BWAILA CLUSTER MOCK EXAMINATIONS
2025 MALAWI SCHOOL CERTIFICATE OF EDUCATION EXAMINATION
Biology
PAPER I
Marking Key
1. a. Nucleus
b. Easy movement towards egg
c. Breaks or dissolves egg walls during fertilization
d. (i) Presence of mitochondria for energy
(ii) Tail for easy movement
2. (i) Quadrat can only be used to sample small plants
(ii) Quadrat cannot be used on a very steep slope
(iii) Cannot be used to sample moving animals
b. (i) More organisms live where temperatures are moderate since enzymes in
the body are more active than under low or very hot conditions
(ii) - Wind influences temperature humidity, seed and spore dispersal, pollination
and rainfall
c. (i) Food production – glucose produced after photosynthesis is used as food
substance by all living organisms including man
(ii) Oxygen production - for respiration
(iii) Reduction of carbon dioxide in the atmosphere
(iv) Source of energy stored in fossils
3. a. A = cortex
B = medulla
C = pelvis
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b. Cortex
c.
RENAL ARTERY RENAL VEIN
Less nitrogenous waste More nitrogenous waste
Less carbon dioxide More carbon dioxide
More oxygen Less oxygen
d. - Kidney cancer
- Kidney stones
- Glomerular nephritis
- Pyelonephritis
4. a. (i) Sound of a bell
(ii) The ear
(iii) Rushing to the classroom
b. Conditioned reflex action
5. a. P – hydrogen
Q – ATP
b. Diffusion
c. Has stomates for gaseous exchange
6. a.- Has membranes that separate the blood vessels of the foetus from those of
the mother
- Has selective membrane that allow some substances to pass through
- Has thin walls for fast diffusion of substances
- Has villi which provides a large surface area for exchange of substances
b. Urea and carbon dioxide
c. - It keeps the foetus moist
- It cushions the foetus from physical damage (force) and shock
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- It gives the foetus a stable environment
d. (i) LH – stimulates ovulation
For development of corpus luteum
(ii) FSH – stimulates the development of graafian follicle in ovary
7. a. Right ventricle
b. Part M
c. - Its walls have a film of moisture to dissolve gases for fast diffusion
- Has thin walls for fast diffusion of gases
- There are numerous to provide a large surface area for gas exchanges
8. a. H = epithelium
J = lacteal
b. - In the mouth by teeth
- In the duodenum done by bile
c. Fatty acids and glycerols
d. They have one cell thick for fast absorption
They are numerous that provide a large surface area for the absorption of
digested food
They are supplied with blood vessels to transport absorbed food
9. a. (i) The green mamba camouflaged with the green vegetation therefore they
were not seen by hawks (predators) their population increased. While the black
mamba was easily seen by predators (hawks) and eaten therefore their population
decreased.
(ii) - Natural selection
(iii) - Large mutation
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- Natural selection
- Geographical barrier that is geographical isolation
- Reproductive isolation
- Ecological isolation
b. Production of new breeds of plants and animals with better production
Production of new varieties of crops with higher output (yield)
10. a. (i) Survival of an organism if it competes effectively.
(ii) Organisms with favorable variations survive and produce more offsprings
b. (i) 1: 1
(ii) Bb - Black parent
bb - White parent
(iii) The allele for white fur in the population will be wiped out because the
animals will be preyed upon by the wild cats since they will be easily seen at
night than the black one which will be masked by darkness
11. Environment determines how an organism grows and characteristics will
develop.
Heredity as what one inherits from both parents influences their outlook.
Mutations can cause changes in characteristics of an offspring.
Sexual reproduction where the fusion of gametes from separate parents result in
differences in characteristics of the offsprings.
Segregation of chromosomes during gamete formation and crossing over during
meiosis.
Age has an influence as characteristics develop and change with age for example
weight and height.
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12. Breathing mechanism in human beings.
During breathing in external intercostal muscles contract while internal
intercostal muscles relax, ribs move upwards and outwards, diaphragm muscles
contract making it flat. Volume in the thoracic cavity increases leading to low
air pressure in the lungs. Air is forced into the lungs from outside. The lungs
inflate.
During breathing out internal intercostal muscles contract while external
intercostal muscles relax, ribs move downwards and inwards, diaphragm
muscles relax making it become dome shaped. The volume in the thoracic cavity
reduces leading to an increase in air pressure inside the lungs. This force air out
of the lungs into the atmosphere. The lungs deflate.
13. - Skin – prevents entry of pathogens into the body as it is waterproof and always
dry, hence difficult for pathogens to survive.
- Tears – contain lysozyme enzymes which kill germs
- Mucus – traps germs and dust which might try to enter the bloodstream and
sneezed or coughed out.
- Cilia – sweep away trapped germs and dust and carry them to the gullet and
swallowed, then excreted.
- Blood clotting – prevents entry of germs into the blood stream by forming a
mesh which traps germs.
- Hydrochloric acid in the stomach which provide an acidic pH for enzyme
pepsin. It also kills bacteria that come into stomach with food.
- Symbiotic defense in babies where the bacteria Escherichia Coli benefits
from food warmth and shelter from the baby, while the baby gets vitamin K
from the bacteria, and it also kills other bacteria entering the intestines to
cause disease.
- Ear wax which traps dust and germs, and insects protecting the ear canal from
damage.
