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Answers to CSEC®
Biology Examination
Practice
Section A
2a i Accurate calculations [2]; parts of pie chart labelled [1];
appropriate title [1]
Pie chart showing the data collected to represent
the organisms found in a sampling area
50 (29 °)
30 (17°) 2 (1°)
550 (313 °)
Key
Producer
Primary consumer
■■ Figure
Secondary consumer
Tertiary consumer
A1
ii Pitfall trap. [1] It is a trapping pit (container placed into
the ground) for small mobile organisms to fall in. Once
they fall into the trap, they cannot escape. [1]
iii A food chain is a diagram that shows the feeding
relationships within an ecosystem or how energy in the
form of food is moved from one organism starting with
the producer to subsequent organisms. [1]
Diagram showing the feeding relationships between
organisms in a sampling area
BIRDS
HIBISCUS LEAVES → WORMS →
(producer) (primary (secondary
consumer) consumer)
[1] for title; [1] for diagram.
iv Producers are first in the food chain and have the
greatest access to energy directly from sunlight. Hence
there is more energy to support a larger number of
organisms. [1] The tertiary consumer get less energy, as
energy is lost as you go up the trophic levels. Therefore
if there is less energy available, there will be fewer
organisms. [1]
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Answers to CSEC® Biology Examination Practice
bi Include an aim; list of apparatus; procedure or sequence
of steps for carrying out the investigation.
For example:
Aim: To determine the percentage of air found in a
sample of soil [1]
List of apparatus and materials: Soil, beaker, triple
beam balance, water, stirring rod [2]
Method: Weigh empty beaker, soil sample and volume
of water being used. [1] Pour water into soil sample and
stir. [1] Stir until no more air bubbles escape or water
reaches surface of the soil. [1] Weigh the mixture of soil
sample and water. [1] Carry out calculations to show
difference in weight of soil sample without water and
soil sample with water. [1]
ii Air in the soil provides oxygen for plant roots [1];
bacteria that are integral to the process of cycling
nutrients need oxygen [1]; the oxygen is used in aerobic
respiration and energy is produced to drive certain
processes such as active take-up of minerals into plant
roots. [1]
iii Three (for [1] mark each) from: mineral particles; humus;
water; air; organisms.
3a i Plant is placed in a dark cupboard for 24 hours. [1]
ii To ensure that the plant uses up the starch that was
stored. [1] Then any starch produced in the investigation
is a result of action of light in photosynthesis. [1]
iii Diagram showing the leaf in a boiling tube of ethanol in
a water bath as it is being heated by the Bunsen burner.
Suitable labels.
boiling tube with ethanol [1]
beaker with water [1],
heated using
Bunsen burner [1]
(heat turned off before
test tube containing
ethanol is placed in
beaker, to avoid risk of
ethanol catching fire)
leaf [1]
tripod stand [1]
■■ Figure A2
iv Green region covered by foil would not contain starch
and would take colour of iodine; white region covered
by foil would be the same; white region not covered by
foil would also take the colour of iodine. [1]
2
Green regions not covered by foil would be blue-black,
indicating starch present. [1]
CSEC® Biology Examination Practice © Kathryn Bennett 2016
Section A
area of leaf
covered by foil
blue-black
red-orange (colour of iodine)
colour of iodine
colour of iodine
Key
Green areas of leaf
blue-black
White areas of leaf
■■ Figure A3
v Light [1] and chlorophyll [1] are necessary for
photosynthesis to take place.
bi To investigate the effect of light [1] on the growth of a
plant. [1]
ii Ensure plants are of the same type [1] and size. [1]
iii First plant would grow upwards [1]; second plant would
bend and grow towards the light [1]; the third plant would
experience rapid growth, yellow leaves, spindly stem. [1]
iv First plant: auxin diffuses evenly down the stem causing
even growth of cells. [2]
Second plant: auxin accumulates on shady side (side
not exposed to light) causing those cells to grow rapidly
resulting in the bending of the stem. [2]
Third plant: since it had no access to light, it used up its
food reserve and grew rapidly in search of light. [2]
4a i Appropriate title [1]; accurate representation of data [3];
label x- and y-axes [2]
ii Continuous [1]
iii Any two named and described from: sexual reproduction
(meiosis); crossing over; environment; mutations.
Sexual reproduction [1]: when a gamete from each parent
fuses to form a zygote, a unique combination of genes is
produced as each gamete has a different set of DNA. [1]
Crossing over [1]: homologous chromosomes pair up and
bits of information are exchanged between them as they
break and re-join, trading genes. [1]
Environment [1]: for example, nutrition affects growth. [1]
Mutations [1]: small changes that occur when cells divide
which may or may not be advantageous. [1]
iv Discontinuous [1]
bi Gametes [1]
ii Chromosomes are pulled to opposite poles [1] with the
sister chromatids still joined at the centromere. [1]
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iii Circle any two chromosomes that are identical in length
or size. [1]
iv Meiosis produces four haploid daughter cells [1] that
are not identical to each other. [1] Mitosis produces two
diploid daughter cells [1] that are identical. [1]
v Allows for variation [2]. Since organisms are not identical,
[1] only those susceptible to a particular disease will be
wiped out, for example. [2]
5a i Obtain three papaya trees of the same size, type, age,
etc. [1] For a month, give each plant the same volume of
water each day; same amount of exposure to sunlight;
apply the same amount of fertiliser. [1]
Get two different fertilisers with different percentages of
nitrogen content. [1]
Do not use any fertiliser on one of the plants (control).
Use one fertiliser on the second plant and the other
fertiliser on the third plant. [2]
Record the colours of the leaves, measure the height of
each plant and sizes of the leaves each day. [1]
ii Two from: same type of papaya plant; same size plants;
equally healthy plants; same volumes of water; same
amount of sunlight. [2]
iii Type of fertiliser (amount of nitrogen in the fertiliser) [1]
iv The control is there to show the comparison between
what would normally happen and what happens when
the independent variable is changed in the experimental
groups. [2]
b Two (for [1] mark each) from: magnesium; iron; phosphorus;
sulfur; potassium; calcium
c Magnesium and iron – help make chlorophyll; phosphorus and
sulfur – needed for protein synthesis; potassium – salt balance
maintained in cells; calcium – needed to make cell walls. [2]
di Plant shoots respond positively to light in order to make
chlorophyll [1] and to photosynthesise. [1]
ii Plant roots respond positively to gravity in order to
obtain water and dissolved minerals from the soil [1] and
also to anchor the plant firmly in the soil. [1]
iii For the root in response to gravity: auxins accumulate
on lower part of the root [1], this slows down the growth
on that side [1], making the cells of the upper side grow
faster. [1]. This results in the downward growth of the
root. [1]
iv No. [1] Auxins respond differently in the shoot and the
root. Shoots need to grow upwards or above ground in
order to make their food. [1]
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CSEC® Biology Examination Practice © Kathryn Bennett 2016
Section A
6a i Accurate, neat drawing [3]; title [1]; accurate labels and
annotations [6]
apex
tip of leaf
blade / margin
edge of leaf
midrib
main vein
vein
transport of substances
through the leaf
lamina
surface of the leaf
petiole
attaches leaf to the
stem of the plant
Drawing of the external structure of a hibiscus leaf
■■ Figure A4
ii For example, using the measurements of the diagram here:
Magnification =
length of drawing
length of actual specimen
=
9.4 cm
10 cm
= 0.94 [2]
iii Diagram half the size; resembles the original drawing [1];
accurate [2]
■■ Figure A5
b •Leaves are broad and flat to increase surface area for
absorption of carbon dioxide and capture of light needed
for photosynthesis. [2]
•Leaves are thin so that gases can diffuse rapidly to and
from cells. [2]
•The cells of the palisade mesophyll layer have numerous
chloroplasts as this layer is closest to the sunlight to trap
the energy to make food. [2]
•Specialised cells/vessels called xylem transport water from
the root to the leaves. [2]
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•Cells of upper epidermis are transparent, allowing light to
enter the leaf and get to the photosynthesising cells. [2]
7a i Before: Test for starch – crush a cotyledon and add a
few drops of iodine in potassium iodide solution and
look for colour change. [4]
After: Test for reducing sugars (Benedict’s test) – crush a
cotyledon and add 2 cm3 of Benedict’s solution. Shake the
mixture and then boil and look for colour changes. [4]
ii Test for starch: colour change to blue-black indicates the
presence of starch. [1]
Test for reducing sugars: colour changes: blue → green
→ yellow → brick-red precipitate indicate presence of
reducing sugars. [1]
iii Starch is present in cotyledon (stored food) before it
germinates. [1] During germination, enzymes break down
the starch into glucose. [1]
iv The cotyledon has stored food for the germinating seed.
[1] Respiration can take place and the energy is used for
growth of the plumule and radicle. [1] The radicles have
enough energy to grow down into the soil and form the
root system. [1] The plumule grows upwards to form the
shoot of the plant. [1]
bi The height of the plants; size of the leaves (length or
width) [3]
ii Growth of the plant [1]
iii Same age seeds [1]; seeds germinated from same set [1];
same amount of sunlight [1]; same size container [1];
same type of soil [1]
8a iAlgae → water flea → small fish → duck [2]
ii Algae at base of the pyramid (20 000); fleas (1930); small
fish (14); at the top of the pyramid is the duck (1) [3]
ducks (1)
small fish (14)
fleas (1930)
algae (20 000)
■■ Figure A6
iii Pyramid of energy OR pyramid of biomass [1]
Pyramid of energy shows the amount of energy found
at each trophic level of the food chain. Energy is lost/
decreases as it moves from one level to the next. [2]
OR
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Pyramid of biomass shows the dry mass of the organisms
at each trophic level. As you go up the trophic levels,
biomass decreases. [2]
CSEC® Biology Examination Practice © Kathryn Bennett 2016
Section A
b, cFood web. [4] Trophic levels marked. [1] Secondary
consumers include: mice, frogs, sparrows, foxes. [1]
Autotroph: grass [1]
Trophic levels
5
4
foxes
hawks
sparrows
3
2
snakes
frogs
rabbits
1
mice
(secondary
consumers)
grasshoppers
grass
(autotroph)
■■ Figure A7
di Mutualism [1]
ii The leguminous plants get fixed nitrogen in the form
of nitrates to make their proteins [2]. The bacteria get
shelter and protection by living within the nodules of
these plants [2].
iii • Commensalism [1], e.g. remora and shark. [2] The
remora benefits by getting food and protection while
the shark is unaffected by its presence, i.e. neither
benefits nor is harmed. [2]
OR
• Parasitism [1], e.g. tick and dog. [2] Tick gets food,
shelter, protection while the host (the dog) is being
harmed in the process. [2]
9a Diagram: correct apparatus [2]; labels [2]
rubber bung
boiling tube
respiring yeast
lime water
■■ Figure A8
bi Describe the apparatus [1]; identify the independent
and dependent variables [2]; list at least two controlled
variables. [2]
Several sets of the apparatus are set up as shown
in part a). Place different organisms in each set of
apparatus (independent variable), for example lice
in one set of apparatus, yeast in the second set of
apparatus and germinating seeds in the third. Ensure
that each set of apparatus is the same size; same
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volume of lime water used in each; use the same
number or mass of organisms (controlled variables). If
lime water changes from transparent to white cloudy
colour for all sets of apparatus, then all the organisms
produce carbon dioxide (dependent variable) when
they respire.
ii Set up experiment as described in part b) i) and include
the use of the stop watch. As the lime water changes
colour from transparent to white precipitate, record the
time. [2]
ci Intercostal muscles, ribcage, diaphragm [3]
ii During inhalation: intercostal muscles contract
to move the ribcage up and out. The diaphragm
muscles contract which results in the flattening of the
diaphragm. [3]
During exhalation: intercostal muscles relax to move
the ribcage down and in. The diaphragm muscles relax
which results in the raising of the diaphragm (domes
upward). [3]
iii The function of the cilia is to move mucus that
contains microorganisms and dust upwards and out
of the lungs. [2]
d Breathing causes air to be taken into the lungs
(inhalation) so that the oxygen can be used by the
cells for respiration. Respiration produces carbon
dioxide, which is removed from the body by breathing
(exhalation). [3]
10a iTable showing number of males and females at six
different heights. Neat table with correct column
headings [2]; correct values [3]
Number of people (1000s)
Height (cm)
Male
Female
140
5
5
150
5
30
155
6
90
160
15
118
165
35
120
170
75
75
ii Most people of a height less than 170 cm are female. [2]
bi Continuous variation. Examples include finger length;
weight; human skin colour; human foot length. [3]
ii Things in the environment like sunlight may affect skin
colour in humans; food humans eat may cause variation
in weight. [2]
iii Diagram showing crossing over (homologous chromosomes
interacting and exchanging genetic material) [4]
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CSEC® Biology Examination Practice © Kathryn Bennett 2016
Section A
homologous
chromosomes
crossing over
between chromatids
■■ Figure A9
ci A mutation is a change in the structure of a gene or the
number or amount of chromosomes resulting in a variant
form that can be passed on to subsequent generations. [2]
ii Bacteria become resistant to antibiotics because of
random mutations. Resistant bacteria will survive an
antibiotic treatment and be able to reproduce more
bacteria that are also resistant to the antibiotic. [4]
iii Evolution is the slow process by which a species adapts
to its environment and may eventually give rise to
another species. Evolution may depend on mutations as
new alleles are created, which allow for more genetic
variation and individuals surviving to pass down their
genes from one generation to the next. [3]
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Section B
2a i Diagram of typical plant and animal cell [2]
mitochondrion
cell membrane
nucleus
cytoplasm
■■ Figure
B1
ii Label the mitochondrion, cell membrane, cytoplasm,
nucleus [4]
bi 1) Muscle cell – contracts and relaxes to bring about
movement [1]
2) Red blood cell – contains haemoglobin for oxygen
transport [1]
3) Sperm cell – fertilises the ovum [1]
ii Palisade cell – rectangular and contains many
chloroplasts that contain chlorophyll to trap sunlight
needed for photosynthesis [2]
Xylem cell – hollow, no living content so that water can
pass through easily [2]
OR
Root hair cell – increases surface area of the root for
more absorption of water [2]
iii Cell membrane only; no cell wall like that of plant
cells [1]
iv In multicellular organisms cell specialisation is important
so that the work is divided, making the organism more
efficient. [1]
3a i Population – a group of organisms of the same species
occupying the same habitat. [1]
ii Community – different populations of organisms
occupying the same habitat/area. [1]
iii Abiotic factors – physical or non-living components of
the environment, for example air, water and soil. [1]
b Any three from: predator/prey – predator hunts and kills its
prey [2]; parasitism – symbiotic relationship in which one
organism benefits (the host) and the other is harmed [2];
commensalism – symbiotic relationship in which one
organism benefits and the other is unaffected [2];
mutualism – symbiotic relationship in which both organisms
benefit. [2]
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CSEC® Biology Examination Practice © Kathryn Bennett 2016
Section B
ci Diagram must include: plants removing carbon dioxide
for photosynthesis; organisms respiring to release carbon
dioxide in the air; death of organisms; fossilisation;
combustion [5]
carbon dioxide
in the air
respiration
combustion/
burning
respiration
feeding
animals
photosynthesis
plants
death and decay
(fossilisation)
fossil fuels
■■ Figure
B2
ii Carbon is used to make carbohydrate, which is a
respiratory substrate. [1]
4a [1] mark for each correct row.
Feature
motility
size of gamete
number of gametes
produced
number of chromosomes
Ovum
non-motile
relatively large
1 produced/matures
each month
23
Sperm
motile
very small
many sperm in one
ejaculation
23
bi Fertilisation occurs in oviduct or fallopian tube. [1]
ii Implantation occurs in the lining of the uterus. [1]
iii The cervix is found at the base/neck of the womb. [1]
iv Oestrogen is produced by the ovaries. [1]
c Oestrogen results in the development of secondary sexual
characteristics of females: hair in armpits and pubic region;
hips widen; breasts enlarge; menstrual cycle. [2]
d The fallopian tube has cilia that help to move the ovum
along. [1]
e Sperm cell has a tail that moves in a whip-like manner
to propel the sperm. [2] The acrosome in the head has
enzymes that digest a path through the layer of cells that
surround the ovum. [2] OR Mitochondria in the sperm
provide energy for movement.
5a The substance the enzyme acts on is the substrate [1]; in this
experiment, hydrogen peroxide. [1]
b The temperature at which the enzyme works best by
making most products. [1]
c Approximately 30 °C [1]
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d The temperature has altered the shape of the enzyme and
so it can no longer fit with its substrate. [1] The enzyme is
said to be denatured. [1]
ei Properties of enzymes include:
1) enzymes are specific – an enzyme will only catalyse
one type of reaction [2]
2) enzymes work best at an optimum temperature – at
low temperatures enzymes are inactive and at high
temperatures they are denatured [2]
3) enzymes work best at an optimum pH – different
enzymes work best in an acidic, alkaline or neutral pH [2]
4) enzymes are not damaged during the reactions they
catalyse and so they can be reused once the active site is
free [2].
ii The enzyme is acting as the lock [1] as it has the active
site which represents the ‘key hole’.
6a i Drawing should show longitudinal section and labels
should be accurately done. [4]
cortex
medulla
renal pelvis
ureter
■■ Figure B3
ii Bowman’s capsule, 1st and 2nd convoluted tubule in the
cortex while the loop of Henle and collecting duct extends
into medulla. Collecting duct should lead to renal pelvis. [2]
iii Afferent and efferent arterioles [1]
b Excretory products in animals: urea, carbon dioxide, uric
acid [2]
Excretory products in plants: oxygen, tannins, calcium
oxalate [2]
c Plants: transfer wastes to old or dying leaves. When the
leaves fall off, the wastes are excreted. Some wastes are
stored in, for example, the bark. [2]
Animals (including humans) get rid of waste like urea
by creating urine and some is removed in sweat. Carbon
dioxide is removed by the lungs by exhaling. [2]
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CSEC® Biology Examination Practice © Kathryn Bennett 2016
Section B
7a i The sea turtle is adapted for getting rid of the excess salt
from its environment. Putting it in fresh water means that
water will enter the animal’s body and it is not adapted to
get rid of excess water. Its kidneys cannot handle the volume
of water. This results in death of the organism as animal cells
swell and burst if they take in too much water. [2]
ii 1) Plant cell will lose water. Cell membrane pulls away
from cell wall. The cell is said to be plasmolysed. [3]
2) No net movement of water as the concentration
within the cell and outside the cell are the same. [2]
bi Fishermen use nets to capture the fish. When turtles come
to the surface for air, they may get caught in nets. [2] The
black-market may kill turtles for their exquisite shells or
to sell their meat for food. [2] Sea turtles lay their eggs in
the sand. If the beach is developed there may not be any
place for them to lay their eggs or baby sea turtles may
have a longer distance to travel to get to the sea, exposing
them to predators or other dangerous factors. [2]
ii Protect beaches used for nesting; dispose of trash
properly so that turtles don’t mistake it for food; educate
persons about sea turtles and the challenges they face. [2]
8a i Autotrophic (most plants), e.g. hibiscus plant, algae, etc. [2]
Heterotrophic nutrition (most animals), e.g. humans, goat [2]
ii A type of heterotrophic nutrition that occurs in saprotrophs,
which feed on dead or decayed organic matter. [2]
b Fewer trees to remove carbon dioxide from air for
photosynthesis (contributes to increased levels of carbon
dioxide in the air) [2]; fewer trees producing oxygen for
organisms to use for respiration [1]; trees may be habitats for
organisms and removal may lead to extinction of the species [1];
less food for birds and other animals [1]; increased soil erosion
c No fishing – to protect sensitive species of fish [2]; no
removal of resources like shells or corals; no littering –
substances thrown away may negatively affect the organisms
living in the area. Protect the habitat for organisms to
successfully age and reproduce. [2]
9a i AIDS: unprotected sex; dirty needles; childbirth – from
mother to baby; by blood transfusions. [4]
Malaria/dengue [1]: transmitted by the mosquito who
bites organisms like humans giving them the disease. [1]
ii AIDS: abstaining from sexual activities; use a condom;
test blood for disease before donation; never share or
use dirty needles. [1½]
Malaria/dengue: destroy vector by using sprays; secure/
cover up stored water that provides vector breeding sites;
cover water with oil; use repellents. [1½]
bi Reproduction occurs at a faster rate (speed); if parent
plants are successful, it is advantageous to make clones. [2]
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ii Asexual methods include cuttings – cut a portion of the
stem of a plant about 7 inches long and at a 45 degree
angle, plant it in a good medium and water regularly [2];
grafting – remove the bud from a deflowering stem with
a smooth straight cut and insert into the stock of a tree.
(Transfer the living tissue from one plant to another.) [2]
iii Crops were identical because of the means of
reproduction. So all plants died from same disease. [2]
10aAccommodation is the ability of the eye to adjust the lens
to see objects at various distances. [1] To see near objects,
the ciliary muscles contract and suspensory ligaments
slacken, causing the lens shape to fatten. [2] To see far
objects, the ciliary muscles relax and the suspensory
ligaments stretch and the lens becomes thin. [2]
b Glaucoma – build-up of pressure in eye that may result in
damage to the optic nerve. [2]
Cataract – clouding of the lens in the eye. [2]
c Differences (two for [2] marks each):
• hormones transmit chemical messages for endocrine system
via the blood circulation while neurons/nerve cells transmit
messages in the form of electrical impulses for nervous system
• messages are transmitted at a slower rate via the
endocrine system; response to stimuli is almost
instantaneous in the nervous system
• effects of the endocrine system may be widespread in
the body while the nervous system has a localised effect.
Similarity: they both detect and respond to stimuli. [2]
11aiAnimal dispersal: animals eat fruits containing seeds
and deposit seeds in their droppings; animals eat fruits
and carry the seeds far away from the parent plant. [2]
Wind dispersal: some seeds have wings or long
feathery tails so that they can be transported by the
wind and travel/fly long distances. [2]
Explosive: the heat from the Sun dries out the water
from these seed pods which causes them to shoot
seeds from the pods at a high speed. [2]
ii Competition for nutrients in the soil; insufficient nutrients
in the soil to supply all the plants; since they are the same
type of plant, they take in the same types of nutrients,
depleting them from the soil making it less fertile. [2]
Competition for light and water. Also, plants cannot
develop their normal shape if crowded together (some
restriction in growth movement would occur). [2]
b Dormancy is when a seed remains inactive until it finds
favourable conditions to germinate and grow into a plant. [2]
c Water is used to initiate chemical reactions within the
seed so that the embryo can germinate [1]; enzymes
convert the insoluble substances like starch, proteins and
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CSEC® Biology Examination Practice © Kathryn Bennett 2016
Section B
lipids stored in the cotyledons into soluble substances –
glucose, amino acids, fatty acids and glycerol. [2]
12ai Natural method – e.g. rhythm [1]
Barrier method – e.g. condom, cap (diaphragm) [1]
Hormonal method – e.g. birth control pills, implants [1]
Surgical method – e.g. tubal ligation, vasectomy [1]
ii For example, for the condom:
Disadvantages: condom not 100% effective;
inconvenient to put on in ‘heat of moment’. [2]
Advantages: may protect individuals against some
sexually transmitted diseases [2]; cheap and easily
accessible in pharmacies without the need of a
doctor’s prescription. [2]
iii Accept any answer that is properly supported. For example:
I would recommend the hormonal methods [1]
as the effects are reversible [1] and they are not
used at the time of sexual intercourse. [1]
b Prostate cancer and cervical cancer [2] OR sexually
transmitted diseases such as syphilis; endometriosis.
13a Diagram for [5] marks.
anther
filament
stamen
petal
stigma
style
carpel/
pistil
ovary
■■ Figure B4
b [2] marks for each correct row.
Characteristic Wind-pollinated flower Insect-pollinated flower
petals
small/inconspicuous
large, brightly-coloured/
conspicuous
anthers
loosely attached and
firmly attached inside flower for
hang outside flower
insects to brush against them
nectary
no nectar
nectar present to attract insects
c After fertilisation, the following changes occur in the flower:
diploid zygote develops into an embryo which forms the
future plant [1]; the ovary develops into a fruit [1]; the
fertilised ovules become seeds [1]; petals and sepals fall off. [1]
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14ai Cell body [1], axon [1], dendrites [1], knob [1]
dendrite
axon
knob
cell body
■■ Figure B5
ii Motor neuron [1]
iii The motor neuron transmits impulses to the effector
muscles. [2]
iv Sensory neuron; intermediate/relay neuron [2]
biSensitive cells (receptors) in the eye detect the stimulus of
light [1]; the sensory neuron takes the impulse to the CNS
[1]. The message is interpreted and the impulse is carried
by a motor neuron to the effector. [1] Pupil constricts [1].
ii The knee-jerk reflex is a spinal response while the pupil
reflex is a cranial response. [2]
15a Hypothalamus, pituitary gland [2]
b Hypothalamus has sensitive cells that detect the concentration
of water in the blood. [1] Message is then sent to the pituitary
gland. The pituitary gland releases antidiuretic hormone
(ADH). [1] The ADH travels in the blood stream to the
kidneys where it makes the nephron more permeable and so
water is reabsorbed back into the blood stream. [2] Urine is
highly concentrated and of small volume. [1]
c Ultra-filtration and selective reabsorption [2]
d The pancreas is malfunctioning. [1] Not enough insulin is
produced to convert glucose to glycogen. [1]
e Negative feedback is a regulatory mechanism of the body
to maintain the normal level of whatever is being regulated
[1]; for example, if there is too much sugar in the blood, the
pancreas produces insulin that converts the excess glucose
to glycogen for storage, which reduces the amount of
sugar in the blood. [2] If there is too little sugar, glucagon
is produced which converts stored glycogen to glucose
increasing the glucose levels in the blood. [1]
16 aiDigestion is the breaking down of large insoluble food
particles into small soluble particles that can be used by the
cells. [1] Egestion is the removal of undigested food. [1]
ii Mouth and stomach [1]: mouth has teeth to crush and grind
food [1]; stomach has muscular walls to churn the food. [1]
iii Test for protein. Biuret test [1] – crush food and add a
little distilled water. Add solution and if a lilac/purple
colour is formed then protein is present. [1]
b Any three from: age, occupation, sex, whether pregnant,
and whether person is affected by deficiency or
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CSEC® Biology Examination Practice © Kathryn Bennett 2016
Section B
physiological diseases (for example, kwashiorkor and
diabetes respectively) [3]
ci Deficiency disease [1]
ii Any two categories and two examples (for [1] marks each,
total [4] marks):
•physiological, e.g. asthma and lung cancer
•hereditary, e.g. sickle-cell anaemia and haemophilia
•pathogenic, e.g. influenza and malaria.
17aFor example, carbon dioxide, oxygen, hormones,
urea, glucose. [5] They dissolve in the blood and are
transported around the body. [1]
biPhagocyte and lymphocyte [2]: the phagocyte engulfs
and destroys invading organism while the lymphocyte
releases antibodies. [2]
ii An antigen is a protein that is found on the surface of
foreign cells invading the body, for example [1], while
an antibody is a protein produced by the body’s own
lymphocytes and is found in the plasma. [1]
c Higher altitude means less oxygen is available. [1] More
red blood cells are made [1] to carry as much oxygen as
possible. [1]
18aDiagram should show the shape of the red blood cell:
disc-shaped/biconcave [1] and no nucleus [1], which is
important for creating more surface area for absorbing
and carrying as much oxygen as possible. [1] Contains the
red pigment haemoglobin to which the oxygen binds. [1]
cytoplasm contains
haemoglobin
spherical and
biconcave shape
no nucleus
within cell
■■ Figure B6
b The skin acts as a barrier and is the first line of defence.
[2] If there is a break in the skin, then platelets are
responsible for blood clotting. [2] White blood cells get
rid of invading organisms by phagocytosis or releasing
antibodies. [2]
c Immunity is the body’s natural ability to resist disease
and infection. [1] Natural immunity can either be passive
(effect is short-lived), e.g. passing of antibodies from
mother to child through breast milk; or active (effect is
long-lasting), e.g. body produces antibodies in response
to direct exposure to the antigen. [2] Artificial immunity
can also be passive, e.g. antibodies from an individual
are injected into another person; or active, e.g. antigens
are injected or given orally as vaccine. The vaccine
stimulates the body to make its own antibodies. [2]
CSEC® Biology Examination Practice © Kathryn Bennett 2016
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Answers to CSEC® Biology Examination Practice
19aDiagram should include representation of a pump and
vessels [3]; should show the blood passing through the
pump twice. [2]
lungs
pump
veins
arteries
body
capillaries
■■ Figure B7
b•Heart – for pumping blood around the body [2]
•Blood – for transporting useful and waste substances
around the body [2]
•Blood vessels – conduct blood throughout the body,
i.e. from heart (arteries) to tissues (capillaries) back to
the heart (veins) [2]
ciA potometer measures the rate at which a plant loses
water as it transpires. A shoot of a plant is cut under
water and inserted into the potometer. A bubble of
coloured dye is inserted into the capillary tube. As
water is lost from the plant, water from the capillary
tube replaces it, pulling the bubble along. The
movement of the bubble is timed to measure the rate
at which transpiration is occurring. [2]
ii Cut the shoot under water so that air bubbles are not
introduced. [1]
Conditions outside the potometer should be kept
constant, e.g. temperature. [1]
20a Missing substances and type of respiration as follows:
• lactic acid [1] – anaerobic respiration [½]
• oxygen, carbon dioxide, water [1] – aerobic
respiration [1]
• carbon dioxide [1] – anaerobic respiration [½]
bi Lime water/calcium carbonate [1]
ii Transparent [1] to cloudy white [1]
ci Alveoli in humans; gills (lamellae) in fish [2]
iiSimilarities:
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CSEC® Biology Examination Practice © Kathryn Bennett 2016
Section B
• thin – walls of alveoli are one cell thick for rapid
exchange of gases; lamellae are thin. [2]
• rich blood supply – dense capillary network to
transport substances to and from the gas exchange
surfaces. [2]
• moist – gases dissolve in water to be transported
across the membrane easily. [1]
21aA stimulus is any change in the environment that can
bring about a response in an organism. A stimulus is
detected by cells found within sense organs. [2]
b To find a mate; in search of food; to find a more suitable
environment. [2]
c Movement in plants is usually growth movement which is
slow [1] and can be described as irreversible. [1] The type
of movement is also ‘part’ movement. [1] Movement in
animals is more rapid and reversible. Animals also move
by locomotion. Animals may do ‘part’ or ‘whole’ movement.
d Choice chamber for small invertebrates. Include list of
materials; logical step-by-step procedure; identify the
variables. For example:
Set up the choice chamber. Cover one-third of the
chamber with black cartridge paper. Cover a second
section with black cartridge paper, but bore holes in the
paper. Leave the third section open to light/uncovered.
[3] Cover the chamber and leave it to equilibrate for
about 5 minutes. [1] Introduce the woodlice into the
chamber via the centre or in a way that doesn’t favour
any of the three conditions. [1] Record the distribution
of the organisms after 10 minutes. [1] Repeat the
experiment for accuracy and reliability. [2]
22aiA species is a group of closely related organisms that are
able to interbreed [1] and produce fertile offspring. [1]
ii Two from the following:
Geographical separation – a physical barrier such
as a body of water or a mountain separates two
populations of the same species, for example the Anole
lizards of the Caribbean Islands. [2]
Ecological differences – changes in the environment
may cause organisms to adapt and change. Once these
changes occur, organisms may no longer recognise
each other as being of the same species and so do not
mate and occupy different niches. [2]
Behavioural differences – organisms develop
differences in behaviours, such as courtship and
mating behaviour, so that groups no longer mate. [2]
b Natural selection is the process by which a population
retains those genes which better adapt it to its environment.
This is driven by naturally occurring processes. [2] With
artificial selection, the selection is imposed by humans. [2]
CSEC® Biology Examination Practice © Kathryn Bennett 2016
19
Answers to CSEC® Biology Examination Practice
ciIn the industrialised areas soot was produced [1] and
so the black peppered moth could blend in with the
environment. [1] Dark moths were not easily identified
by their predators and so were able to survive and
become common [1], unlike the light coloured
peppered moths that were no longer camouflaged and
became easy targets for their predators.
ii Charles Darwin concluded that biological evolution
was as a result of natural selection. Some organisms are
more likely to survive and reproduce than others. If the
advantageous traits are inherited, the next generation will
also have these advantageous traits and hence be more
likely to survive and reproduce in that environment. [2]
23ai Diabetes [1]
ii Exercise; changes in diet; drugs (insulin injections) [3]
iiiMaking insulin from bacteria:
1) Enzyme is used to cut a piece of circular DNA in
bacteria. [1]
2) Human insulin gene is isolated/extracted from
human pancreatic cells. [1]
3) The insulin gene is placed/inserted into the
bacterial plasmid. [1]
4) The recombinant DNA is introduced into a bacterium. [1]
5) Plasmids are produced as the bacteria multiply. [1]
b Social – control genetic diseases like cystic fibrosis; loss
of genetic diversity as small farmers would choose to
stop growing local varieties of crop plants as it would
not be beneficial to them economically. [2]
Ethical – exploitation of living things and/or misusing
the environment for the benefit of humans. [2]
c Any two from the following (for [1] mark each):
• development of high performance food crops that will
grow quickly and use less fertiliser
• resistance to insect pests in many crop plants
• increase in yield and size of many crops and cattle and
dairy animals
• more nutritious food.
24aSickle/crescent-shaped red blood cells; joint pains;
shortage of oxygen in blood [2]
bi Individuals 1, 4 and 11 [2]
ii 3 and 4 – married/couple; 4 and 5 – siblings [2]
iiiHeterozygous (Aa) [1]; produced a daughter that
has the disease. Hence both parents must have the
recessive allele to produce an offspring with the
disease that exists in homozygous recessive (aa). [1]
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CSEC® Biology Examination Practice © Kathryn Bennett 2016
Section B
ivLet A represent normal allele
Let a represent sickle-cell allele
Genotype of individual 5
Genotype of individual 6
Gametes
Aa
Aa
A
a
AA
Aa
×
A
a
Aa
aa
Random
fertilisation
Offspring
[1]
Probability 1/4 or 25% chance [1]
■■ Figure
B8
ciCodominance: both alleles expressed in the
heterozygous genotype. [1]
ii Human blood groups are an example of codominance.
Blood group is controlled by alleles A, B and O. [1] A
and B are equally dominant and both are dominant to
O. [2] Hence four phenotypes are possible: blood type
A (AA or AO); B (BB or BO); AB; and OO. [1]
25a
i sclera; ii aqueous humour; iii cornea; iv lens; v optic
nerve [5]
b Stimulus: any change in the environment (internal or
external) that brings about a response from an organism.
Light is the stimulus detected by the eye. [2]
c Rods: sensitive to dim light and only let you see in black
and white. [2]
Cones: let you see colour in bright light. [2]
d In bright light, the circular muscles of the iris contract,
which makes the pupil small so that the retina isn’t damaged
by excessive light. [2] In dim light the radial muscles of the
iris contract, making the pupil dilate or get larger. [2]
CSEC® Biology Examination Practice © Kathryn Bennett 2016
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Answers to CSEC® Biology Examination Practice
Multiple Choice Answers
Number
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
22
Answer
B
D
B
A
D
C
B
B
D
C
A
B
A
B
D
Number
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
Answer
D
D
A
B
C
D
C
B
A
D
D
A
B
A
D
Number
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
CSEC® Biology Examination Practice © Kathryn Bennett 2016
Answer
A
C
B
D
D
B
A
B
D
C
C
D
A
C
C
Number
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Answer
D
B
C
C
B
A
A
A
D
A
D
A
A
C
A