TYPE B ANSWERS

OBJ Answers (Type B)

01-10: A A C B A C A D C C

11-20: B D A D D C D A D D

21-30: C B A C A C C B C C

31-40: D D A D C D D B C A

41-50: C D B A D C C D B D

Theory Answers — Type B

PART I

Question 1

(1a) Advantages of multicellularity:
(i) It allows division of labour, where different cells, tissues, and organs perform specialized functions efficiently.
(ii) 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: (i) They consist of many similar cells living together in a colony. (ii) Individual cells can often survive independently when separated.
• Filamentous organisms: (i) They consist of cells arranged end-to-end forming threads or filaments. (ii) Individual cells usually cannot survive independently when separated.

(1bii) Colonial organism: Volvox | Filamentous organism: Spirogya.

(1c) Diagram of a colonial organism (label as required in the question).

PART II

Question 2

(2ai) Pollination is the transfer of pollen grains from the anther of a flower to the stigma of the same flower or another flower of the same species.

(2aii) 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.

(2bi) 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.

(2bii) Diagram of a typical flower showing main parts as required.

Question 3

(3ai) Good soil characteristics:
• Contains adequate nutrients/mineral salts.
• Has good water-holding capacity and drainage.
• Contains plenty of humus and supports soil organisms.

(3aii) Methods of improving poor soil:
• Application of manure or fertilizers.
• Crop rotation (or bush fallowing).

(3b) Methods of vegetative propagation with examples:
• Cutting – e.g. cassava, sugarcane, rose.
• Layering – e.g. cocoa, bougainvillea, mango.
• Grafting/Budding – e.g. citrus, mango.
• Underground stems (suckers/rhizomes/tubers) – e.g. banana, ginger, yam.

(3c) Vegetative propagation:
Advantages: (i) Produces true-to-type offspring. (ii) Leads to early maturity and fruiting. (iii) Useful for plants with no viable seeds.
Disadvantages: (i) Low genetic variation. (ii) Easy transmission of diseases from parent to offspring. (iii) Low multiplication rate.

PART III

Question 4

(4a) Diagram of the human digestive system (label as required in the question).

(4bi) Teeth: Used for biting, cutting, tearing, crushing and grinding food; increase the surface area of food for enzyme action; make swallowing easier.

(4bii) Tongue: Mixes food with saliva to form a bolus; helps in swallowing; contains taste buds for detecting different tastes.

(4biii) Saliva: Moistens and lubricates food; contains salivary amylase (ptyalin) which begins the digestion of starch.

(4biv) Stomach: Stores and churns food; secretes enzymes and hydrochloric acid for protein digestion; destroys harmful microorganisms in food.

Question 5

(5a) Sense organs and their functions:
• Eye – vision.
• Ear – hearing and balance.
• Nose – smell.
• Tongue – taste.

(5bi) Myopia (short-sightedness): The affected person can see nearby objects clearly but distant objects appear blurred. The eyeball is too long or the eye lens is too powerful, so light rays are focused in front of the retina.

(5bii) Diagram showing correction of myopia using a concave lens.

(5ci) Cerebrum: Controls voluntary actions, thinking, memory and reasoning.

(5cii) Cerebellum: Controls balance, posture and coordination of body movements.

PART IV

Question 6

(6ai) Sex-linked genes: Genes found on the sex chromosomes (X or Y) whose inheritance is associated with the sex of an individual.

(6aii) Dominance: The ability of one allele (the dominant one) to express itself and mask the expression of the other (recessive) allele in a heterozygous condition.

(6aiii) Hybrid: The offspring produced by crossing two genetically different individuals of the same species.

(6bi) Variation: The differences that exist among individuals of the same species in appearance, physiology, behaviour and genetic makeup.

(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 adaptation to changing environments; increases the chances of survival of a species; provides raw materials for evolution and natural selection.

TYPE D ANSWERS

OBJ Answers (Type D)

01-10: C D D A D C D C C B

11-20: D B A D C C D D D C

21-30: D A A B C D D B C A

31-40: C B D A A C B A D C

41-50: A D C C D C A C A B

Theory Answers — Type D

PART I

Question 1

(1a) Advantages of multicellularity:
(i) It allows division of labour, where different cells, tissues, and organs perform specialized functions efficiently.
(ii) 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: (i) They consist of many similar cells living together in a colony. (ii) Individual cells can often survive independently when separated.
• Filamentous organisms: (i) They consist of cells arranged end-to-end forming threads or filaments. (ii) Individual cells usually cannot survive independently when separated.

(1bii) Colonial organism: Volvox | Filamentous organism: Spirogya.

(1c) Diagram of a colonial organism (label as required in the question).

PART II

Question 2

(2a) Methods of vegetative propagation: Cutting (cassava, sugarcane, rose); layering (cocoa, bougainvillea, mango); grafting/budding (citrus, mango); underground stems – suckers/rhizomes/tubers (banana, ginger, yam).

(2b) Advantages and disadvantages of vegetative propagation:
Advantages: True-to-type offspring; early maturity/fruiting; useful for plants with no viable seeds.
Disadvantages: Low genetic variation; easy disease transmission from parent; low multiplication rate.

(2ci) Characteristics of good soil: Adequate nutrients and mineral salts; good water-holding capacity and drainage; plenty of humus to support 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.

(3bi) Pollination: The transfer of pollen grains from the anther to the stigma of the same flower or another flower of the same species.

(3bii) Features of an insect-pollinated flower: Large brightly coloured petals; presence of scent and nectar; sticky, heavy pollen; sticky, non-feathery stigma.

PART III

Question 4

(4ai) Myopia: A defect of vision in which a person can see nearby objects clearly but distant objects appear blurred because the eyeball is too long or the eye lens is too powerful, so light rays focus in front of the retina.

(4bi) Cerebrum: Responsible for voluntary actions, thinking, memory and reasoning.

(4bii) Cerebellum: Controls balance, posture and coordination of body movements.

(4c) Sense organs and their functions: Eye – vision; Ear – hearing/balance; Nose – smell; Tongue – taste.

PART IV

Question 5

(5ai) Teeth: Used for biting, cutting, tearing, crushing and grinding food; increase the surface area of food; make swallowing easier.

(5aii) Tongue: Forms the bolus and helps in swallowing; contains taste buds which detect different tastes.

(5aiii) Saliva: Lubricates and moistens food; contains salivary amylase which digests starch.

(5aiv) Stomach: Churns food; secretes enzymes and hydrochloric acid; helps destroy microorganisms in food.

Question 6

(6ai) Sex-linked genes: Genes located on the sex chromosomes whose inheritance is associated with the sex of the individual.

(6aii) Dominance: A situation in which one allele (the dominant one) expresses itself and masks the effect of the other (recessive) allele in a heterozygous condition.

(6aiii) Hybrid: An offspring produced by crossing two genetically different individuals of the same species.

(6bi) Variation: The differences that exist among individuals of the same species in appearance, physiology, behaviour and genetic makeup.

(6bii) Examples of variation: Continuous: Height, body weight, skin colour, intelligence. Discontinuous: Blood group, tongue rolling, sex, fingerprint pattern.

(6biii) Importance of variation: Enables adaptation; increases survival chances; provides raw materials for evolution and natural selection.