KENDRIYA VIDYALAYA ITI MANKAPUR, GONDA
FIRST PRE-BOARD EXAMINATION 2014-15
BIOLOGY (THEORY)
CLASS – XII
Time Allowed:3hours
Maximum Marks :70
General Instructions :
(i)
(ii)
(iii)
(iv)
All questions are compulsory.
This question paper consists of five Sections A, B, C, D and E. Section Acontains
5questions of one mark each, Section B contains 5 questions of two marks each,
Section C contains 12 questions of three marks each, Section D contains one
question of four marks and Section E contains 3 questions of five marks each.
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 three questions of 5 marks
weightage. A student has to attempt only one of the alternatives in such questions.
Wherever necessary, the diagrams drawn should be neat and properly labelled.
Section - A
1. Why do frogs and fishes produce large number of offspring?
2. Mention one point of difference between Homo erectus and Neanderthal man.
3. Define niche.
4. “Honeybee males (drones) do not have father and thus cannot have sons, but have
grandfather and can have sons”. How is it possible?
5. What would be the ploidy of a tapetum cell and generative cell of pollen?
Section – B
6. Mention the fate of corpus luteum and its effect on the uterus in the absence of fertilization
of the ovum in human female.
OR
Mention the site of action of the hormones GnRH and FSH during spermatogenesis in human
males. Give one function of each of the hormones.
7. In the table given below, select and enter the correct device out of the fallowing :
oral pills condom, copper T, Saheli, vasectomy, diaphragm, tubectomy, and cervical cap.
Methods of birth control
1- Barrier
2. IUD
3. Surgical technique
Administering hormone
Device
-----------------------------------------------------
8. A plant of Antirrhinum majus with red flowers was crossed with another plan of same species
with white flowers. The plants of F1 generation bore pink flowers. Explain the pattern of
inheritance with the help of cross.
9. Following are the steps in MOET programme for herd improvement in which a cow has been
administered hormones with FSH – like activity. Arrange steps A to D in their correct sequence.
A. Transferred to a surrogate mother.
B. It is either mated with an elite bull or artificially inseminated.
C. Fertilized eggs at 32 cell stage are recovered non-surgically.
D. It produces 6-8 eggs instead of one egg which they normally yield per cycle.
10. (a) How do virus- infected cells provide innate immunity to healthy cells?
(b). Why does a doctor administer tetanus antitoxoid and not a tetanus vaccine to a children
injured in a roadside accident with bleeding wound?
Section – C
11. Study the graph given below and answer the questions that follow:
(a) How is biochemical oxygen demand (BOD) and dissolve oxygen in water related?
(b) How would they affect the aquatic life in river?
(c) Why is it said to avoid eat fishes from river for few days during beginning of rainy season?
12. Alien species are highly invasive and are a threat to indigenous species. Substantiate this
statement with any three examples.
OR
Which materials are to be known as detritus? How is decomposition affected by different
factors? Discuss.
13. Draw a labelled diagram of a sectional view of semeniferous tubule of a human.
14.
(i) Identify a, and b in the above diagram. Why are they so important?
(ii) How is the coding sequence of - galactosidage considered a better marker than the ones
identified by you in the diagram? Explain.
15. (a) How is activated sludge formed during sewage treatment?
(b) This sludge can be used as an inoculum or as a source of biogas. Explain.
16. (a) Why do the symptoms of malaria not appear immediately after the entry of sporozoites
into the human body, when bitten by female anopheles?
(b) Which toxin is responsible for the appearance of symptoms of malaria in humans?
17. Study the given pedigree chart and answer the questions that follow:
(a) Is the trait recessive or dominant?
(b) Is the trait sex linked or autosomal?
(c) Give the genotypes of the parents in generation I and of their third and fourth child in
generation II.
(d) State one example of the above and its genetic specialty.
18.
a
b
U A C G A G
A G A U UU
Study the m-RNA segment given above, which is complete to be transferred into a polypeptide
chain.
(i) Write the codons `a’ and `b’.
(ii) What do they code?
(iii) How is peptide bond formed between two amino acids in the ribosomes?
19. In an instance a woman with blood group `A’ married a man with blood group `B’. Show all
possibilities in blood groups of progeny. Show allelic combination in each case too.
20. Study the table given below and answer the questions that follow:
Species A
(+)
(-)
(+)
(+)
Species B
(+)
(-)
(-)
(0)
+ = Beneficial interaction , - = Detrimental interaction,
Name of Interaction
A
B
C
d
0 = Neutral interaction.
Identify a, b, c, and d in the given table and explain any one of them with example.
21. Trace the event that occur in human body to cause immunodeficiency, when HIV makes
entry into the body.
22. A wild variety of wheat plant is resistant to a particular fungal disease, and the cultivated
variety is not resistant to that disease but is productive. How would you develop a hybrid that
would respond productive as well as disease resistant? Explain.
Section - D
23. Use of chemical pesticides and fertilizers create pollution at the level of production and use
in villages and cities. One more problem is seen in rural as well as suburban areas, that people
defecate in open. At certain locations there are public toilets for use. These can be used with
nominal payment by people. These toilets not only meet out the pollution but also produce
biogas that can be used at site. The first problem discussed can be solved by organic farming
which being done by a farmer, Ramesh Chandra Dagar in Sonepat, Haryana.
(a) How does organic farming reduce the use of harmful chemicals?
(b) How is biogas production ecofriendly?
(c) How can open defecation harm our environment and people?
(d) Indicate the values seen (involved) in above instance.
Section - E
24. (a) Natural selection operates when nature selects for fitness. Explain.
(b) The rate of appearance of new forms is linked to the life span (life cycle) of an organism.
Explain with suitable example.
OR
(a) Give any points in favour that RNA was the first genetic material.
(b) How did Alfred Hershey and Martha Chase unequivocally prove that DNA is the genetic
material? Why did they select T2 bacteriophage only?
25. (a) How is a transgenic tobacco plant protected against Meloidegyne incognitia?
(b) How has Elly Lilly solved the problem of maturation of human insulin?
OR
(a) With the help of diagrams, show the different steps involved in the formation of
recombinant DNA by the action of restriction endonuclease enzyme EcoRI.
(b) How is elution done?
26. (a) Name the phases preceded and followed by ovulation in a menstrual cycle. Explain the
events occurring during these phases.
(b)Explain the role of pituitary hormones in the regulation of menstrual cycle.
OR
(a) Fertilization is essential for production of seed, but in some angiosperms seeds
developed without fertilization. Explain how seeds are developed in such angiosperms by
different ways?
(b) Mention the characteristic features of a wind pollinated flower.
THE END
KENDRIYA VIDYALAYA ITI MANKAPUR
FIRST –PREBOARD EXAMINATION 2014-15
Class XII
Marking Scheme
Subject: Biology
1. To ensure survival, as the offspring are extremely vulnerable to predators threatening their
survival up to adulthood.
1 mark
2.Homo erectus had a brain size of 900 cc. // probably ate meat / Neanderthal man had a brain
size of 1400cc. // used hides to protect their body // buried their dead.(one from each side of
/)½ mark for each
3. Each organism has an invariably defined range of conditions that it can tolerate, diversity in
resources it utilizes and a distinct functional role in the ecological system, all these together
comprise its niche.
1 mark.
4. It is an effect of haplodiploid sex determination,
½ mark
Unfertilized egg (n=16) produced by female, develops as a male hence no father is required
but female develops from fertilized egg (16+16=32), hence grandfather and grandson are seen.
½ mark.( if shown diagrammatically allot mark)
5. Tapetum cell = diploid (2n), Generative cell = haploid (n). ½ mark for each.
6. Corpus luteum degenerates, and changes into corpus albicans / causes disintegration of the
endometrium, leading to menstruation.
1 + 1 mark.
GnRH acts on the anterior pituitary gland to secrete gonadotropins – FSH(follicle stimulating
hormone) and ICSH (interstitial cell stimulating hormone) or lutenizing hormone/ FSH act on
sertoli cells and stimulates secretion of some factors which help in the process of
spermatogenesis in testes.
1+1 mark
7.
Methods of birth control
Device
1- Barrier
Condom, diaphragm, cervical cap
2. IUD
Copper T
3. Surgical technique
Tubectomy, vasectomy
Administering hormone
Oral pill, saheli.
½ mark for each ( but do not allot mark if any mistake seen in each step.)
8. This is an example of incomplete dominance, where neither of the parental traits appear in
F1 generation but intermediate of two is obtained.
1 mark
For correct cross with labelling ½ + ½ mark.
9.
D BCA
½ mark for each correct sequence.
10. (a) Viral affected cells produce interferons that protect non-infected cells.
1 mark
(b) It is an example of passive immunity, where readymade antibodies are given to protect
the body from infection. Child required immediate protection that is possible by tetanus
antitoxoid.
1 mark
A tetanus vaccine would take much time to develop immunity, till that child may suffer from
tetanus.
1 mark
11. (a) In a polluted water BOD is highest and dissolved oxygen is least, and in non polluted
water ratio is reverse.
1 mark
(b) Under high BOD and poor oxygen concentration, it is difficult for life forms to survive.
1 mark
(c) During beginning of rainy season much toxins reaches the body of fishes through
biological magnification or bioconcentration, which may harm us.
1 mark.
12. i) The Nile perch introduced into lake Victoria in east Africa led eventually to the extinction
of more than 200 species of cichlid fish in the lake,
ii)Parthenium, Lantana and Ecchornia have caused much damage to our environment,
iii) Introduction of the African catfish, Clariasgariepinus for aquaculture purposes is posing
threat to indigenous catfishes in our rivers.
1x3=3 marks.
OR
Dead plant remains such as leaves, bark, flowers, and dead remains of animals, including fecal
matter, constitute detritus.
1 mark.
Affected by chemical composition, and climatic conditions. ½ mark.
Detritus rich in lignin and chitin shows slow decomposition, ½ mark
If rich in nitrogen, sugars and acids decompose faster,
½ mark.
Warm and moist environment favours decomposition, whereas low temperature and
anaerobiosis inhibits decomposition.
½ mark.
13 . Please refer Fig. 3.5 on page no. 47 of NCERT BOOK OF BIOLOGY CLASS XII.½ mark foreach
correct labeling.
14. (i) a= ampR , / b= tetR/ these are selectable markers used for separating transformant from
non-transformant. ½ x3= 1 ½ marks.
(ii) Selection of recombinants due to inactivation of antibiotic-resistance is cumbersome,
requires plating of two plates having different antibiotics i.e. tetracycline and ampicillin./
A recombinant DNA is inserted within the coding sequence of an enzyme, 1 ½ marks
-galactosidase, this inactivates the enzyme, which is referred to as insertional inactivation./
The presence of a chromogenic substrate gives blue coloured colonies if the plasmid in the
bacteria does not have an insert. Recombinants having inactivated enzyme do not produce any
colour, thus identified.
1/2x3= 1 ½ marks.
15. (a)During secondary treatment, the primary effluent is passed into large aeration tanks
where it is constantly agitated and aerated./ aerobic decay of organic material takes place,
which reduces BOD greatly and due to that a thick growth of microbes forms flocs, (masses of
bacteria associated with fungal hyphae to form mesh like structures) takes place./ Now the
effluent is sent to settling tanks, where flocs sediment to form activated sludge. ½ x3 = 1 ½
mark.
(b) A small part of flocs is sent back into aeration tanks as starter or inoculum to begin the
aerobic decay of organic matter.
½ mark
When activated sludge is pumped into anaerobic sludge digesters, the anaerobic bacteria
digest the flocs; / during this process gases like methane, hydrogen sulphide and carbon
dioxide are formed, which constitute biogas.
½ + ½ =1 mark.
16. (a) Initially sporozoits enter the liver cells and complete many cycles to increase their
numbers asexually, due to that liver cells get damaged,/ now parasites enter into RBCs, multiply
and come out by bursting them./ Toxins are released from ruptured RBCs cause fever and other
symptoms also appear.
½ x3 = 1 ½ marks.
(b) Haemozoin.
½ mark.
Parasites reproduces asexually in red blood cells, rupturing causes symptoms, / Released
parasites infect new red blood cells and repeats the cycles, that is why symptoms are seen
periodically.
½ x2 = 1 mark.
17. (a) Recessive trait. ½ mark.
(b) Autosomal.
½ mark.
(c) Genotype of parent in I generation --- Aa, and Aa. ½ mark.
Third child --- Aa, Fourth child ---- aa.
½ mark
(d) Sickle-cell anemia, ½ mark
Homozygous individuals produce sickled red blood cells, heterozygous individuals appear
apparently unaffected but they are carrier of the disease. ½ mark.
18. (i) a = AUG start codon, b = UAA or UAG or UGA stop codon ---
1 mark
(ii)a- methionine, b- none, but ends translation process. ----- 1 mark
(iii) There are two subunits of ribosomes, together help in translation.Larger subunit
consists of two sites A and P, where amino acids bind as per codon / and the enzyme
peptidyltransferase there, joins amino acids to form peptide bond between them. ½ + ½ =1
mark
19. All four types of blood group possibilities may be in progeny when both are heterozygous
(IA IO and IB IO).
1 mark
Correct depiction of inheritance phenotypes with genotypes. ½ x4 = 2 marks.
20. a- Mutualism, b- Competition, c- Predation or Parasitism, d- Commensalism. ½ x4 =2 marks
Mutualism- Both the species are benefited. / For example in Lichens the phycobiont get
moisture and minerals and mycobiont gets food. Or any other example. ½ + ½ = 1 mark.
21. After entering the body of a person, the virus enter s the macrophages. / The viral genome
i. e. RNA directs reverse transcription to form viral DNA with the help of rivers transcriptase./
The viral DNA joins the DNA of cells and directs these cells to produce virus particles. Thus
macrophages acts as HIV factory. / Thereafter these HIVs move out of macrophages and infect
the helper T-lymphocytes and replicate to produce progeny viruses. / The progeny viruses
released in the blood attack new helper T-cells and kill them. / This process is repeated and
there is a progressive decrease in the number of helper T-cells, thus loss of immunity (AIDS).
½ x 6 = 3 marks.
22. The conventional method of breeding for disease resistance is that of hybridization and
selection.
½ marks
The various sequential steps are :
SCREENING OF GERMPLASM: The germplasm is evaluated for desired resistance.The selected
plant is multiplied. Pure breed lines are created wherever desirable and possible.
HYBRIDIZATION OF PARENTS: The parents are allowed cross hybridization that genetically
combine the desired characters in one plant. It is not necessary that the hybrids do combine the
desirable traits; usually only one in few hundred to a thousand crosses shows the desired
combination.
SELECTION AND EVALUATION OF HYBRIDS: This step yields plants that are superior to both of
the parents. These are self pollinated for several generations till they reach a state of
homozygosity.
TESTING, RELEASE AND OF NEW VARIETY: The newly selected lines are evaluated for their yield
and other agronomic traits of quality, disease resistance etc. This is done in research fields
under observation for various needs. Then these are grown in farmers’ fields at least for three
growing seasons at different locations in the country.
Now it is ready for commercialization.
½ x 5 = 2 ½ marks.
23. (a) Use of harmful chemicals like fertilizers and pesticides is restricted, instead compost,
vermicompost, biofertilizers and biopesticides are used. 1 mark
(b) Biogas is produced either from human feces or animal excreta, thus no pollution caused
but is productive in nature.
1 mark
(c) Defecation in open creates pollution as well as different vector born diseases like cholera,
polio, typhoid, dysentery etc are spread and make people sick. 1 mark.
(d) Concern towards environment and health of society. Or any other values – 1 mark.
24. (a) There are some organisms which are better adapted to survive in an otherwise hostile
environment because they have inherited such genes, so there must be a genetic basis for
getting selected and to evolve.--1 mark
Adaptive ability is inherited and it has a genetic basis; hence fitness is the end result of the
ability to adapt and get selected by nature. ---1 mark.
(b) Microbes have the ability to divide and multiply to produce millions of progeny within
hours. / A colony of bacteria (say A) growing on a given medium, has built-in variation in terms
of ability to utilize resources. / A change in composition of the medium will allow only few
individuals who can survive in that change condition. / In due course of time, the variant
population (say B) would outgrow the population A and appear as a new species; this would
happen within a few days./ Use of pesticides like DDT againstmosquitoes has resulted in
mosquito populations with DDT resistance within a few years./ Whereas in a fish or fowl it may
take million years, as their life spans are in years. ½ x 6 = 3 marks.
OR
Correct explanation of Hershey and Chase experiment as per NCERT BOOK OF BIOLOGY CLASS
XII page number 101& 102. ½ x8 = 4 marks.
T2- bacteriophage consists of only DNA and Protein coat. / It was easier to label the protein
(35 S) and DNA (32P) with different radioisotopes.
½ x 2 = 1 mark.
25. (a) A novel strategy has been developed, RNA interference (RNAi) or silencing a gene,is
being used to control the pathogen Meloidegyne incognitia that attack the tobacco plants. /
This method involves silencing of a specific mRNA due to a complementary dsRNA molecule
that binds to and prevents translation of the mRNA (silencing). / The source of this
complementary RNA could be from an infection by viruses having RNA genomes or mobile
genetic elements (transposons) that replicate via an RNA intermediate./ Using Agrobacterium
vectors, nematode specific genes were introduced into the host cells. / The introduction of DNA
was such that it producedboth sense and anti-sense RNA in the host cells./ These RNAs being
complementary to each other formed a double stranded (dsRNA) that initiated RNAi and thus,
silenced specific mRNA of the nematode. The pathogen could not survive and plant was
protected.
½ x6 =3 marks.
(b) Human insulin is secreted as pro-hormone, it consists of A,B and C polypeptide chains. / For
maturation C has to be removed and A and B are to be joined. The main challenge was to form
mature insulin./ In 1983, Eli Lilly an American company prepared two DNA sequences
corresponding to A and B, chains of human insulin and introduced them in plasmids of E.coli to
produce insulin chains./ Chains A and B were produced separately , extracted and combined by
creating disulphide bonds to form human insulin. ½ x4 = 2 marks.
OR
(a) Please refer to the figure 11.1 of NCERT BOOK OF BIOLOGY CLASS XII PAGE NUMBER 196.
Allot 1 mark on each step if explained otherwise ½ mark on figure of each step.= 3 marks
(b)The DNA fragments in gel electrophoresis are stained with ethidium bromide/ then exposed
to UV light, this visualizes the DNA fragments in bright orange colour./ The separated bands of
DNA are cut out from the agarose gel / and extracted from the gel piece. This step is known as
elution.
½ x4 = 2 marks.
26. (a) Ovulation is preceded by Proliferative or Follicular phase and followed by Luteal or
Secretory phase.
Follicular phase : The primary follicles in the ovary grow and become a fully grown Graafian
follicle (under the influence of FSH). / The endometrium of uterus is regenerated by
proliferation of the cells. / The changes are due to the increased level of FSH, LH and estrogen. /
Both FSH and LH reach their peak level in the middle of the cycle, that causes ovulation.
1 ½ marks
Luteal phase : The ruptured follicle is transformed into corpus luteum. It secretes large amount
of progesterone. / The endometrium thickens further and its gland becomes cork screw shaped.
/ In the absence of fertilization the corpus luteum degenerates and no more progesterone is
available that leads to loss of endometrium (next menstruation).
1 ½ marks
(b) Pituitary hormones : FSH and LH FSH stimulates growth in follicle that secretes estrogens
which cause growth in the endometrium. /Oogenesis is completed under the influence of
FSH./Both FSH and LH, when at peak, together cause ovulation./LH causes formation of corpus
luteum that secretes progesterone.
1 ½ marks.
OR
(a) The process of seed formation without fertilization is apomixes, such seeds are called
apomictic seeds. Examples are members of family Asteraceae , mango, citrus, etc.
In some species, a diploid egg cell is formed without meiosis . This develops into embryo
without fertilization.
In some species like mango and Citrus, some of the cells of nucellus around the embryo sac
enter into it and behave as embryo to show polyembryony.
1x3 = 3 marks
(b) i) Stamens are well exposed, Ii) The stigma is often large and feathery, Iii) The pollens are
lighter and non-sticky, iv)Large amount of pollens are produced, V) Small flowers together
form inflorescence, and v)There is single ovule in the ovary of these flowers.
Any four ½ x4 = 2 marks.