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

(1bii)

• Colonial organism example: Volvox
• Filamentous organism example: Spirogyra

(1c)

Question 2

(2ai) Characteristics of good soil for agriculture

• It contains adequate nutrients or mineral salts for plant growth.
• It has good water-holding capacity and good drainage.
• It contains plenty of humus (organic matter) and supports soil organisms.

(2aii) Methods of improving poor soil

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

(2b) 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).

(2c) Advantages of vegetative propagation

• It produces true-to-type offspring.
• It leads to early maturity or early fruiting.
• It is useful for plants that have no viable seeds.

Disadvantages of vegetative propagation

• There is low genetic variation among offspring.
• There is easy transmission of diseases from the parent plant.
• It often has a low multiplication rate compared with seed propagation.

Question 4

(4ai) Myopia (short-sightedness)

The eye defect is called myopia (short-sightedness). It is a condition in which a person can see nearby objects clearly but distant objects appear blurred. This defect occurs when the eyeball is too long or the eye lens is too powerful, causing light rays from distant objects to focus in front of the retina instead of directly on it.

(4aii)

(4bi) Function of the cerebrum

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

(4bii) Function of the cerebellum

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

(4c) Sense organs and their functions

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

Question 5

(5ai) Functions of the teeth

Teeth are used for biting, cutting, tearing, crushing, and grinding food into smaller particles. This increases the surface area of food for the action of digestive enzymes and makes swallowing easier.

(5aii) Functions of the tongue

The tongue mixes food with saliva to form a bolus and helps in swallowing. It also contains taste buds which enable the animal to detect different tastes in food.

(5aiii) Functions of saliva

Saliva moistens and lubricates food, making it easier to swallow. It also contains the enzyme salivary amylase (ptyalin) which begins the digestion of starch into simpler sugars.

(5aiv) Functions of the stomach

The stomach stores and churns food, mixing it with gastric juice. It also secretes enzymes and hydrochloric acid for the digestion of proteins and destroys harmful microorganisms present in food.

(5b)