PART I

Question 1

(1a) Advantages of multicellularity

• It allows division of labour, where different cells, tissues, and organs perform specialized functions efficiently.
• It increases the efficiency and survival of organisms by enabling them to carry out complex life processes.

(1bi) Differences between colonial and filamentous organisms

Colonial organisms	Filamentous organisms
They consist of many similar cells living together in a colony.	They consist of cells arranged end-to-end forming threads or filaments.
Individual cells can often survive independently when separated.	Individual cells usually cannot survive independently when separated.

(1bii) Colonial organism: Volvox  |  Filamentous organism: Spirogyra

(1c)

PART II

Question 2

(2a) Methods of vegetative propagation with examples

• Cutting – e.g. cassava, sugarcane, rose.
• Layering – e.g. cocoa, bougainvillea, mango.
• Grafting/Budding – e.g. citrus (orange), mango.
• Use of underground stems (suckers/rhizomes/tubers) – e.g. banana (suckers), ginger (rhizome), yam (tuber).

(2b) Advantages and disadvantages of vegetative propagation

• Advantages: True-to-type offspring; early maturity and fruiting; useful for plants with no viable seeds.
• Disadvantages: Low genetic variation; easy transmission of diseases from parent plant; low multiplication rate.

(2ci) Characteristics of good soil

• Contains adequate nutrients and mineral salts.
• Has good water-holding capacity and drainage.
• Contains plenty of humus and supports soil organisms.

(2cii) Methods of improving poor soil

• Application of manure or fertilizers.
• Crop rotation (or bush fallowing).

Question 3

(3ai) Functions of a flowering plant

• Produces food through photosynthesis.
• Carries out reproduction through flowers.
• Absorbs water and mineral salts from the soil.
• Provides support and transport of materials within the plant.

(3aii)

(3bi) Pollination

Pollination is the transfer of pollen grains from the anther of a flower to the stigma of the same or another flower of the same species.

(3bii) Features of an insect-pollinated flower

• Large and brightly coloured petals.
• Presence of scent and nectar.
• Pollen grains are sticky and heavy.
• Stigma is sticky and not feathery.

PART III

Question 4

(4ai) Myopia (short-sightedness)

• A person with myopia can see nearby objects clearly but distant objects appear blurred.
• The eyeball is too long or the eye lens is too powerful.
• Light from distant objects is focused in front of the retina.

(4aii)

(4bi) Cerebrum

The cerebrum controls voluntary actions, thinking, memory, and reasoning.

(4bii) Cerebellum

The cerebellum controls balance, posture, and coordination of body movements.

(4c) Sense organs and their functions

• Eye – vision.
• Ear – hearing and balance.
• Nose – smell.
• Tongue – taste.

Question 5

(5ai) Teeth

• Biting, cutting, tearing, crushing and grinding food.
• Increase the surface area of food for enzyme action.
• Make swallowing easier.

(5aii) Tongue

• Mixes food with saliva to form a bolus.
• Helps in swallowing.
• Contains taste buds that detect tastes.

(5aiii) Saliva

• Moistens and lubricates food.
• Contains salivary amylase (ptyalin) which begins the digestion of starch.

(5aiv) Stomach

• Stores and churns food with gastric juice.
• Secretes enzymes and hydrochloric acid (HCl) for protein digestion.
• Destroys many harmful microorganisms in food.

(5b)

PART IV

Question 6

(6ai) Sex-linked genes

Sex-linked genes are genes located on the sex chromosomes (X or Y) whose inheritance is associated with sex; the traits they control are called sex-linked traits.

(6aii) Dominance

Dominance is the ability of one allele to express itself and mask the effect of another (recessive) allele.

(6aiii) Hybrid

A hybrid is an offspring produced by crossing two genetically different individuals or varieties of the same species.

(6bi) Variation

Variation refers to differences among individuals of the same species in physical appearance, physiology, behaviour, and genetic constitution.

(6bii) Examples of variation

• Continuous variation: Height, body weight, skin colour, intelligence.
• Discontinuous variation: Blood group, tongue rolling, sex, fingerprint pattern.

(6biii) Importance of variation

• Enables organisms to adapt to environmental changes.
• Increases the chances of survival of the species.
• Provides raw materials for evolution and natural selection.