA is cut by useof restriction
enzymes. Agarose gel electrophoresis used to check the progression of restriction
enzymes digestion.
вќ‘ Amplification of gene of interest using PCR : Amplification is theprocess of making
multiple copies of desired DNA segment in vitro. Polymerase chain reaction involves
three steps:
(a) Denaturation : The target DNA is heated to high temperature (94В°C),resulting the
separation of two strands of DNA. Each strand acts as template.
(b) Annealing : Two oligonucleotide primers anneal to each of the singlestranded
DNA template.
(c) Extension of primers : DNA polymerase (Taq polymerase) extends theprimers
using the nucleotides provided in the reaction.
(iv) Ligation : The cut out ‗gene of interest� from the source of DNA and cutvector with
appropriate space, are mixed and ligase enzyme is added. This results recombinant
DNA (r-DNA).
(v) Transfer of recombinant DNA into the host : The ligated DNA isintroduced into the
recipient cell. The recipient cell makes itself ‗competent� to receive and take up DNA
present in the surrounding.
(vi) Obtaining the foreign gene product : The cell containing the foreigngene is cultured
on suitable medium and the product can be extracted from the medium.
Bioreactors are used for processing large volume of culture for obtaining products of
interest in sufficient quantities.
7. Downstream Processing : The products so obtained undergo a seriesof processes
before putting them in market as a finished product. The processes include separation
and purification.
The products are formulated with suitable preservation and subjected to quality control
testing and clinical trials. (in case of drugs)
Essential features required to facilitate cloning into vector : Ori,Selectable marker,
Recognition site, small size.
Some of the Biotechnological products and processes : rDNA vaccines,Gene therapy,
Test tube babies, Synthesis of a gene and introduction of it into a target cell/organism.
Steps in creating GMO :
t and transfer of the DNA to its
progeny.
Gel Electrophoresis : DNA fragments are regatively charged molecules. Theycan be
separated by forcing them to move towards anode under an electric field through a
medium. Agarose gel is used as medium. Ethidium bromide is used as stain for DNA,
which on exposure to UV-light appear as orange coloured bands. Separated bands of DNA
are cut out from agrose gel. This is called elution. These DNA fragments are used in
recombinant DNA by joining them with cloning vectors.
QUESTIONS
VSA (1 MARK)
11. A restriction enzyme digests DNA into fragments. Name the technique used to check
the progression of this enzyme and separate DNA fragments.
12. Name two commonly used vectors in genetic engineering.
13. Some enzymes are considered as molecular scissors. in genetic engenrring. What is the
name assigned to such enzymes?
14. Write conventional nomenclature of EcoRI.
15. A linear DNA fragment and a plasmid has three restriction sites for EcoRI how many
fragments will be produced from linear DNA and plasmid respectively.
пѓ� An extra chromosomal segment of circular DNA of a bacterium is used to carry gene of
interest into the host cell. What is the name given to it?
пѓ� Identify the recognition sites in the given sequences at which E.coli will be cut and
make sticky ends.
5´–GAATTC–3´
3´–CTTAAG–5´
SA-II (2 MARKS)
8. Name two main steps which are collectively referred to as down streaming process.
Why is this process significant?
9. How does plasmid differ from chromosomal DNA?
10. A bacterial cell is shown in the figure given below. Label the part ‗A� and ‗B�. Also
mention the use of part ‗A� in rDNA technology.
11. Mention two classes of restriction enzymes. Suggest their respective roles.
12. In the given process of separation and isolation of DNA fragments, some of the steps
are missing, Complete the missing steps –
A : Digestion of DNA fragments using restriction endonucleases
B : ..............................................................
C : Staining with ethidium bromide
D : Visualisation in U.V. light
E : .............................................................
F : Purification of DNA fragments.
SA-I (3 MARKS)
пѓ� Since DNA is a hydrophillic moelcule, it cannot pass through cell membranes. Name
and explain the technique with which the DNA is forced into (ii) a bacterial cell (ii) a
plant cell (iii) an animal cell.
пѓ� How will you otbain purified DNA from a cell?
пѓ� In recombinant DNA technology, vectors are used to transfer a gene of interest in the
host cells. Mention any three features of vectors that are most suitable for this purpose.
� Why is “Agrobacterium–mediated genetic engineering transformation‖ in plants
considered as natural genetic engineering?
пѓ� Observe the given sequence of nitrogenous bases on a DNA fragment and answer the
following question –
5´ – CAGAATTCTTA – 3´ 3´ –
GTCTTAAGAAT – 5´
(a) Name a restriction enzme which can recognise this DNA sequence.
(b) Write the sequence after digestion.
(c) Why are the ends generated after digestion called sticky ends?
18. A selectable marker is used in the section of recombinants on the basis of their ability
to produce colour in presence of chromogenic substrate.
(a) Mention the name of mechanism involved.
(b) Which enzyme is involved in production of colour?
(c) How is it advantageous over using antibiotic resistant gene as a selectable marker?
LA (5 MARKS)
19. The development of bioreactors is required to produce large quantities of products.
(a) Give optimum growth conditions used in bioreactors.
(b) Draw a well labelled diagram of simple stirred – tank bioreactor.
(c) How does a simple stirred – tank� bioreactor differ from sparged stirred
– tank� bioreactor?
20. In the given figure, one cycle of polymerase chain reaction (PCR) is shown–
(a) Name the steps A, B and C.
(b) Give the purpose of each of these steps.
(c) State the contribution of bacterium Thermus aquaticus in this process.
7. Study the figure of vector pBR322 given below in which foreign DNA is ligated at the
Bam H1 site of tetracyline resistance gene.
Answer the following questions :
10. Mention the function of rop.
11. What will be the selectable marker for this recombinant plasmid and why?
12. Explain transformation.
ANSWERS
VSA (1 MARK)
1. Gel electrophoresis
2. Plasmid and Bacteriophage.
3. Restriction Enzymes.
4. E. – Escherichia; co – coli; R – Name of Strain; I – order in which enzyme isolated
from strain of bacteria.
5. Number of fragments of linear DNA = 4 Number of
fragments of plasmid = 3
6. Plasmid.
7.
SA-II (2 MARKS)
8. вќ‘ Separation and Purification
вќ‘ This process is essential because before reaching into market, the product has to be
subjected for clinical trial and quality control.
9.
Plasmid DNA
(i) Circular DNA
Occurs only in bacterial
(ii) cells
(iii
) Used as Vector
in rDNA technology
Chromosomal DNA
(i) Linear DNA
(ii Occurs in nucleus of
) eukaryotic cells
and bacterial cell.
(iii) Not used as vector in rDNA
technology.
10. A – Plasmid, B – Nucleoid
Plasmid is used as vector to transfer the gene of interest in the host cell.
11. Exonucleases and endonucleases
Exonucleases remove nucleotides from the ends of the DNA.
Endonucleases cut DNA at specific sites beween the ends of DNA.
12. ❑ B – Gel Electrophoresis
❑ E – Elution
SA I (3 MARKS)
13. (i) Chemical treatment and exposure to cold and high temp. (42В°C) alternatively.
(Bacterial cell)
(ii) Biolistics or gene gun. (Plant cell)
(iii) Micro-injection. (animal cell)
Explanation – Refer page 200, biology Text Book for class XII.
14. вќ‘ Cells are treated with appropriate enzymes to release DNA. Lysozyme (bacteria),
cellulase (plant cells), chitinase (fungus).
вќ‘ RNA and proteins are removed by treatment with ribonuclease and protease
enzymes respectively.
15. (ii) Have origin of replication(Ori)
(ii) Have a selectable marker
(iii) Have at least one recognition site.
16. Agrobacterium tumefaciens is a pathogen in many dicot plants. It is ableto deliver a
piece of DNA (T–DNA) to transform normal plant cell into a tumor and directs these
tumor cells to produce the chemicals required by pathogen.
17. (a) EcoRI
(b)
(c) These are named sticky ends, because they form hydrogen bonds with their
complementary cut parts.
18. (a) Insertional inactivation
(b)
-galactosidase.
(c) Selection of recombinants due to inactivation of antibiotics requires simultaneous
plating on two plates having different antibiotics. (Refer page 200 NCERT Biology
for class XII)
LA (5 MARKS
19. (i) Temperature, pH, susbtrates, salts, vitamins and oxygen.
(ii) Figure 11.7(a) simple stirred–tank bioreactor Page No. 204 NCERT Text book,
Biology - XII
(iii) The stirrer facilitates even mixing and oxygen availability throughout simple–
stirred tank bioreactor, whereas in case of sparged stirred-tank bioreactor, air is
bubbled throughout the reactor for proper mixing.
20. (A) Denaturation – Heat denatures DNA to separate complementary strands.
(B) Annealing : Primers hybridises to the denatured DNA strands.
(C) Extension : Extension of primers resulting in synthesis of copies oftarget DNA
sequence. Enzyme Tag polymerase is isolated from the bacterium Thermus
aquaticus. This enzyme induces denaturation of double stranded DNA at high
temperature.
21. (a) ‗rop� codes for the proteins involved in the replication of plasmid
(b) Selectable marker – ampicillin resistance gene. It will help distinguishing
transformants from non-transformants after plating them on ampicillin containing
medium.
(c) Transformation – It is the phenomenon by which the DNA isolated from one type
of cell and introduced into another type and is able to bring about some of the
properties of former to the later.
BIOTECHNOLOGY- PRINCIPLES AND PROCESSES
HOTS
1)Forensic scientists have to work often with extremely small samples of DNA obtained
from the hair or other sources of suspected criminals . How could they obtain sufficient
DNA for DNA finger printing? Name the technique? Name the three main steps involved
in the technique.
A)Amplification of a particular segment of DNA .The technique is polymerase chain
reaction .The three main steps of PCR are no (1) Denaturation (2)Annealing of primers (3)
Primer extension.
2) Having become an expert on gel electrophoresis you are asked to examine a gel for a
colleague .Where do you find the smallest segments of DNA?
A) The smallest segment of DNA are found near the positive electrode farthest away from
the wells.
3) What are the sticky ends of fragmented DNA molecule made up of ? Why they are
named as sticky ends?
A) The sticky ends are made up of unpaired bases . They are named so because they form
hydrogen bonds with their complementary cut counterparts. This stickiness of the ends
facilitates the action of enzyme DNA ligase.
4) Which of the following is not a tool for constructing recombinant DNA?
(a) Heat shock (b) micro injection (c)gene gun (d) insertional inactivation
A) Insertional inactivation.
5) After completion of the bio synthetic stage the products have to be subjected to a series
of processes before it is ready for marketing.
(a) List these processes?
(b) What are they collectively known as ?
(c) List any other measures to be taken care of ?
A)
(a) Separation , purification
(b) Downstream processing
(c) Quality control testing.
VALUE BASED QUESTIONS
1. Suresh was vegetable grower. He used to grow tomato and got very good yields since
the vegetables market was far from his village and he had no transport facility, most of his
harvest was rotten due to delay. He consulted his friend in Agriculture University who
suggested him to grow transgenic tomatoes with delayed ripening genes. Answer the
question that follow: a) What are the transgenic organisms?
b) How are the transgenic tomato produced?
c) What value was displayed by Suresh�s friend?
ANSWER:-a) Those organisms which contains functional foreign gene.
b) Produced by the introduction of foreign gene in tomato plant which delay ripening
and offers high shelf life. Thus it helps in reducing post harvest losses.Flavr Savr
Tomato was created by Agrobacterium mediated gene transformation in which the
transfer ofT DNA contained a copy of tomato PG(polygalacturonase) encoding gene
in the antisense orientation
c) He is concerned about his friend ‗s welfare and making his friend aware of the
new techniques for delaying the ripening of tomato.
2. In the newspaper there was a news under heading ―new stem cell treatment to cure
cancer ―professor Reuven head of bone marrow transplantation at IA medical center in
Jerusalem said the technique uses specialized harvested cells to produce infection fighting
bone marrow .patients with blood cancer have most of their bone marrow destroyed when
given radiation or chemotherapy.
a) What are stem cells?
b) Which diseases can be cured by this life saving treatment?
c) What is the effect of bone marrow transplantation?
ANSWER: - a) stem cells are young and immature cells which can be made to differentiate
into any type of cells, tissues or organs under specific condition.
b) Leukemia, myeloma and lymphoma.
c) Bone marrow transplantation rebuilds the body�s immune system.
3. Agrobacterium tumifaciens is a pathogen of several dicot plants. It converts normal
plants cell into tumour cell and directs the tumour cell to produce the chemical required by
the pathogen.
a) Name the extra genetic material present in the agrobacterium?
b) How the bacteria converts the normal cells.
c) Name the structure which helps in introduction of genetic material into host organism.
ANSWER: - a) plasmid
b) The bacteria delivers a piece of DNA know as T-DNA in the genome of
host plant cell to transform it into a tumour cell.
c) Cloning vector.
4. A newspaper reported that an American company has patented neem. Indian government
fought against this patent. What will you call this act of American company?
ANSWER:- bio piracy
VALUES: - awareness and justice for the country.
5. Sangita has a transgenic crop . she want to grow this crop directly in the field .As a
biology student will you allow her to do so. what will you suggest her ?
ANSWER:- No, I will not allow her to do so because genetically modified organism may
pose threat to the environment or living organisms . I will ask her to approach GEAC
VALUES -: Sense of responsibility and understanding
UNIT IX
CHAPTER XII
BIOTECHNOLOGY AND ITS APPLICATIONS
IMPORTANT TERMS AND DEFINITIONS
Biopesticides : Biological agents that are used to control weeds, insects andother pests.
Cry Gene :The Bt toxins are coded by a gene named Cry.
Cry Protein :The insecticidal protein which is produced by Bacillus thuringiensis.
Green Revolution : Substantial increase in crop yields due to use of highyielding varieties,
use of fertilisers and pesticides, imrpoved agricultural practices etc.
Genetically Modified Organisms (GMO) : The organisms which have alteredgenes in
them. These are also known as transgenic organisms.
Molecular Diagnosis : Refers to early detection of diseases usingrecombinant DNA
molecules and techniques like PCR and autoradiography.
RNA Interference (RNAi) : Process used to develop pest resistant plants. Itinvolves
silencing of a specific mRNA due to complementary double stranded RNA.
Sustainable Agriculture : It involves organic farming and other integratedmanagement
practices which maintain soil fertility while increasing crop productivity.
Uses of GM Plants : Tolerant to abiotic stress, Reduced dependence onchemical
pesticides, less post harvest-loss, Efficient use of minerals, enhanced nutritional value.
Uses of Transgenic Animals : To study normal physiology and development,to study
diseases, to get biological products, to test vaccine and chemical safety testing.
Gene Therapy : It is a technique of inserting genes into the cells and tissueof an individual
to treat a hereditary disease.
вќ‘ The first clinical gene therapy was given in 1990 to a four year old girl with adenosine
deaminase (ADA) deficiency. ADA enzyme is required for proper functionng at
immune system.
вќ‘ This disorder is caused due to the deletion of the gene for adenosine deaminase
enzyme.
вќ‘ In some children ADA deficiency can be cured by bone marrow plantation.
Lymphocytes from the blood of patient are grown in a culture. A functional ADA
cDNA is then introduced into these lymphocytes using retroviral vector. The
lymphocytes are transferred into the body of patients.
вќ‘ As these cells are not immortal, the patient required periodic infusion of such
genetically engineered lymphocytes.
вќ‘ If a functional gene is introduced into a bone marrow cells at early embryonic stage, It
could be a permanent cure of ADA deficiency.
Bt. Cotton : The soil bacteriumBacillus thuringiensisproduced crystal proteincalled cry
protein that kills certain insects larvae such as tobacco budworm, armyworm, beettles and
flies.
вќ‘ Bt toxin protein exists as inactive protoxins, but once an insect ingest this inactive
toxin, it is converted into active form of toxin due to the alkaline pH of the gut which
solubilise the crystal. This causes swelling and lysis of epithelial cells of midgut
leading to death of insect larvae.
вќ‘ Bt toxin genes were isolated from Bacillus thuringiensis and incorporated into the
several crop plants such as cotton.
вќ‘ The proteins encoded by the genes :
crylAc and cryllAb control the cotton bollworms and crylAb control corn borer.
Pest Resistant Plants : A nematodeMeloidegyne incognitiainfectstobacco plants and
reduces their yield.
вќ‘ Nematode specific genes were introduced into the host plant using
Agrobacterium as a vector.
вќ‘ The introduction of DNA was such that it produced both sense and anti-sense RNA in
the host cells.
вќ‘ These two RNAs being complementary to each other formed a double stranded RNA
(dsRNA) making it inactive.
вќ‘ This dsRNA molecule binds to and prevents translation of mRNA (silencing) of the
nucleotide by the process called RNA interference (RNAi).
The result was that the parasite could not survive in the transgenic host and the transgenic
plant got protected for the parasite.
Three Critical Research Areas of Biotechnology
(i) Providing best catalyst in the form of improved organism usually a microbe.
(ii) Creating optimal conditions for a catalyst to act.
(iii) Downstreaming processing technologies to purify the desirable product.
QUESTIONS
VSA (1 MARK)
1. Name the technique based on the principle of antigen-antibody interaction used in
detection of a virus (HIV).
2. Development of a transgenic food crop may help in solving the problem of night
blindness in the developing countries, name this crop plant.
3. Which nematode infects the roots of tobacco plant and causes a great reduction in
yield?
4. The first transgenic cow, produced human protein – enriched milk. Name the cow and
the protein found in milk.
5. The insulin produced using recombinant DNA technology is more advantageous than
the insulin extracted from pancreas of slaughtered cattle and pigs. How?
6. Name two pest resistant plants produced by using recombinant DNA technology.
SA-II (2 MARKS)
8. What are the two methods for correcting ADA deficiency in a child?
9. Some crop plants are modified genetically by manipulating their genes. How are they
made beneficial?
10. GEAC is one of the organisation set up by Indian Government. Write its full form.
Give its two objectives.
11. ―Industrialised nations are exploiting the bioresources of under industrialised nations‖.
Justify the statement with a suitable example.
SA-I (3 MARKS)
16. Some multinational companies and other organisations are using bioresources for
commercial benefits, without proper authentication and compensation to concerned
authorities.
(a) Give the term for this unauthorised act.
(b) Suggest any two ways to get rid of this.
17. A bacterium Bacillus thuringiensis produces a toxic protein named ‗cry protein� that is
lethal to certain insects but not to bacterium
(a) Why this toxin does not kill the bacteria?
(b) What type of changes occur in the gut of insects on consuming this protein?
(c) How man has exploited this protein for his benefit?
18. Given below is an incomplete flow chart showing the process of production of
nematode resistant tobacco plants based on RNAi technique.
(i) Write the missing steps in proper sequence
(ii) At which level RNAi silences the gene?
LA (5 MARKS)
14. The clinical gene therapy is given to a 4 years old patient for an enzyme which is crucial
for the immune system to function.
Observe the therapeutical flow chart and give the answer of the following:
(a) Complete the missing steps (B) and (D)
(b) Identify the disease to be cured.
(c) Why the above method is not a complete solution to the problem?
(d) Scientists have developed a method to cure this disease permanently. How?
15. In the given figure, Agrobacterium is utilized for the production of a transgenic crop.
Explain the steps a, b, c, d and e shown in the figure.
16. In the given figure, Form (A) and Form (B) represents different forms of a
proteinaceous hormone secreted by pancreas in mammals.
(a) What type of bonding is present between chains of this hormone?
(b) What are these form (A) and form (B). How these forms differ from each other?
(c) Explain how was this hormone produced by Eli Lilly, an American company, using
rDNA technology.
ANSWERS
VAS (1 MARK)
1. ELISA (Enzyme linked immuno - sorbent Assay)
2. Golden Rice
3. Meloidegyne incognitia.
4. Rosie, alpha-lactalbumin
5. Insulin obtained from animal source causes allergy.
6. Bt Cotton, Bt Corn, Bt Brinjal.
SA-II (2 MARKS)
8. Bone marrow transplantation having functional ADA enzyme and Enzyme replacement
therapy.
9. More tolerant to abiotic stresses; pest resistant; reduction in post harvest losses;
increased nutritional value of food.
10. GEAC – Genetic Engineering approval committee. Objectives of GEAC are
(i) To make decisions regarding validity of GM research.
(ii) Safety of introducing GMO for public use.
13. Industrialised nations are collecting and patenting the genetic resources of under
industrialised country like India. An American Company got patent rights on
Basmati rice.
Valuable biomolecules obtained from bioresources are patented and used for commercial
purposes.
SA-I (3 MARKS)
11. (a) Biopiracy
(b) (i) Benefits of bioresources should be shared between developed and developing
nations
(ii) Laws should be developed to prevent unauthorsied exploitation of them
bioresources.
12. (a) Produced in inactive form as Prototoxins.
(b) Prototoxin becomes active toxin in alkaline pH of gut of insects. Toxins bind to
surface of midgut and cause perforation, swelling, lysis of cells ultimately leading
to death.
(c) Specific Bt toxin genes isolated from Bacillus thuringiensis and incorporated into
several crop plants such as cotton and corn which become pest resistant against
certain insects.
13. (i) Using Agrobacterium as a vector, introduced into
(b) tobacco
(d) dsRNA (double stranded RNA)
(f) Silenced specific mRNA of the nematode
(g) Parasite could not survive.
(ii) RNAi silences the gene at translation level
LA (5 MARKS)
14. (a) Step (B) : Lymphocytes are grown in culture medium.
Step (D) : Infusion of genetically engineered lymphocytes into patients.
(b) Adenosine deaminase (ADA) deficiency.
(c) As genetically engineered lymphocytes are not immortal, the patient requires
periodic infusion of cells.
(d) If the gene isolated from bone marrow cells producing ADA is introduced into cells
at early embryonic stages, it could be a permanent cure.
15. Step (a) Plasmid is removed and cut open with restriction
endonuclease.
Gene of interest is isolated from another organism
Step (b) and
amplified using PCR
Step (c) New gene is inserted into plasmid
Step (d) Plasmid is put back into Agrobacterium
Step (e) Agrobacterium based transformation.
16. (a) Disulphide bonds
(b) Form (A) – Proinsulin Form (B) – Mature
insulin.
Proinsulin contains an extra stretch called C – peptide which is absent in mature
insulin.
(c) Eli Lilly company prepared two DNA sequences corresponding to A and B peptide
chains of human insulin and introduced them in plasmid E. coli to produce insulin
chains. Chains A and B were producedseparately, extracted and combined by
creating disulphide bonds to form insulin.
HIGHER ORDER THINKING SKILLS
1) A baby loses his mother in infancy he was totally dependent on breast feeding as cow�s
milk creates digestive problems. Name the first cow whose milk is nutritionally more
balanced than normal cow�s milk. Which extra element does it contain and how much
magnitude?
A) GM cow (transgenic cow) Rosie. Rosie produced milk rich in human protein .
Human protein-human alpha lact albumin (2.4g/lit).
2) Name the transgenic food crop which may help in solving the problem of night
blindness in developing countries . How is it produced?
A) Golden rice is rich in vitamin A and prevents blindness. It has been produced by
introducing three genes (trans genes) for the production of vitamin A in Taipei
variety of rice.
3) What are transposons? Name the scientist who discovered the jumping genes.
A) Transposons are short movable DNA sequences that can change its relative position
with in the genome of a single cell. Barbara McClintock discovered the jumping
genes.
4) Name the organization which has been set up by the Indian government to make
decisions regarding the validity of GM research and the safety of introducing GM
organisms for public services.
A) GEAC (Genetic Engineering approval committee)
5) Proteins encoded by genes cry l Ac and cry llAb and that of cry l Ab are slightly
different in their control. Explain.
A) Proteins encoded by genes cry lAc and cry llAb control boll worms. proteins
encoded by genes cry l Ab controls corn borer.
VALUE BASED QUESTIONS
1) Few hair strands were found from the crime scene. The policemen wants to proceed
for DNA fingerprinting but the amount of DNA is very less .In your opinion what
could be the solution to this problem ? Write the basic steps of this technique
A) He can amplify the DNA with the help of PCR technique
Basic steps
Denaturation
Annealing
Extension
Values –Critical Thinking and Awareness
2) Sunil�s uncle is very worried as his crop is destroyed by insects. He suggested his
uncle to use Bt crop. His uncle says that such crops produce toxins which can harm
the consumers of this crop. Whom do you support and why?
A) I support sunil
Bt -Crops produce protoxin which changes into active from in the
intestine of the insects in alkaline pH . It is completely safe for other
animals and human beings.
Values – Empathy and Awareness.
3) A newspaper has reported that an American company has patented turmeric. Indian
Government is fighting against this patent. What will you call this act of American
company?
A) Biopiracy
Values – Awareness, justice for country.
4) Sangeeta has developed a transgenic crop and wants to grow this crop directly in the
field. Will you allow to do so? What will you suggest to her?
A) No as GMO may pose some threat to environment or living organisms.
I will ask her to approach GEAC
Values – sense of responsibility and awareness.
5 ) Recently Indian council of agricultural research prohibits research on rabbits.
Lalitha was very happy to hear the news. What do you call this act of ICAR as a
student of biology ?
Ans. As a student of biology laiitha was worried about the suffering of rabbits
as lab animals.Values—sense of responsibility and awareness to conserve animals.
UNIT X
CHAPTER 13
ORGANISMS AND POPULATIONS
Adaptation : Any attributes of the organism (morphological, physiological,behavioural)
that enables the organism to survive and reproduce in its habitat.
Aestivation : Strategy to escape in time during summers (summer sleep). E.g.,Snails and
some fishes.
Allen’s Rule : Mammals from colder climates generally have shorter ears andlimbs to
minimise heat loss.
Carrying Capacity : Maximum number of individuals of a population which canbe
provided with all the necessary resources for their healthy living.
Commensalism : One organism is benefitted while the other is neither harmednor
benefitted except to a negligible extent.
Competition : Rivalry between two organisms for obtaining the sameresources.
Ectoparasite : Parasites which live on the surface of their host.
Emigration : Number of individuals of the population who have left the habitatand gone
elsewhere during a given time period.
Exponential Growth Curve : Shows that if food and space for a populationare unlimited
and each species has the ability to grow, then the population grows in exponential or
geometric ratio.
Hibernation : Strategy to escape in time during winters (winter sleep). E.g.,Polar bears.
Homeostasis : Maintaining constancy of internal environment despite varyingexternal
environmental conditions.
Immigration : Number of individuals of the same species that have come intothe habitat
from elsewhere during a given time period.
Ecology : A branch of science that studies the reciprocal relationships betweenorganism
and their physical environment. Ecology is basically concerned with four levels of
biological organisation– organisms, populations, communities and biomes.
Organisms : Organisms form the basic unit of study in ecology. Organisms withsimilar
features and the potential interbreed among themselves and produce fertile offspring,
constitute a species.
Populations : Population is a group of individuals of the same species,inhabiting in a given
area. Interspecific competition for basic needs operate among the individuals of a
population.
Biological Community : Biological community is constituted by an assemblageof the
populations of all different species that live in an area and interact with each other. A biotic
community has a distinct species composition and structure.
Biomes : Biome is a very large unit, constituting of a major vegetation typeand associate
fauna found in a specified zone. Annual variations in the intensity, duration of temperature
and precipitation account for the formation of major biomes like desert, rain forest and
tundra.
Major Biomass of India : Tropical rain forest, deciduous forest, desert, seacoast. Regional
and local variations within each biome lead to the formation of a wide variety of habitats.
Environment : Environment is a sum total of all biotic and abiotic factors thatsurround
and potentially influence an organism. Temperature, water, light and soil are the major
abiotic factors.
Response to Abiotic Factors :
вќ‘ Regulators : Some organisms are able to maintain homeostasis byphysiological (Some
times behavioural) means which ensures body temperature, constant osmotic
concentration. All birds and mammals, a very few lower vertebrates and invertebrates
are regulators (Thermoregulation and osmoregulation). For example, human beings
maintain their body temperature by sweating in summer and shivering during winter
season. Plants do not have such mechanisms to maintain internal temperatures.
вќ‘ Conformers : Majority of animals and nearly all plants cannot maintaina constant
internal environment. Their body temperature changes with the ambient temperature. In
aquatic animals the osmotic concentration of the body fluids change with that of the
ambient water and osmotic concentration. Some species have evolved the ability to
regulate, but only over a limited range of environmental conditions, beyond which they
simply conform.
A diagrammatic representation of organismic response is shown below.
❑ Partial regulators : Hair on the body – Hair on body acts as heat insulator.Surface
area and volume ratio – In smaller organisms the surface area is large as compared to
the volume. But in large animal this ratio is small. So, the larger animals effectively
controls the body temp erature.
вќ‘ Migration : The organisms can move away temporarily from the stressfulhabitat to a
more hospitable area and return when stressful period is over.
вќ‘ Suspend : The organisms may avoid the stress by escaping in time. Bearsgo into
hibernation winter, some snails and fish go into aestivation in summer.
Age Pyraminds of Populations : A population at any given time is composedof
individuals of different ages. If the age distribution is plotted for the population, the
resulting structure is called an age pyramid. The shape of the pyramids reflects the growth
status of the populations (a) Whether it is growing (expanding) (b) Stable or (c) Declining.
A pyramids for human population (males and females) are represented below.
Population Growth : If ‗N� is the population density at time ‗t�, then its densityat time t +
1 is :
Nt+1 = Nt + [(B + I) – (D + E)]
Where B = The number of births
I = The number of immigrants D = The number of
deaths
E = The number of Emigrants. N = Population
Density
r = Intrinsic rate of natural increase
вќ‘ = Time period
(iv) = Carrying capacity (The maximum population size that an environment
can sustain)
Population Interactions :
Predation : Interaction between species involving killing and consumption ofprey is called
predation. The species which eats the other is called the predator and the one consumed is
termed the prey. The predator keeps check on prey population. The reduction in predator
population may lead to increase in prey population.
Competition – In this fitness of one species is significantly lower in presenceof another
species
Competitive release – A species whose distribution is restricted to a smallgeographical
area because of a competitively superior species, is found to expand its distributional range
when the competing species is experimentally removed
Competitive Exclusion Principle – Two closely related species competing forthe same
resources cannot co-exist indefinitely and the competitively inferior one will be eliminated.
Resource partitioning – If two species compete for the same reasource, theycould avoid
competition by choosing different times for feeding.
Commensalism : This is the interactio in which one species benefits and theother is neither
harmed nor benefited under normal conditions.
Parasitism : Parasitism is a kind of relationship between two species in whichone derives
its food from the other (host). Parasitism also involves shelter, in addition to food obtained
by a parasite. Parasites may be ectoparasites or endoparasites.
Mutualism : In mutualism both the interacting species are benefited mutually.It is also
known as symbiosis.
Co-evolution – 1) Fig species and wasp. Female wasp uses the fruit as anqviposition (egglaying) and also uses the developing seeds within the fruits for nourishing its larvae. Wasp
pollinates the fig inflorescence while searching for egg laying site, in return big offers
developing seeds as food for developing larvae. 2) Mediternanean orchid Ophrys and bee.
Amensalism : Interaction between two different species, in which one speciesis harmed
and the other is neither benefited nor harmed.
Examples of Parasitism :
7. Cuscuta growing in shoe flower plant
8. Head louse and humans
9. Ascaris, Taenia, Plasmodium causing diseases in humans
Examples of Brood parasitism :
(i) Koel laying its eggs in crow�s nest.
Examples of Commensalism :
12. Clown fish living among tentacles of sea anemone
13. Pilot fish (Remora) accompanies sharks
14. Orchid growing on mango tree
15. Sea anemone on the shell of hermit crab
16. Barnacles on back of whales
17. Egret and grazing cattle
Examples of Mutualism
19. Mycorrhiza living in roots of higher plants
20. Rhizobium in root nodules of legumes
21. Algae and fungi in lichens
22. Orchid Ophyrs and bee for pollination (employs sexual deceit)
Example of Amensalism
пѓ� Penicillium whose toxin kills many bacteria is neither benefitted nor harmed
Examples of Predation
13. Biological control methods to control pests
14. Carnivorous animals like tiger eating deers, snake eating frog
15. Insectivorous plants like Nepenthes, Drosera, Utricularia
Growth Models : The two growth models are :
пѓ� Exponential growth model
Exponential Growth Equation is Nt = N0ert Where
Nt = Population density after time t N0 = Population
density at time zero r = intrinsic rate of natural increase
e = the base of natural logarithms (2.71828)
пѓ� Logistic growth model
Verhulst-Pearl Logistic Growth is described by the following equations :dN/dt = rN
(K–N / N)
Where N = Population density at time t r = Intrinsic rate of
natural increase
K = Carrying capacity
2
Exponential growth (‗J� shape curve is obtained).
* When responses are not limiting the growth.
* Any species growth exponentially under unlimited resources conditions can reach
*
enormous population densities in a short time.
Growth is not so realistic.
(ii) Logistic Growth (Sigmoid curve is obtained)
* When responses are limiting the Growth.
* Resources for growth for most animal populations are finite and become limiting.
* The logistic growth model is a more realistic one.
QUESTIONS
VSA (1 MARK)
1. Which are the factor responsible for the wide variety of habitat formed within each
biome?
2. Fresh water animals are unable to survive for long in sea water. Give reason.
3. With which population growth model is the Verhulst Pearl equation associated?
4. Define diapause. Which organisms exhibit it?
5. Calculate the death rate if 6 individuals in a laboratory population of 60 fruit flies died
during a particular week.
6. In biological control method, one living organism is used against another to check its
uncontrolled growth. Which kind of population interaction is involved in this?
7. An organism has to overcome stressful condition for a limited period of time. Which
strategies can it adopt to do so?
8. Write what do phytophagous insects feed on?
SA-II (2 MARKS)
17. What are the four levels of biological organisation with which ecology basically deals?
18. Differentiate between stenohaline and euryhaline organisms.
19. List four features which enable the Xeric plants to survive in the desert conditions.
20. Mention the attributes which a population has but not an individual organism.
21. Differentiate between stenothermal and eurythermal organisms.
22. What are the four ways through which the living organisms respond to abiotic factors?
23. Why do clown fish and sea anemone pair up? What is this relationship called?
SA-I (3 MARKS)
(d) How does the shape of age pyramid reflect the growth status of a population?
(e) Darwin showed that even a slow growing animal like elephant could reach enormous
number in absence of checks. With the help of your understanding of growth models,
explain when is this possible? Why is this notion unrealistic?
(f) How will you measure population density in following cases?
fish in a lake
tiger census in a national park
single huge banyan tree with large canopy.
(g) Species facing competition might evolve mechanism that promotes co-existence rather
than exclusion. Justify this statement in light of Gause�s competitive exclusion
principle, citing suitable examples.
LA (5 MARKS)
20. What is altitude sickness? What its causes and symptoms? How does human body try
to overcome altitude sickness?
21. Orchid flower, Ophrys co-evolves to maintain resembelance of its petal to female bee.
Explain how and why does it do so?
ANSWERS
VSA (1 MARK)
1. Regional and local variations
2. Due to osmotic problems.
3. Logistic Growth.
4. A stage of suspended development, zooplanktons.
5. 6/60 =0.1 individuals per fruitfly per week.
6. Predation.
7. (i) Migration
(ii) Suspension of active life by hibernation/aestivation/spore formation.
8. Plant sap and other parts of plant.
SA-II (2 MARK)
9. Organisms, population, communities and biomes.
10. Euryhaline : Organisms tolerant in wide range of salinities. Stenohaline :
Organisms tolerant to narrow range of salinities.
11. (i) thick cuticle
(ii) Stomata in deep pits
(iii) Stomata closed during day time
(iv) leaves reduced to spines (CAM photosynthetic pathway).
12. Birth rate, Death rate, Sex ratio, age groups.
13. Eurythermal : Organisms that can tolerate and thrive in wide range oftemperatures
Stenothermal : Organisms restricted to a narrow range of temperature.
14. (i) Regulate (ii) Conform (iii) migrate (iv) Suspend
15. Clown fish lives in tentacles of sea Anemone and gets protection from predators.
Interaction – commeasalisn.
SA-I (3 MARKS)
16. Shape of pyramids reflects growth statusof the population (a) growing (b) Stable (c)
declining.
Refer page 227, Fig. 13.4, NCERT book, Biology - XII
17.Possible if the growth model is Exponential, i.e., having unlimited resources. Its an
unrealistic situation because resources are limited. Hence, it follows logistic growth
model.
18. (a) fish caught per trap.
(b) number per unit area
(c) percentage cover in biomass.
19. State Gause�s competitive exclusion principle. Mechanisms is resource partitioning.
E.g., experiment of Mac Arthur on Warblers (Refer page 325, NCERT book, Biology XII).
LA (5 MARKS)
b
Breathlessness at high attitudes.
Cause : Low atmospheric pressure at high altitudes due to which bodydoes not get
enough oxygen.
Symptoms : Nausea, fatigue and heart palpitations.
Body adapts by :
(f) increasing red blood cell production
(g) decreasing binding affinity of haemoglobin
c
(h) by increasing breathing rate.
❑ employs ‗Sexual deceit�
вќ‘ one petal bears uncanny resemblance to female of the bee.
❑ Male bee is attracted to what it perceives as a female ‗pseudocopulates,� during
which pollen dusted on male beeВЎВ¦s body.
вќ‘ Male bee transfers pollen to another flower when the same bee pseudocopulates
with another flower.
вќ‘ Ophrys does so because pollination success will be reduced unlessit co-evolves with
female bee.
HIGHER ORDER THINKING SKILLS
1) An animal can live from birth to death with out drinking water .Name the animal,
adaptation and the source of water .
A) Kangaroo rat conserves water by excreting solid urine. The source of water is the
metabolic water obtained through its internal fat oxidation in which water is a by
product.
2) Why you never see any cattle or goats browsing the calotropis plants ? Give reason.
A) The calotropis plant produces highly poisonouss cardiac glycosides show a
chemical defense against the herbivores.
3) An orchid plant is growing on the branch of a mango tree How do you describe the
interaction between the orchid and the mango tree?
A) Commensalism – in this interaction one species benefits that is orchid and the
other(mango tree) is neither harmed nor benefitted.
4) Why do some organisms enter diapause?
A) To avoid unfavourable conditions. example Zooplankton .
5) Why very small animals are rarely found in polar regions ?
A) Small animals have a larger surface area relative to their volume, they tend to lose
body heat very fast when it is cold out side, then they have to expend much energy
to generate body heat through metabolism.
VALUE BASED QUESTIONS
1)
Rani is a poor girl but she is intelligent . She depends on Geetha for side books. On
the otherhandGeetha is rich girl but not well in study. She depends on Rani to clear
her concepts when she face difficulties .
(a) What type of dependence is it?
(b) What values do you incur from this question?
A) Mutalism
B) This interaction confers benefits on both the girls. This type of interactions
prevent quarrels , battles wars from the society.
Values: concern for others
2) The city government is planning to bring metro rail to your area but this will require
around twenty- thousand trees to be cut .Do you think that government should go ahead
with the project . Justify your answer?
ANSWER-: Yes, but the track of the metro railway should be so changed that minimum
number of trees are cut. Track can also be made underground and more trees can be
planted after the project is over .
VALUES:- love for nature
Sensitivity towards environment
Decision making
3) One of your friends Harsha has gone to a jungle safari with his family . On returning he
is sharing his experiences with you and tells that his father hunted a deer with his gun
.what will you suggest your friend after knowing about their expedition?
ANSWER:- Yes, It is unethical and leads to loss of biodiversity and
results in imbalance of ecosystem
VALUES:- concern about animals , empathy .
4) Ajay a notorious boy often involved in destruction of plants and killing animals .how
can you explain him about importance of each and every organism present in the world
.what hypothesis will you use for it ?
ANSWER:- explanation through rivet popper hypothesis
VALUES:- social responsibility and concern about ecosystem .
5) A team of research workers observed that the population of fish eating birds is declining
every year after the establishment of pesticide factory near by five years ago .
a) What may be the possible reason in your opinion . explain
b) Can you suggest alternative to pesticide so that the factory may be stopped ?
ANSWER:- a) pesticide entering in food chain and resulting in bio
magnification
c) Bio controlling agent to remove pests
VALUES:- problem solving , critical thinking .
UNIT X
CHAPTER 14
ECOSYSTEM
Startification : Vertical distribution of different species occupying differentlevels in an
ecosystem.
Primary Production : Amount of biomas or organic matter produced per unitarea over a
time period by plants during photosynthesis.
Productivity : Rate of biomass production. Its unit is g/m2/year.
Gross Primary Productivity : Rate of production of organic matter duringphotosynthesis.
Net Primary Productivity : Gross primary productivity minus the respirationlosses.
Ecosystem : Relationship between living organisms and their abioticsurroundings.
Secondary Productivity : Rate of formation of new organic matter byconsumers.
Detritus : Dead leaves, twigs, animal remains etc. constitute detritus.
Detrivore : Organisms who break down detritus into smaller particles. e.g.,earthworm.
Ecological succession : The successive and orderly replacement of onecommunity by the
other community in an area, over a period of time.
Ecological Pyramids : The sequential graphic representation of an ecologicalparameter
(number/ biomass/energy) depicting different trophic levels in a food chain.
Climax community : The stable and final biotic community that develops atthe end of
ecological succession and is in perfect harmony with its physical environment.
Pioneer species : The species that invade a bare area at the onset ofecological succession.
Process of Decomposition : The decomposers break down complex organicmatter into
inorganic substances like carbon dioxide, water and nutrients. This process is called
decomposition. Steps of decomposition are :
вќ‘ Fragmentation : Break down of detritus into smaller particles bydetritivores
(earthworm).
вќ‘ Leaching : Water soluble inorganic nutrients go down into the soil horizonand get
precipitated as unavailable salts.
вќ‘ Catabolism : Bacterial and fungal enzymes degrade detritus into simpleinorganic
substances.
вќ‘ Humification : Accumulation of a dark coloured amorphous substancescalled humus.
вќ‘ Mineralisation : The humus is further degraded by some microbes andrelease of
inorganic nutrients occur.
Energy Flow : Energy flow is the key function in the ecosystem. The plants(producers)
capture only 2 – 10 percent of the photosynthetically active radiation (PAR). Unidirection
flow of energy is taken place from the sun to producers and them to consumers. About 10%
energy flows from one trophic level to another.
Grazing Food Chain : It begins with producers.
Detritus Food Chain : It begins with dead organic matter. It is made up ofdecomposers
(Fungi, Bacteria). They meet their energy and nutrient requirements by degrading detretus.
These are also known as saprotrophs.
Ecological Pyramids
вќ‘ Pyramid of Numbers : (Grass land system)
вќ‘ Pyramid of Energy : (Always upright in all Ecosystems)
вќ‘ Pyramid of Biomass :
Ecological Succession : The gradual and fairly predictable change in the species
composition of a given area is called ecological succession. The species that invade a bare
area is called pioneer species. The final community is an ecological succeesion that is in
near equilibrium with the environment is called climax community
Secondary Succession begins in the area where natural biotic communities have been
destroyed (burned or cut forests, land that have been devastated by flood).
Succession on a Bare Rock (Xerarch)
Succession in Aquatic environment (Hydrarch)
Nutrient Cycling – Movement of nutrient elements through the variouscomponents of an
ecosystem also called Biogeochemical cycles.
Carbon cycle – occurs through atmosphere, ocean, and though living anddead organisms.
Considerable amount of carbon returns to atmosphere as CO2 through respiratory activities,
decomposers also contribute to Carbon di-oxide pool, burning of wood, forest fire and
combustion of organic matter, fossil fuels, volcanic activity also release CO2 is atmosphere.
Phosphorous cycle – Sedimentary cycle Rocks contain phosphorous in theform of
phosphates
P
1
1
Carbon Cycle
(v) Amount of atmospheric inputs more in amount
(vi) Degree of exchanges between organism and environment high
ABBREVIATIONS
PAR : Photosynthetically Active Radiation
GAP : Gross Primary Productivity
NPP : Net Primary Productivity
DFC : Detritus Food Chain
GFC : Grazing Food chain
QUESTIONS
VSA (1 MARK)
18. Decomposition is faster if deteritus is rich in nitrogen and water soluble substance like
sugars. When is the decomposition process slower?
19. If we count the number of insects on a tree and number of small birds depending on
those insects as also the number of larger birds eating the smaller, what kind of
pyramid of number would we get?
20. Differentiate between Sere and Seral communities.
21. Who are generally the pioneer species in a Xerarch succession and in a Hyararch
succession?
22. Which metabolic process causes a reduction in the Gross Primary Productivity?
23. What percentage of photosynthetically active radiation is captured by plants?
24. Name the pioners of primary succession in water.
SA-II (2 MARKS)
23. What is the shape of pyramid of biomass in sea? Why?
24. Give an example of an ecological pyramid which is always upright. Justify your
answer.
25. Differentiate between primary succession and secondary succession. Which one occurs
faster?
26. Gaseous nutrient cycle and sedimentary nutrient cycles have their reservoir. Name
them. Why is a reservoir necessary?
27. Fill up the missing links depicted as A, B, C and D in the given model of primary
succession.
пѓ� In the model of phosphorus cycle given below, what does A, B, C and D refer to?
16. Differentiate between Hydrarch and a Xerarch succession.
17. What is the effect on decomposition rate if :–
Detritus is rich in lignin and chitin
Detritus is rich is nitrogen and sugars
18. What are the limitations of ecological pyramids?
19. Name any four ecosystem services. Who gave the price tags on nature�s life support
services? Which is the most important ecosystem service provider?
20. Study the table given below and fill the blanks from ‗A� to ‗F�.
Component of
the Ecosystem
Position of the
trophic level
Organism
present in
the Food chain
1.
E
Fourth trophic
level
F
2.
Secondary
consumer
D
Bird, fish, wolf.
C
S.No
3.
B
Second trophic
level
4.
Primary
producer
A
Phytoplankton,
grass, tree.
19. In the pyramid of biomass drawn below, name the two crops (i) one which is supported
(ii) one which supports in which ecosystem is such a phyramid found?
LA (5 MARKS)
20. Detrivores like earthworm are involved in the process of decomposition of dead plants
and animals. Describe the different steps involved in the process of decomposition.
ANSWERS
VSA (1 MARK)
19. Its slower if detritus is rich in lignin and chitin.
20. Inverted Pyramid of Number.
21. Sere : Entire sequence of communities that successively change in a givenarea.
Seral community : Individual transitional community.
22. Pioneer species in Hydrarch succession are usually the small phytoplanktons and that in
Xerarch succession are usually lichens.
23. Respiration.
24. 2 – 10%
25. Phytoplanktons
SA-II (2 MARKS)
9. Inverted, because biomass of fishes far exceeds that of phytoplankton.
10. Pyramid of energy is always upright and can never be inverted, because when energy
flows from a trophic level to the next trophic level some energy is always lost as heat at
each step.
11. Primary Succession : A process that starts where no living organisms arethere.
Secondary succession : A process that starts in areas which have lostall the living
organisms that existed there.
12. Reservoir for Gaseous nutrient cycle : Atmosphere; for sedimentary nutrient cycle :
Earth�s crust. Reservoir is needed to meet with the deficit which occurs due to
imbalance in the rate of influx and efflux.
A = Submerged plant
12. stage
C = Scrub stage
13. A = Detritus
C = Weathering
B = Reed Swamp
Stage
D = Forest stage
B = Decomposition
D = Producers.
24. Hydrarch Succession : Starts in water proceeds from hydric (aquatic) tomesic (neither
dry nor wet) situations.
Xerarch succession : Starts on barren rock Proceeds from Xeric (dry)conditons.
25. a) Decomposition rate is slower
Decomposition rate is faster.
26. (i) Does not take into account same species belonging to two or more trophic levels.
(ii) Assumes simple food chain, does not accomodate food web.
(iii) Saprophytes have not been given any place in ecological pyramids.
17. Forest (ecosystem) purify water and air вќ‘ Mitigate Droughts
and floods
Nutrient cycling
Generate fertile soil
Provide habitat for wildlife вќ‘ Pollinate flower
Maintain Biodiversity
Provide aesthetic, cultural & spiritual values
Robert Constanza gave price tags to ecosystem services. вќ‘ Most important
ecosystem services provider : Soil formation.
18. A = First trophic level B = Primary
consumer
C = Zooplankton, Cow, Grass hopper D = Third trophic
level
E = Tertiary consumer F = Man, Lion
19. (i) Supported trophic level is founded by zooplanktons
(ii) Supporting trophic level is formed by phytoplanktons ecosystem It is found in
aquatic ecosystem.
20. The dead remains of plants and aminals called detritus undergo decomposition and are
converted into simpler substances. The steps of this process are :
Fragmentation : Breakdown of detritus into smaller pieces bydetrivoures like
earthworm.
Leaching : Water soluble inorganic nutrients go down into soil horizonand get
precipitated as unavailable salts.
Catabolism : Bacterial and fungal enzymes degrade detritus intosimpler inorganic
substances.
Humification : It leads to accumulation of dark coloured amorphoussubstance
called humus which is highly resistant to microbial action so decomposes at slow
rate and is rich in nutrients.
Mineralisation : Humus is further degraded by some microbes andrelease of
inorganic nutrients occurs.
HIGHER ORDER THINKING SKILLS
1) How is the rate of decomposition controlled by chemical composition of detritus and
climatic factors ?
A) Decomposition rate is low, if detritus is rich in lignin and chitin and quick if rich
in nitrogen and sugars. Warm and moist environment favors decomposition
where as low temperature and anaerobiosis inhibit decomposition.
2) Why the pyramid of energy is always upright can never be inverted explain?
A) Because when energy flows from a particular trophic level to the next trophic
level some energy is lost as heat at each step.
3) In a terrestrial ecosystem DFC and GFC are interlinked at certain level justify the
statement.
A) DFC and GFC are interlinked at same level in the terrestrial ecosystem, energy flow
occurs via DFC then GFC . DFC can be connected to GFC at some level as source
of organisms of DFC are prey to GFC animals.
4) Why are earthworms called the ‗friends of farmer�?
A) Earthworm are detrivores they break detritus in to small fragments by
fragmentation, loosen soil, increase the soil fertility.
5) Briefly describe the structure of Ecosystem?
A) 1. Input (Productivity)
2. Transfer of energy (food chain, food web, nutrient cycling)
3. Output (degradation and energy loss)
VALUE BASED QUESTIONS
1)
In nature , the structure
and composition of biotic communities constantly remain changing with change in
natural and physical environment. It is predictable in an area that remains base. It
may be rock or water . Various species colonise , some disappear and at last a
stable climax community appears .
(a)
In the above case ,explain
primary succession?
(b)
How is succession on
rock different from succession on water body?
A)
The Xeric
succession
begins with bare rock , inhabited by lichens, moss , grasses, shrubs and finally the
climax community – forest.
Hydrarch
succession occurs in water and
progress to mesic
conditions.Phytoplanktons are pioneer species .In Xerarch succession begins
with bare rock and progresses to mesic conditions. Lichens are pioneer species.
2)
During his tour to a
renowned forest Ravi saw a highway being constructed which passes of through
the middle of the forest .He was unhappy . On return he contracted the local Eco club
and approached the concerned department to stop the work.
a)
What values did Ravi
reflect here?
b)
What would be the effect
on ecosystem if the highway is constructed?
A)
Love for nature and
environmental consciousness. He was brave focussed having vision to see the
disaster in the future.
Ecosystem is disturbed .Animals get confined to smaller area. Fragmentation
characteristically reduces species richness and taxon diversity and may reduce
the efficacy of ecosystem functioning.
3)
Seema was maintaining a vermicompost pot in her garden. This compost use for
growth of various types of plants in her garden. During summer the decomposition was
delayed.What is the reason for this delay? What are the climatic factors which regulate
the decomposition process. What values are shown by seema?
A)
Decomposition rate is
delayed due to the climatic factors like high temperature and low soil moisture
during summer.Values shown by seema (if chemical fertilizers are used the soil
organisms are killed. Seema used vermicompost which is very cheap and she can
save the soil organisms) Love for nature, save the environment, soil
conservation etc.
4) Frog dissection is banned in educational institutions. Suresh brought a live frog to the
biology lab for dissection. Kavitha opposed suresh . What values did Kavitha show.What is
the effect of killing frogs on the ecosystem.
A)
Kavitha showed values
like love for nature, responsibility & care for animals. If frogs are killed it will
have an adverse effect on the other organisms. The insect population will increase
and the snake population will decrease and the whole ecosystem will be
disturbed.
5)
Egrets are often seen along with grazing cattle. How do you refer to this
interaction.Kalpana was a keen bird watcher.She explained this interaction to her
classmates. What values were shown by Kalpana.
A)
The egrets always forage
close to where the cattle are grazing close because the cattle as they move stir up
and flush out insects from vegetation otherwise might be difficult for egrets to
find and catch.In this interaction egrets are benefitted .
Values interest towards nature and ecosystem interactions.
UNIT X
CHAPTER 15
BIODIVERSITY AND CONSERVATION
IMPORTANT TERMS AND DEFINITIONS
Biodiversity : Term used to describe diversity at all levels of biologicalorganisation. Term
coined by socio-biologist Edward Wilson and was also used by Walter G Rosen for the
diversity of life forms. Biodiversity refers to totality of genes in species and ecosytems of a
region.
Three inter-related levels of Biodiversity : Genetic diversity, Speciesdiversity,
Ecological diversity.
вќ‘ Genetic diversity : Diversity in the number and types of genes, as wellas chromosomes
present in different species and the variations in the genes and their alleles in the same
species. It helps in speciation.
вќ‘ Species diversity : Varieties in the number and richness of the speciesof a region.
вќ‘ Ecological diversity : Variety in the types of ecosystems.
IUCN : International Union for Conservation of Nature and Natural Resources.It is
situated in Morges, Switzerland.
India has : More than 50,000 genetically different varieties of rice; 1000varieties of
mango;
вќ‘ India has 1,42,000 known species of plants and animals (Around 45,000 species of
plants and rest of animals);
вќ‘ India has 8.1% of share of global biodiversity.
вќ‘ India is one of 12 Mega diversity countries of the world.
Latitudinal Gradients
вќ‘ In general, species diversity decreases as we move away from the equator towards the
poles.
вќ‘ With very few exceptions, tropics (latitudinal range of 23.5ВўX N to 23.5ВўXS) harbour
more species than temperate or polar areas.
(vii) Colombia located near the equator has nearly 1,4000 species of birds while New
York at 41В°X N has 105 species and Greenland at 71В°X N only 56 species.
(viii) India has more than 1,200 species of birds.
(ix) A forest in a tropical region like Equador has up to 10 times as many species of
vascular plants as a forest of equal area in a temperate region like the Midwest of the
USA.
(x) The largely tropical Amazonian rain forest in South America has the greatest
biodiversity on earth.
Species-Area relationships
German naturalist and geographer Alexander von Humboldt observed that within a
region species richness increased with increasing explored area, but only up to a limit.
The relation between species richness and area for a wide variety of taxa (angiosperm
plants, birds, bats, freshwater fishes) turns out to be a rectangular hyperbola.
On a logarithmic scale, the relationship is a straight line decribed by the
equation
log S = log C + Z log A
Where S = Species richness, A = Area; Z = slope of the line (regression coefficient)
C = Y – intercept.
Value of Z lies in the range of 0.1 to 0.2, regardless of the taxonomic group or the
region.
The species-area relationships among very large areas like the entire continents has
much steeper slope of the line (Z values in the range of 0.6 to 1.2).
Causes of Biodiversity Losses
Habitat loss and fragmentation : This is most important cause of plantsand animals
extinction. For example : Tropical rain forest being destroyed fast. The Amazonian rain
forest is called the ‗lungs of the planet�. It is being cut for cultivating soyabeans.
Over–exploitation : Many species extinctions are due to over exploitationby humans.
eg :- extinction of steller�s cow, passenger pigeon is last 500 years.
Alien Species Invasions : When alien species are introduced some ofthem turn invasive
and cause decline or extinction of indigenous species. eg. :- Carrot grass (Parthenium),
Lantana and water hyacinth (Eichornia) posed threat to native species.
Co-extinctions : When a species becomes extinct, the plant and animalspecies
associated with it in an obligating way also become extinct. eg.:-When a host fish
species becomes extinct, its assemblage of parasites also becomes extinct.
Reasons for Conservation of Biodiversity
пѓ� Narrowly utilitarian : Humans derive countless direct economic benefitfrom nature
food (cereals, pulses, fruits), firewood, fibre, construction material, industrial products
(tannins, lubricants, dyes, resins, perfumes) and products of medicinal importance.
пѓ� Broadly utilitarian : Biodiversity plays a major role in many ecosystemservices that
nature provides.
пѓ� Ethical : every species has an intrinsic value, even if it may not be ofany current
economic value to us. We have a moral duty to care for their well-being and pass on
our biological legacy in good order to future generations.
Types of Conservation Strategies
In-situ conservation : Conservation and protection of the whole ecosystemand its
biodiversity at all levels in order to protect the threatened species. Endangered species
protected in natural conditions.
пѓ� Sacred Groves : Tracts of forest are set aside and all the trees andwildlife within are
venerated and given total protection. E.g., some forest in Khasi and Jaintia hills in
Meghalaya, Aravalli hills of Rajasthan.
пѓ� Hot Spots : Areas with high density of biodiversity or mega diversity. E.g.,Out of 34
hot spots in world, 3 occur in India. i.e., Western Ghats and Sri Lanka, Indo-Burma
(North-East India) and Himalaya.
пѓ� Protected Areas : Ecological or Biogeographical areas where biologicaldiversity with
natural and cultural resources are protected. E.g., National parks, sanctuaries and
Biosphere reserves.
Ex-situ conservation : Conservation and protection of selected rare plantsor animals in
places outside their natural homes.
пѓ� Offsite collections : Live collections of wild and domesticated species inBotanical
gardens, Zoological parks etc.
пѓ�
Gene Banks : Institutes which maintain stock of viable seeds, live growingplants,
tissue culture and frozen germplasm with the whole range of genetic variability.
Cryopreservation : Preservation of seeds, embryos etc. at ВЎV196ВўXC in liquidnitrogen.
Co-extinction : Extinction of a species can cause extinction of plants andspecies associated
with it.
National Parks : Areas reserved for wild life where they are able to obtain allthe required
natural resources and proper habitats. India has 89 national parks at present.
Sanctuaries : Tracts of land with or without lake where animals are protectedfrom all
types of exploitation and habitat disturbance. India has 492 sanctuaries at present.
Biosphere Reserves : Large tracts of protected land with multiple usepreserving the
genetic diversity of the representative ecosystem by protecting wild life, traditional life
styles of the tribals and varied plant and animal genetic resources. India has 14 biosphere
reserves.
Red Data Book : Record of threatened species of plants and animalsmaintained by IUCN.
Important Wild Life Projects in India :
(iii) Project tiger : Started in 1973 to check depletion in population of tiger.Jim Corbett
National Park.
Biodiversity Hotspots : Regions of high endemism and high level of speciesrichness.
Endemic Species : Species which are confined to a particular region and notfound
anywhere else.
Exotic or Alien Species : New species which enter a geographical regions.
Bio prospecting : Exploration of molecular, genetic and species level diversityfor products
of economic importance.
International Efforts for Biodiversity Conservation :
World Conservation Union (formerly IUCN) : provides leadership, common approach
and expertise in the area of conservation.
The Earth Summit : Historical convention on Biological diversity held in 1992 at Rio de
Janerio, Brazil.
The World Summit on Sustainable Development : Held in 2002 in Johannesburg, South
Africa to pledge to reduce biodiversity losses at global and local levels.
QUESTIONS
VSA (1 MARK)
1. Habitat loss and fragmentation has caused severe damage to a particular type of
ecosystem. Name it.
2. What trend is observed in respect of species diversity when we move from equator to
poles?
3. Which region is considered as the one with highest biodiversity on earth? What is the
name given to such region.forests?
4. Ecologists have discovered that value of ВЎВҐZВЎВ¦ lies in range of 0.1 to 0.2 regardless of
taxonomic group or region. When will the slope of line steeper in species area
relationship?
5. Define cryopreservation. Why is it useful in conserving biodiversity?
6. What is the reason
Rauwolfiavomitoria?
for
genetic
variation
shown
by
medicinal
plant
7. How many species of plants and animals have been described by IUCN in 2004? What
is global species diversity according to Robert May?
8. Explain co-extinction with a suitable example.
9. Study the pie-diagram and answer the questions which follows : What do A, B,
C and D represent in these diagrams.
SA-I (3 MARKS)
10.Hot spots are the regions of exceptionally high biodiversity. But they have become
regions of accidental habitat loss too. Name the three hot spots of our country. Why
are they called ‗Hot spot�?
11.
Study the diagram of the earth given below. Give the name of the pattern of
biodiversity therein. Suggest any two reasons for this type of occurance.
12.What is so special about tropics that might account for their greater biological
diversity?
13.Why is the sobriquet ‗The Evil Quartet� used in context of biodiversity? Name the
members of this quartet. Why do we grieve for the genes when a species is lost?
14. Describe at least two approaches each for ex-situ conservation and in situ conservation
as a strategy for biodiversity conservation.
ANSWERS
VSA (1 MARK)
1.Tropical Rain Forest.
2.In general, species diversity decreases as we move away from the equator towards
poles.
3Amazonian rain forests. They are also called the ‗Lungs of the planet�.
4.Slope of line is much steeper if one analyses the speciesВЎVarea relationship among
very large areas like entire continents.
5Preserving a material in liquid nitrogen at – 196°C. It can be done to preserve
threatened species in viable and fertile condition for long period.
6.Genetic variation might be in terms of potency and concentration of the active
chemical reserpine produced by plant.
7.IUCN (2004) has described slightly more than 1.5 million species of plants and
animals.
According to Robert MayВЎВ¦s estimates the global species diversity is about 7 million.
8.Coextinction refers to the disappearance of species with extinction of another species
of plant or animal with which it was associated in an obligatory way. e.g., Plantpollinator mutualism.
9.
A
Insects
C
Fungi
SA-I (3 MARKS)
10. Westerm Ghats and Sri lanka; Indo-Burma; Himalaya called ВЎВҐbiodiversity hot spotsВЎВ¦
as they show
(i) High level of species richness
(ii) High degree of endemism
11. Latitudinal gradients
(i) More solar energy available in tropics, more productivity.
(ii) Tropical environments are less seasonal, so more predictable.
12a) Speciation is a function of time, unlike temperate regions subjected to frequent
glaciations in the past, tropical latitude have remained relatively undisturbed for million
of years and thus had long evolutionary time for species diversification
b) Tropical environment are less seasonal, more constant and predictable
c) More solar energy awailable in the tropics contributing to high productivity leading
to greater diversity.
LA (5 MARKS)
13. The ‗Evil Quartet� is used as a sobriquet to refer to the cause of loss of biodiversity :
(i) Habitat loss and fragmentation : When large habitats are brokenup into smaller
fragments due to various human activities, the animals requiring large territories
(elephants, birds etc.) are badly affected and their populations decline.
(ii) Over-exploitation : When need of a resource becomes greed. e.g.,over
exploitation of passenger pigeon led to its extinction. Also marine fish is at brink of
being endangered due to over exploitations.
(iii) Alien species invasion : Intentional or non-Intentional introductionof a species to a
nearby area may disturb the harmony of existing species. e.g., Eichhornia after
introduction posed a big threat to the native species.
(iv) Co-extinction : Extinction of one species invariably leads to extinctionof another
when they are associated with each other in an obligatory way. e.g., when host
species is extinct, obligate parasites dependent on it also die.
(v) We grieve for the loss of genes, because the wild forms are hardy and more
resistant to pathogen attack and can be beneficial in crop breeding programmes.
14. In situ conservation :
(i) Identification and maximum protection of ‗hot spots�
(ii) Legal protection to ecologically rich areas.
(iii) Biosphere reserves, national parks and sanctuaries
(iv) Sacred groves.
Ex situ Conservation :
(i) Creation of zoological parks, botanical garden, wild life sanctuary
(ii) Cryopreservation
(iii) Seed bank.
HIGHER ORDER THINKING SKILLS
1) Hot spots are the regions of very high level of species richness .Explain.
A) Hot spots are the richest & most threatened reservoirs of plant & animal life on
earth. Hot spots concept was developed by N.Meyers to designate priority area in
situ conservation. The two criteria used for determining a hot spot – 1. Number of
endemic species.2. Degree of threat measured in terms of habitat loss. Two hot
spots – Western ghats, Eastern Himalayas.
2) Alien species invasion is posing threat to our native species .Describe taking 3
examples.
A) I, Invasion of carrot grass.
II, Nile perch introduced into lake Victoria, caused extinction of 200 sps. Of
Cichlid species.
III, Introduction of water hyacinth.
3) What are the major zones of biosphere reserve.
A) Total 425 biosphere reserves in the world.
I, Core zone – No humanity.
II, Buffer zone – limited activity.
III, Transition zone – Controlled human activity.
Wild populations, tribals domesticated plants & animals, genetic resources are
protected.
4) What are the different type of extinction?
A) I, Natural extinction –change in environmental conditions, species disappear.
II, Mass extinction – due to catastrophes, large number of species extinct.
III, Anthropogenic - due to human activities , organisms become extinct.
5) What is ‗rivet popper hypothesis�? Who gave it? What is the effect of loss of riverts
?
A) ‗Rivet popper hypothesis� compares rivets in the airplane with that of the species
in the ecosystem.
It was given by Paul Ehrlich. As the rivets of the plane are remove gradually will
effect the flight safety , same way when the species become gradually extinct , it
will affect ecosystem functioning . Also depending on which key species are
removed.
VALUE BASED QUESTIONS
1) A snake charmer came to house and smelled the presence of cobra which the
residents have never seen in the last 10 years . The landlord agreed to allow the
charmer to search, catch and take away the snake with him. Little jazzman
disagreed and drove the man away.
a) Did jazzman do the right thing?
b) What values did he show?
c) What is importance of snake in nature?
A) a) Scientific attitude
b) Obligation to maintain biodiversity in nature.
c) Important member in a food chain as well as food web in terrestrial ecosystem
as a carnivore.
2) In Orissa farmers put electric wires around the sugarcane field to protect it from
Elephants . How far is this practice good ? Give your views?
A) This practice is not at all good as just for personal interest we are killing animals
.each organisms has an intrinsic value, it may not be of any current economic
value to us. We have a moral duty to care for their well being. Some other methods
can be used to drive them out as loud sounds etc.
Q3) A lady was travelling to India from Malaysia. She was stopped by a quarantine
officer in the
Airport as she was carrying a plant with beautiful flowers from Malaysia. The
person did not allow to her to take the plant to India.
A) Was the quarantine officer right in stopping her from carrying the plant? What
type of responsibility was shown by him?
B) Why an exotic plant should not be brought?
A) The quarantine officer was very right in prohibiting the lady from getting the plant
. He showed his responsibility towards the nature ,society as well as his country.
An exotic plant need not to be brought without quarantine , as the plant may be a
threat to native species. Also if it may propagate fast as it will not be having any
natural predators.
Q4. A sacred grove is located at Aravilli hills of Rajasthan . How is this important
to mankind ?
What type of responsibility is shown by these people?
A) Sacred groves are certain areas in the world which have been protected by the
people inhabiting those areas , as tribal etc. These groves are regions of large
number of rare &threatened organisms , which are getting protected by these
people. They have responsibility & love & respect for nature.
Q5) Shyam who was passing by a street on his cycle stopped to see the gathering in
front of a
house . He got annoyed to see the children throwing stones at a snake on a tree moving up
&
down . Immediately he stopped the children from throwing stones& called the snake
helpline number.
A) Did Shyam do the right thing?
B) What values did he show?
C) What do the persons working with snake helpline do? Which organization works
for animals?
Ans) A, Yes , he did the right thing by showing concern for the animal .
B, He showed scientific attitude , love & concern for nature & biodiversity.
The persons working with snake helpline come to the spot & catch the snake
live& leave them in their natural habitat.The organization is people for animals.
UNIT X
CHAPTER16
ENVIRONMENTAL ISSUES
IMPORTANT TERMS AND DEFINITIONS
Pollution : Undesirable physical/chemical/biological characteristics of air/water/land
which cause damage to the animals/plants/humans and architectural structures.
Pollutants : Agents which cause pollution.
Slash and Burn Agriculture (Jhum Cultivation) : Farmers cut down treesand burn the
plant remains. Ash is used as a fertiliser and the land is then used for farming or cattle
grazing.
Reforestation : Process of restoring a forest that was removed at some pointof time in the
past.
Effluents : Something flowing over a large body of water (may be sewage orindustrial
effluents).
CPCB : Central Pollution Control Board BOD :
Biological Oxygen Demand CNG : Compressed Natural
Gas FOAM : Friends of Arcata Marsh
JFM : Joint Forest Management.
Biochemical Oxygen Demand (BOD)
вќ‘ BOD refer to the amount of oxygen that would be consumed if all the organic matter is
one litre of water were oxidized by bacteria. The BOD test measures the rate of uptake
of oxygen by micro-organisms in a sample of water.
вќ‘ Indirectly BOD is a measure of the organic matter present in the water. The greater the
BOD of waste water, more is its polluting potential.
вќ‘
In the given figure the effect of sewage on some imporant characteristic of a river is
Algal Bloom : Presence of large amounts of nutrients in water causesexcessive growth of
algae, called an algal bloom.
Harmful effect of algal bloom are :
вќ‘ Fish mortality
вќ‘ Deterioration of water quality
вќ‘ Toxic to animals and human beings.
Biomagnification
вќ‘ It refers to increase in concentration of toxic substances at successive trophic levels.
вќ‘ Biomagnification of DDT in an aquatic food chain
Harmful Effect : High concentration of DDT disturbs calcium metabolism inbirds, which
causes thinning of egg shell and their premature breaking, causing decline in birds
population.
Eutrophication : It the process of nutrient enrichment of water and subsequentloss of
species diversity like fishes. Excess nutrients causes algal bloom which may cover the
whole surface of water body and release toxins. It causes oxygen deficiency in water that
leads to the death of aquatic animals like fishes.
Global Warming : Increase in the level of greenhouse gases is mainlyresponsible for
global warming. (Increase in mean global temperature due to trapping of infrared
radiation). Carbon dioxide, Methane, CFCs, N2O are the
main gases that causes greenhouse effect.
Harmful effects of global warming :
(xi) Melting of glaciers
(xii) Over many years, this will result in a rise in sea level that can flood the coastal
plains.
Measures of Control Global Warming
12. Minimise the use of fossil fuel.
13. Improving efficiency of energy usage.
14. Reducing deforestration.
15. Planting trees.
Ozone Depletion :
25. Ozone gas is continuously formed by the action of UV-rays on molecular oxygen and
also degraded into molecular oxygen in stratosphere.
26. The thickness of the ozone-layer in a column of air from the ground to the top of the
atmosphere is measured in tems of Dobson units (DU).
27. Ozone layer absorbs the harmful UV-rays. These rays cause the skin cancer, damages
genes, causes inflammation of cornea.
28. Chlorofluro Carbons deplete the ozone layer. The part of atmosphere with lesser
concentration of ozone is called ozone hole.
Steps leading to ozone depletion
28. UV-rays split CFCs and release atomic chlorine (Cl)
29. UV-rays also split ozone into oxygen.
30. Chlorine atoms trap oxygen atoms and ozone is not formed again from oxygen. This
leads to depletion of ozone in the stratosphere.
e Hole : Large area of thinned ozone layer over Antartica.
Control of Vehicular Air Pollution in Delhi : All the buses of Delhi wereconverted to run
on CNG by the end of the 2002. Other steps to reduce air pollution in Delhi include.
пѓ� Phasing out of old vehicles.
пѓ� Use of unleaded petrol and low sulphur petrol and diesel.
пѓ� Use of catalytic converters in vehicles.
пѓ� Application of Euro-IV norms for vehicles from April, 1, 2010.
Auto Fuel Policy : The Government of India has laid out a road map to cutdown the
vehicular air pollution in many cities of India. The goal of this policy is to reduce Sulphur
to 50 ppm in petrol and diesel and reduce levels of aromatic hydrocarbons to 35% of the
fuel. The Bharat Stage II will be applicable to all automobiles in all cities April, 1, 2005.
The cities (like Delhi, Mumbai, Chennai, Kolkata etc.) will have to meet Euro III emission
norms from April 1, 2005 and Euro IV Emission norms from April 1, 2010.
QUESTIONS
VSA (1 MARK)
21. Why should the velocity of air between the plates of an electrostatic precipitator be
low?
22. PM2.5 is responsible for causing greatest harm to human health. What is it? How is it
harmful?
23. What is the noise level that can cause permanent impairment of hearing ability of
human beings?
24. Why was the Montreal Protocol signed?
25. Jhum cultivation has been in practice from earlier days, but its considered more
problematic these days. Why?
26. A radiation causes ageing of skin, skin cancer, and inflamation of cornea called snow
blindness. It also damages DNA. Name the radiation.
SA-II (2 MARKS)
пѓ� Landfills are not much a solution for getting rid of solid wastes. Why?
пѓ� Electrostatic precipitator can remove over 99% particulate matter present in exhaust
from a thermal power plant. How?
пѓ� Why is a scrubber used? Which spray is used on exhaust gases passing through a
scrubber?
пѓ� There is a sharp decline in dissolved oxygen downstream from the point of sewage
discharge. Why? What are its adverse effects?
пѓ� Catalytic converters use expensive metals as catalysts.
Name the metals generally used.
What precaution should be observed while using catalytic converter.
пѓ� What are e-wastes? Why are they creating more problem in developing countries in
comparision to developed countries?
пѓ� Water logging and salinity are some of the problems that have come in the wake of
Green revolution. How does water logging create problems of salinity?
пѓ� What is the relationship between BOD, mcro-organisms and amount of bio-degradable
matter?
SA-1 (3 MARKS)
21. Deforestation is creating a lot of problems in the environment. List the consequences of
deforestation.
22. Enlist four harmful effects caused to the humans living in areas having polluted air.
Suggest two measures to reduce air pollution.
23. People have been actively participating in the efforts for the conservation of forests.
Name the award instituted in respect of Amrita Devi to promote such efforts.
Name the movement launched to protect the trees by hugging them.
Name the step Government of India has undertaken in 1980�s to work closely with
the local communities for protecting and managing forests.
LA-(5 MARKS)
18. Pollutant released due to human activities (like effluents from industries and homes)
can radically accelerate the ageing process of the water body.
(a) Explain how does this process occurs during natural ageing of lake.
(b) Give the term used for accelerated ageing of water bodies. Also give the term used
for the natural ageing of lake.
19. In Arcata, the town�s people have created an integrated waste water treatment process
within a natural system. A citizen group called FOAM helps in upkeep of this project.
(a) What are the main steps in waste water management done in this way?
(b) ‗Ecosan� in Kerala and Sri Lanka is also an intiative for water conservation. How?
20. What are the contribution of Ahmed Khan in Bangalore and Ramesh Chandra Dagar in
Sonipat?
ANSWERS
VAS (I MARK)
13. To allow the dust to fall.
14. PM2.5 stands for particulate matter of size 2.5 micrometers or less in diameter. Its
responsible for causing greatest harm to human health as it can be inhaled deep into
lungs and cause breathing problems.
15. 150 dB or more
16. To control emission of ozone depleting substances.
17. Enough time gap is not being given for the natural process of recovery of land from the
effect of cultivation.
18. Ultraviolet B rays (UV-B rays)
SA-II (2 MARKS)
19.
Landfill sites are getting filled very fast due to large amount of garbage generation.
Also underground water resources may get polluted due to seepage of chemicals.
20.
21.
22.
23.
Electrode wire at thousand volts, produce corona to release electrons, electrons
attach to dust particules giving them net negative charge, charged dust particules
attracted/collected by collecting plates which are grounded.
To remove gases like sulphur dioxide. Spray of water or lime is used.
Following discharge of sewage into river, micro organisms involved in
biodegradation of organic matter present in sewage consume more oxygen. This cause
mortality of fish and other aquatic creatures.
(a) Catalysts : platinum - palladium and Rhodium
Motor vehicles equipped with catalytic converters should use unleaded petrol as lead
inactivates the catalysts.
24.
(a) Irrepairable computers and other electronic wastes.
Recycling in developing countries involves manual participation thus exposing
workers to toxic substances. In developed countries its mechanised so less
dangerous.
25.
Water logging draws salt to surface of soil. Salt deposited on land surface as a thin
crust or at the roots of the plants.
26.
Increase in amount of biodegradable matter leads to rapid multiplication of micro
organisms to degrade it, thereby increasing BOD level of the water body.
SAI (3 MARKS)
11. вќ‘ Enhanced CO2 concentration in atmosphere
(i) Loss of biodiversity
(ii) Soil erosion
(iii) Desertification
(iv) Disturbed hydrological cycles.
12. Breathing problems, irritation and inflammation, Damage to lungs, Premature death.
(i) Reduce emission from automobile exhaust
(ii) Growing more trees.
13. (i) Amrita Devi Bishnoi Wildlife Protection Award.
14. Chipko movement
15. Joint Forest Management (JFM).
7. (a) The phenomeon is eutrophication. More nutrients in water, aquatic life increases
organic remains deposited on lake bottom, lake grows shallower and warmer,
gradually transforms into land due to deposition of silt and organic debris.
Cultural or Accelerated eutrophication Natural ageing is
Eutrophication.
8. (a) Conventional sedimentation, filtering and chlorine treatment. Absorption and
assimilation of pollutants by algae fungi and bacteria.
‗Ecosan� derived from ecological sanitation. Handling human excreta using dry
composting toilets. Its practical, hygienic and cost effective method.
9. Refer page No. 279-280, ncert Text of Biology Class XII (the benefits of polyblend and
organic farming.)
ENVIRONMENTAL ISSUES
1) Suppose if sewage water is disposed off in the river. Show its effect on BOD and
dissolved oxygen.
A) Its BOD increases and Dissolved oxygen reduces as microbes consume oxygen
during their metabolism.
2) Domestic sewage contains certain substances which are difficult to remove. Name
any four of them.
A) Non – biodegradable wastes like nitrates, ammonia, phosphates, sodium, calcium.
3) What can you conclude about the status of a lake where there is algal bloom ? Name
the sources of this water pollution.
A) Eutrophication due to nutrient enrichment of water . Excessive use of nitrogen
and phosphorus fertilizers.
4) Noise is considered as an air pollutant . Justify your answer.
A) Noise is undesired high level sound which travels through air in the form of
waves and causes psychological disorders.
5) What are the practices or events done in integrated organic farming?
A) Agriculture , composting , dairy management , beekeeping, water harvesting.
HIGHER ORDER THINKING SKILLS
1) Now –a-days CDs and DVDs are common for storing of information , music ,
movies . It creates a lot of pollution. Name the type of waste created by it. How
does it affect the people ?What will you do to control it? Which values would be
shown here?
A) –e-waste .Toxic wastes and chemicals affect the people manually recycling of ewaste in environment friendly way. Concern about people and environment
awareness.
2) Amit and Anitha are partners and established a factory . After a few months
electrostatic precipitator became out of order. Amit wanted to replace it but
Anitha expressed the view that they have no effect of it on productivity as well as
income; therefore they should not waste money to replace it.
a) Out of these partners whom do you support and why?
b) Suggest any two measures to stop such negligence.
A) Amit because he is concerned about environment and people�s health. Strict
vigilance by Govt.authorities should impose heavy fine, if pollution control
measuresare not followed by factories.
3) A cow died because it had consumed polythene while eating garbage and the
intestine blasted .You go to market and see all shopkeepers giving polythene .You
as a responsible citizen of India what will you suggest to the shopkeeper ? What
will you do yourself?
A) To shopkeeper - either stop keeping polythene bags or given after charging a
big amount . I will create awareness among people about non – biodegradable,
highly toxic polythenes.
4) Ganga action plan was started to clean Holy River Ganges and suggest two ways
by which we can control further pollution in the Ganges?
A) Holy , perennial river flowing through of our country , necessary for
irrigation,source of drinking water .
Stoppage of sewage water disposal in Ganga ,dumping of industrial wastes,
burning of dead bodies .
5) Soma is displeased to see a lot of water hyacinth covering the pond near her home.
Foul smell spreading everywhere which is troubling the people in society . She
plans to remove the weed during vacations. How will she convince her to join her
in this campaign? Which values is she exhibiting? What are the ill effects of water
hyacinth on aquatic life?
A) Water hyacinth growth is due to eutrophication . (Mineral enrichment of a pond
leading to aging process) . This stops DO for aquatic life killing aquatic
organisms which when decompose in reduce O2 atmosphere produce foul
smell. Removal of this weed will keep the aquatic life surviving ,foul smell
stops coming ,pond watercan be used and will have aesthetic value also.
Concern about environment , awareness , critical thinking ,leadership.
MODEL QUESTION PAPERS
KENDRIYA VIDYALAYA SANGATHAN
BHUBANESWAR REGION
CLASS:XII
M.M:70M
SUB: BIOLOGY
TIME:3 HRS.
GeneralInstructions:
(i) Allquestionsarecompulsory.
(ii) ThisquestionpaperconsistsoffourSectionsA,B,
CandD.SectionA
contains8
questionsofonemarkeach,SectionBisof10questionsoftwomarkseach,Section
Cisof9questionsofthreemarkseachandSectionDisof3questionsoffivemarks each.
(iii) There is no overall choice. However, an internal choice has been provided in one
question of 2 marks, one question of 3 marks and two questions of 5 marks
weightage.Astudenthastoattemptonlyoneofthealternativesinsuchquestions.
(iv) Wherever necessary,thediagrams drawn should be neat and properly
labelled.
SECTION A
Q1. Which of the following represents female heterogametic condition?
XO, XY, XX, ZW.
Q2. After successful in-vitro fertilization the fertilized egg begins to divide. Where is this egg
transferred before it reaches the 8 celled stage and what is the technique named?
Q3. A multinational company outside India tried to sell new varieties of turmeric without
proper
patent rights. What is such an act referred to?
Q4. A person is bitten by a dog and transferred to a hospital and given an anti-rabies vaccine
by
the doctor. What type of immunity is it?
Q5. Why should only unleaded petrol be used in automobiles fitted with catalytic converter?
Q6. Why the crystals of bt toxin produced by some bacteria do not kill the bacteria
themselves?
Q7. Identify (a) and (b) in the pie chart given below.
Q8. Name the compound used for staining of isolated DNA in the gel electrophoresis and
mention how to separate DNA from the gel medium?
SECTION B
Q9. Identify A, B, C, D in the following table:
Crop
Variety
Wheat
A
Cow pea
Pusa komal
Pusa sadabahar
C
Brassica
Pusa gaurav
Resistant to disease
Leaf and stripe rust
B
TMV and Leaf curl
D
OR
What is LAB? Mention any two functions performed by them in our body.
Q10. Explain why children eating golden rice are unlikely to suffer from ‗night blindness�?
Q11. Name the following:
(i)A fine powder of recycled modified plastic which is used for road laying.
(ii)The system of human waste disposal with a proper recycling of waste, working in many
areas of Sri Lanka and Kerala.
(iii)Irreparable computer and electronic goods.
(iv)The unit measuring thickness of ozone.
Q12. (i) A short length of a DNA molecule contains 120 Adenine and 120 Cytosine bases.
What
is the total number of nucleotides in that DNA fragment.
(ii)A DNA contains 20000 base pairs. How many nucleotides would be present in it?
Q13.How do Darwin�s finches illustrate adaptive radiation ?
Q14. State the location and function of the following cells
(a) Serotoli cells
(b) Leydig cells
Q15. I) Differentiate between GPP and NPP.
II) Give two examples of inverted pyramid in an ecosystem.
Q16. A woman with blood group ―O‖ married a man with blood group ‗AB�. Show the
possible
blood groups of the progeny. List the alleles in this inheritance.
Q17. I) Why do bacteria produce Restriction enzyme ?
II) Why is the DNA of microorganism not degraded by the Restriction enzyme it
produces ?
Q18. How do seals adapt to their natural habitat? Explain.
SECTION C
Q19. A) Name the scientist who conducted simulation experiment as shown in the figure.
A) Name the mixture of inorganic substances used in spark discharge container.
B) What was the purpose of the experiment and name the compounds synthesized in
this experiment.
Q20. Answer the following questions based on Meselson and Stahl�s experiment.
I) Write the name of the chemical substance used as a source of nitrogen in the experiment
by them?
II) Why dis the scientists synthesize the light and the heavy DNA molecules in the
organism used in the experiment ?
III) How did the scientists make it possible to distinguish the heavy DNA molecule from
the light DNA molecule? Explain.
Q21. Give technical term for the following.
a. Preventing m-RNA translation in a cell.
b. Method of controlling ADA deficiency.
c. Two strands of DNA reading the same nucleotide sequence.
d. An organism carrying a foreign gene in its cell.
e. Technique used to introduce alien DNA into cell by the help of Tungsten micro particle.
f. A procedure through which a piece of DNA is introduced in a host bacterium to change
the characteristics of later.
Q22. a. What is contact inhibition and metastasis?
b. Name a physical , chemical and biological carcinogen.
c. Name the chemical used in immunotherapy of a cancer patient.
Q23. Draw a diagram of male gametophyte of angiosperm. Label any four parts. Why
sporopollenin is considered the most resistant organic material ?
Q24.
A graph of species – area relation is given above.
a. Give the equation for the curve (I) and (II)
b. Who proposed the concept?
c. What is the usual Z Value ?
OR
Name the type of interaction seen in each of the following examples.
a. Ascaris worms living in the intestine of humans.
b. Wasp pollinating fig inflorescence
c. Clown fish living among the tentacles of sea anemone.
d. Mychorrhizae living on the roots of higher tree.
e. Orchid growing on a branch of mango tree.
f. Disappearance of smaller barnacles when balanus dominated in the coast of Scotland.
Q25. DDT content in the water of a lake that supplies drinking water to the nearby villages, is
found to be 0.003 ppm. The kingfishers is that area were reported to have 2 ppm of DDt.
Why the concentration increased in these birds ? What harm will this cause to the bird
population. Name the phenomena.
Q26. Explain the role of baculoviruses as biological control agents. Mention their importance
in organic farming.
Q27.
Study the graph given above.Showing the levels of ovarian hormones during menstruation
and
correlate the uterine events that take place according to the hormonal levels.
2. 6-15 days
2. 16-25 days
3. 26-28 days ( if the ovum is not fertilized)
SECTION D
Q28. What does the LAC- Operon consist of ? How is the operator gene turned off and on in
the expression of genes in the operon ? Explain.
OR
Explain the pattern of inheritance of colour blindness in humans. Why the possibility of a
human female becoming a colour blind extremely rare ?
Q29. A. Draw the embryo sac of a flowering plant and label.
i.Central cell
ii. Chalazal end of the embryo sac
iii. Synergids
B. Name the cell that develops in to the embryo sac and explain how this cell leads to the
formation of Embryo sac. Also mention the role played by various cells of the embryo
sac.
OR
Show diagrammatically the stages of embryonic development from zygote upto
implantation in humans.
Q30. Three friends Mani, Adil and Ronney met at a marriage party,. Mani and Ronney wanted
to drink and compelled Adil who has never had a drink before. Adil is in dilemma. On
the
one hand he does not want to lose his friendship but on the other hand he is conscious
that nobody in his family drinks.
a. What would you have done if you were in place of Adil ?
b. Write 2 harmful effects of alcohol on health.
c. How can one prevent and control alcohol addiction.
*************
MARKING SCHEME
XII BIOLOGY
Q No
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
Value points
ZW
Fallopian tube , ZIFT
Biopiracy
Passive immunity
Lead will inactivate the catalyst
Toxin is inactive
a) Birds
b) Amphibians
Ethidium bromide, elution
A. Himgiri B. Bacterial blight C. Chilli D. White rust
OR
LAB- lactic acid bacteria-checking the disease causing
microbes & increasing Vitamin B12
Golden rice is genetically engineered, Vitamin a rich
variety of rice, lack of vitamin a causes night blindness
i)Polyblend ii) Ecoscan iii) e-waste iv) Dobson unit
i) 480 ii) 40,000
Explanation
Serotoli cell- inside the seminiferous tubule, nourishment
of sperm
Leydig cell- interstitial space in between seminiferous
tubule- androgen secretion
GPP- Gross primary product- rate of production of organic
matter during photosynthesis.
GPP- respiratory loss= NPP (net primary product)
Aquatic habitat the pyramid of biomass
Tree ecosystem (any two correct answer)
Possible groups A,B
Alleles- IA, IB and I Draw punnet square
Restrict the propagation of any foreign DNA in a
Marks
1
ВЅ + ВЅ =1
1
1
1
1
ВЅ + ВЅ =1
ВЅ + ВЅ =1
ВЅ x4=2
1+ВЅ+ВЅ=2
1+1=2
ВЅ x4=2
1x 2= 2
2
1+1=2
ВЅ x4=2
1+1=2
1+1=2
18
19
20
21
22
23
24
25
bacterium by recognizing and cutting it at specific DNA
sequence
By adding methyl group to one or two bases within the
sequence recognized by RE/restriction- modification
system
By developing a thick layer of fat (blubber) below their
skin that acts as an insulator and reduce excess heat
a. Miller and Urey
b. CH 4, NH3, H2O, H2
c. To prove the chemical evolution of life
d. Amino acids
a. NH4Cl
b. To check if DNA replication was semi conservative
c. The heavy and light DNA molecule are
distinguished by centrifugation in a Cesium chloride
density gradient
a. RNA-i
b. Gene therapy
c. Palindrone
d. Transgenic
e. Gene-gun (biolistic)
f. Transformation
i)Contact inhibition- inhibition of cell division through cell
contact
Metastatis- cancerous cell migrating from its primary
source different body parts
ii) Physical-x-ray/UV ray (any one)
Chemical- nicotine
Biological- viral oncogene
iii) a interferon
Correct diagram with four parts labeling
Can withstand high temperature and strong acids and
alkalis. Also it cannot be degraded by any enzyme
i)S=CAZ
ii) Log S= Log C+Z Log A
iii) Alexander Van Humboldt
iv) 0.1 to 0.2
OR
i) Parasitism ii) mutualism iii) Commensalism
iv) Mutualism v) Commensalism vi) Competition
DDT being toxic gets accumulated in organism and passes
2
1
1
ВЅ
ВЅ
1x 3=3
ВЅ x6=3
ВЅ
ВЅ
ВЅ
ВЅ
ВЅ
ВЅ
ВЅ x4=2
1
1
1
ВЅ
ВЅ
ВЅ x6=3
ВЅ
26
27
28
29
to next higher trophic level because it cannot be
metabolized or excreted
ВЅ
DDT concentrated in higher trophic level, i.e bird
Disturbs calcium metabolism- > thinning of egg shell>premature breaking-> decrease in bird population
Bio magnification
Pathogens that attack insects and other anthropods
Genus Nucleopolyhedrovirus used
1.5
Species specific and do not show negative impact on
plants and non- target insects
To conserve beneficial insects and kills harmful ones
i.)Regeneration of endometrium
ii).Uterus gets highly vascularised ready for embryo
implantation
iii) Disintegration of endometrium leading to
menstruation
Lac operonRegulator gene
Promotor gene
Operator gene
Structural gene
Explanation ‗ON�
Explanation ‗OFF�
1
OR
Colour blindness are X chromosome linked recessive
disorder. Males have only one copy of X chromosome
without corresponding alleles in Y chromosomes.
Presence of single defective X chromosome results in
disorder.
Women can develop this disorder if both the defective
copies of X chromosome, which is rare.
a. Diagram NCERT text book Fig 2.79d) and correct
labeling
b. Functional megaspore mother cell
c. Detailed explanation
d. Egg cell--- forms zygote & future embryo
e. Polar nuclei--- form PEN and provide nourishment
to the embryo
ВЅ
ВЅ
ВЅ
1
1x 3=3
ВЅ x4=2
1.5
1.5
3+2=5
ВЅ x3=1.5
ВЅ
1.5
ВЅ
ВЅ
ВЅ
f. Antipodals--- degenerate
OR
Ref. NCERT text book fig 3.11
Fallopian tube, zygote undergoes change to form
blastomeres and develop 8-16 cell stage the morula, then
blastocyst- implantation
I will deny in having drink in an assertive way to maintain
the friendship. Any 2 harmful effects;
a. Affects nervous system
b. Peptic ulcer
c. Hepatitis
Prevention and control
a. Avoid undue peer pressure
b. Seeking help from parents/ (any other correct two
points)
30
S.NO.
Type of
question в†’
Units↓
1
Sexual
reproduction
Genetics &
Evolution
Biology &
Human
welfare
Biotechnology
& its
Applications
Ecology &
Environment
Total
2
3.
4.
5.
BIOLOGY (THEORY)
CLASS –XII
Blue Print
Class (XII)
VSA
SA-II
SA-I
(1
(2
(3
mark) marks)
marks)
4+1=5
1
1 x 2=2
1 x 2=2
LA
(5
marks)
Total
2 (2)
4(2)
6(2)
-
12(6)
2(2)
4(2)
9(3)
5(1)
20(8)
1(1)
2(1)
9(3)
-
12(5)
2(2)
2(1)
3(1)
5(1)
12(5)
1(1)
8(4)
-
5(1)
14(6)
8(8)
20(10)
27(9)
15(3)
70(30)
QUESTION PAPER
BIOLOGY (THEORY)
CLASS –XII
TIME -3 HRS
MAX MARKS -70
General Instructions :
All the questions are compulsory :
1. The question paper consists of four sections A, B, C and D. Section –A
contains 8 questions of 1 mark each, section-B is of 10 questions of 2
marks each, section-C has 9 questions of 3 marks each whereas
section-D is of 3 questions of 5 marks each.
2.There is no overall choice. However an internal choice has been
provided in one question of 2 marks, in one question of 3 marks and in
all the three questions of 5 marks weightage. A student has to attempt
only one of the alternatives in such questions.
3. Wherever necessary the diagram drawn should be neat & properly
labeled.
SECTION-A
1What is the importance of flowering pattern of Strobilanthus kunthiana?1
2. Mention any two probable reasons for rapid rise of population in our
country from about 350 million at the time of independence to about
billion by the year 2000.
1
3. The gene ‗I� that controls the ABO blood grouping in human being has
three alleles IA, IB & I.
(a) How many genotypes are likely to be present in human population?
(b) How many phenotypes are possibly present?
ВЅ+ВЅ
4. State any two reasons to explain why RNA virus mutates and evolves
faster than other viruses?
1
5. Name the test used for diagnosing Typhoid fever
1
6. What would be the impact on the environment around a thermal power
plant, if its electrostatic precipitator stops functioning?
1
7. Why is thermoregulation more effectively achieved in larger animals than
in smaller ones?
1
8. A plasmid and a DNA sequence in a cell need to be cut for producing
recombinant DNA. Name the enzymes which act as molecular scissors
in genetic engineering.
1
SECTION-B
9. Even though each pollen grain has two male gametes, why are at least
ten pollen grains and not five pollen grains required to fertilize ten
ovules present in a particular carpel.
2.
10. When a red flowered Antirrhinumplant was crossed with a white
flowered Antirrhinumplant, the F1-offspring had pink flowers. Mention
(a) the genotype of F1 plant and
(b) the reason why it did not bear the parental red or white coloured
flowers?
1+1
11. Draw schematically a single polynucleotide strand. Provide labels and
directions.
OR
2
Choose and arrange any four of the following groups of plants in an
ascending evolutionary scale
Cycads; Gnetales; Monocotyledons; Rhynia like plant; Cholorophyta
ancestors; Dicotyledons and seed ferns.
12. Fill in the blanks a, b, c, d in the different columns of the table
given below
2
Disease
Causal organism
Amoebiasis
Entamoeba
histolytica
b
Trichophyton
Mode
of Symptoms
Transmission
a
Abdominal pain and cramps ,
stools with excess mucous and
blood clots, constipation
Using towel of Dry,scaly,lesion on skin
infected person
Affect nose, sore throat
c
Common cold
Ascaris
Ascariasis
Droplets from
sneezing
of
infected person
Through
contaminated
water,
vegetables and
fruits
d
13. In which part of the body of the hosts do the following events in the life
cycles of Plasmodium takes place (Name body part and host both)
(a) Fertilization
(b) Development of gametocytes
(c) Release of sporozoites
(d) Asexual reproduction
2
14. A person injured in a road accident and requiring an urgent immune
response was brought to a doctor.
2
(a) What did the doctor immediately do?
(b) What kind of immunity was he providing to the patient?
15. Why does a beekeeper keep beehives in crop fields during flowering
season?
2.
16. List any four advantages of genetically modified crop plants over their
Wild/domesticated relatives.
2
17. As the sewage is discharged in the water body, there is a sharp decline in DO but
exponential increase in BOD as depicted in the graph. Study the graph carefully and fill in the
gaps A-D.
2
18. The figure given below shows relative contributions of various
greenhouse gases to the global warming.
2
(i) Name the gas (a) and (b)
(ii) Explain how increase in green house gases in earths atmosphere lead to melting of ice
caps.
SECTION-C
19. Explain why ecological succession will be faster in a forest devastated by
fire than on a bare rock? Also compare succession in case of abandoned
land after floods with that on bare rock.
3
20. What is the cause of adenosine deaminase deficiency in a person? Why
is it that even after infusion of genetically modifiedlymphocytes into
the patient suffering from deaminase deficiency, the cure is not
permanent.
3.
21. A policeman finds a very small piece of blood tissue from the site of
crime and takes it to the forensic department.
(a) By which technique will they amplify DNA collected from the tissue
sample?
(b) Mention in a sequence, the three steps involved in each cycle of this
technique?
(c) What is the role of thermostable DNA polymerase in this technique?
3
22. In case of Bt Cotton, how does the toxic insecticide protein provided by
the bacterium kill the insect pest but not the cell of Bacillus
thuringenesiswhere the toxic protein is generated?
3
23.You have been deputed by your school Principal to train local villagers in
the use of biogas plant. With the help of labeled sketch explain various
parts of the biogas plant.
3
24. Study the figures (a) and (b) given below and answer the questions:
a).
b).
(i)
(ii)
(iii)
Under the influence of which type of natural selection would graph (a) becomes like
graph (b)
What could be the likely reasons of new variations arising in the population?
Who suggested natural selection as a mechanism of evolution?
3
OR
Illustrate schematically the process of initiation, elongation and
translation during transcription of a gene in a bacterium.
25. How did Louis Pasteur successfully demolish the popular theory of
spontaneous generation? What were his conclusions?
3
26. If a true breeding homozygous pea plant with green pod and axial flower
as dominant characters is crossed with a recessive homozygous pea
plant with yellow seeds and terminal flower, then what would be(a) Genotype of the two parents?
(b) Phenotype and genotype of the F1 offspring?
(c) Phenotypic ratio in F2 generation?
3
27. Describe the fate of two released male gametes into the cytoplasm of the synergid and
also name the unique phenomenon in the embryo sac of the angiosperms.
3
SECTION-D
28. (a) Draw a longitudinal sectional view of maize grain. Label any four
major parts in it.
(b) In angiosperms, why does endosperm mature first than embryo?
(c). Categorise wheat and castor seeds as monocots or dicots. 3+1+1
OR
(a)When and where does spermatogenesis in human male begin to take
place?
1
(b) With the help of schematic labeled diagram trace the development of
mature spermatozoa in human male.
2
(c) Draw the labeled diagram of human sperm.
2
29. (a) Describe the experiment conducted by Hershey and Chase for
identification of genetic material.
(b) Why is it considered path breaking in the field of molecular biology?
4+1
OR
Look at the above figure depicting lac operon & answer the following questions.
a). What could be the series of events when an inducer is present in the medium in which
Escherichiacoliis growing .
b). Name the inducer.
Q 30: Give an account of energy flow in an ecosystem with help of
diagrammatic representation of different trophic levels.
5
OR
(a) Write an equation for logistic growth where
N=population density at a time ―t‖,
r= intrinsic rate of natural increase and
K= carrying capacity.
1
(b) Draw a graph for a population whose density has reached the
carrying capacity.
2
(c) Why is the logistic growth model considered a more realistic one for
most animal populations?
1
(d) Draw a growth curve where resources are not limiting to growth of
population.
1
CLASS-XII
BIOLOGY (Theory)
MARKING SCHEME
Q.NO.
SOLUTION/VALUE POINT
MARKS
SECTION-A
1.
2.
3.
4.
5.
6.
7.
8.
It flowers once in 12 years
Rapid decline in death rate/rapid decline in MMR/Rapid decline
in IMR/increase in no. of individual in reproductive age (any
two)
(a) 6
(b) 4
RNA being unstable mutates at faster rate/ 2-OH groups
present at each nucleotide make it more reactive(anyone).
Widal test
Air pollution will increase because particulate matter will not be
absorbed
Smaller animals lose body heat much faster while larger
animals lose less body heat
Restriction enzymes /Endonucleases or Exonucleases)
1
ВЅ+ВЅ
ВЅ+ВЅ
1
ВЅ+ВЅ
1
1
ВЅ+ВЅ
SECTION-B
9.
10.
11.
(I) Only one pollen tube enters an ovule so 10 pollen tubes will
be required for 10 ovules.
(ii) Out of two male gametes per pollen tube, one is used in
syngamy and other gamete in triple fusion.
(a) Rr
(b) None of the parental allele for colour is dominant or
recessive showing incomplete dominance.
1+1=2
1+1=2
Single Polynucleotide chain
1+1
12.
a- transmitted through house flies from faeces of infected
persons to water,food and food products and thereby by
contaminating them
13.
14.
15.
16.
17.
18.
b- Ringworm
c- Rhinovirus
d- Internal bleeding/anaemia/muscular pain (any one)
(a) Intestine of mosquito
(b) RBCs of human
(c) Salivary gland of mosquito
(d)Liver cell/ RBCs of human
ВЅx4
ВЅx4
(a) Inject antitoxin/tetanus injection
(b) Passive immunity
1+1
(a) Bees are pollinators of crop plant
(b) Provide better yield of honey for bees.
1+1
(a) More tolerant to abiotic stress
(b) Provide better yields of crop
(c) Reduced post harvest losses
(d) Increased nutritional value of food.
ВЅx4
(a)kills fish (b) disappearance of clean water(c)reappearance of
clean water (d) reappearance of clean water
1+1
(i) (a) N2O (b) CFCs
(ii) Green house gases cause global warming which in turn
causes melting of ice caps.
ВЅx2+1
SECTION-C
19.
20.
21.
(i)Ecological succession requires soil
(ii) Forest destroyed by fire has some soil
(iii) Bare rocks has no soil and takes lot of time before soil can
be formed on bare rocks(any Two)
Even after floods the land mass has plenty of soil and thus
ecological succession will be faster
1x2+1
A disorder caused due to deletion of the gene for enzyme
adenosine deaminase.
Since life span of such genetically engineered lymphocytes is
very short, the patient need repeated introduction of such
lymphocytes into body
1+2
(a) Polymerase Chain Reaction
(b) Denaturation, Annealing and Extension
(c) Thermostable DNA polymerase remains stable at high temp.
1+1+1
22.
Toxin binds to the surface of epithelial cells of the midgut,
creates pores in these cells , causes swelling of cells leading to
lysis of cell.
In bacterium toxin is released in its inactive form and becomes
active when enters into gut.
2+1
23.
Explanation of dung and water chamber, digester and Sludge
chamber and evolution of biogas by the action of methanogens.
24.
(i) When natural selection is disruptional
(ii) Recombination, gene flow, genetic drift, mutation.
(iii) Charles Darwin.
OR
1ВЅ+1ВЅ
1+1+1
1ВЅ+1ВЅ
25.
2+1
Diagram and Explanation of three steps.
26.
27.
Paster’s Two Flask experiment
- Two flasks used were pre-sterilised
- Pre-killed yeast placed in both of them
- One flask was open to air while the other was covered.
- Flask open to air had new life but not the other one.
Life comes from the pre-existing life.
1+1+1
ВЅx6=3
a). GGAA and ggaa
b).GgAa
c). 9:3:3:1
28.
Male gamete + egg cell(n)
(n)
Male gamete + 2 polar nuclei ---(n)
(n)
Section D
a).
2(n)
(3n)
1ВЅ+1ВЅ
1ВЅ+1ВЅ
1
ВЅ+ВЅ
b). As endosperm stores and supplies nutrients for developing
embryo.
c). Wheat – Monocot
Castor – Dicot.
1
OR
a). At puberty ; in seminiferous tubules of testis
b).
2
c).
2
29.
a). Step wise description with diagram
2+2
1
2+3
30.
b). It conclusively proved that the genetic material was DNA
OR
a). Repressor mRNA produces repressor, inducer binds with
repressor ; makes repressor inactive ; operator gene becomes
active; structural genes z,y,a
transcribe mRNA ; LAC – mRNA translates z, y,a genes to give
enzymes ОІ- galactosidase , permease and transacetylase.
b). Lactose acts as inducer.
1+2
1
OR
(a). and (b).
1
c). Because resources are pre-stable so carrying capacity
controls the population causing the growth curve to be flatter at
the end.
d) .
-------------------------------------------------------------------------------------------
BIOLOGY
CLASS XII
TYPES OF OUESTIONS
VSA
SA II
SA I
LA
TOTAL
UNITS
(1
MARK) (2 MARKS)
(3
(5
MARKS) MARKS)
SEXUAL REPRODUCTION
2 (2)
1 (2)
1 (3)
1 (5)
12
GENETICS AND EVOLUTION
2 (2)
2 (4)
3 (9)
1 (5)
20
BIOLOGY AND HUMAN
WELFARE
1 (1)
4 (8)
1 (3)
--
12
BIOTECHNOLOGY AND IT'S
APPLICATIONS
1 (1)
1 (2)
3 (9)
--
12
ECOLOGY AND
ENVIRONMENT
2 (2)
2 (4)
1 (3)
1 (5)
TOTAL
8 (8)
10 (20)
9 (27)
3 (15)
--
14
30 (70)
CLASS: XII
MAXIMUM MARKS:70
TIME:3 Hrs.
GENERAL INSTRUCTIONS:
1. All questions are compulsory.
2. the question paper consists of four sections a, B, C and D. Section A contains 8 question of
1 mark each. Section B is 10 questions of 2 marks each, section c has nine questions of
3 marks each whereas section D is of three questions of 5 marks each.
3. There is no overall choice. However, an internal choice has been provided in one question
of 2 marks, one question of 3 marks and all the three questions of 5 marks weightage. A
student has to attempt only one of the alternatives in such questions.
4. Wherever necessary, the diagrams drawn should be neat and properly labeled.
SECTION – A
1. When a tall pea plant was self pollinated, one-fourth of the progeny were dwarf. Give the
genotype of the parent and dwarf progenies.
2. Define geitonogamy?
3. Mention any two commonly observed symptoms of withdrawl syndrome in a drug addict?
4. Cut pieces of Bryophyllum leaf when put into wet soil produce new plants. Give a reason.
5. Write any two adaptations shown by xerophytes?
6. Mention two applications of gel electrophoresis in biotechnology.
7. Give an example where percentage cover is more meaning measure of the population size.
8. Write the phenotypic and genotypic ratio obtained in the F2 generation in the inheritance of
flower
colour in snapdragon?
SECTION – B
9. How do Cry proteins kill the insect pests? How man has exploited them for his
advantage?
OR
i. How is biotechnology useful in the treatment of emphysema?
ii. Why is thermostable polymerase needed in PCR? Name the organism from which it is
obtained.
10. Arrange the following stages in the primary hydrarch succession in their proper natural
sequence in which they occur.
Scrub stage, Submerged plants, Marsh meadow stage, Phytoplankton, Reed swamp stage,
Submerged free floating stage, forest.
11. (i). How do cyanobacteria function as biofertilizer?
(ii). What is the commercial use of lipases?
12. What is inbreeding? What are the advantages of inbreeding in animals?
13. What are algal blooms? How do they affect other living organisms?
14. Give the scientific name of the causative organism of typhoid? Write two symptoms of
the disease at the advanced stage?
15. How are plants like potato and banana cultivated?
16. Why is genetic code described as :
(i) Unambiguous
(ii) Degenerate?
17. Differentiate between covergent evolution and divergent evolution?
18. (i). Mention any two methods used for the detection of cancer.
(ii). Why are cancer patients given biological modifiers like interferons?
SECTION C
19. (i). Mention the different methods in which IUD�s function as contraceptives.
(ii). Give two characteristics of a good contraceptive.
20. Represent diagrammatically the formation of recombinant DNA by the use of Restriction
enzyme EcoRI.
21. Describe the functions of anaerobic sludge digestera in sewage treatment plant.
OR
(i)What is LAB?
(ii)Write the scientific name of the organism involved in the production
of the
of each
following :
(a)Large holes in Swiss cheese
(b)Cyclosporin A
(c)Citric acid
(d)Statins
22. How is nematode resistance introduced into tobacco plants using genetic engineering?
23. Describe how pesticide residues enter the organisms and the process they undergo in the
organisms with an example.
24. A woman with blood group O married a man with AB blood group. Show the possible
blood groups of the progeny. List the alleles involved in this inheritance.
25. Why is Agrobacterium tumefaciens is a good cloning vector? Explain.
26. Describe any three factors that modify Hardy-Weinberg�s equilibrium
27. How did Hershey and Chase differentiate between DNA and protein in their experiment to
prove that DNA is genetic material in bacteriophases?
SECTION D
28. A cross was made between a pea plant with yellow and smooth seeds (heterozygous for
both the traits) and other plant with green and wrinkled seeds. Work out the phenotypes
and genotypes of the progeny using a Punnet square. What type of a cross is this? State the
Law pf Mendel illustrated in the above inheritance.
OR
i) A strand of DNA has the following base sequence. 5� ATGC GCTA ATGC 3�. Will it
be the coding strand or template strand for transcrtion? Why?
ii) What is meant by charging of tRNA? Why is it necessary?
iii) Differentiate between satellite DNA and Repetitive DNA.
iv) Explain the process of splicing in eukaryotes. Why is it necessary?
29. i) Draw a labeled diagram of a fertilized embryo sac.
ii)What is double fertilization in angiosperms. Expalin briefly.
OR
What is spermatogenesis? Where does it occur? Describe the stages of this process with
the
help of a schematic representation.
30. i) Why is biodiversity in tropics more than in temperate regions ?
ii) Differentiate between primary and secondary productivity
iii) Mention three functions the predators perform in any ecosystem.
OR
1.It is stated that pyramid of energy is always upright. Justify.
ii)What is climax community?
iii)Enumerate the ‗Evil quartet� that lead to loss of biodiversity?
MARKING SCHEME
CLASS:XII
MAX.MARKS:70
SECTION-A
1. Tt –Parent, tt – dwarf progeny
(1)
2.Transfer of pollen grains from the anther to the stigma of another flower of the same
plant.(1)
3.Anxiety, shakiness, nausea, sweating.(Any two)
1/2 +1/2 = (1)
4,Because adventitious buds arise from the notches present at the margins of of leaves.
(1)
5. (a)Thick cuticle on the leaf surface.
(b)Stomata are in deep pits.
(c)Leaves are reduced into spines.(Any two)
1/2+1/2 =
(1)
6. (a)Separation of DNA fragments.
(b)Isolation of DNA fragments.
1/2
1/2
7. A single banyan tree with a large canopy.
8. Phenotypic ratio:1:2:I, Genotypic ratio:1:2:1
ВЅ+1/2= 1
(1)
SECTION-B
9.
(1/2)
(i) Cry protein enters into the insect and converts into an active form
(ii) Protein crystal binds to the midgut of the insect create pores ,swelling and
Lysis.
(1/2)
(iii)Man exploited this protein to produce insect resistant cotton plants.
(1)
10. Phytoplanktons-- Submerged plants-- Submerged free floating plants-- Reed swamp
stage--
Marsh meadow stage--Scrub stage
11.
12.
(i)Cyanobacteria fix atmospheric nitrogen.
(1)
(ii)Lipases are used in detergent formulations.
(1)
(i)Breeding with animals of same breed.
(ii) Produce pure lines.
13.
(1)
(2)
(1)
(1)
(i)Excessive growth of plank tonic algae in the water body.
(ii)Algal blooms cause deterioration of water quality and fish morality.
(1)
o
14.
Typhoid –Salmonella typhi –Intestinal perforation and sustained high fever (39 - 40o)
(1+1/2+1/2)
15.
Potato – Buds(eyes)
Banana – Rhizomes
(1+1=2)
16.
(i)One codon codes for only one amino acid.
(ii)Some amino acids are coded by more than one codon.
(1+1=2)
17. Convergent evolution: Different structures evolving for the same function.
Eg: Analogous organs
Divergent evolution: Same structure developed in different directions for different
needs.
Eg: Homologous organs
18.
(i)Biopsy, CT Scan and MRI . (Any two)
(ii)Interferons activate immune system and helps in destroying the tumor.
(1+1=2)
SECTION-C
19. (i)(a)To delay pregency.
(1/2)
(b)To space children.
(1/2)
(ii)User friendly,easily available,effective(Any two points)
(1+1=2)
20. Diagrammatic representation in page 196 (11.1) of NCERT biology text book.
21. Anaerobic sludge contains bacteria and fungi that are digested by sludge digesters
producing a mixture of gases. These gases form biogas and can be used as source of
energy as it is inflammable. (1)
OR
(i)Lactic acid bacterium?
(1)
(ii)(a)Propionibacterium sharmani.
(b)Immunosuppressive agent.
(c)Aspergillus niger.
(d)Monascus purpureus
ВЅ+1/2+1/2
1/2+
22.. –Introduction of nematode specific genes into the host plant.
-Production of sense and antisense RNA.
_
-Silencing of mRNA
(1+1+1)
23 -Biomagnification.
-DDT enters into water
fish eating birds
Zooplankton
small fish
large fish
-Explanation on the process
(1+1+1)
IA, IB,ii.
24. Blood groups A and B.
(2+1)
25. It is able to deliver a piece of DNA, transform normal plant cells into tumor, direct the
tumor cells to produce chemicals required by the pathogen.
(1+1+1)
26. recombination
–gene migration
–mutation
–genetic drift
–natural selection
(1+1+1)
(Explanation on any three factors)
27. Correct explanation on
–infection
–blending
–centrifugation
1+1+1
SECTION D
28. Punnette square and phenotype
–test cross
(3)
(1)
–Law of independent assortment
(1)
OR
-coding strand
-coding strand has 5�
3� polarity
(1)
(ii)Linking of activated amino acids to t-RNA.It is important for the formation of a
peptide bond
between two amino acids.
(1)
(iii)Removal of introns from hn RNA
(1)
Introns cannot code for an amino acid
(iv)Small peaks of DNAfragments formed during density gradient centrifugation .
Some specific regions on DNA where DNA sequences are repeated.
(1+1)
29. (i)Figure 2.13 page 34 of NCERTbiology text book
(3)
(ii)Definition
(1)
Explantion
(2)
OR
--Definition –
(1)
--Seminiferous tubules
(1)
--Description of process
--Diagram
30 .Reason pg,No.262 of NCERT text book
(1)
(2)
(1)
Primary productivity: The amount of biomass produced per unit area over a time
period by plants.
Secondary productivity:Rate of formation of new organisc matter by consumers.
(1)
Transfer energy through trophic levels, keep prey population under
control,maintain species
diversity.
(1+1+1)
(1)
OR
Energy at lower trophic level is always more than the energy at a higher trophic
level
(1)
Definition
Explanation
(1)
(3)

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