1
SECONDARY SCHOOL IMPROVEMENT PROGRAMME
(SSIP) 2015
GRADE 12
SUBJECT:
LIFE SCIENCES
LEARNER NOTES
(Page 1 of 124)
© Gauteng Department of Education
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TABLE OF CONTENTS
SESSION
NO
TOPIC
PAGE
11
Human Endocrine System and Homeostasis
3 - 29
12
Responding to the Environment – plants
Evolution Part 1
29 - 50
13
Evolution Part 2
50 - 71
14
Consolidation Paper 1 A
72 - 87
15
Consolidation Paper 1 B
88 - 99
16
Consolidation Paper 2 A
100 - 112
17
Consolidation Paper 2 B
113 - 124
© Gauteng Department of Education
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SESSION NO: 11
TOPIC:
HUMAN ENDOCRINE SYSTEM AND HOMEOSTASIS
SECTION A: TYPICAL EXAM QUESTIONS
QUESTION 1: 10 minutes
Learner Note: Knowledge and application: Please ensure that you know what chemical
co-ordination is; the differences between the endocrine and exocrine glands; basic
characteristics of hormones; location and function of hormones produced by the endocrine
glands; what negative feedback is; causes, prevention and symptoms of some diseases
like diabetes, thyroid disorders, growth disorders and infertility; structure versus function of
the different parts of the skin; how to regulate body temperature.
SECTION A: TYPICAL EXAM QUESTIONS
QUESTION 1:
12 minutes
(Taken from DoE May/June 2008 Paper 2)
The graph below shows the change in mass of two young mice from the same litter (born
from the same parents) over time. One of the two mice was injected with a substance
secreted by an endocrine gland. Study the graph and answer the questions that follow.
[Hint: For any graph question – study the graph first. Look at the heading and take note
of what is being graphed. Then read the dependent (Y-axis) and independent (X-axis)
variables carefully. Always use a ruler when you read data off from a graph as this will
ensure that you are accurate. You need to use a pencil and then draw lines across the
points that you are required to get information from. Where the lines cross – this will be
the point that you are looking at. It will also show you what the readings are at the X and Y
axis without error. Graphs are the easiest way to score marks. Make sure that you
practice your graphing skills.]
© Gauteng Department of Education
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1.1
1.2
1.3
1.4
1.5
1.6
1.7
Name the endocrine gland that secretes the substance that was injected into
one of the mice.
Which mouse (I or II) was injected with the secretion?
Name the secretion that was injected into the mouse mentioned in
QUESTION 1.2.
Explain your answer to QUESTION 1.3.
At what time was there approximately a hundred percent difference in mass
between the two mice?
Explain why each of the following needs to be kept constant for the two mice
during the investigation:
a)
Temperature
b)
Diet
It was found that the secretion from the gland identified in QUESTION 1.1 did
not have a significant effect on an adult mouse. Give a possible explanation
for this.
(1)
(1)
(1)
(2)
(2)
(2)
(2)
(3)
QUESTION 2:
7 minutes
(Taken from DoE May/June 2008 Paper 2)
Give an explanation for each of the following observations made by a person watching an
athletics event:
2.1. A light-skinned athlete participating in the 100-metre event looks pale just
before the race begins.
(4)
2.2. The light-skinned athlete appears reddish immediately after the 100-metre
race.
(4)
© Gauteng Department of Education
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QUESTION 3:
10 minutes
(Taken from DoE May/June 2008 Paper 2)
Various changes occur in the body as a result of changes in the environment.
3.1.
A 5 000-metre athlete and a spectator (someone sitting in the shade watching) of
the same sex, age and mass have the same concentration of water in their bodies
before the race.
Tabulate ONE difference between a spectator sitting in the shade and an athlete
who has just run the 5 000-metre race for each of the following:
[Hint: When you are asked to tabulate, you will get marks for drawing the table.
Read the question carefully because all the information that is required in your table
is given to you in the question.]
a) State of contraction/relaxation of the hair erector muscles
b) Amount of water excreted by the kidneys immediately after the race
c) Amount of thyroxin in the blood
3.2
3.3
Explain your answer to QUESTION 3.1(b).
State THREE ways in which heat is lost from the human body.
(7)
(3)
(3)
QUESTION 4:
12 minutes
(Taken from BIOS BEST 2007 HG)
Study the diagram of the human skin and answer the questions that follow:
4.1.
4.2.
4.3.
Provide labels for structures A, B, C, D and E.
State ONE function of C and D respectively.
Describe the role played by the skin in regulating blood temperature on a
cold day.
© Gauteng Department of Education
(5)
(4)
(9)
6
QUESTION 5:
18 minutes
(Modified from BIOS BEST 2007 HG)
Read the passage and then answer the questions that follow:
5.1.
5.2.
5.3.
5.4.
5.5.
Define the terms hormones and homeostasis.
(4 x 2)
Which cells in the pancreas secrete insulin?
What stimulates the three centres of the three-part control system?
Explain why the interaction between the liver and the pituitary gland is referred
to as a negative feedback system.
Apart from the hormones named in the passage, there is one other hormone
that plays a major role in the utilization of glucose. Name this hormone and
describe its role in glucose metabolism.
© Gauteng Department of Education
(8)
(2)
(1)
(14)
(3)
7
SECTION B: NOTES ON CONTENT
TOPIC 1:
ANIMAL RESPONSES TO THE ENVIRONMENT:
ENDOCRINE SYSTEM AND THERMO REGULATION
TERMS and DEFINITIONS
Hormones: organic chemical messengers secreted directly into the blood by an
endocrine gland. Hormones cause target organs to perform a specific function.
Hyperthyroidism: Increased levels of thyroxin in the blood due to over-activity of the
thyroid.
Hypothyroidism: Decreased levels of thyroxin in the blood due to under-activity of the
thyroid.
Homeostasis: is the process of maintaining a constant internal environment within
narrow limits, despite changes that take place internally and externally. Negative
feedback mechanism: when there is an increase from normal, a corrective mechanism
causes a decrease and vice versa to maintain a balanced system.
Thermoregulation: a regulatory process to keep a constant body temperature in
homoeothermic animals like birds and mammals.
Sweating: the secretion of water and dissolved waste substances from the sweat glands
through ducts, onto the skin surface to cool the body down by evaporation.
Vasodilation: is the widening of blood vessels by relaxing the smooth muscle cells in the
walls of the arteries, veins and capillaries to decrease the pressure of the flow of blood.
Vasoconstriction: is the narrowing of blood vessels by contracting the smooth muscle
cells in the walls of the arteries, veins and capillaries to increase the pressure of the flow of
blood.
Hypothermia: when the body becomes so cold that the internal mechanisms cannot
keep the internal core body temperature constant. (Remember the O in hypothermia and
the O in cold – go together).
Hyperthermia: when the body becomes too hot and the internal mechanisms are unable
to cool the internal core body temperature down sufficiently.
IMPORTANT CONCEPTS:
Differences between the Endocrine System and the Nervous System
Endocrine system
Nervous system
1.
2.
3.
4.
5.
1.
2.
3.
4.
Made up of glands
Produces hormones
Hormones transported by the blood
Effects are slower and more general
Hormones control long-term changes
(e.g. growth)
Made up of nerves
Produces nerve impulses
Impulses transmitted along the nerves
Effects are very quick and very
specific
5. Nerve impulses control short-term
changes (e.g. sneezing, lifting your
arm)
© Gauteng Department of Education
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Exocrine Glands:
Exocrine glands are glands that secrete substances into ducts that lead into cavities in
the body or lead directly to the external environment. Examples are sweat glands,
mammary glands, the liver, salivary glands and the pancreas.
Endocrine Glands:
The Endocrine system works in conjunction with the Nervous system. The endocrine
system is responsible for chemical coordination, regulating the functioning of all the
organs in the body.
 The endocrine glands produce organic chemical messengers called hormones.
 All endocrine glands are ductless so hormones are secreted directly into the
blood.
 Each gland has a rich supply of blood to transport the hormones to the target
organs.
 Hormones generally consist of proteins and fats, but some (like the sex hormones)
consist of fats only.
 Hormones control the activities of a target organ, but do not themselves perform
the activity.
 Hormones work together as an integrated system where they either stimulate or
inhibit organs.
Endocrine glands in the body and the hormones that they secrete:
** LEARN THIS DIAGRAM WELL (It will assist with learning the following table)
© Gauteng Department of Education
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Endocrine Gland table (Learn Well):
Hormone
Gland
Growth hormone Anterior lobe
(somatotrophin) of the pituitary
gland
Follicle
stimulating
hormone (FSH)
Luteinising
hormone (LH)
Anterior lobe
of the pituitary
gland
Anterior lobe
of the pituitary
gland
Location
Function
Base of the
For growth, repair
brain and
and replacement of
attached to the cells
hypothalamus
Effect of underand oversecretion
Oversecretion:
Children – giantism
Adults – acromegaly
Undersecretion:
Children – pituitary
dwarf
Adults – premature
senility
Base of the
brain and
attached to the
hypothalamus
In males: stimulates No over- or
spermatogenesis
undersecretion
effects
In females:
Base of the
brain and
attached to the
hypothalamus
In males: stimulates No over- or
the synthesis of the undersecretion
hormone
effects
testosterone by the
Leydig cells in the
testes
stimulates the
development of the
follicle for process of
ovulation
In females: LH
stimulates the
release of the
secondary oocyte
from the Graafian
follicle and then the
development into
the corpus luteum
Thyroidstimulating
hormone (TSH)
Anterior lobe
of the pituitary
gland
Base of the
brain and
attached to the
hypothalamus
Stimulates the
production of
thyroxin by the
thyroid gland
Antidiuretic
hormone (ADH)
Neurosecretor
y cells of the
hypothalamu
In the centre of Regulates
the brain
osmoregulation in
the kidneys (in the
© Gauteng Department of Education
Oversecretion:
goitre
Undersecretion:
lack of production of
thyroxin – thyroid
gland is understimulated
Oversecretion:
water retention and
swelling (oedema)
10
s (ADH is
stored in the
posterior lobe
of the pituitary
gland)
Thyroxin
Thyroid gland
Below the
larynx in the
neck region
distil convoluted
tubules and the
collecting tubules)
Undersecretion:
dehydration

Oversecretion:
goitre



Aldosterone
Adrenalin
(fight-and-flight
hormone)
Cortex of the
adrenal gland
Medulla of the
adrenal gland
Above the
kidney
Above the
kidney
Regulates the
basal metabolic
rate of the cells
in the body
Affects growth
and functioning
of the heart and
the nervous
system
Stimulates
growth and
differentiation of
tissue in a foetus
and in children
Regulates the
body
temperature
when stimulated
by the
hypothalamus
Undersecretion:
Children – cretinism
Adults – myxodema
Helps the uptake of
sodium ions in the
loop of Henle in the
kidneys
Oversecretion:
oedema (water
retention)
Prepares the body
to deal with stress:
 Increase in
heartbeat rate
 Increase in
breathing rate
 Increase in blood
pressure
 Increase in
muscle tone
 Increase in blood
sugar levels
 Decrease in
blood supply to
There are no known
over- or
undersecretion
effects. The
sympathetic and
parasympathetic
nervous system
controls the release
of adrenalin
© Gauteng Department of Education
Undersecretion:
Addison’s disease
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
the skin and
digestive system
Causes pupils to
dilate
Glucagon
Islets of
Langerhans –
alpha cells
Endocrine cells Controls the
No over- or
of the
increase in the
undersecretion
pancreas
blood sugar level by effects
causing the
conversion of
glycogen to glucose
Insulin
Islets of
Langerhans –
beta cells
Endocrine cells 
of the
pancreas

Testosterone
Gonads:
testes
Leydig cells in
the testes of
males located
in the scrotum
at the bottom
of the pelvis



Oestrogen
Gonads:
ovaries
Located in the
lower
abdominal
region with
each ovary
located within
the pelvic

Controls blood
sugar by causing
the conversion of
glucose into
glycogen
Inhibits the
functioning of
glucagon
Oversecretion:
obesity
Testosterone is
responsible for
the secondary
sexual
characteristics in
males like a
deeper voice,
pubic hair, hair
on face
Necessary for
the normal
development of
sperm
Activates genes
in the cells of
Sertoli to
promote the
differentiation of
the
spermatogonia
Oversecretion:
aggression. In
females, it results in
secondary sexual
characteristics
similar to that in
males
Oestrogen
promotes the
development of
the secondary
sexual
characteristics in
females like
Oversecretion: may
cause cancer
© Gauteng Department of Education
Undersecretion:
diabetes
Undersecretion:
lack of secondary
sexual
characteristics and
lack of healthy
sperm production
Undersecretion:
menstruation cycle
is affected, ovulation
may be prevented
leading to infertility,
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bones (in line
with the balland-socket
joints of the
femurs)



Progesterone
Gonads:
ovaries
Located in the
lower
abdominal
region with
each ovary
located within
the pelvic
bones (in line
with the balland-socket
joints of the
femurs)




breasts, the
onset of menopause
thickening of the may occur
endometrium
(uterus) and the
female body
shape
Necessary for
the process of
ovulation
Oestrogen
inhibits the
secretion of FSH
by the anterior
pituitary gland so
that only one
follicle is
produced during
ovulation
High oestrogen
levels will trigger
the secretion of
luteinising
hormone (LH)
Progesterone
prepares the
endometrium of
the uterus for
implantation
once fertilisation
of the egg cell
has occurred
Necessary for
the production of
the mucus plug
to prevent sperm
or other
substances from
entering the
uterus during
pregnancy
Decrease in
progesterone
levels causes
menstruation
Progesterone
improves
memory and
© Gauteng Department of Education
Undersecretion:
during pregnancy,
will cause a
spontaneous
miscarriage
13
cognitive ability
Prolactin
Anterior lobe
of the pituitary
gland
Base of the

brain and
attached to the
hypothalamus

Oversecretion: can
Stimulates the
cause impotence
mammary
and loss of libido
glands to
produce milk
Counteracts the
effect of
dopamine which
is responsible for
sexual arousal
Homeostasis in humans:
Homeostasis is the process of maintaining a constant internal environment within the
body. The internal environment refers to the blood and tissue fluid that surrounds the cells
of the body. Homeostasis enables the body to function efficiently, despite changes that
might occur in the external or internal environment. Homeostasis is controlled by the
nervous system.
Changes in temperature, glucose levels, carbon dioxide levels, water levels and salt levels
of the internal environment, affects the homeostatic balance of the body. Negative
feedback mechanisms operate in the human body, to detect changes or imbalances in the
internal environment and to restore the balance.
NEGATIVE FEEDBACK MECHANISMS:
Homeostasis of the endocrine system occurs through the negative feedback
mechanism. Feedback systems are important because they ensure that all the systems
are interrelated and work together. When there is an increase from normal, a corrective
mechanism will cause it to decrease and vice versa. This ensures that a balance is
maintained within the body.
General sequence of events in a negative feedback mechanism:
Step 1:
An imbalance is detected.
Step 2:
A control centre is stimulated.
Step 3:
Control centre responds.
Step 4:
Message sent to target organs/s.
Step 5:
The target organ responds.
Step 6:
It opposes/reverses the imbalance.
Step 7:
Balance is restored.
© Gauteng Department of Education
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The regulation of blood glucose levels in the internal environment:
The blood glucose level is controlled by the Islets of Langerhans in the pancreas.
Pancreas secretes
insulin
Glucose is converted to
glycogen
Glucose level
increases
Glucose level
decreases
Normal Glucose Levels in blood
Glucose level
decreases
Pancreas secretes
glucagon
Glucose level
increases
Glycogen is converted
to glucose
Explanation:
When the glucose level in the blood INCREASES above normal levels:
Step 1
Step 2
Step 3
Step 4
Step 5
Step 6
Step 7
Glucose levels in the blood increase above normal levels
The beta cells of the pancreas are stimulated
to secrete insulin into the blood
Insulin travels in the blood to the liver and muscle cells (target
organ/s)
where it stimulates the conversion of excess glucose to glycogen
which is then stored
The glucose level in the blood now decreases
and returns to normal
© Gauteng Department of Education
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When the glucose level in the blood DECREASE below normal levels:
Step 1
Step 2
Step 3
Step 4
Step 5
Step 6
Step 7
Glucose levels in the blood decrease below normal levels
The alpha cells of the pancreas are stimulated
to secrete glucagon into the blood
Glucagon travels in the blood to the liver and muscle cells (target
organ/s)
where it stimulates the conversion of stored glycogen to glucose
The glucose level in the blood now increases
and returns to normal
**When there is an imbalance, it results in diabetes mellitus – see Endocrine table under
Insulin undersecretion.
Diabetics take insulin by injection. It is absorbed into the bloodstream at a much faster
rate and works almost immediately. If taken orally, there is a chance that digestive
enzymes will denature insulin because it is a hormone and consists of proteins. Proteins
will be effected/denatured by the acids in the stomach and the alkaline medium of the
small intestine.
The regulation of TSH and the control of Thyroxin:
Explanation:
Step 1
Step 2
Step 3
Step 4
Pituitary gland secretes TSH into the blood
TSH stimulates the thyroid (target organ) to release thyroxin into the blood
More thyroxin causes increased cell metabolism
Increased thyroxin levels in the blood will inhibit the pituitary gland and
cause less TSH to be secreted into the blood
Step 5 Less TSH means that the thyroid is less stimulated and releases less
thyroxin into the blood
© Gauteng Department of Education
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Step 6 Less thyroxin in the blood causes a decrease in cell metabolism
Step 7 and stimulates the Pituitary gland to increase the release of TSH into the
blood
**When there is an imbalance, it results in thyroid disorders – see Endocrine table for TSH
and Thyroxin over and under secretion.
The regulation of carbon dioxide (CO2) levels in the internal environment:
Cells need a constant supply of oxygen for cellular respiration and the carbon dioxide
formed is toxic. It must be removed from the body in order to have a stable internal
environment. The circulatory system (blood system) is vital for this purpose.
 Normal breathing can be voluntary for short periods e.g. for speech, holding one’s
breath under water etc.
 Normal respiration is however controlled by the medulla oblongata of the brain.
When the CO2 level in the blood INCREASES above normal levels:
Step 1 CO2 levels in the blood increase above normal levels
Step 2 Receptor cells in the carotid artery in neck are stimulated
Step 3 to send impulses to medulla oblongata in the brain (Central Nervous
System)
Step 4 Medulla oblongata stimulates breathing muscles (intercostal muscles and
diaphragm) and the heart
Step 5 Breathing muscles contract more actively (quickly), thereby increasing the
rate and depth of breathing. The heart beats faster so that the
oxyhaemoglobin (oxygen rich blood) can be distributed to the tissue and
cells quickly
Step 6 More CO2 is taken to the lungs and exhaled from the lungs
Step 7 The CO2 level in the blood returns to normal


Yawning is stimulated by excess carbon dioxide in the blood and results in prolonged
inspiration/inhalation (a long breath).
The formation of lactic acid during strenuous exercise, causes a change in the pH of
the blood and lactic acid also immobilises the muscles. That is why the muscles feel
numb. This immobilising of the muscles means that the muscles will no longer require
so much oxygen at that time. It gives the body a chance to rectify the oxygen - carbon
dioxide balance. As the oxygen levels increase, so the lactic acid is worked out of the
muscle tissue. This is why an athlete needs to warm down after a training session. If
they do not warm down – muscle stiffness results because of excess lactic acid.
The regulation of water balance in the internal environment (osmoregulation):
Cells function best under the correct pH and osmotic pressure. Water, mineral salts
and metabolic wastes affect the pH and osmotic pressure if they are not kept at a constant
level. Osmoregulation and excretion are very important processes in maintaining the
normal functioning of cells.
© Gauteng Department of Education
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


Excretion: removal of metabolic wastes from the cells and tissue fluid, so that cells
are able to function normally.
Osmoregulation: maintaining the water and salt (ion) balance. If tissue fluid is
HYPERTONIC (less water), cells lose water and shrink (crenation). If tissue fluid is
HYPOTONIC (more water) then the cells gain water and will burst (cytolysis).
Hormones control the amount of water and salts that are reabsorbed.
Pituitary secretes more ADH
Water level decreases
Permeability of collecting ducts
and distal convoluted tubules
increases
More water reabsorbed into blood.
More concentrated urine.
Normal Water Levels in blood
Water level increases
Pituitary inhibited from
secreting ADH so
Less ADH is secreted
Less water reabsorbed into blood.
Dilute urine is released.
Permeability of collecting ducts
and distal convoluted tubules
decreases
Explanation:
When the blood has LESS water than normal (Hypertonic):
Step 1 Blood has less water than normal
Step 2 The hypothalamus is stimulated
Step 3 and sends impulses to the pituitary gland to secrete more ADH into the
blood
Step 4 ADH travels in the blood to the kidneys (target organ)
Step 5 ADH increases the permeability of the collecting ducts and the distal
convoluted tubules of the kidney so
© Gauteng Department of Education
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Step 6 More water is re-absorbed by the surrounding blood vessels so urine is
more concentrated
Step 7 The water level in the blood returns to normal
When the blood has MORE water than normal:
Step 1 Blood has more water than normal
Step 2 The hypothalamus is stimulated
Step 3 and sends impulses to the pituitary gland to secrete less ADH into the
blood
Step 4 Less ADH travels in the blood to the kidneys (target organ)
Step 5 The collecting ducts and the distal convoluted tubules of the kidney
become less permeable to water
Step 6 Less water is re-absorbed by the surrounding blood vessels so more
water is released in the urine (urine becomes more dilute)
Step 7 The water level in the blood returns to normal
The regulation of salt balance in the internal environment:
Adrenal gland secretes
more aldosterone
Re-absorption of sodium
ions increases
Salt level decreases
Salt level increases
Normal Salt Levels in blood
Salt level increases
Adrenal gland stops/is
inhibited from secreting
aldosterone/less
aldosterone secreted
Salt level decreases
Reabsorption of
sodium ions
decreases
© Gauteng Department of Education
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Explanation:
When the salt level in the blood DECREASES:
Step 1 The salt level in the blood decreases
Step 2 Receptor cells in the afferent and efferent arterioles of the kidney detect
the low salt level
Step 3 The adrenal gland is stimulated
Step 4 to secrete more aldosterone into the blood
Step 5 Aldosterone increases the re-absorption of sodium ions from the renal
tubules in the kidney into the surrounding blood vessels
Step 6 The salt level in the blood vessels increases
Step 7 and returns to normal
When the salt level in the blood INCREASES:
Step 1 The salt level in the blood increases
Step 2 Receptor cells in the afferent and efferent arterioles of the kidney detect
the high salt level
Step 3 The adrenal gland is inhibited
Step 4 so less aldosterone is secreted into the blood
Step 5 This causes a decrease in the re-absorption of sodium ions from the renal
tubules in the kidney into the surrounding blood vessels
Step 6 The salt level in the blood vessels decreases
Step 7 and returns to normal
Temperature regulation (Thermoregulation):
Body temperature must be kept constant in homoeothermic organisms like birds and
mammals. Optimal body temperature in humans is between 36,6 ºC and 37 ºC. If the
temperature is too high, the proteins will denature and be unable to function. If the
temperature is too low, the proteins will become inactive – the body temperature must be
kept constant. The hypothalamus stimulates various systems to regulate the body
temperature. When the body is hot, the hypothalamus will stimulate the pituitary to release
more ADH and less thyroxin. When the body is cold, the opposite will take place.
The Skin:
The skin is well adapted to aid in temperature regulation. The skin has a large surface
area, with many blood vessels and capillaries, numerous sweat glands, hairs with
erector muscles and adipose tissue (fat deposits) in the subcutaneous layer and
thermoreceptors (receptors that are sensitive to changes in temperature) that are
stimulated when the temperature goes up or down from normal.
© Gauteng Department of Education
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Diagram of the skin (Sourced from Biology for IGCSE – Heinemann 1994)
Hot conditions Explanation:
 If the environmental conditions are too hot or too much heat is produced in the body,
the warmed blood or surrounding temperature stimulates the thermoreceptors in the
skin causing an automatic internal response.
 The stimulus is converted into an impulse and sent to the Central Nervous System
(hypothalamus), which causes the blood vessels in the skin to dilate/vasodilation
(open wider) so more blood flows to the surface. This causes greater heat loss by
radiation, convection and conduction.
 More blood is also supplied to the sweat glands and more sweat will be secreted,
which evaporates, cooling the skin.
 The erector muscles relax, so the hairs lie flat so no warm air will be trapped.
 If the loss of heat is still not enough, the muscle tone is lowered (less TSH is
released) and one becomes less active.
 Panting: dogs have very few sweat glands and lose heat by evaporation of water
(saliva) from their mouth and tongue. Panting increases the breathing rate and more
heat is lost from the lungs.
Hyperthermia: occurs when the body become too hot and is unable to cool the internal
core temperature down sufficiently. This results in dehydration, heat stroke and heat
exhaustion and may cause death.
© Gauteng Department of Education
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**KNOW THIS DIAGRAM: Skin on a HOT DAY (Compare with COLD DAY diagram)
(Sourced from Biology for IGCSE – Heinemann 1994)
**KNOW THIS DIAGRAM: Skin on a COLD DAY (Compare with HOT DAY diagram)
(Sourced from Biology for IGCSE – Heinemann 1994)
© Gauteng Department of Education
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Cold conditions Explanation:
 If the temperature is too low or the body loses heat more rapidly than it can be
replaced, the thermoreceptors in the skin are stimulated.
 The stimulus is converted into an impulses and sent to the Central Nervous System
(the hypothalamus).
 The hypothalamus responds by stimulating the pituitary gland to cause the blood
vessels of the skin to constrict, so less blood flows to the surface and less heat is lost
by radiation, convection and conduction.
 The erector muscles contract, causing the hairs to stand on end, so a thick layer of
warm air is trapped (goose-bumps on the surface of the skin).
 Muscle tone is increased, by greater oxidation in the muscle cells, producing more
heat. Voluntary muscles contract and relax resulting in a shiver action.
Hypothermia (HypO – Ohhh, it is Cooooold): occurs when the body is exposed to cold
and the internal mechanisms cannot keep the internal core body temperature
constant. Blood is drawn from the limbs and the person becomes very tired so that little
energy is used by the voluntary muscles. The blood is directed to keep the vital organs
functioning. When extreme hypothermic conditions, the person will lie down, fall into a
deep sleep and eventually even the vital organs shut down, leading to death.
Hot day – ADH and skin
Cold day – ADH and skin
The body gets hot:
 You need more water in the blood to
make more sweat to cool you down
 More ADH is released by the pituitary
gland to keep more water in the blood
 Blood vessels near the surface of the
skin dilate (vasodilation), so more
blood reaches the sweat glands
 More sweat evaporates, cooling the skin
and the blood in the vessels near the
surface of the skin
 This means that you will produce more
concentrated urine (less water in the
urine)
 The hairs in the skin lie flat so no heat is
trapped between the skin and the hairs
 The pituitary gland inhibits the thyroid
so less thyroxin is released causing a
decrease in cell metabolism, so less
energy is released – body cools down
The body gets cold:
 You need less water in the blood as you
do not need to produce sweat
 Less ADH is released by the pituitary
gland to keep less water in the blood
 Blood vessels near the surface of the
skin constrict (vasoconstriction), so
less blood reaches the sweat glands
 No sweat evaporates, so there is no
cooling of the skin and the blood in the
surface vessels
 This means that you will produce less
concentrated urine (dilute urine)
 The hairs in the skin are pulled upright
by the erector muscles to trap warm air
(goose bumps)
 The pituitary gland stimulates the
thyroid so more thyroxin is released,
causing an increase in cell metabolism.
More energy is released and causes
shivering – body warms up
© Gauteng Department of Education
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SECTION C:
HOMEWORK QUESTIONS
QUESTION 1:
10 Minutes
(Adapted from various sources)
Write down the correct biological term for each of the following descriptions.
1.
The secretions that are produced in small quantities by endocrine glands.
2.
The endocrine gland which controls the hormonal secretions of most of the other
endocrine glands.
3.
The endocrine gland that can be regarded as the ‘master gland’ in the human body.
4.
A system of all the hormone-secreting glands in the human body.
5.
An enlarged thyroid gland, resulting from an iron deficiency.
6.
The pair of endocrine glands located just above each kidney.
7.
A disease in which the hormonal control of blood glucose is defective because of an
absolute or relative deficiency of insulin.
8.
The hormone secretion of the Islets of Langerhans which lowers the glucose level in
the blood.
9.
The system informing the human body of changes in its internal and external
environment.
10.
The endocrine gland, which secretes adrenalin.
11.
The autonomic response to a stimulus, which is not under conscious control.
12.
The secretion of the thyroid gland.
13.
The hormone that stimulates the secretion of the hormone of the thyroid gland.
14.
The hormone that prepares the body for an emergency.
15.
An aspect of the control system in which the ultimate effects of the system will
counteract the original stimulus.
(15)
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QUESTION 2: 30 Minutes
The graph below shows the level of the blood sugar of a healthy person during a 12 hour
period. Study the graph and answer the questions that follow:
2.1.
At what time of day is the level of the blood sugar:
a) the lowest and
(1)
b) the highest?
(1)
2.2.
What is the level of the blood sugar at:
a) 10:00 and
(1)
b) 16:00?
(1)
2.3.
During which hour is the level of the blood sugar:
a) 140mg/100 cm3, and
(1)
3
b) 75mg/100 cm blood?
(1)
2.4.
During which hour was the rate of increase in the level of blood sugar:
a) the greatest and
(1)
b) the smallest?
(1)
2.5.
What occurred at point A and B on the graph to cause the subsequent changes
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2.6.
in the levels of the blood sugar?
(4)
At points 1, 2 and 3 on the graph, the concentration of blood sugar drops.
a) Which hormone is responsible for the decrease in concentration?
b) Where in the body is this hormone produced?
(1)
(2)
2.7.
There is an increase in the concentration of the blood sugar between 17:00 and
18:00.
a) Which hormone is responsible for this increase?
(1)
b) Where in the human body is this hormone produced?
(2)
c) Briefly describe the role played by this hormone mentioned in Question 2.7 b)
in decreasing the level of the blood sugar.
(4)
2.8.
At 20:00 the person got a fright/was frightened.
a) What do you expect to happen to the level of the blood sugar at point C?
b) Which hormone is involved now?
c) Where in the human body is this hormone produced?
d) What are the effects of the hormone mentioned in Question 2.8 c) on the
person’s body in times of fright?
e) Which part of the autonomic nervous system produced similar effects on the
human body to those mentioned in Question 2.8 d)?
2.9.
What is the pathological condition called when the sugar level in the blood is
abnormally high? What would the normal level be?
SECTION D:
SOLUTIONS FOR SECTION A
QUESTION 1:
1.1
Pituitary gland √ (1)
1.2
Mouse I √ (1)
1.3
- Growth hormone (GH) / Somatotrophic hormone (STH) √ (1)
1.4
- for the same time period √
- it showed a greater increase in mass √ (2)
1.5
Fourth / 4th √ month √ (2)
1.6
(a) - Lower temperature √ for either of the mice
- will cause more food to be oxidized / increased metabolic rate and
less food will be available for growth√
(2)
(b) - Less food √ available for either of the mice
- will lead to a smaller body mass since food is used for growth√ (2)
OR
- Different food types √
- contribute differently to the growth of an organism√ (2)
1.7
- One of the target organs of GH is bone tissue √
- Bone length cannot be increased in adult mice√
- because bone growth has stopped √
© Gauteng Department of Education
(3)
(1)
(1)
(1)
(5)
(1)
(2)
26
QUESTION 2:
2.1
- More blood needed by muscles √
- to provide sufficient oxygen √
- and glucose √
- for oxidation to provide energy. √
- The arterioles in the skin are thus constricted √
- causing less blood to reach the skin √ (MARK ANY 4) (4)
OR
- Nervous √
- therefore adrenalin produced √
- therefore less blood to skin √
- more blood to muscles √
(MARK ANY 4)
2.2
(4)
- Increased respiration/oxidation during race√
- generates a large amount of heat. √
- The arterioles in the skin dilate √
- to allow more blood with heat to reach the skin√
- so that excess heat can be lost to the environment √ (MARK ANY 4)
QUESTION 3:
3.1.
(6) + TABLE = (1)
(7)
3.2
- Athlete sweats more √
- to use more body heat to evaporate sweat√
- in order to cool down the body/lower the body temperature √ (3)
OR
- Spectator sweats less √
- therefore less body heat used to evaporate sweat√
- because he is less active/his body temperature is not very high √ (3)
3.3
- Radiation √
- Convection √
- Evaporation √
- Urination √
- Defecation √
- Expiration / Breathing √ (Mark first 3 answers only)
© Gauteng Department of Education
(3)
(4)
27
QUESTION 4:
4.1. A = oil gland / sebaceous gland
B = epidermis
C = erector muscle
D = sweat gland
E = subcutaneous fat tissue / adipose tissue
4.2.
(5 x 1)
(5)
C: when the erector muscle contract √, it pulls the hair up
to a more vertical position to trap warm air√
(2)
D: secrete sweat √ to cool the body by evaporation √
(2)
4.3. The body gets cold:
 Less water is needed in the blood √ because you do not need to produce sweat
 Less ADH is released by the pituitary gland √ to keep less water in the blood √
 Blood vessels near the surface of the skin constrict (vasoconstriction), √ so less blood
reaches the sweat glands √
 Sweat glands produce less sweat √
 No sweat evaporates, so there is no cooling of the skin and the blood in the surface
vessels √
 This means that less concentrated urine (dilute urine) is produced √
 The hairs in the skin are pulled upright by the erector muscles to trap warm air√ (9)
QUESTION 5:
5.1. Hormones: are organic chemical messengers √, that are secreted by ductless√
endocrine glands and carried by the blood √ to a target organ √. (4)
Homeostasis: is the maintenance √ of a relatively constant √ internal environment
for normal tissue functioning √ controlled by the autonomic nervous system √.
5.2. Beta cells √ of the Islets of Langerhans in the pancreas √ (2)
5.3. the presence of glucose in the blood / blood glucose level √ (1)
5.4.
When the glucose level in the blood INCREASES above normal levels:







Glucose levels in the blood increase above normal levels√
The beta cells of the pancreas are stimulated√
to secrete insulin into the blood√
Insulin travels in the blood to the liver and muscle cells (target
organ/s) √
where it stimulates the conversion of excess glucose to
glycogen which is then stored√
The glucose level in the blood now decreases√
and returns to normal√
When the glucose level in the blood DECREASE below normal levels:



Glucose levels in the blood decrease below normal levels√
The alpha cells of the pancreas are stimulated√
to secrete glucagon into the blood√
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



Glucagon travels in the blood to the liver and muscle cells (target
organ/s) √
where it stimulates the conversion of stored glycogen to glucose √
The glucose level in the blood now increases√
and returns to normal√
(14)
5.5.






Thyroxin regulates the basal metabolic rate of a person √. With increased thyroxin
secretion, the basal metabolic rate is increased √
Thyroxin stimulates the use of oxygen and glucose for respiration √
Thyroxin accelerates cellular metabolism and therefor energy release (ATP and
heat) √
Thyroxin stimulates protein synthesis which has an effect on growth in general √
Thyroxin promotes the breakdown and use of fats √
Thyroxin stimulates the excretion of cholesterol in bile, which lowers the blood
cholesterol levels √
Increased levels of thyroxin will inhibit the pituitary gland from releasing TSH. √
(Mark any 3 points)
(3)
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SESSION NO: 12
TOPIC:1: RESPONSES TO THE ENVIRONMENT - PLANTS
TOPIC 2: EVOLUTION PART 1
SECTION A: TYPICAL EXAM QUESTIONS
QUESTION 1:
8 minutes
(Taken from DoE Nov 2005 Paper 2)
Study the following graph and answer the questions that follow.
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1.1
1.2
1.3
1.4
1.5
What will your observation be, if a young shoot was exposed to a wavelength
of light of 650 nm from one side for a few days?
(1)
Explain your answer in QUESTION 1.1.
(2)
Comment on the effectiveness of indigo light on phototropism in young
shoots.
(2)
Give the name of the plant growth substance that is responsible for
phototropism in plants.
(1)
Explain ONE advantage of phototropism for a plant.
(2)
[8]
QUESTION 2:
10 minutes
(Taken from DoE Exemplar 2011 Paper 2)
A group of Grade 12 learners wanted to investigate the effect of light coming from one
direction on the growth of shoots. They planted some wheat seeds in two seed trays and
allowed it to germinate. When young shoots appeared above the soil level, the shoots
were exposed to light from all directions for three days. After three days, the trays received
different treatments as follows:
Tray A: The shoots were exposed to light from all directions.
Tray B: The shoots were exposed to light from one direction only.
The diagrams below show the effects of these treatments. Study it and
answer the questions that follow.
2.1.
2.2.
2.3.
2.4.
Formulate a hypothesis for the investigation above.
(2)
Explain why it was important to include tray A as part of this investigation. (2)
State ONE conclusion that may be drawn from this investigation.
(2)
A third tray (C) was set up in a similar way as tray A and tray B. The tips
of the shoots were covered with aluminium foil. The diagram below shows the
appearance of the shoots at the start and after being exposed to light from one
direction only.
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2.5.
What conclusion can you draw from the results obtained in tray C?
Name ONE agricultural use of the following:
(a) Auxins
(b) Gibberellins
(2)
(1)
(1)
[10]
TOPIC 2: EVOLUTION PART 1
QUESTION 3:
13 minutes (Adapted from DoE Exemplar 2008 Paper 2)
The different species of finches (A, B, C and D) below are found on different Galapagos
Islands and are thought to have originated from a seed-eating ancestral species from the
mainland of South America. They resemble each other with respect to their internal body
structure but differ with respect to the shapes and sizes of their beaks and hence their
feeding habits.
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3.1.
3.2.
3.3.
3.4.
Define a species.
(3)
Explain what is meant by geographical isolation of a population.
(2)
(Geographical will mean the geography of the landmasses. Isolation
means to be on one’s own)
Why do you think the different finch species became adapted to eat
different food types?
(1)
Explain how speciation occurs through geographical isolation (Allopatric
speciation).
(10)
[16]
QUESTION 4: 20 Minutes
(Adapted from DoE November 2008 Paper 2)
Tens of thousands of years ago, the animals that evolved into giraffes were not as tall as
modern giraffes. Over a long period of time, the necks of giraffes became longer. They
could reach leaves high in the trees and reach down for water.
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4.1
Describe how the long necks of modern giraffes would have been explained by the
following:
(a)
Darwin
(4)
(b)
Lamarck
(4)
4.2
Explain why Lamarck's theory is not accepted.
(2)
(You must know Lamarck’s theory and you should also be able to explain the
difference between Lamarck and Darwin’s theories)
4.3.
Describe how each of the following sources of variation, contributes to variation
amongst individuals of the same species:
a) Crossing over during meiosis
(4)
b) Random arrangement of chromosomes during meiosis
(2)
c) Chance/random fertilisation
(4)
d) Mutations
(4)
[24]
SECTION B: NOTES ON CONTENT
TOPIC 2: RESPONSES TO THE ENVIRONMENT - PLANTS:
TERMS and DEFINITIONS
 Tropism: means ‘to turn’ and occurs when external stimuli affect the direction in which
a plant grows and develops
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







Auxins: are plant growth hormones that stimulate cell elongation and cell
differentiation at the growth points.
Gibberellins: are plant hormones that cause elongation of the internodes of stems,
development of flowers, sprouting of buds and germination of seeds.
Abscisic acid: inhibits the growth of apical buds, seeds and roots in plants.
Phototropism: is the growth movement of a plant when stimulated by light.
Geotropism: is the growth movement of a plant in response to the force of gravity.
Apical dominance: when the growth point at the tip of the stem grows upwards. This
action inhibits the development of auxillary buds on the lateral branches below. If the
tip is removed the auxillary buds develop into lateral branches causing the plant to
grow thicker on the sides.
Phototropism and Geotropism experiments: The experiment = stationary
clinostat. The control = revolving clinostat.
Plant defense mechanisms: Plants have adapted to prevent herbivores from eating
them with chemical defences, thorns, prickles and splines.
IMPORTANT CONCEPTS:
Growth is the increase in the size of plants. Cell division occurs and the cells differentiate
in order to develop. Growth and development is affected by:
 internal factors such as hormones
 external stimuli such as water, light, gravity, gases and contact.
The word tropism means ‘to turn’. A tropism is the response to an external stimulus,
causing a plant to grow towards (positive tropism) or away (negative tropism) from the
stimulus.
Hormonal control in plants
Auxins are growth hormones found in plants. Auxins stimulate or inhibit (prevent) growth
in areas. A high concentration of auxins in an area will stimulate cell elongation and cell
differentiation, especially in stem tips (growth tips). This results in apical dominance,
when the growth point at the tip of the stem grows upwards. This action inhibits the
development of auxillary buds on the lateral branches below so they don’t grow because
all the plant’s energy is used to grow upward. If the tip is removed the auxillary buds
develop into lateral branches causing the plant to grow thicker on the sides (like when
cutting a hedge).
Auxins cause:
 cell division
 formation of adventitious roots in cuttings
 development of flowers and fruit
 abscission (breaking off) of leaves and ripe fruit
Gibberellins cause:
 elongation of internodes in stems
 development of flowers
 sprouting of buds
 germination of seeds
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Abscisic acid:
 inhibits growth of apical buds, seeds and also roots
 regulates the abscission of leaves
 plays a role in the opening and closing mechanism of stomata (for transpiration)
Phototropism (Photo = light)
Phototropism is the growth movement of a plant when stimulated by light. When the stem
of a plant grows towards a unilateral (one-sided) light stimulus, it is positively
phototrophic. Auxins stimulate cell elongation in the stem and move to the dark,
shaded side. Cell elongation occurs more rapidly on the dark side because of the higher
concentration of auxins. The stem bends towards the light stimulus. Roots are negatively
phototrophic and always grow away from light, down into the soil.
Experiment to demonstrate phototropism: Make sure that you know this experiment:
Remember: The experiment = stationary clinostat. The control = revolving clinostat.
Geotropism (Geo = gravity)
Geotropism is the downward growth movement of a root in response to a unilateral
gravitational force. When a root is placed horizontally (onto its side), only one side is
exposed to the force of gravity. The auxin concentration will now be high on the lower
side of the root because gravity attracts the auxins. The root will grow more on the upper
side because the higher concentration of auxins on the lower side inhibits growth. The
root will bend downwards towards gravity. Roots are positively geotrophic. Stems are
negatively geotrophic, because they grow away from gravity.
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Experiment to demonstrate geotropism: Make sure that you know this experiment:
Remember: The experiment = stationary clinostat. The control = revolving clinostat.
Role of auxins in phototropism and geotropism: LEARN VERY WELL
Role of auxins in phototropism
Produced at the tip of stem/shoot
Auxins move downward evenly
This even distribution brings about equal
growth on all sides of the stem
As a result the stem grows upward
When the stem is exposed to unilateral
light (light from one side only)
the auxin concentration will be high on
the dark side – light destroys auxins
More growth occurs on the dark side
because auxins stimulates growth on the
dark side
As a result the stem bends towards the
light
Role of auxins in geotropism
Produced at the tip of roots
Auxins move upwards evenly
This even distribution brings about equal
growth on all sides of the root
As a result the root grows downward
When the root is placed horizontally (only
one side exposed to gravity)
the auxin concentration will be high on the
lower side of the root - gravity attracts
auxins
More growth occurs on the upper side
because auxins on lower side inhibits
growth
As a result the root bends downwards
Plant defense mechanisms
Plants have adapted to prevent herbivores from eating them.
 Chemical defences: plants produce chemicals called phytoecdysteroids to defend
against insects. The chemicals cause insects to moult prematurely, lose weight and if
enough is ingested, metabolic damage and death. Cultivated tobacco plants produce
nicotine. The leaves are eaten by insects and kills them. The leaves of mopane trees
contain high levels of tannins making the leaves distasteful to herbivores.
 Thorns: this is a common term for a sharp structure found on plants for protection
against herbivores. There are various types of sharp structures:
© Gauteng Department of Education
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


Prickles are modified extensions of the cortex and epidermis of a plant that shape
into a sharp, needle-like structure, for example rose bushes.
Thorns are modified branches or stems that form hard, pointed and sharp ends that
can pierce the skin of herbivores. Examples are acacia trees, kei apples and lemon
trees.
Spines are modified leaves that have a cylindrically shaped hard and sharp point,
for example aloes and cacti. Spines also reduce water loss by the plant.
TOPIC 2: EVOLUTION PART 1
TERMS and DEFINITIONS
 Evolution: total change over time (a slow process of change by which organisms
acquire distinct characteristics)
 Biological evolution: any genetic change in a population that is inherited over several
generations. These changes may be small or large, noticeable or not so noticeable.
 Hypothesis: (from Greek meaning ‘to suppose’) is a suggested explanation for an
observable phenomenon or proposal that predicts a possible outcome.
 Theory: is an explanation for something which is reasonable or scientifically
acceptable, but which has not yet been proved to be true.
 Theory of evolution: is regarded as a scientific theory since various hypotheses
relating to Evolution, have been tested and verified over time.
 Micro-evolution: small changes that take place within a species to adapt to survive
 Macro-evolution: large changes in many species that take place over a long period
of time
 Fossil: the word is derived from Latin and is defined as the imprint, traces or
preserved remains of an organism that once lived. A fossil may be plant and animal
body parts as well as impressions in rocks or traces left by the organisms.
 Fossilisation: the process that took place to produce the fossil over a period of time.
Anthropology: the study of the human race, including the different belief systems,
customs and social habits.
 Palaeontology: the study of the earliest known periods of human existence, e.g.: the
Stone Age.
 Archaeology: the study of ancient times by examining the buried remains of buildings,
tools, animal and plant fossil remains found in rock strata.
 Archaeologist: a scientist that digs up, studies and traces fossil remains in rock
strata. Archaeologists use carbon dating to determine when the animals and plants
lived.
 Palaeontologists and anthropologists use information from archaeologists to record
findings and determine what lead to extinction or evolutionary changes.
 Biodiversity: the variety of different plant and animal species found on earth where
diversity is the result of change over time
 Natural selection: is the process of change over time, that takes place in species
 Species: a group of organisms that are similar in appearance, share the same DNA
sequences, perform the same mating rituals and interbreed to produce viable
offspring.
 Population: a group of organisms of different ages, that belong to the same species,
live in the same area and interbreed.
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








Variation: means small changes that will assist an organism where phenotypic
variation (physical appearance) is as a direct result of genetic variation.
Continuous variation: the variation of a trait in a population, where the trait ranges
continuously from one extreme to another preventing the subdivision into distinct
classes, e.g.: a person’s height or size of feet.
Discontinuous variation: the variation of a trait in a population that can be ascribed to
two or more distinct forms, e.g.: blood groups, eye colour, whether one can roll one’s
tongue.
Artificial selection: is the selective breeding of plants and animals where specific
traits are modified, to satisfy human needs
Speciation: is the evolutionary process by which new biological species arise, due to
the splitting of the lineage. Speciation by natural selection may be allopatric or
sympatric.
Genetic diversity: is the level of biodiversity and refers to the total number of genetic
characteristics in the genetic makeup of a species.
Genetic divergence: is the process of one species diverging over time, into two or
more species where genetic characteristics are passed from one generation to the
next. The sequence of the genes as they appear on the DNA that will differ from
species to species, so when the genetics are altered, divergence takes place.
Extinction: all the individuals of a species die and are eliminated permanently
because they are unable to adapt to survive.
Allopatric speciation: results when geographical separation/isolation by water
masses or a mountain range creates a physical barrier between two populations.
Evidence that Evolution has occurred:
Theories of human evolution are based on research and scientific evidence that support
the concept of continual change. Sources like geology, anatomy, embryology, genetics
and physiology have been used as explanations for the theories. Further lines of evidence
are fossil records, modification of descent, Biogeography and genetics.
a) Fossil evidence: The evidence that shows characteristics that make us similar to or
different from African apes comes largely from a study of fossils (thousands of fossil
fragments). The first record of living material preserved as a fossil, is from the
Palaeozoic era (540 million years ago).
Two methods that are used to determine the age of a fossil:
 Relative age: sedimentary rocks are formed over a long period of time and each layer
will contain the organisms that lived at a certain period of time. Each layer is covered
over with a new layer of sedimentary rock and soil. Fossils found in the upper layers
will be newer that those found lower down so the depth of the fossils will determine
their relative age. Fossils found in one stratum of rock are compared to strata from later
periods resulting in a progression of forms. Organisms without a backbone show
modifications and development into organisms that have a backbone. The
archaeologists have also recorded fish that have modified into amphibians, amphibians
that have modified into reptiles and in later strata, the reptiles into mammals. Fossil
evidence supports these progressions.
 Absolute age: is accurate and is measured in years. Two techniques are used by
Archaeologists to deter the absolute age of a fossil:
© Gauteng Department of Education
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o Radio-active dating: there are radioactive elements like uranium in rocks
and as these rocks age, the uranium converts into lead. Scientists
measure the uranium and lead levels to determine the age of the fossils
embedded in the rocks. This method can only be used for fossils believed to
be older than 100 million years because the process of the uranium to lead
conversion takes a long time.
o Carbon dating: all living organisms contain a radioactive atom called
Carbon-14. When the organism dies, the Carbon-14 atom is converted
into nitrogen over time. Scientists know the rate of the conversion and the
period of time this takes. Once the level of Carbon-14 is determined in the
fossil, the age can calculated. This method will only be used for fossils
believed to be less than 50 000 years old.
b) Genetic evidence: Scientists state that organisms are closely related and are
likely to have a common ancestor if they have:
 Identical DNA structure
 Similar sequence of genes and
 Similar portions of DNA with no functions
Species that are closely related, have a greater similarity to each other than distant
species.
c) Modifications by descent: modifications obtained from the study of the details of the
structures of body parts and systems of organisms that belong to a specific phylum.
 Homologous organs: (homo = the same) similarity of the formation of a body part or
organ due to a common evolutionary origin, e.g.: the structure of the pentadactyl limb
in seals, bats and humans. The bones, muscles and nerves are arranged in a similar
manner in a front paw, wing and arm.

Nice to know:
Analogous organs: different structures of a body part or organ but with a similar
function, e.g.: lungs of mammals, trachea or air tubes of insects and gills of fish. These
organs have evolved in a different way to meet a common need to obtain oxygen in
mammals, insects and fish.
d) Cultural evidence: Cultural evidence from studies of tools and weapons, as well as
language is also used to show similarities and differences between humans and African
apes.
Sources of variation
The genotypes and therefore phenotypes (appearance) of individuals are different from
each other because:
a) Crossing over in Prophase I of meiosis involves an exchange of genetic material,
leading to new combinations of maternal and paternal genetic material in each new
cell resulting from meiosis
b) Random arrangement of maternal and paternal chromosomes at the equator
during metaphase allows different combinations of chromosomes/chromatids to go
into each new cell resulting from meiosis making them different
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c) Chance/ Random fertilisation between different egg cells and different sperm
cells formed by meiosis result in offspring that are different from each other
d) Random mating between organisms within a species lead to a different set of
offspring from each mating pair
e) Mutation changes the structure of a gene and therefore the organisms genotype.
Since the genotype influences the phenotype, it creates organisms with new,
different characteristics from one generation to the next.
Origins about the ideas about origins:
Lamarckism
Darwinism
Jean Batiste de Lamarck
(1744 to 1829)
Charles Darwin
(1809 to 1888)
De Lamarck suggested two
main themes:
1. ‘Use and disuse’: the
environment gives rise to
changes in animals e.g.:
blindness in moles, the
presence of teeth in
mammals, the absence of
teeth in birds and vestigial
organs (reduced pelvic
structures present in a
whale skeleton).
2. ‘Inheritance of acquired
characteristics’ that
caused change in
organisms de Lamarck
used the giraffe to explain
his theory - as the giraffe
stretched it’s neck to reach
higher leaves, it’s neck
stretched and grew longer
with each generation.
Lamarck’s theories are
based on his belief that
there are two forces he saw
as comprising evolution;
 a force driving animals
Charles Darwin wrote On
the Origin of Species,
published in 1859. Here he
concludes that organisms
have evolved by small,
gradual changes that took
place over many successive
generations.
Darwin was influenced by
the writings of Alfred
Wallace and stated that the
present species are
modified descendants
from the species of the past,
i.e.: one common ancestor.
Evolution can be explained
as the constant change
that has taken place.
Darwin’s book was the first
theory about evolution to be
published. His theory was
supported by scientific
evidence and was regarded
as credible.
The process of change was
called natural selection.
Punctuated
Equilibrium
(Theory proposed by Mayr in
1954 and recognised in
1972 after a paper was
submitted by Eldredge and
Gould)
A theory based on
evolutionary biology where
little change occurs within a
species (called stasis) until a
rare geological event takes
place. Cladogenesis results
after this event, which is the
splitting of a species into two
distinct and different
species. This is opposite to
the gradual transformation
process within a species into
a different species as
proposed by Darwin.
Punctuated equilibrium
extends from the theories of
allopatric speciation,
where a new species results
when a geographical barrier
like a water mass or
mountain range causes
separation or isolation of a
population. The physical
barrier between the two
populations allows genotypic
and phenotypic divergence
within each isolated
population, so they
eventually become so
different that they cannot
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
from simple to complex
forms, and
a force adapting animals
to their local
environments thereby
differentiating them from
each other.
The long-term changes in
the species were called
evolution.
The result of this change
over time results in
Diversity.
Reason for theory being
rejected:
It is agreed that physically
stretching the neck cannot
alter the gene make-up of
the animal. Only the
genetics of the organism
can cause a physical
change.
interbreed.
This would explain the
discontinuity in physical
structures found in fossil
sample and records.
Generally, punctuated
equilibrium is used to
explain evolution in nonsexual species like viruses
and bacteria.
Observations upon which Darwin based his theory:




Organisms of a species produce a large number of offspring.
The offspring show a great deal of variation.
Of the large number of offspring produced, only a few survive.
Characteristics are inherited from the surviving parents to the offspring.
Darwin’s theory of evolution by natural selection:









Organisms produce a large number of offspring.
There is a great deal of variation amongst the offspring.
Some have favourable characteristics and some do not.
When there is a change in the environmental conditions or if there is competition,
the organisms with characteristics that make them more suited, will survive.
While organisms with characteristics that make them less suited, will die.
The organisms that survive, will be able to reproduce,
thus they will pass their favourable characteristics on to their offspring.
The next generation will therefore have a higher proportion of individuals with the
favourable characteristics.
Organisms adapt to survive in their environment. The variation between individuals is
due to differences in genes. Only individuals who have characteristics that are adapted to
the environment will survive. They reproduce and pass the suitable characteristics to the
next generation by natural selection and so, evolution results. If the characteristics are
not suitable for survival, the organism cannot adapt and will die leading to eventual
extinction of the species. Conservation is a process to ensure that biodiversity is
maintained so that populations do not become extinct.
Artificial selection in plants and animals
Artificial selection is the selective breeding of plants and animals, where specific traits are
modified, to satisfy human needs. Humans have conducted experiments to develop
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organisms with selected and desirable characteristics, like cattle that produce better
quality and quantity meat and milk, drought resistant wheat and sugar cane with more
sugar etc.
This is an evolutionary mechanism that results in:
 new breeds (animals)
 new strains (micro-organisms) and
 new varieties (plants).
New varieties of plants and animal breeds are produced relatively quickly by selecting
parent organisms with the desired traits. The commercially viable organism would be
homozygous for all the genes involved, whether dominant or recessive, for their desired
trait.
Animals
Inbreeding
Outbreeding
What is it?
Inbreeding is the mating or
Outbreeding is the mating of
breeding of two genetically
individuals of totally unrelated
related individuals to enhance
strains. This leads to offspring that
the desirable traits.
are better adapted for survival, than
either of the parents. This
phenomenon is termed hybrid
vigour.
Examples:
 thorough bred racing and
 mongrel dogs are crossed from
show jumping horses
two different dog sub-species and
are far stronger and hardier than
 milk producing cows
highly pedigreed purebreds.
 many varieties of dog breeds
 sheep with better quality and  mules are a cross between a
horse and a donkey and are
quantity of wool production
much stronger and better suited
to many more tasks than either
parent.
Advantages:
Desirable traits are enhanced in When sub-species are crossed, a
the species without
stronger more resilient breed results
contamination from other
since desirable traits are bred into
species, resulting is a very pure the species.
breed. Animals with
undesirable or weak traits
should be culled.
Disadvantages: The gene pool becomes
In some cases of cross species
restricted. The strain may
breeding, the hybrid may not be able
become homozygous for
to reproduce, because chromosomes
multiple defective traits:
cannot form homologous pairs during
meiosis. This will result in hybrid
 certain dog breeds like
sterility, e.g.: mules are unable to
German shepherds are
breed.
vulnerable to hip dysplasia
(weak hips) and congenital
femur dislocation
 fighting dogs like the South
African Boerboel often
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become very aggressive and
go mad as adults resulting in
them having to be put to
sleep.
Something interesting: Cheetahs are an endangered species. The closed gene pool
has meant a very low genetic diversity. This in turn has resulted in poor sperm quality,
impacting breeding and survival of the young difficult where only about 5% of cheetahs
survive to adulthood. It is estimated that about 10,000 years ago, all cheetah species died
out, except the jubatus cheetahs. The species encountered a population bottleneck and
close family relatives were forced inbreed. Zoologists have found that the female cheetah
can mate with more than one male per litter because they undergo induced ovulation.
This means that a new egg is produced each time a female mates while in season. When
a female has multiple mates per litter, she is able to increase genetic diversity within her
litter.
Plants: Artificial selection in plants is the deliberate altering of the genetic make-up.
The interbreeding of desired traits continues until a new variety is produced. Homologous
recombination of the chromosomes is used to generate genetic diversity. Crosspollination between varieties would be part of the process. For example, fast growing
wheat may be crossed with high-yielding but slow growing wheat. The offspring will be
crossed again until a new species results that is fast growing and high yielding. Refer to
Mendel’s tall and short varieties of pea plants. Plant breeding and genetic engineering is
used to produce crops that are high-yielding, fast growing, pest and disease resistant,
drought resistant, frost resistant and require less water.
Similarities between natural selection and artificial selection:
 Organisms with the desirable traits survive and pass these traits on to their offspring
 Organisms that are weak or with the undesirable traits do not survive
 Hybrids are often sterile e.g.: mules, seedless fruit etc.
Differences between natural selection and artificial selection:
Natural Selection
Artificial Selection
The environment or nature is the
selective force
Selection is in response to suitability to
the environment
It occurs within a species
Humans are the selective force
Selection is in response to satisfying
human needs
May involve 1 or more species e.g.: cross
breeding different traits in each species
Punctuated Equilibrium:
Based on Darwinism, it is thought that evolution takes place through an accumulation of
small and gradual changes that occur over a long period of time. This is supported by the
many transitional fossils in fossil records, that show the progressive changes over time.
Punctuated equilibrium explains the speed at which evolution takes place as follows:
 According to punctuated equilibrium, evolution is not gradual as proposed by
Darwinism.
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



Evolution involved long periods of time where species do not change or they change
very little (know as equilibrium).
This alternates with (is punctuated by) short periods of time where rapid changes occur
through natural selection.
As a result, new species develop in a short period of time, relative to the long periods
where little or no change occurred.
This is supported by the absence of transitional fossils (usually termed the ‘missing
links’) indicating the period of rapid change.
Formation of new species
Remember: a species is a group of organisms that are similar in appearance, share the
same DNA sequences, perform the same mating rituals and interbreed to produce
viable offspring. A population is a group of organisms of different ages, that belong to the
same species, live in the same area and interbreed.
Speciation is the evolutionary process so that new biological species develops, due to
the splitting of the lineage. This results in the variety of different plant and animal species
found on earth, because diversity is the result of change over time. But, when the new
species is unable or not adapted to cope with changes in the environment, all the
individuals of a species will die. This means that they are permanently eliminated because
they are unable to adapt to survive. This is called extinction. Speciation by natural
selection may be allopatric or sympatric.
Speciation results because of:
 Allopatric speciation:
o If a population of a single species
o Becomes separated by a geographical barrier (sea, river, mountain, lake)
o Then the population splits into two populations.
o There is now no gene flow through the two populations.
o Since each population may be exposed to different environmental conditions,
o Natural selection occurs independently in each of the two populations
o So that the individuals of the two populations become very different from each
other
o Genotypically (their genes are different) and phenotypically (their physical
appearance)
o Even if the two populations were to mix again,
o They will not be able to reproduce with each other/
o They have become TWO different species.
An example of Allopatric Specialtion: Galapagos finches
Darwin stated that the present species are modified descendants from the species of the
past. It was supported by scientific evidence and was regarded as credible.
Darwin spent time on the Galapagos Islands (about 965 km west of Ecuador) where he
studied the fauna and flora. Darwin carefully recorded the appearance of the Galapagos
finches. Darwin’s conclusion: the variation between the finch species was due to
lifestyle and behaviour. He suggested that this proved his theory of natural selection.
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Keeping species separate:
When one species gives rise to two new species (speciation), the two new species cannot
reproduce with each other if they mix. They remain as separate species due to
mechanisms that restrict gene flow between them. This is termed reproductive isolation
and result because of:
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



Seasonal isolation: when breeding/reproduction takes place at different times of the
season or year. In plants, anthers and stigma mature at different times, to prevent
cross-pollination.
Behavioural isolation: animals behave differently during courting and mating rituals
- females are not responsive, so no mating takes place.
Mechanical isolation: when male and female reproductive parts change, making
gene transfer impossible. In flowers, the stigma normally releases enzymes to
stimulate the growth of the pollen tube. In this case, the enzyme will not stimulate
growth, so pollen grain will not grow. In animals, the genitals change so the sperm
cannot be transferred into the female, should mating be attempted.
Gamete isolation: when genes change, gametes become chemically altered, so
fusion of the gametes is impossible. Should the gametes fuse, gamete isolation will
prevent the recycling of the genetic material, e.g.: donkey + horse = infertile offspring
called a mule.
Evolution in present times:
Natural selection and evolution are still taking place in present times. Select One
example:
 DDT (dichloro-diphenyl-trichloroethane)
Many years ago, mosquito breeding areas were sprayed with an insecticide called DDT
to prevent malaria by killing the mosquito larvae and was initially very effective.
However, some insects with mutations in their sodium channel gene were resistant to
DDT and with breeding took about 7 years for DDT to loose its effectiveness. This that
the genetic trait that caused the resistance to DDT was homozygous recessive and
eventually resulted in the evolution of the mosquito into a new DDT resistant species.
However, the impact of DDT on the environment continues because it is nonbiodegradable and toxic. DDT was washed from the soil and leached into underground
water and eventually the sea. The weak solution of DDT was absorbed by microorganisms and through the food chain link, the concentration increased and resulted
in bio-accumulation. Cancer and many other diseases may result in humans. In
animals and birds, the toxin accumulation results in uncharacteristic behaviour, eggshell thinning and death. In 1972, the use of DDT was officially banned worldwide.

Resistant strains of TB
Tuberculosis is caused by a bacterium called Mycobacterium tuberculosis that attacks
the lungs, kidneys and bones. Symptoms would include chest pains, fever, coughing,
loss of weight and shortness of breath. Eventually, mucus and pus block the alveoli
causing them to burst, resulting in the person coughing infected spray droplets of
blood. Loss of alveoli causes lack of oxygen, resulting in physical weakness. TB is
also transmitted in infected milk. The TB bacteria are destroyed when exposed to
sunlight and infected people should be isolated and treated with antibiotics for a
minimum of six months. Children are immunised with inoculations at the local clinics.
The TB bacteria have evolved into ‘multi-drug resistant strains’ (MDR-TB), where
normal drugs are ineffective. In 2006, ‘extensively drug-resistant tuberculosis’
(XDR-TB) was identified. MDR-TB tends to develop when patients miss doses of
antibiotics or do not complete the full treatment. This strain seems less virulent and
does not appear to dominate naturally. But XDR-TB has a much higher mortality rate
than MDR-TB and does not seem to transmit in healthy populations but appears to be
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more prevalent in individuals who are HIV positive. With the XDR-TB strain, from
onset of the disease to death takes approximately 15 to 20 days as this strain does not
respond to any of the drugs presently available in South Africa.
SECTION C:
HOMEWORK QUESTIONS
QUESTION 1: 20 minutes
(Taken from DoE Additional Exemplar 2008 Paper 2)
Since 1972, biologists Peter and Rosemary Grant from Princeton University USA have
studied finch populations in the Galapagos Archipelago. The table below shows their data
for one finch population on one island (Daphne Major), for a period of 7 years.
1.1.
1.2.
1.3.
1.4.
1.5.
Use the information in the table to draw a line graph to show the number of
finches from 1974 until 1980.
(11)
(Your clue here is in the question: you must show the number of finches and
the years (time). Time ALWAYS goes onto the X-axis because it is the
INDEPENDENT variable. The number of finches will be on the Y-axis because
it is the DEPENDENT variable. Remember to do a heading for your graph and
make sure that the spacing of the points on the X-axis is the same as the
spacing on the Y-axis.)
In which year were the largest drop in rainfall, number of seeds and number of
finches recorded?
(1)
Explain how the three events mentioned in QUESTION 1.2 are related to each
other.
(3)
When the number of finches decreased, there were still plenty of large seeds on
the island. What does this tell you about the seed eating habits of the finches
that died?
(2)
Do you think there was a difference in the beak sizes of the dead finches and
the surviving finches? Explain your answer.
(3)
[20]
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QUESTION 2:
17 minutes
(Taken from DoE Preparatory Examination 2008 Paper 2)
Study the diagram below and answer the questions that follow.
2.1.
2.2.
2.3.
Define a population.
Describe how sub-population B could form a new species.
Tabulate 3 differences between natural selection and artificial selection.
SECTION D:
(4)
(6)
(7)
[17]
SOLUTIONS FOR SECTION A
QUESTION 1:
1.1. Shoot grows without any change in direction / upright / no change ✓(1)
1.2. Has no effect ✓on phototropism beyond any wavelength in the rage 580 to
590 nm ✓ (2)
1.3. - shorter wavelength increases ✓effectiveness
- longer wavelength decreases ✓effectiveness (2)
OR
- has the greatest influence ✓on phototropism ✓
1.4. Auxins / Indole acetic acid / IAA ✓ (1)
1.5. Leaves are exposed more favourably to light ✓to enhance photosynthesis ✓(2)
[10]
QUESTION 2:
2.1
Shoots ✓will grow towards ✓the light
OR
Shoots ✓will grow away ✓from the light
OR
Light has no ✓influence ✓on the shoot (2)
2.2
It is the control ✓- To verify the results of the experiment ✓/To allow for
one variable only. (2)
2.3
Shoots grow ✓towards the source of light ✓. (2)
2.4
The auxins ✓that make the shoot to grow towards the light is in the tips
of the shoots ✓. (2)
2.5
(a) Apical dominance ✓ (1)
(b) Tall growth of a plant/stimulate seed germination ✓
(1)
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49
QUESTION 3:
3.1
A species is one or more populations whose members actually or potentially
interbreed ✓under natural conditions, produce fertile offspring ✓and are
reproductively isolated ✓from other such groups. (3)
3.2
When a geographical barrier ✓ e.g. mountain, river, sea, etc.
separates a subpopulation of breeding individuals from the parent population ✓ (2)
3.3
(Less) seeds available on the island ✓/competition for seeds available/availability of
different sources of food (1)
3.4
Allopatric speciation:
o If a population of a single species✓
o Becomes separated by a geographical barrier (sea, river, mountain, lake) ✓
o Then the population splits into two populations. ✓
o There is now no gene flow through the two populations. ✓
o Since each population may be exposed to different environmental conditions✓,
o Natural selection occurs independently in each of the two populations✓
o So that the individuals of the two populations become very different from each
other✓
o Genotypically (their genes are different) and phenotypically (their physical
appearance) ✓
o Even if the two populations were to mix again, ✓
o They will not be able to reproduce with each other✓
o They have become TWO different species. ✓ (any 10)
[16]
QUESTION 4:
4.1
(a) Darwin
- As a result of genetic variation ✓in the giraffe population
- some giraffes have longer necks ✓ than others
- Environmental change ✓/competition for resources occurred
- causing those with shorter necks to die ✓
- and those with longer necks to survive ✓
- This is natural selection ✓/survival of the fittest
- The genes ✓/genotype for longer necks
- were passed on to subsequent generations ✓ most of which now have long necks
any (4)
(b) Lamarck
- All giraffes had short necks ✓originally
- Giraffes frequently stretched ✓/used their necks to reach
- for leaves of tall trees ✓
- necks become longer ✓
- The long necks acquired ✓in this way
could be passed on to the next generation ✓ /were inherited any (4)
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4.2
Acquired characteristics ✓are not inherited ✓/do not cause any change to the
DNA of an organism's gametes (sperms or ova)
OR
Organisms did not evolve because they want to evolve ✓✓/
Lamarck’s theory is deterministic ✓✓ (2)
4.3.
a) Crossing over in Prophase I ✓of meiosis involves an exchange of genetic
material✓, leading to new combinations✓of maternal and paternal genetic material
in each new cell ✓resulting from meiosis (4)
b) Random arrangement of chromosomes at the equator during metaphase✓
allows different combinations of chromosomes✓ / chromatids to go into each new
cell ✓resulting from meiosis making them different (2)
c) Chance/ Random fertilisation between different egg cells ✓and different sperm
cells ✓formed by meiosis ✓result in offspring that are different from each other✓(4)
d) Mutation changes the structure of a gene ✓and therefore the organisms
genotype✓. Since the genotype influences the phenotype✓, it creates organisms
with new, different characteristics from one generation to the next✓. (4)
[24]
SESSION NO: 13
TOPIC: EVOLUTION 2
SECTION A: TYPICAL EXAM QUESTIONS
QUESTION 1:
10 Minutes (Taken from DoE November 2008 Paper 1)
The following two questions refer to the characteristics of Homo sapiens and African apes.
1.1
State FOUR structural characteristics of Homo sapiens that are similar to African
apes.
(4)
1.2
Tabulate FOUR structural differences between the skull of Homo sapiens
and that of African apes.
(9)
QUESTION 2:
8 Minutes
(Taken from DBE November 2010 Paper 2)
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Study the diagrams below of the upper jaw, skull and the foot of two organisms A and B.
The diagrams are NOT drawn to scale.
2.1.
With regard to the drawings above:
(a) Tabulate TWO visible differences between the upper jaws of organisms
A and B.
(5)
(b) Name ONE visible difference between the feet of organisms A and B.(2)
2.2.
2.3.
Which organism (A or B) is more likely to be bipedal?
Give a reason for your answer to QUESTION 2.2.
QUESTION 3: 5 minutes
(Taken from DoE Feb/March 2010 Paper 2)
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(1)
(2)
52
The diagram below shows a phylogenetic tree based on DNA similarities. The
percentage next to each branch shows the amount of difference in the genome (DNA
nucleotide sequence) of the two relevant groups.
3.1.
3.2.
3.3
From the diagram, determine how long ago the chimpanzees split from the
line to humans.
(2)
(HINT: Use a ruler so that you are accurate in your readings)
Which organism is most closely related to humans?
(1)
Calculate the DNA similarity between the genome of the chimpanzee and
the human.
(2)
QUESTION 4: 8 minutes
(Taken from DoE Feb/March 2009 Paper 2)
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A comparison of the anatomical features of organisms has helped scientists to propose
evolutionary relationships. Please study the following diagram and answer the questions
that follow:
4.1.
4.2.
4.3.
Tabulate THREE observable differences between the side view of the skulls
of Homo and the chimpanzee.
(7)
(Hint: When you are asked to tabulate, you must draw a table. You get marks
for this. Always compare the same things in each point)
Which ONE of the organisms (Australopithecus or chimpanzee) is/was a
quadruped?
(1)
Give ONE observable reason for your answer to QUESTION 4.2.
(1)
QUESTION 5: 6 minutes (Taken from DoE Preparatory Examination 2008 Paper 2)
In an investigation a biotechnologist injected chimpanzee blood into a rabbit. The immune
system of the rabbit recognized the chimpanzee blood protein as foreign and produced
antibodies. The rabbit's antibodies were then extracted and developed as a serum.
When the serum is added to blood samples in different test tubes removed from a variety
of different animals, a precipitate forms. The more precipitate forms, the more closely
related the animal is to the chimpanzee.
Study the table below that shows the percentage precipitate formed in this investigation,
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and answer the questions that follow.
5.1.
5.2.
5.3.
5.4.
What is the composition of the serum?
(2)
According to the above information, which animal is least closely related to
chimpanzees? Give a reason for your answer.
(2)
Formulate a hypothesis for the investigation above.
(2)
Name TWO variables that had to be kept constant in this investigation. (2)
QUESTION 6: 8 minutes
(Taken from DoE Additional Exemplar 2008 Paper 2)
During the study of the fossil records the following timeline of hominids were constructed.
Study it and answer the questions that follow.
6.1.
6.2.
How many million years ago did the hominid group split (at A) into two
groups?
(1)
What is the main characteristic that caused the hominids to split into two
separate groups at A?
(1)
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6.3.
6.4.
6.5.
Which organism is thought to be the immediate ancestor of A. robustus? (1)
What are the common names of the TWO Australopithecus species fossils that
were discovered in South Africa?
(2)
List FOUR characteristics that African apes and humans have in common.(4)
QUESTION 7: 10 minutes (Taken from DoE Feb/March 2010 Paper 2)
Study the two skulls on the next page (drawn to the same scale) and answer the questions
that follow.
7.1.
7.2.
7.3.
Tabulate THREE visible differences from the two skulls shown above
that scientists have used to differentiate between Homo sapiens and African apes.
(7)
Give THREE examples of fossils of Australopithecus that were discovered
in Southern Africa.
(3)
Explain the importance of the discoveries of the skulls of Australopithecus
in understanding the evolutionary development of humans.
(2)
QUESTION 8: 10 minutes (Taken from DoE Exemplar 2008 Paper 2)
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The diagrams below represent the skull, the upper jaw and lower jaw of three organisms,
the Taung child (Australopithecus africanus), a modern human (Homo sapiens) and a
gorilla (Gorilla gorilla). The arrow indicates the position of the foramen magnum (the
opening that allows the spinal cord to connect with the brain). Study the diagrams and
answer the questions that follow.
8.1.
8.2.
8.3.
8.4.
8.5.
Identify the organisms that are represented by each of A, B and C.
(3)
[Hint: make sure you read the passage provided properly]
Assuming that the diagrams were drawn to scale, name TWO observable
differences between the skulls of organisms A and B.
(4)
Which organism (A, B or C) represents a carnivore?
(1)
Explain your answer to QUESTION 8.3 using features visible in the
diagram.
(2)
Name TWO organisms that are best adapted for walking on two legs rather
than four legs, by looking at the position of the foramen magnum (indicated
by the arrows on the diagram above).
(2)
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SECTION B: CONTENT SUMMARY
Human evolution
Anthropogenesis is the study of human evolution and the development of Homo sapiens
as a distinct species from the ancestral superfamily, Hominoidea. Scientific disciplines
like anthropology, primatology, archaeology and genetics are used to map out the origin of
humankind.
Evidence of common ancestors for living hominids, including humans
The term ‘Homo’ refers to the genus and means ‘human’. Studies of human evolution
must include hominids such as the Australopithecines, as it is theorized that the Homo
genus diverged (split) from them about four million years ago in Africa. Scientists have
estimated that humans branched from their common ancestor with the chimpanzee about
five to six million years ago. Other species of Homo like Homo erectus and Homo
neanderthalus have all become extinct. Substantial fossil proof exists to explain hominid
evolution, although it is not enough to make specific conclusions.
Fossil Evidence:
 Scientists estimate that the earth is more than 5 billion years old.
 Geological evidence indicates that simple forms of life on earth appeared 3,5 billion
years ago.
 There are many hypotheses but none have been irrefutably proven.
 Archaeologists have provided fossil evidence to prove that relationships existed
between the Early Stone Age cultures in Europe and Northern Africa.
 Discoveries in South Africa, Kenya and Zimbabwe have been used to prove and
validate that Africa was the home of early man.
Genetic Evidence:
 Scientists generally theorize that the Homo/Pan split of Hominini occurred over a
period of 4 million years and took place about 5 to 6 million years ago. This is based
on studies of the key gene sequences of modern humans and chimpanzees.
 Generally, species that belong to the same subfamily should generally share more than
97% of their DNA. But the similarity between the modern human genome and the
chimpanzee genome is only about 70%.
 When DNA segments are analyzed and compared, the genetic sequence divergence
(the process of one species diverging over time, into two or more species where
genetic characteristics are passed from one generation to the next) varies significantly
between humans and chimpanzees.
 Chimpanzee, gorilla and orangutan genomes have been sequenced and have 24 pairs
of chromosomes. Humans only have 23 pairs of chromosomes, because the
human chromosome 2 represents a fusion of two chromosomes that remained
separate in the rest of the primates.
 Mitochondrial DNA: You have already learned that MtDNA is the smallest
chromosome located in the mitochondria and forms part of the organisms’ genome. In
most species, mtDNA is inherited from the mother (maternal inheritance). The
sequencing of the mtDNA shows a link in phylogenetics and evolutionary
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relationships between species. The age of the common ancestral mtDNA can be
estimated to have existed approximately 140,000 to 290,000 years ago linking humans
to Mitochondrial Eve.
Cultural evidence: tool-making
 The earliest hominids to use simple tools known as Oldowan stone tools, were Homo
habilis that lived around 2.6 Ma and signifies the start of the Stone Age.
 Homo habilis fossils have been found in many parts of Africa with tools that were made
of stone and used to aid hunting and cutting of food.
 Homo erectus developed more advanced tools that included sharpened stones
placed on wooden handles, like an axe.
 They were also the first species to use flints and quartzite to make fire.
 Later fossil evidence shows tools like scrapers probably used to clean animal skins,
slicers and needles used to sew animal pelts into the first form of clothes.
 From this point, tools progressed to knives and blades used by the Neanderthals
used for hunting and protection.
 Fossil evidence shows that as the different species developed larger brains and greater
intelligence, so their tools became more complex.
Phylogenetic trees:
A phylogenetic tree is a schematic form that shows the evolutionary relationships within a
set of organisms or groups of organisms. Phylo = organism’s phylum group and genetic =
from the genes/relationship between the genes
Hints on interpreting phylogenetic trees:
(Modified from Mind the Gap: Grade 12 Life Sciences)
Reading a phylogenetic tree is similar to understanding a family tree. The base of the tree
represents the oldest ancestor and the tips of the branches represent the most recent
descendants of that ancestor. As you move from the base of the tree, to the tips of the
branches, you are moving forward in time. For example: your Great grand Father = the
tree base. Your grandfather and all his brothers and sisters = branches of the tree. Your
father and all his brothers and sisters = smaller branches that divide from your grand
father’s branch. You = tip of your father’s branch.
When speciation occurs, it is represented as branching on the tree. A single ancestral
lineage (family line) gives rise to two or more daughter lineages. Daughter lineages does
not mean girl children or offspring – it means the individuals that are related to the original
ancestor.
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Each lineage has a part of its history that is unique and parts that are shared with other
lineages. (Like your father is related to his father/your grandfather, but will share
characteristics that he inherited from his mother/your grandmother as well.)
Similarly, each lineage has ancestors that are unique to that lineage and
common ancestors that are shared with other lineages. (Like your father will share
characteristics with his brothers and sisters and you will share some characteristics with
your cousins/children of your uncles and aunts from your father’s side.)
Phylogenetic tree in schematic form, to show the place of the family Hominidae in
the animal kingdom: Scientific classification of African apes.
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Characteristics that humans share with other Africa apes:
 opposable thumb with power grip and precision grip (so we are able to hold grasp and
wrap the fingers around objects while the thumb stands loose to hold around the other
side)
 bare finger tips – for a better sense of touch
 long arms (primates have much longer arms than humans, to enable them to swing in
trees and for a more fluid movement)
 freely rotating arms and hands - due to the ball-and-socket joint at the shoulder and
the gliding joint in the wrist both joints are able to rotate through 180o
 stereoscopic vision – where two eyes are able to focus on one object and perceive
depth
 visual acuity – eyes have an increased number of rod AND cone cells with their own
nerve cells where cone cells enable us to see colour
 large brain when compared to body mass – allowing for intelligence and thinking
patterns
 brain centres that are able to process information from the senses are enlarged and
function well - sense of touch and sight especially
 olfactory centre (sense of smell) in the brain is reduced
 few offspring – humans and primates have longer gestation periods, less offspring
and increased parental care
 upright posture and bipedalism (bi = two and pedal = walk, so bipedalism means
walking on two legs. Primates sometimes move on two legs but often use their arms to
assist them)
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
social dependency – group cohesion and living together enjoying shared activities
Characteristics that make humans different from other Africa apes:
 humans are always bipedal as we always only walk on two legs and never use our
hands on the ground. Walking on two legs has implications beyond those affecting the
skeleton and muscles as scientists theorize that the upright posture and subsequent
changes to the nervous system resulted in the enlargement of the cerebral
hemispheres. (see figure 21-7 below)
 a human face and skull is flat with no prognathous (protruding jaw structure) (see
diagram a below)
 dentition (teeth) is similar to that of monkeys and apes but different from that of older
primates like the gorilla with smaller canines since humans do not require large
canines to rip flesh to eat or for defense. Teeth are aligned into the jaws in a gentle
curve/’u’ shape (see diagram c below)
 larger brain than primates (brain size varies from 1200ml to 1800ml with the average
size being 1400ml) (see diagram b below)
 humans have learned to communicate through language
Anatomical differences between Humans (Homo sapiens) and African Apes
FEATURE
Cranium
Brow Ridges
Cranial ridges
Humans (Homo sapiens)
Large cranium/brain
Brow ridges are not well
developed
More curved spine
Short, wide pelvis
Small canines
Small and semi-circular
- Small jaws
- Less protruding
jaws/less-prognathous
No cranial ridge
Foramen
Magnum
Foramen magnum in a
forward position
Spine
Pelvic girdle
Canines
Palate shape
Jaws
African Apes
Small cranium/brain
Brow ridges well developed
Less curved spine
Long, narrow pelvis
Large canines
Long and rectangular
- Large jaws
- More protruding jaws/
more prognathous
Cranial ridge across the top of the
cranium
Foramen magnum in a backward
position
The process of the gradual transition to becoming human is called hominization and
refers not only to the physical changes that took place like diet, movement and skeletal
structure, but also the accelerated development of social behaviour.
Hominization is believed to have been influenced by:
 the development of speech (oral communication)
 changes in sexual behaviour with pair bonding, favouring and protection of mate and
increased parental supervision of offspring
 the development of a communal and social structure that allowed individuals to group
together to hunt, share food and work as a unit to survive
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Out of Africa hypothesis and evidence for African origins of modern
humans
The Out of Africa hypothesis was developed by Chris Stringer and Peter Andrews. This
hypothesis states that modern Homo sapiens evolved in Africa about 200,000 years ago
and migrated outwards to Europe and Asia, according to the Southern Dispersal theory.
Most scientists agree that modern humans (Homo sapiens) evolved in Africa and
spread outwards across the continents.
There is evidence that defines the origin and evolution of humankind with fossils of
several specimens of early hominids, dating back to between 4,5 million and 2,5 million
years.
Fossil Records:
What was found:
The first Ardipithecus.
ramidus fossils was
discovered dating to
between 4.35 and 4.45
million years old and
called ‘Ardi’
NOTE: Ardipithecus is
regarded as the last
common chimpanzeehuman ancestor
An excavated 40% of a
3.2 million year old
skeleton of an
Australopithecus
afarensis called ‘Lucy’
Who found it:
Tim White
1983
Where was it
found:
Middle Awash
Valley of
Ethiopia’s
Afar
Depression
(Africa)
Relevance:
Brain size 20% of the
modern Homo sapiens
brain. Teeth were less
sharp, smaller than
common chimpanzees
and show an
omnivorous diet and
more like ancestral
hominids. Feet were
better suited for walking
than climbing
Lucy’s skull capacity
was small like apes, but
showed bipedalism like
humans proving the
theory that bipedalism
preceded the increase of
the human brain size
Team:
Maurice Taieb,
Donald
Johnson, Mary
Leakey and
Yves Coppens
1974
Hadar in the
Awash Valley
of Ethiopia’s
Afar
Depression
(Africa)
The near-complete 3.3
million year old
Australopithecus
skeleton called Little
Foot
Dr Ronald J
Clarke
1997
Swartkrans in
the Cradle of
Humankind
(South Africa)
Also found evidence for
the controlled use of fire
dating back to 1 million
years ago
A juvenile
Australopithecus
africanus skull called the
‘Taung Child’
Raymond Dart
1924
Taung is a
small town in
the North
West
Province
called
Sterkfontein
(South Africa)
The Taung Chil’s skull
shows that it was
positioned directly above
the spine, indicating an
upright posture. This is a
trait seen in humans, but
not other primates.
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A 2,3-million year old
fossil of Australopithecus
africanus, commonly
know as the famous ‘Mrs
Ples’
Dr Robert
Sterkfontein
Broom and
Caves
John Robinson (Africa)
1947
A 1,8 million fossil of
Homo habilis that was
called ‘Twiggy’
Peter Nzube
1968
A Homo erectus skeleton Bernard
1,9 million years old
Ngeneo
1975
Tanzania
(Africa)
Kenya
(Africa)
The uncovering of Mrs
Ples provided further
proof of the development
of humankind and
supported the findings of
the Taung Child
Average brain size
approx. 650 cc (46% of
human brain size).
Showed bipedalism.
Teeth were similar to
humans with no
pronounced canines.
Primitive stone tools
found at excavation
sites.
Homo erectus was taller
than Homo habilis, skull
looked more ape-like
with teeth more similar
to humans. More
advanced stone tools
were found.
Other important anthropologists, archaeologists and palaeontologists are:
Lee Berger: in 1991 he discovered the first hominid specimens at the Gladysvale site, 13
km northeast from Sterkfontein, in the Cradle of Humankind. In 2001, together with
Steven Churchill, they found early modern human skeletons at Plover’s Lake and the first
hominid fossils and stone tools at Coopers.
Andre Keyser: in 1994 he discovered the most complete Australopithecine female skull
ever excavated at the site of Drimolen, near Sterkfontein. In 1997 he found two children’s
skulls at the same site.
Mitochondrial DNA research supports the Out of Africa hypothesis:
 Researches using mitochondrial DNA and genetic, linguistic (language) and
archaeological evidence (from fossils) have concluded that all were descended from
one woman from Africa, called Mitochondrial Eve.
 The Out of Africa theory is supported by the fact that genetic diversity is the highest
among African populations.
 Anthropologists and palaeontologists have collected substantial evidence to prove that
humans moved from Africa to settle in Europe and Asia, approximately around the
glacial period. Some underwent a process of bleaching, which resulted in the fairskinned, light-eyed and blonde-haired people of Britain, Scandinavia and Germany.
 The oldest centres of civilisation are located in Egypt, Mesopotamia and the Indus
basin. The question is: why did early humans emigrate from Africa to Europe and
Asia? One possible explanation is that the glacial period altered the climate in
Northern Africa from very hot and dry to very cold. Food sources like plants and
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animals would have been severely impacted, so movement to a warmer place where
there was an abundance of food took place.
Extra Info: The Cradle of Humankind
The Cradle of Humankind is a World Heritage Site first named by Unesco in 1999. It is
located about 50 km northwest of Johannesburg, South Africa. Hominid remains have
been excavated at the Cradle of Humankind. Many anthropologists believe that hominids
lived all over Africa, but their remains are only found at sites where their bones were
preserved into fossils, like at the Cradle of Humankind. Archaeological caves in the
Makapan Valley show traces of human occupation and evolution dating back about 3,3
million years.
SECTION C: HOMEWORK
QUESTION 1: 6 Minutes (Taken from WCED September 2009 Paper 2)
1.1
The rise of humans has been meteoric. What features of humans account for
this success?
(3)
1.2
Why is the Kromdraai area west of Johannesburg known as the “Cradle of
Mankind”?
(1)
1.3
Fossil remains of early man are comparatively rare. Why is this so?
(2)
QUESTION 2: 15 Minutes
(Modified from DoE Preparatory Examination 2008 Paper 2)
(HINT: This question is very similar to the question in Section A. Please note how a
similar question can be asked around the same topic.)
The diagram below shows the skull and pelvis of three mammals. Study the diagram and
answer the questions that follow.
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2.1.
2.2.
2.3.
2.4.
2.5.
Tabulate FOUR observable differences of the skull and pelvis of a
human and a chimpanzee.
(9)
Which organism(s) is/are bipedal?
(2)
Give ONE reason, observed from the diagram, for your answer to
QUESTION 2.2.
(2)
State ONE visible difference between the skull of Australopithecus and a
human.
(2)
Bipedal locomotion and upright posture is a distinctive trait of human beings.
Describe THREE advantages of bipedalism to humans today.
(3)
QUESTION 3: 6 Minutes
The size of the cranial cavity is used to estimate the size of the brain. The size of the
brain is used to roughly indicate intelligence. The table below shows the brain size of
apes and humans.
Name of living or fossil primate
Cranial capacity (in mm3)
Modern apes
Gibbon
100
Orang-utan
395
Chimpanzee
400
Gorilla
510
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Australopithecines
Early forms
450
Late forms
660
Early humans
Java man
870
Peking man
1050
Neanderthal man
1450
Modern humans
Cro-Magnon man
1660
Living man
1450
The early Australopithecines lived about 3 million years ago and the late
Australopithecines about 1,7 million years ago. It took about one million years for the size
of the human brain to double.
3.1. What is the size difference between the brain of Living man and Java man?(1)
3.2. Which early humans had the same size brain as Living man?
(1)
3.3. Think of possible reasons why Cro-Magnon man, who lived during the
Stone Age, had a larger brain than Living man.
(2)
3.4. Which of the Australopithecines had a brain size more or less the same
size as the modern apes?
(1)
3.5
What is a person called that would have dug up and studied the different
types of skulls in order to record the size of the brain?
(1)
QUESTION 4: 18 Minutes
(Taken from GDE Preparatory Examination 2009 Paper 2)
Study the pictures below on the parts of the skeletal structures of primates and answer the
questions that follow:
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4.1.
4.2.
4.3.
4.4.
4.5.
State ONE reason why apes and humans are referred to as ‘hominids’.
(2)
Name the term used to describe the locomotion of:
a)
humans
(1)
b)
chimpanzees
(1)
Suggest TWO ways in which locomotion of modern humans will be disadvantaged,
if they had the skeletal structure of apes and
chimpanzees.
(2)
Distinguish between the skeletal structure of man and the chimpanzee, other than
those mentioned in Question 4.3.
(5 x 2)
(10)
Predict the shortcomings (challenges) the ape would experience if it had the
phalanges of Homo sapiens.
(2)
[Hint: phalanges are the bones in the hand and foot]
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SECTION D: SOLUTIONS TO SECTION A
Question 1:
1.1
- Upright posture✓
- Long upper arms✓
- Freely rotating arms✓
- Elbow joints allowing rotation of forearm✓
- Rotate hands at least 180º✓
- Flat nails instead of claws✓/bare finger tips
- Opposable thumbs✓which work in opposite direction to their fingers
- Large brains/skulls compared to their body mass✓
- Eyes in front✓/binocular vision/stereoscopic vision
- Eyes with cones✓/colour vision
- Sexual dimorphism✓/distinct differences between male and female
- Olfactory brain centres reduced✓/reduced sense of smell
- Parts of the brain that process information from the hands and eyes are
enlarged✓
- Two mammary glands only✓
(Mark first FOUR answers only in learner’s script) any (4)
1.2.
(any 4 x 2 = 8 + 1 for table) (9)
Question 2:
2.1 (a)
Differences in jaws:
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(Mark first TWO only) any 2 x 2 +1 for Table (5)
(b)
2.2
2.3
Differences in Feet:
In A the big toe is close to the other 4 smaller toes and points forward ✓
In B the big toe is apart from the other 4 smaller toes and points outwards✓
OR
In A the heel bone is relatively larger ✓ and in B it is relatively smaller ✓
OR
In A the bones in the foot are straight ✓and in B they are curved ✓
OR
In A phalanges are relatively shorter ✓and in B they are relatively longer ✓
any 1 x 2 (Mark first ONE only) (2)
A✓
Foramen magnum ✓more towards the centre ✓of the skull in A / more
forward
OR
In B the foramen magnum✓more towards the back✓of the skull (2)
Question 3:
3.1
5P mya ✓ (1)
3.2
Chimpanzee ✓
3.3
98,6 ✓% ✓
Question 4:
4.1.
Homo
1. Canines not well developed ✓
Chimpanzee
1. Canines well developed ✓/form
fangs
2. Less protruding jaws ✓/not prognathus 2. Protruding jaws/prognathus ✓
3. Brow-ridge less pronounced ✓
3. Heavily pronounced brow- ridge ✓
4. Proportionally large cranium ✓
4. Proportionally smaller cranium ✓
5. Proportionally shorter cheek bone ✓
5. Proportionally larger cheek bone ✓
6. No ridge at base/back of skull ✓
6. Ridge at base/back of skull ✓
(Mark first THREE only) (any 3 x 2) 1 mark for table (7)
4.2
4.3
Chimpanzee ✓ (1)
The foramen magnum is towards the posterior/back of the skull ✓ (1)
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Question 5:
5.1
The serum contains antibodies √ against chimpanzee protein√ (2)
5.2
Pig, √ it only forms an very low % √ precipitate when the blood is exposed to
serum. (2)
5.3
A high percentage√ of precipitate formed indicates a close relationship√ with
chimpanzees
OR
A low percentage √ of precipitate formed indicates a no √ relationship with
chimpanzees
OR
A high percentage √ of precipitate formed indicates a weak √ relationship with
chimpanzees
OR
A low percentage √ of precipitate formed indicates a strong √ relationship with
chimpanzees (2)
5.4
Temperature√, pH√, concentration of serum√ amount of serum and blood the
same√ Any 2 (2)
Question 6:
6.1
4,6 – 4,8 ✓million years ago (1)
6.2
Bipedalism✓ (1)
6.3
Australopithecus afarensis ✓(1)
6.4
-Little foot
-Mrs Ples
-Taung child (any 2) (2) (Mark first TWO only)
6.5
Bare finger tips✓
Long arms ✓
Freely rotating arms ✓
Stereoscopic vision ✓
Eyes with cones (in addition to rods) ✓
Large brain compared to body mass ✓
Portions of brain centres that process information from hands and eyes
enlarged ✓
Olfactory brain centres✓
Few offspring ✓
(Mark first FOUR only) (4)
Question 7:
7.1
Homo sapiens
A. africanus
1
No prominent brow ridge ✓
1 Prominent brow ridge present ✓
2
Flat face ✓
2 Prognathous face ✓
3
More rounded skull ✓
3 Less rounded skull ✓
4
Teeth arranged on a gentle(round) 4 Teeth arranged in a less curved
curve ✓/more rounded upper jaw
way ✓/less rounded upper jaw
5
Smaller upper jaw ✓
5 Larger upper jaw ✓
6
Smaller cheekbone ✓
6 Larger cheekbone ✓
7
Deeper set eye sockets ✓
7 Shallower set eye sockets ✓
(Mark first THREE only) (3x2 + 1 for table) (7)
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7.2
7.3
Little foot ✓
Mrs Ples ✓
Taung child ✓
(3) (Mark first THREE only)
Foramen magnum of the australopithecine was towards the centre✓ indicating that
these were the first bipedal hominids ✓on Earth OR Large jaws✓indicate a mainly
vegetarian diet ✓ (any 2) (2)
[12]
Question 8:
8.1
A - Modern human (Homo sapiens) ✓
B - Gorilla (Gorilla gorilla) ✓
C - Taung child (Australopithecus africanus) ✓(3)
8.2.
8.3
8.4
8.5
(Mark first TWO only)
B✓(1)
It has most developed✓canines✓ (2)
A✓and C✓ (2) (Mark first TWO only)
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SESSION NO: 14
TOPIC: CONSOLIDATION PAPER 1 A
End of year examinations: Grade 12
The examination will consist of two exam papers of 2½ hours and 150 marks each. The
weighting per topic serves only as a guideline and may vary slightly in each of the exam
papers. The weighting and topics in Paper 1 and Paper 2 will be as follows:
Paper 1:
Topic








Weighting
%
7
4
21
27
10
7
7
17
Marks
11
6
31
40
15
11
11
25
100%
150
Meiosis
Reproduction in Vertebrates
Human Reproduction
Responding to the Environment (humans)
Human Endocrine System
Homeostasis in Humans
Responding to the Environment (plants)
Human Impact (Grade 11)
Totals
Paper 2:
Topic





Weighting
%
19
7
30
15
29
Marks
27
12
45
23
43
100%
150
DNA: Code of Life
Meiosis
Genetics and Inheritance
Evolution through Natural Selection
Human Evolution
Totals
REMINDER: When answering questions in an exercise, test or exam:
 Read the question first and underline the operative words so that you are clear about
what is being asked of you.
 Take careful note of the mark allocation, as this will guide you to the number of facts
that you need to write. Do not waste time writing 5 facts when the examiner only asked
for 2. They will only mark the 1st two answers.
 Answer the question as if you are answering someone whom you like, is intelligent but
knows nothing about Life Science – then you will not leave anything out.
 Please note: an examiner will never ask 2 questions with the same answer. If you
have written the same answer then one of them is definitely wrong. Please re-read
each of the questions and you will see that each one requires a different answer.
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



When you are asked to write your ‘view’ or ‘belief’ or ‘what do you think….’ Then only
write one type of view. For example: What is your view on abortion? Here you must
be either pro-abortion or anti-abortion. You must not write about both views. You must
take a stance on one view.
When you are asked to debate something – then you are required to look at the issue
from both sides and you will be expected to provide both sides for marks.
If you are asked to ‘tabulate’ – then you must answer in the form of a table. You will be
penalized if your points are not listed in a table format.
When you are asked to compare two things, then rather use the table format. This way
you will remember to write equally about both of the factors.
When answering multi-choice questions:
1. Read the question and cover the option answers.
2. Think about the question and think of the correct answer, then uncover the possible
answers and find your answer there.
3. If you are given possible answers that are combinations of answers, then read each
option carefully and decide if it is correct or not.
4. Correct = place a √ at the end of the sentence/word.
5. If you think it is not correct = place an X after the sentence/word.
6. Then look at the √ versus the X and select the correct option.
When answering questions with diagrams:
1. Study the diagram and write missing labels in on the diagram itself FIRST.
2. Now read through the questions and answer each one.
3. If you do not know the answer, then write the number on your answer page, look at the
mark allocation and leave enough lines to write the answer in later, i.e.: if the mark
allocation is 2, then leave two lines open.
Graphs and Pie charts:
 Make sure that you know the difference between a line graph, bar graph, histogram
and a pie chart.
 Make sure that you practice the skill of graphing and representing data from a table as
a graph.
 Make sure that you are able to read information from a graph accurately. Use a ruler
and draw lines on the graph – through the X and Y-axis so that your readings are
accurate.
 Please use a compass and a protractor when drawing a pie chart.
Calculations:
 You will be expected to do calculations in a test and exam.
 Make sure that you take a calculator in with you.
 Make sure that you understand how to calculate the average, the difference between
and percentage.
 Generally, the examiner will ask you to show your calculations. You must write out
your calculation step by step otherwise you will only be awarded a mark for the answer
– if it is correct.
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SECTION A: TYPICAL EXAM QUESTIONS
Learner Note:
The following Consolidation Exercises have been extracted from past examination papers
to assist with exam technique and time allocation. Please adhere strictly to the time
allocations for each question. Please ensure that you mark your answers accurately and
that you write in all the corrections.
QUESTION 1: 10 minutes
(DBE Exemplar 2014 Paper 1)
Various options are provided as possible answers to the following questions. Choose the
correct answer and write only the letter (A to D) next to the question number (1.1 to 1.11)
in the ANSWER BOOK.
QUESTIONS 1.1.1 AND 1.1.2 REFER TO THE DIAGRAM BELOW SHOWING THE
STRUCTURE OF THE HUMAN EAR.
1.1.
Which part sends vibrations to the ossicles?
A 3
B 1
C 4
D 5
1.2
Which part maintains equal pressure on either side of the tympanic membrane?
A 4
B 3
C 2
D 1
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1.3
Below is a set of events following fertilisation in humans.
1. The embryo is embedded in the uterine wall in humans.
2. A zygote is formed in the Fallopian tube.
3. Cell division occurs to form a ball of several hundred cells.
4. The blastocyst remains free for several days in the uterus.
Which ONE of the following represents the correct order in which the above
events occur?
A 2,3,4,1
B 2,1,3,4
C 3,2,4,1
D 1,3,2,4
1.4
The following are effects of the secretion of different hormones:
1. An increase in the blood glucose level
2. An increase in the heart rate
3. An increase in the amount of digestive enzymes
4. An increase in blood flow to the skeletal muscles
Which ONE of the following combinations of the above effects is due to
adrenalin?
A 1,3 and 4
B 2,3 and 4
C 1,2 and 4
D 1,2,3 and 4
1.5
The control centre in the body that will be activated when an athlete is dehydrated is
the….
A cerebellum
B cerebrum
C corpus callosum
D pituitary gland
1.6.
The following blood vessels carry blood to or from the placenta in humans:
1. Mother's artery
2. Mother's vein
3. Umbilical artery
4. Umbilical vein
Which blood vessels contain blood with a larger amount of oxygen and nutrients?
A 1 and 3 as compared to 2 and 4
B 1 and 4 as compared to 2 and 3
C 2 and 3 as compared to 1 and 4
D 2 and 4 as compared to 1 and 3
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1.7.
Which ONE of the following is an advantage of the testes being held in the scrotum,
outside the body cavity?
A More sperm can be stored in the scrotum.
B Sperm formation is more efficient at temperatures below the normal body
temperature.
C The testes are better protected in the scrotum than in the body cavity.
D There is more time for prostate secretions to be added to the sperm.
1.8
Meiosis in diploid cell results in…
A four identical gametes
B four haploid gametes
C two different diploid gametes
D four gametes having the same chromosome number as the parent cell
1.9
The list below gives some of the stages involved in gamete and zygote formation.
1. Prophase I
2. Prophase II
3. Metaphase I
4. Fertilisation
Which ONE of the following combinations of the above stages contributes to genetic
variation?
A 1, 2 and 3
B 1, 3 and 4
C 2 and 3
D 3 and 4
QUESTIONS 1.9 AND 1.10 ARE BASED ON THE DIAGRAM BELOW.
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1.10
Which combination of labels for 2, 3 and 4 respectively is CORRECT?
A Hypothalamus, cerebrum, cerebellum
B Cerebrum, cerebellum, hypothalamus
C Hypothalamus, medulla oblongata, cerebellum
D Medulla oblongata, cerebrum, cerebellum
1.11
What is the function of the part numbered 1?
A Responsible for muscle tone
B Responsible for all voluntary muscular movements
C Controls important reflex actions
D Regulates the rate of the heartbeat
(11 x 2)
QUESTION 2: 6 minutes
[22]
(DBE Exemplar 2014 Paper 1)
Give the correct biological term for each of the following descriptions. Write only the term
next to the question number (2.1 to 2.9) in the ANSWER BOOK.
2.1.
2.2.
2.3.
2.4.
2.5.
2.6.
2.7.
2.8.
2.9.
The period of development of an embryo in the uterus between fertilisation and birth
Disease characterized by a lack of insulin production
Tube that connects the pharynx and the middle ear
A process by which nutrients become highly concentrated in a body of water,
leading to increased growth of organisms such as algae
A stage in the development of humans in which the embryo consists of a layer of
cells surrounding a cavity
The structure at the tip of a sperm cell containing enzymes and which makes
contact with the egg cell during fertilisation
The gland in the male reproductive system of humans that produces an alkaline
fluid to counteract the acid environment of the vagina
The duct leading from the testis to the urethra in human males
The process by which the ovum is formed through meiosis in the ovary
(9 x 1) [9]
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QUESTION 3: 6 minutes
(DBE Exemplar 2014 Paper 1)
Indicate whether each of the statements in COLUMN I applies to A only, B only, both A
and B or none of the items in COLUMN II. Write A only, B only, both A and B, or none
next to the question number (1.3.1 to 1.3.6) in the ANSWER BOOK.
(6 x 2)
[12]
QUESTION 4: 8 minutes
(Taken from DBE Feb/Mar 2014)
The diagram below represents a cross-section of a human seminiferous tubule in which a
process is occurring.
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4.1.
Name the specific process illustrated in the seminiferous tubule, which leads
to the formation of structure A.
(1)
4.2.
Name the hormone produced by the organ containing seminiferous tubules.
(1)
4.3.
4.4.
Give ONE function of the hormone named in QUESTION 4.2.
How many chromosomes are there in each:
a)
Spermatogonium cell
b)
Spermatid
Make a labelled drawing to show the structure of the cell labelled A.
4.5.
(1)
(1)
(1)
(5)
[10]
QUESTION 5:
8 minutes
(Taken from DBE Feb/Mar 2014)
The graph below shows changes in a person's body temperature over a period of 30
minutes.
5.1.
By how many °C did the temperature change during this period of 30
minutes?
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5.2.
Account for the changes in the body temperature during period X.
(8)
[10]
QUESTION 6: 10 minutes
(DBE Exemplar 2014 Paper 1)
A Grade 12 learner performed an investigation to determine the effect of light on the
growth of plant shoots. The learner divided the plants that were used into three groups as
follows:
Group A – The tip of the shoot was intact.
Group B – The tip of the shoot was removed.
Group C – The tip of the shoot was covered by a cap that does not allow light to pass
through.
The diagram below shows each shoot at the start of the investigation and next to each, the
same shoot at the end of the investigation.
The arrows indicate the direction of light in each investigation.
6.1.
6.2.
6.3.
6.4.
6.5.
Name the dependent variable in this investigation.
(1)
State TWO factors that must be kept constant in this investigation.
(2)
The influence of which plant hormone is being investigated?
(1)
Explain the results observed in investigations A and C, as illustrated in the diagram
above.
(6)
State TWO ways in which the learner could improve the reliability of this
investigation.
(2)
[12]
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QUESTION 7: 8 Minutes
(Taken from DBE Feb/Mar 2014)
Study the diagram and the graph below and answer the questions that follow.
7.1.
7.2.
7.3.
7.4.
7.5.
Explain ONE way in which part B is suitable for its function.
Explain how and why the part labelled A makes adjustments when a
person moves from bright light into a dark room.
Which NUMBER (1–4) on the graph represents C in the diagram?
Give a reason for your answer to QUESTION 7.3.
Name the part of B in the diagram which corresponds to number 2 on the
graph.
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(5)
(1)
(1)
(1)
[10]
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QUESTION 8: 8 minutes
(DBE Exemplar 2014 Paper 1)
The diagram below shows a section through the mammalian skin.
8.1.
8.2.
Give labels for parts A, B and C.
Describe how parts B and C play a role in reducing the body temperature
back to normal when it increases above the normal level.
(3)
(6)
[9]
QUESTION 9: 7 minutes
(DBE Exemplar 2014 Paper 1)
The carbon dioxide concentration in the atmosphere was recorded at 400 parts per million
(ppm) in May 2013 compared to 316 parts per million (ppm) in 1958. This change is due to
an increase in the use of fossil fuels as well as an increase in deforestation.
9.1.
9.2.
9.3.
9.4.
Describe how deforestation contributes to the high carbon dioxide concentration
in the atmosphere.
(2)
State ONE other impact of deforestation on the environment.
(1)
Explain why we should be concerned about the rising carbon dioxide levels. (3)
Suggest ONE way in which the government can reduce carbon emissions
caused by the generation of electricity.
(1)
[7]
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SECTION C:
QUESTION 1:
HOMEWORK QUESTIONS
12 minutes
(Taken from Mind the Gap series)
Kruger National Park
Limpopo)
Gauteng
Limpopo
Mpumalanga
North West
Eastern Cape
Free State
Kwa-Zulu Natal
Northern Cape
Total Illegally hunted
1.1.
1.2.
1.3.
1.4.
1.5
(part
of
Tota
l
2010
2009
2008
2006
Province
2007
Study the following table showing a summary of the rhino poaching incidents in South
Africa from 2006 – 2010.
17
10
36
50 109 222
0
0
2
0
0
0
5
0
24
0
0
3
0
0
0
0
0
13
0
7 15 22
23 16 37 76
2
6 12 25
7 10 44 61
1
3
2
6
0
2
3
5
14 28 23 70
0
0
2
2
83 122 247 489
How many rhinos were illegally hunted in 2009?
(1)
Suggest THREE ways in which the poaching of rhinos can be stopped.
(3)
Describe the general trend observed in the table.
(2)
By what percentage did the poaching of rhino incidents increase in North
West from 2008 to 2010? Show all working.
(3)
Use the data in the table and draw a bar graph to show the number of rhinos
poached from 2006 to 2010 in the South Africa.
(7)
[16]
QUESTION 2: 8 minutes
(Taken from DBE Nov 2013)
The diagrams below show chromosome pair 21 in the nucleus of a cell of the ovary of a
woman. The chromosomes are involved in a process that takes place in a phase of
meiosis.
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2.1.
3.2.
2.3.
2.4.
Give labels for A and B.
(2)
Rearrange the letters X, Y and Z to show the correct sequence in which the
events take place in this phase.
(1)
Explain why the chromosomes in Diagram X and Diagram Y are different in
appearance.
(3)
The diagram below shows the nuclei of the four cells that resulted from meiosis
involving the chromosomes in Diagram X above.
a)
b)
Explain why nuclei O and P do NOT have chromosomes.
(2)
Name and explain the disorder that will result if diagram M represents
an egg cell that fuses with a normal sperm cell.
(3)
[11]
SECTION D:
SOLUTIONS FOR SECTION A
QUESTION 1
1.1
D
1.2
A
1.3
A
1.4
C
1.5
D
1.6
B
1.7
B
1.8
B
1.9
B
1.10 C
1.11 B
(11 x 2)
QUESTION 2:
2.1
Gestation
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2.2
2.3
2.4
2.5
2.6
2.7
2.8
2.9
Diabetes mellitus
Eustachian tube
Eutrophication
Blastocyst
Acrosome
Prostate
Sperm duct / vas deferens
Oogenesis
QUESTION 3:
3.1
A only
3.2
None
3.3
Both A and B
3.4
B only
3.5
Both A and B
3.6
Both A and B
(9 x 1)
[9]
(6 x 2)
[12]
QUESTION 4:
4.1. spermatogenesis 
4.2. testosterone  







4.3. Stimulates the development of primary male sex organs
Stimulates the development of secondary male characteristics
Stimulates development of sperm
4.4. a) 46 chromosome 






b) 23 chromosome 
Mark allocation for diagram:
Caption
Any 4 correct labels
(5)
QUESTION 5:
5.1. 1,6 °C
5.2.
(1)
(1)
(1)
(1)
(1)
[10]
(2)
Increase in temperature when exercise starts:
- Due to exercise
- the body temperature increased from 36,8 °C to 38,2 °C
- because of heat produced
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- from an increase in the rate of cellular respiration 
- to meet the energy demands during exercise
Any
(3)
Decrease in body temperature when exercise ends:
- The temperature decreased/from 38,2 °C back to 36,8 °C after the exercise
- when the heat-regulating centre in the brain/hypothalamus was stimulated by the
increased temperature
- causing the blood vessels of the skin to dilate/vasodilation
- allowing more blood flow through the skin
- resulting in greater heat loss
- Also more sweat evaporates from the skin surface
- cooling down the skin Any
(5)
[10]
QUESTION 6:
2.1.1 Growth of plant shoots

2.1.2 Same environment in which the shoots are placed
Same type of shoot  (mark only the first two answers)
6.3
Auxins

6.4
In investigation A:
− Light from the right 
− caused auxins to move to shaded side of the shoot 
− leading to increased cell elongation and division 
− There was therefore greater growth on the shaded side 
− thus bending the shoot in the direction of the source of light (any 4)
(1)
(2)
(1)
(4)
In investigation C:
− Light has no influence on the distribution of auxins 
− therefore the shoot grew upright 
(2)
6.5
- Repeat the investigation 
− Use more than one plant for each treatment  (Mark first TWO only) (2)
[12]
QUESTION 7:
7.1. Have photoreceptors/rods and cones to convert light stimuli into impulses (1)
7.2. The iris contains 2 sets of muscles
The radial muscles contract
and the circular muscles relax 
causing the pupil to dilate
allowing more light to enter the eye
to form a clear image
Any
(5)
7.3. Number 3
7.4. The relative clarity of the image is the best /has greatest number of cones for
colour vision.
(1)
7.5. Blind spot 
(1)
[10]
QUESTION 8:
8.1
A Sweat pore
B Sweat gland
C Blood vessel
(3)
8.2
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− Impulses sent from hypothalamus  to C (blood vessels)
− Blood vessels dilate/vasodilation occurs
− More blood carrying heat comes to the skin surface
− and therefore more heat is lost from the body  (any 3)
− B (Sweat glands) produce more sweat 
− When sweat evaporates from the skin surface 
− More heat is lost from the skin
− leading to a drop in the body temperature  (any 3)
(3)
(3)
[9]
QUESTION 9:
9.1
- There will be less trees
(1)
- so less carbon dioxide will be used from the atmosphere for
photosynthesis 
(2)
9.2
Can lead to the loss of biodiversity/habitat destruction/soil erosion
(Mark first ONE only)
(1)
9.3
- Increased carbon dioxide levels lead to the enhanced greenhouse effect 
- which causes an increase in the global temperatures 
- This could lead to rise in sea levels because of melting ice/ floods/change in
climate
- which can lead to the extinction of some organisms. (any 3)
(3)
9.4
Use alternate source of energy
(1)
(Mark first one only)
[8]
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SESSION NO: 15
TOPIC: CONSOLIDATION PAPER 1 B
SECTION A: TYPICAL EXAM QUESTIONS
QUESTION 1:
12 Minutes
(Taken from DoE Feb/Mar 2011 Paper 1)
Study the following diagrams representing different phases of meiosis.
1.1.
1.2.
1.3.
1.4.
1.5.
Label structures A, B and C.
(3)
Which phase is represented by:
(a) Diagram 1
(1)
(b) Diagram 2
(1)
Write down the numbers of the diagrams to show the correct sequence in
which the phases occur.
(2)
Tabulate THREE differences between the first and second stages of meiosis. (7)
Name and explain TWO processes/mechanisms that ensure that the gametes
produced at the end of meiosis are genetically different from each other.
(4)
[18]
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QUESTION 2: 8 Minutes
Match column A with the statements in column B:
[10]
QUESTION 3:
9 minutes
(Modified from DoE Exemplar 2011 Paper 2)
Study the diagram below and answer the questions that follow:
3.1.
3.2.
3.3.
Identify the parts labelled B, C and F and name ONE function of each.
Explain how the pinna of the ear is suited for its function.
Name TWO functions of G.
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(2)
(2)
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3.4.
Write the letter of the part which:
(a)
Contains receptors for balance
(b)
Channels sound waves
(b)
Transmits impulses to the brain
(1)
(1)
(1)
[13]
QUESTION 4: 7 minutes
(Taken from DBE Exemplar 2014)
The diagram below represents the interaction between two important endocrine glands.
The gland labelled A is found at the base of the brain, while the gland labelled C is present
towards the front of the neck.
4.1.
4.2.
4.3.
4.4.
Give a label for gland A.
Name hormone B.
State TWO functions of hormone D.
Describe the negative feedback mechanism that operates when the level of
hormone D is higher than normal in the blood.
© Gauteng Department of Education
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(1)
(2)
(5)
[9]
91
QUESTION 5:
6 minutes
(Taken from DoE Exemplar 2011 Paper 2)
The graph below shows the effect of strenuous exercise, followed by a cold shower, on the
body temperature of an athlete.
5.1.
5.2.
5.3.
5.4.
5.5.
5.6.
Which part of the brain responds to the temperature changes that occur at
A and B on the graph?
What was the maximum temperature reached?
For what period of time did the person engage in strenuous exercise?
Why should body temperature not be allowed to fluctuate too much?
Which diagram (I or II) would represent the condition of the skin after
15 minutes?
Explain your answer to QUESTION 5.5.
© Gauteng Department of Education
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(1)
(1)
(2)
(1)
(2)
[8]
92
QUESTION 6:
6 minutes
(Taken from various sources)
The pot plant in the diagram below was placed onto its side. After a day the stem started
to grow upwards.
6.1.
6.2.
6.3.
6.4.
6.5.
Give the term used to describe this phenomenon.
(1)
Provide a definition for the term.
(1)
Which chemical substance is involved in this phenomenon?
(1)
What is meant by the term apical dominance?
(2)
How could you apply the theory of apical dominance to grow a thick hedge
around your home?
(3)
[8]
QUESTION 7:
3 minutes (Taken from DBE Exemplar 2014)
The diagram below represents a portion of the central nervous system of humans.
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Write down the LETTER ONLY of the part which:
1.
Regulates heartbeat and breathing rate
2.
Coordinates movement while walking
3.
Interprets what you see
4.
Has its hemispheres connected by the corpus callosum
5.
Controls balance and equilibrium
(1)
(1)
(1)
(1)
(1)
[5]
QUESTION 8: 10 minutes (Taken from DBE Exemplar 2014)
The Human Sciences Research Council (HSRC) conducted a survey on food security
across the provinces. The results showed that the overall percentage of food-secure
households in South Africa is 45,6% as opposed to 48% in 2008.
The results, indicating the percentage of food-insecure households in each province
according to the latest survey, are shown in the table below.
8.1.
8.2.
8.3.
8.4.
8.5.
What is meant by food security?
(2)
Use the data in the table to draw a bar graph for the four provinces that have
the highest percentage of food-insecure households.
(7)
State how the use of fertilisers by farmers can:
a)
Increase food security for a country
(1)
b)
Decrease food security for a country
(1)
State how the use of pesticides by farmers can:
a)
Increase food security for a country
(1)
b)
Decrease food security for a country
(1)
State TWO factors, other than the use of fertilisers and pesticides, which may
have led to a decrease in the percentage of food-secure households in South
Africa since 2008.
(2)
[15]
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SECTION C:
HOMEWORK QUESTIONS
QUESTION 1:
7 minutes
(Taken from DoE Exemplar 2011 Paper 2)
Study the diagram below and answer the questions that follow:
1.1.
1.2.
1.3.
Give labels for the glands numbered 1 and 2.
Name hormone A.
Describe the negative feedback mechanism that operates when the
thyroxin level in the blood is too high, as indicated by process C.
QUESTION 2: 5 minutes
Study the diagram below.
(Taken from DBE Nov 2013)
© Gauteng Department of Education
(2)
(1)
(4)
[7]
95
Match the structures (A to F) with the descriptions below. A letter may be used more than
once, or not at all.
2.1. Where gaseous exchange occurs between the mother and the foetus
(1)
2.2. Removes excretory products from the foetus
(1)
2.3. Contains strong muscles which will push the foetus out during birth
(1)
2.4. Clamped and cut after the baby is born
(1)
2.5. Acts as a shock absorber for the developing foetus
(1)
[5]
QUESTION 3:
10 minutes
(Taken from DBE Exemplar 2014)
Study the diagram below, which shows a reflex arc.
3.1.
Give labels for each of the following:
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3.2.
3.3.
3.4.
3.5.
(a)
Region D
(b)
Neuron E
Write down the LETTER of the part which:
(a)
Transmits impulses to the central nervous system
(b)
Contains cerebrospinal fluid
Explain the effect on the reflex action if part B was damaged.
The nerve pathway in the above response is about 1,5 metres in length.
A nerve impulse travels at 75 m s-1.
Use this information to calculate the time taken for this reflex action to occur.
Show all working.
Explain the significance of a reflex action.
SECTION D:
(1)
(1)
(1)
(1)
(2)
(3)
(2)
[11]
SOLUTIONS FOR SECTION A
QUESTION 1:
1.1
A – Chromatid /chromosome (1)
B – Centromere (1)
C – Spindle fibre /thread (1)
1.2
(a) Metaphase 2
(1)
(b) Prophase I (1)
1.3
Diagram 2, Diagram 3, Diagram 1, Diagram 4 [Sequence must be correct] =
(2)
1.4
(Mark first THREE only) any 3 x 2 + 1 table
1.5
(7)
Crossing over Pieces of chromatids /groups of genes are exchanged between homologous
chromosomes
Random independent assortment of chromosomes Maternal and paternal chromosomes assort themselves randomly / independently
on either side of the equator during metaphase (4)
[18]
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QUESTION 2:
2.1.
D
2.2.
J
2.3.
F
2.4.
K
2.5.
B
2.6.
G
2.7.
E
2.8.
H
2.9.
M
2.10.
I
(10 x 1)
[10]
QUESTION 3:
3.1
B - tympanic membrane to vibrate and transfer the sound wave to the
Ossicles / hammer (2)
C - malleus/hammer to vibrate and transfer the sound to the anvil /amplify sound
(2)
F – cochlea to convert the stimulus of the sound waves into an impulse
(2)
3.2
Pinna has many ridges to direct the sound waves along the auditory canal Extends outside the head / large flaps / funnel shaped to trap sound waves (Mark first answer only) (any 2)
(2)
3.3
Maintain air pressure on both sides of the eardrum To drain fluid from the middle ear into the throat (2)
3.4
(a) D (1)
(b) G (1)
(c) E (1)
[13]
QUESTION 4:
4.1. Pituitary gland/hypophysis (1)
4.2. B – TSH/thyroid-stimulating hormone (1)
4.3. − Controls metabolism
− Influences heart rate
− Influences functioning of central nervous system
(Mark first TWO only) (any 2)
(2)
4.4.
− High levels of thyroxin is detected by the hypophysis
− which leads to a decrease
− in the secretion of TSH
− Activity of thyroid is slowed down /less thyroxin produced
− Thyroxin level drops to normal
(5)
[9]
QUESTION 5:
5.1
Hypothalamus 5.2
37,5oC 5.3
10 minutes
5.4
Most human activities is controlled by enzymes and enzymes require
optimum temperatures to function
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(1)
(1)
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5.5
5.6
Diagram I Blood vessels dilated to bring more blood to the surface and more
heat will be lost OR
Increased sweat production which will cool down the body (1)
(2)
[8]
QUESTION 6:
5.1
Phototropism (1)
5.2
The growth movement of a plant when stimulated by light.
(1)
5.3
Plant hormone / auxin
(1)
5.4
When the growth point at the tip of the stem grows upwards and
development of the auxillary buds on the lateral branches is inhibited
(2)
5.5
The growth point at the tip of the stem continues to grow upwards and
inhibits the development of auxillary buds on the lateral branches below.(3)
[8]
QUESTION 7:
7.1 C
7.2 B
7.3 A
7.4 A
7.5 B (5 x 1)
[5]
QUESTION 8:
8.1
Having access to enough food on a daily basis, so as to ensure healthy
living 8.2.
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Mark allocation for the graph:
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8.3
8.4
8.5
(7)
(a) Fertilisers provide nutrients that increase crop growth
(1)
(b) Fertilisers are expensive – causes food prices to increase/ over-use of
fertilisers can cause oxygen deprivation in soil which will eventually reduce
crop production
(1)
(a) Pesticides ensure that pests do not cause large-scale damage to crops (1)
(b) Pesticides could kill pests as well as their predators – hence more
pesticides would have to be used, raising the cost of food
(1)
− Massive unemployment in the country
− Increase in the size of the human population
− Farms destroyed for development
− Decrease in subsistence farming − Prolonged unfavourable environmental conditions
(Mark first TWO only) (any 2 x 1)
(2)
SESSION NO: 16
TOPIC: CONSOLIDATION PAPER 2 A
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SECTION A: TYPICAL EXAM QUESTIONS
QUESTION 1:
10 minutes
(Taken from DBE Exemplar 2011 Paper 1)
Various options are provided as possible answers to the following questions. Choose the
correct answer and write only the letter (A–D) next to the question number.
1.1.
In humans, the allele for brown eyes is dominant over the allele for blue eyes. The
probability of two parents, heterozygous for brown eyes, having children with blue
eyes is …
A
75%.
B
50%.
C
25%.
D
0%.
1.2.
The nitrogenous base which replaces thymine in a RNA molecule is …
A
guanine.
B
uracil.
C
adenine.
D
cytosine.
1.3.
Human blood type is determined by three different alleles known as IA, IB and i.
The IA and IB alleles are co-dominant and the i allele is recessive.
The possible human phenotypes for blood groups are type A, type B, type AB and
type O.
Blood type A and B individuals can be either homozygous (IAIA or IBIB respectively)
or heterozygous (IAi or IBi respectively).
A woman with type A blood and a man with type B blood could have offspring with
the following blood types:
A
A and B only
B
B and AB only
C
O only
D
A, B, AB or O
1.4.
During an investigation the DNA of an animal cell was analyzed in a laboratory and
the results are shown in the table below.
Which of the following is a CORRECT identification of the bases
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called X, Y and Z?
A
B
C
D
1.5.
X
Cytosine
Adenine
Thymine
Guanine
Y
Guanine
Thymine
Cytosine
Adenine
Z
Thymine
Cytosine
Adenine
Thymine
Assume that plant A has an unknown genotype but shows the dominant trait. This
means that plant A could be either homozygous or heterozygous for that trait. To
determine which of these two genotypes apply, plant A can be crossed with another
plant showing the recessive trait.
Which of the following predictions can be made by studying the offspring from such
a cross of complete dominance?
A
If all the offspring show the dominant phenotype, then plant A is
heterozygous.
B
If all the offspring show the recessive phenotype, then plant A is
homozygous.
C
If 50% of the offspring show the dominant phenotype and 50% of the
offspring show the recessive phenotype, then plant A is heterozygous.
D
If all the offspring show an intermediate characteristic, then plant A is
heterozygous.
1.6.
If all 18 nucleotides of a DNA strand code for amino acids, how many amino acids
will be present in the polypeptide that is formed?
A
9
B
18
C
7
D
6
QUESTIONS 1.7 and 1.8 refer to the information below.
Some characteristics are controlled by more than one gene. Human skin colour is
controlled by at least three genes (three different pairs of alleles). There is incomplete
dominance between the allele for dark pigmentation and the allele for light pigmentation.
A heterozygous individual will therefore have an intermediate colour. Assume that the
alleles A, B and C control dark pigmentation and the alleles a, b and c control light
pigmentation. A person with the genotype AABBCC would have a very dark skin colour
and someone with the genotype aabbcc would have a very light skin colour.
1.7.
The phenomenon whereby a characteristic is controlled by more than one pair of
alleles is called …
A
incomplete dominance.
B
complete dominance.
C
polygenic inheritance.
D
dihybrid cross.
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1.8.
Which ONE of the following is a possible heterozygous combination of the three
genes for skin colour?
A
AABBCC
B
AaBbCc
C
aabbcc
D
ABC
1.9.
Study the following statements:
1
The same characteristic has more than two different alleles for the same
gene.
2
The different alleles for the same characteristic are on the same locus.
3
The alleles for the same characteristic are on different loci.
4
More than one gene controls a characteristic.
The following combination of statements refer to multiple alleles:
A
1, 2, 3 and 4
B
1 and 2 only
C
1, 2 and 3 only
D
3 and 4 only
1.10. During protein synthesis the following steps take place in order:
A DNA unwinds, transcription by mRNA, anticodons produced by tRNA,
amino acids combine to form polypeptides
B DNA unwinds, anticodons produced by mRNA, transcription by tRNA,
amino acids combine to form polypeptides
C DNA unwinds, transcription by mRNA, codons produced by tRNA, amino
acids combine to form polypeptides
D DNA unwinds, transcription by mRNA, anticodons produced by rRNA,
amino acids combine to form polypeptides
(10 x 1) [10]
QUESTION 2:
4 Minutes
(Taken from DBE Exemplar 2011 Paper 1)
Give the correct biological term for each of the following descriptions. Write only the term
next to the question number.
2.1. The pair of chromosomes in a diploid individual that have the same shape and size,
and control the same set of characteristics.
2.2. The type of genetic cross where an intermediate phenotype is expressed in F1,
while parental phenotypes reappear in F2.
2.3. The law that accounts for gametes having only one allele for a characteristic due to
a separation of the pair of alleles during meiosis.
2.4. A ring of DNA found in bacteria that is used in the production of insulin.
2.5. A study of the transmission of characteristics from parents to offspring.
2.6.
Chromosome condition of a cell resulting from meiosis, having only one set of
chromosomes.
(6 x 1) [6]
QUESTION 3: 6 minutes
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Indicate whether each of the statements in COLUMN I applies to A ONLY, B ONLY,
BOTH A AND B or NONE of the items in COLUMN II. Write A only, B only, both A and
B or none next to the question number (3.1 to 3.8) in the ANSWER BOOK.
(8 x 2) [16]
QUESTION 4:
10 Minutes (Taken from DBE Feb/March 2011 Paper 1)
The diagrams below represent the process of protein synthesis.
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4.1.
4.2.
4.3.
4.4.
Identify compound M and organelle R.
(2)
Write down the sequence of the FIRST THREE nitrogenous bases on the DNA
strand that led to the formation of Z.
(2)
Name the part/stage of protein synthesis that is illustrated in O.
(1)
The table below shows the base triplets of DNA and the amino acid each codes for.
With reference to the diagram in QUESTION 4.4. and the table above:
(a)
Name the amino acid labelled P.
(2)
(b)
State the base sequence of the molecule labelled Q.
(2)
(c)
What name is given to the triplet of tRNA bases that codes for each
amino acid?
(1)
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(d)
Describe how the composition of the protein molecule changes if the base
sequence at X is UGU instead of UCA.
(2)
[12]
QUESTION 5:
10 Minutes
(Taken from DBE Exemplar 2011 Paper 1)
Study the genotypes and phenotypes below that show how the alleles for colour-blindness
are inherited. X and Y represent sex chromosomes. A carrier does not suffer from colourblindness but can pass the allele for colour-blindness to their children.
NAME OF PERSON
Lindi
Beauty
Sarah
Paul
Thabani
5.1.
5.2.
5.3.
5.4.
5.5.
GENOTYPE
B
B
X X
XB Xb
XbXb
XB Y
XbY
PHENOTYPE
Normal female
Carrier female
Colour-blind female
Normal Male
Colour-blind male
State why colour-blindness is referred to as a sex-linked disorder?
(2)
Is colour-blindness caused by a dominant or a recessive allele?
(1)
Explain your answer to QUESTION 5.2 above.
(2)
Explain why Thabani is colour-blind.
(2)
Sarah and Paul marry and have two children, a son and a daughter.
Represent this genetic cross by using the information in the table above to
determine the genotypes and phenotypes of the son and the daughter.
(6)
[13]
QUESTION 6:
6 Minutes
(Taken from DBE Feb/Mar 2011 Paper 1)
Study the pedigree diagram of a family where some individuals have haemophilia.
Haemophilia is a sex-linked disorder. Use H for normal blood clotting and h for the
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haemophiliac trait.
6.1.
6.2.
From the pedigree diagram above, state the relationship between gender
and haemophilia.
(2)
Write down all the possible genotypes of individuals:
(a) Peter
(b) Enid
(c) Clarence
(6)
[8]
QUESTION 7:
12 Minutes
(Taken from DBE Exemplar 2011 Paper 1)
Diagrams A and B below illustrate the skulls of Homo sapiens and Homo
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erectus. The diagrams are drawn to scale.
7.1.
7.2.
7.3.
7.4.
Which of the diagrams (A or B) represents the following:
(a)
Homo sapiens
(1)
(b)
Homo erectus
(1)
Tabulate TWO visible differences between the skulls in diagrams A and B
that represent changes in the structure that characterizes human evolution. (5)
Describe the significance of Homo erectus to the 'out of Africa' hypothesis. (3)
List FOUR similarities between Homo sapiens and African apes.
(4)
[14]
QUESTION 8: 7 minutes
(Taken from DBE Exemplar 2014)
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The phylogenetic tree below shows one interpretation of the origin of humans. The dotted
lines indicate the possible evolutionary relationships, and the vertical bars show the period
during which the organisms are believed to have existed on earth.
Homo sapiens
Present
1 MYA
Homo
neanderthalensis
Homo
erectus
Homo heidelbergensis
Homo
ergaster
2 MYA
3 MYA
Homo
habilis
Paranthropus
robustus
Paranthropus
boisei
Australopithecus
africanus
Paranthropus
aethiopicus
4 MYA
Australopithecus
afarensis
5 MYA
Australopithecus
anamensis
KEY:
MYA = Million Years Ago
8.1.
8.2.
8.3.
8.4.
Use the diagram to identify ONE organism that may have competed with Homo
heidelbergensis for resources.
(1)
Identify the common ancestor that gave rise to both Paranthropus and
Homo.
(1)
a)
For what period of time did A. africanus exist on Earth? Show all
working.
(3)
b)
Name ONE piece of evidence that could be used to prove that
A. africanus existed during the time period calculated in QUESTION 8.3(a).
(1)
a)
Which organism, H. ergaster or H. neanderthalensis, is more
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b)
closely related to modern-day humans?
Explain your answer to QUESTION 2.2.4(a) using information in
the diagram.
SECTION C:
(1)
(2)
[9]
HOMEWORK QUESTIONS
QUESTION1: 6 minutes
(Taken from DBE Nov 2013)
A scientist gathered information about the affected and unaffected individuals for a certain
genetic disorder. The genetic disorder is caused by a dominant allele. The findings of the
scientist are represented in the pedigree diagram below.
1.1.
1.2.
1.3.
Using the letters R and r to represent the dominant and recessive alleles
respectively, state the genotype of individual:
a) A
(1)
b) D
(1)
What is the percentage chance of individual X having a genetic disorder? (2)
If individual C marries an unaffected male, state the possible genotype(s) of their
offspring.
(2)
[6]
QUESTION 2:
20 Minutes
(Taken from DoE Exemplar 2011 Paper 1)
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Describe how proteins are formed in a cell and explain the impact of the two types of
Gene mutations on the formation of proteins.
Content: (17)
Synthesis: (3)
[20]
SECTION D:
QUESTION 1:
1.1
C
1.2
B
1.3
D
1.4
A
1.5
C
1.6
D
1.7
C
1.8
B
1.9
B
1.10 A
SOLUTIONS FOR SECTION A
(10 X 1) [10]
QUESTION 2:
2.1 Homologous 2.2 Incomplete dominance
2.3 Law of Segregation 2.4 Plasmid 2.5 Genetics 2.6 Haploid (6 x 1) [6]
QUESTION 3:
3.1
A only ✓✓
3.2
A only✓✓
3.3
A only✓✓
3.4
B only✓✓
3.5
A only✓✓
3.6
Both A and B ✓✓
3.7
Both A and B ✓✓
3.8
A only
[16]
QUESTION 4:
4.1
M – DNA
(1)
R – Ribosome (1)
4.2
AGT (2)
4.3
Transcription
(1)
4.4
(a) Threonine (2)
(b) CCG (2)
(c) Anticodon (1)
(d) A different protein may form because it has cysteine instead of
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serine /have different amino acids
(2)
[12]
QUESTION 5
5.1. The genes for colour-blindness is carried on the sex chromosomes (2)
5.2. Recessive (1)
5.3. The trait only shows up if it is in the homozygous recessive / not in
the heterozygous state.
(2)
5.4. Thabani has only one X chromosome with a recessive allele for
colour-blindness, the Y chromosome does not carry an allele for the characteristic
(2)
5.5.
Please note:
Phenotype carrier daughters and colour blind sons and NOT normal daughters
Max (6)
[13]
QUESTION 6:
6.1
Haemophilia occurred in males 
only 
(1)
6.2
(a) XhY (b) XHXh (c) XHY 

QUESTION 7:
7.1
(a) B 

(2)
(2)
(2)
[8]
(1)
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(b) A (1)
7.2
DIAGRAM A
1 Brow ridges more pronounced
2 Smaller cranium/brain
3 Jaw protrudes (prognathous)
4 No obvious chin
DIAGRAM B
1 Brow ridges less pronounced
2 Larger cranium/brain
3 Jaw does not protrude
4 Pronounced chin
5 Elongated cranium
5 shorter cranium
6 Zygomatic arch well developed
6 Zygomatic arch less developed
(Any two matching differences = 4 + 1 for table) = (5)
- H.erectus was the first Homo species to move out of Africa.
- Their large bodies and well adapted pelvic girdles made them better
bipedal runners and walkers over long distances than H.sapiens
Max (3)
7.4. - Large brains/skulls compared to their body mass - Olfactory brain centres reduced/reduced sense of smell - Parts of the brain that process information from the hands and eyes are
enlarged - Eyes in front/binocular vision/stereoscopic vision - Eyes with cones/colour vision - Freely rotating arms - Long upper arms - Elbow joints allow rotation of forearm - Rotate hands at least 1800 - Flat nails instead of claws/bare finger tips - Opposable thumbs which work in opposite direction to their fingers - Upright posture - Sexual dimorphism/distinct differences - Two teats only (Any 4) =
(4)
[14]
QUESTION 8:
8.1
H. erectus
(1)
8.2
A. afarensis
(1)
8.3
(a) 3 mya – 2,4 mya = 0,6 mya
OR
3 mya – 2,3 mya = 0,7 mya
(3)
(b) Fossils
(1)
8.4
(a) H. neanderthalensis
(1)
(b) H. neanderthalensis and H. sapiens share a common ancestor
OR
Both evolved from H. heidelbergensis (2)
[9]
7.3.
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SESSION NO: 17
TOPIC: CONSOLIDATION PAPER 2 B
SECTION A: TYPICAL EXAM QUESTIONS
QUESTION 1:
10 Minutes
(Various sources)
1.1.
Micro-evolution is a term that describes …
A. the process by which new genera and families of organisms are formed.
B. small changes that occur in the genotypes of organisms within the same
species.
C. changes that can be seen without a microscope.
D. an increase in the size of individuals of a population over a long period of time.
1.2.
According to Charles Darwin, organisms that will be most successful biologically,
are those that …
A. are best adapted to their environment.
B. are the largest in the population.
C. reproduce the slowest.
D. do not change.
1.3.
The evidence that related species in similar biomes across the world developed
from a common ancestor, is obtained from …
A. micro-evolution.
B. embryology.
C. biochemistry.
D. biogeography.
1.4.
Extinction occurs….
A. When a species is unable to survive in their environment.
B. When only a few of a species survives.
C. When a species goes into hiding until conditions improve.
D. The gradual depletion of a population.
1.5.
Which ONE of the following is an example of a pair of analogous structures?
A. A whale's flipper and a bat's wing
B. A bird's wing and an insect's wing
C. A hawk's wing and a sparrow's wing
D. A dog's leg and a horse's leg
1.6.
The following is needed for new species to form….
A. an extinction event
B. an homologous structure
C. an analogous structure
D. reproductive isolation
1.7.
Macroevolution is a term that describes …
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A. an increase in the size of individuals of a population over a long period of
time.
B. the process by which new genera and families of organisms are formed.
C. a gradual change in the number of species found in the fossil record.
D. changes that can be seen without the need for a microscope.
1.8.
Which of the following is NOT a fossil?
A. Tyrannosaurus rex skull, 65 million years old
B. Oil formed from microorganisms, 150 million years old
C. Stone tool made by ancestors of human, 2,6 million years ago
D. 195 million-year-old dinosaur footprint imprinted in rock
1.9.
The theory of evolution based on the principle of use and disuse was proposed
by …
A. Darwin.
B. Mendel.
C. Lamarck.
D. Wallace.
1.10. According to Charles Darwin, organisms that will be most successful biologically,
are those that …
A are best adapted to their environment.
B are the largest in the population.
C reproduce the slowest.
D do not change.
1.11. Study the following characteristics:
1. Olfactory brain centres reduced
2. Bare fingertips
3. Flat face (not prognathous)
4. Always bipedal
Which combination of characteristics makes humans different from other primates?
A 2, 3 and 4 only
B 1, 2 and 3 only
C 3 and 4 only
D 1, 2 and 4 only
1.12. An example of non-random mating is ....
A. artificial selection.
B. inbreeding.
C. natural selection.
D. macroevolution.
(12 x 1)
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QUESTION 2:
5 Minutes
(Taken from DoE Exemplar 2011 Paper 1)
Indicate whether each of the statements in COLUMN 1 applies to A only, B only, both A
and B or none of the items in COLUMN 2. Write A only, B only, both A and B or none next
to the question number.
COLUMN 1
2.1 Provides genetic evidence for the 'out of Africa'
hypothesis
2.2 Organism(s) which is/are bipedal
2.3 Proposed natural selection as an explanation of
evolution
2.4 Genetic disorder(s) which lead(s) to absence of
blood clotting factors
2.5 Natural shape of a DNA molecule
2.6 Evidence for evolution
2.7 Fossil(s) found in South Africa
2.8 Transfer of a gene for drought resistance from
one species to another
COLUMN 2
A: Mitochondrial DNA
B: DNA from X chromosomes
A: Homo habilis
B: Australopithecus africanus
A: Darwin
B: Lamarck
A: Down's syndrome
B: Haemophilia
A: Double helix
B: Single-coiled strand
A: Biogeography
B: Fossil records
A: Australopithecus sediba
('Karabo')
B: 'Nutcracker Man'
A: Cloning
B: Genetic engineering
(8 x 1)
[8]
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QUESTION 3:
7 Minutes
(Taken from DoE Exemplar 2011 Paper 1)
Study the pedigree diagram below showing the inheritance of black or brown spots in
Dalmatian dogs. The colour of the spots is determined by a gene, which has two alleles.
The allele for black spots (B) is dominant over the allele for brown spots (b).
3.1
3.2
3.3
Name the colour and gender of each of the following:
(a)
B
(b)
G
Name the genotype of:
(a)
A
(b)
F
(c)
E
If C and D have another puppy, what is the percentage probability of each
of the following:
(a)
The puppy being female
(b)
The puppy having black spots
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(2)
(1)
(1)
(1)
(1)
(1)
[9]
118
QUESTION 4: 5 minutes (Taken from DBE Nov 2013)
The diagram below shows a part of the process of protein synthesis.
4.1.
4.2.
4.3.
Name the stage of protein synthesis represented in the diagram above.
Identify:
a) Molecule X
b) Molecules Y
c) Structure 1
The table below shows the DNA base triplets that code for different amino
acids found in human proteins.
(1)
(1)
(1)
(1)
Using the information in the table and the diagram above, write down the sequence
of the amino acids that correspond with structures 1, 2 and 3.
(3)
[7]
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QUESTION 5: 8 minutes (Taken from WCDE – Z Bothma 2014)
Study the diagram and answer the questions that follow:
5.1.
5.2.
5.3.
5.4.
5.5.
5.6.
Which type of cell division is shown in the diagram?
Give a reason for your answer.
Provide labels for the parts numbered A to F.
Give the 2n value of this cell.
State a visible reason why this is still considered to be a diploid cell.
Name the process that is taking place at the part labelled Z.
Give TWO important functions of mitosis.
(2)
(6)
(1)
(1)
(1)
(2)
[13]
QUESTION 6: 8 minutes
(Taken from DBE Nov 2013)
Gregor Mendel conducted breeding experiments with pea plants to study the inheritance
patterns of four different traits (plant height, seed shape, seed colour and seed coat
colour).
For each trait, for example plant height, he crossed homozygous tall plants with
homozygous dwarf plants. The offspring obtained in the F1-generation were then interbred
to form the F2-generation. He did the same for each of the other traits.
The results obtained for the F2-generation are shown in the table below.
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6.1.
6.2.
6.3.
6.4.
6.5.
6.6.
What is the expected phenotypic ratio for a trait involving two heterozygous
parents?
(1)
From the results, calculate X and Y. Also state which trait provided a ratio
closest to the expected phenotypic ratio mentioned in QUESTION 3.2.1.
Show ALL working.
(3)
Give a possible reason why the ratio selected in QUESTION 3.2.2 was
closest to the theoretical ratio.
(2)
Using the results, state whether the allele for round seeds or for wrinkled
seeds is dominant.
(1)
State TWO factors that Mendel controlled during these breeding experiments.(2)
Write down Mendel's law of segregation.
(2)
[11]
QUESTION 7:
5 minutes
(Taken from DBE Exemplar 2014)
Study the table below, which indicates some of the hominid fossils found in different parts
of the world.
SPECIES
AREA WHERE IT
PERIOD OF EXISTENCE
WAS FOUND
Australopithecus afarensis
Eastern Africa
3,4–2,8 mya
Australopithecus africanus
Southern Africa
2,1–2,8 mya
Australopithecus sediba
Southern Africa
2,0–1,9 mya
Homo habilis
Sub-Saharan (Africa)
2,3–1,4 mya
Homo erectus
Africa, Europe, Asia
1,5–0,2 mya
Homo heidelbergensis
Europe, China
0,6–0,35 mya
Homo neanderthalensis
Europe, Western Asia
0,35–0,03 mya
Homo sapiens
Worldwide
0,2 mya–present
[Adapted from The Evolutionary Road, Jamie Shreeve, National Geographic, July 2010]
7.1.
7.2.
Explain why the information in the table supports the 'Out of Africa' hypothesis. (2)
Describe how the analysis of mitochondrial DNA is used to support the 'Out of
Africa' hypothesis.
(3)
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[5]
QUESTION 8: 4 minutes
(Taken from DBE Exemplar 2014)
8.1. Study the diagrams below showing structures of different organisms.
Diagram 1
Diagram 2
Diagram 3
Butterfly wing
Diagram 4
Bat wing
Whale limb
Human limb
8.1.
8.2.
8.3.
Which diagram represents a structure that is analogous to the structure
in Diagram 4?
(1)
Write down the numbers of any TWO diagrams that represent homologous
structures.
(2)
What information do analogous and homologous structures provide about
evolution?
(2)
[5]
SECTION C:
HOMEWORK QUESTIONS
QUESTION 1:
5 minutes
(Taken from DBE Exemplar 2014)
The pedigree diagram below shows the inheritance of Daltonism in a family. Daltonism
(red-green colour-blindness) is sex-linked. The allele for Daltonism is recessive to the
allele for normal colour vision.
1
2
3
4
KEY:
Normal male
Colour-blind male
Normal female
5
1.1
6
Colour-blind female
Use the symbols XD, Xd and Y to state the genotype of the following:
a)
Individual 2
b)
Individual 3
© Gauteng Department of Education
(2)
(2)
122
1.2.
1.3.
How many family members not affected by Daltonism are definitely carriers? (2)
Use a genetic cross to determine the possible genotypes and phenotypes of
the offspring that may be formed by individuals 5 and 6.
(6)
[12]
QUESTION 2: 20 minutes
(Taken from DBE Nov 2013)
Describe the structural changes to the skull that characterise the evolution of modern
humans from their ape-like ancestors, and explain the significance of these changes.
Content:
(17)
Synthesis: (3)
[20]
NOTE:
NO marks will be awarded for answers in the form of flow charts or diagrams.
QUESTION 3: minutes (Taken from DBE Exemplar 2014)
Scientists investigated the resistance of mosquitos to DDT.
The following steps were followed:
•
They captured a sample of mosquitos from the environment.
•
The mosquitos were then exposed to a standard dose of DDT
(4% DDT for 1 hour) in the laboratory.
•
The number of mosquitos that died was counted.
•
Those that survived were left to reproduce.
•
A sample was taken from this population every two months and the same
procedure was followed for a period of 16 months.
The results are shown in the table below.
3.1.
3.2.
TIME
(IN MONTHS)
MORTALITY OF MOSQUITOES (%)
0
2
4
95
87
80
6
8
69
60
10
12
54
35
14
16
27
22
Identify the:
(a)
Independent variable
(b)
Dependent variable
Formulate a hypothesis for this investigation.
© Gauteng Department of Education
(1)
(1)
(3)
123
3.3.
3.4.
3.5.
3.6.
Draw a line graph to show how the mortality of mosquitoes changed over
the period of the investigation due to the application of DDT.
(6)
State TWO factors, other than those mentioned, that should be controlled
in this investigation.
(2)
State TWO ways in which the scientists could improve the reliability of their results.
(2)
Explain, in terms of natural selection, how mosquitoes may develop
resistance to DDT.
(8)
[23]
SECTION D:
SOLUTIONS FOR SECTION A
QUESTION 1:
1.1
B
1.2. A
1.3. D
1.4. A
1.5. B
1.6. D
1.7. B
1.8. C
1.9
C
1.10 A
1.11 C
1.12 A (12 x 1)
[12]
QUESTION 2:
2.1
A only
2.2
Both A and B
2.3
A only
2.4
B only
2.5
A only
2.6
Both A and B
2.7
A only
2.8
B only
QUESTION 3:
3.1
(a) Female black spots
(b) Male brown spots 3.2.
(a) Bb (b) Bb (c ) bb (8 x 1)
[8]
(2)
(2)
(1)
(1)
(1)
© Gauteng Department of Education
124
(a) 50% (1)
(b) 75% (1)
[9]
QUESTION 4:
4.1
Translation
4.2
(a) mRNA
(b) tRNA 





c) Codon
4.3
Histidine glycine methionine (correct Sequence)
3.3.
(1)
(1)

(1)
(1)
(3) [7]
QUESTION 5:
5.1
Metaphase homologous chromosomes are at the equator
5.2
A = centriole
B = spindle fibre
C = cytoplasm
D = chromatid
E = centromere
F = cell membrane





(6)
5.3
6
5.4
Chromosomes are still in homologous pairs 


5.5
crossing over 5.6
Repair of damaged cells Replacement of damaged cells
Growth (Any TWO functions)
(2)


QUESTION 6:
6.1. 3:1 6.2. X: Seed shape = 5474 = 2,96 : 1/2.95:1
1850
Y: Seed colour = 6022 = 3, 01 : 1
2001
Closest: Seed colour/(Y)
6.3. Y has the larger sample size
6.4. Roundseeds
6.5. All the plants must be homozygous in P1
All the plants must be heterozygous in P2
Same type of plant /species
Same environmental conditions
Same method of pollination
(Mark first TWO only) Any
6.6. During gamete formation, members of each allele pair separate
such that each gamete only contains one allelefor a particular trait (2)
(1)
(1)
(1)
(2)
[13]
(1)
(3)
(2)
(1)
(2)
[11]
QUESTION 7:
7.1. The oldest fossils of human ancestors were only found in Africa
7.2. − Mitochondrial DNA is passed down from mother to child
© Gauteng Department of Education
(2)
125
− mutations on the mitochondrial DNA
− were traced to an ancestral female that existed in Africa
(3)
[5]
QUESTION 8:
8.1. Diagram 1
(1)
8.2. Diagrams 2 & 3/ 2 & 4/ 3 & 4
(2)
8.3. Analogous structures show that two organisms evolved independently of
each other
Homologous structures show that two organisms have a common ancestor.(2)
[5]
© Gauteng Department of Education