KCSE Past Papers 2021 Biology Paper 1 (231/1)

Kenya Certificate of Secondary Education


Answer all the questions in the spaces provided.

1. Explain why it is necessary for plants to have their leaves spread out. (2 marks)

2. The diagram below represents the transverse section through a young dicotyledonous stem and a structure, F, obtained from the same section.

a.i. Identify the part labelled E. (1 mark)

ii. State the function of the part labelled E. (1 mark)

b.i. Label the part Z, on the section from which structure E was obtained. (1 mark)

ii. State two ways in which structure E is structurally adapted to its functions. (2 marks)

3. State two ways in which herbaceous plants obtain their mechanical support. (2 marks)

4.a. Name the proteinous substance that makes up the exoskeleton of members of Phylum Arthropoda. (1 mark)

b. State two functions of the exoskeleton. (2 marks)

c. State one disadvantage of the exoskeleton to members of Phylum Arthropoda (1 mark)

5. Explain how each of the following structures adapt the fish to movement in water.

a. Swim bladder (1 mark)

b. head (1 mark)

6. The diagram below represents the anterior view of a mammalian vertebra.

a.i. Identify the vertebra. (1 mark)

ii. Name the region of the vertebral column where the vertebra was obtained from. (1 mark)

b. Name the part labelled G. (1 mark)

c. Name the bone in the mammalian endoskeleton that articulates with the vertebra at the part labelled L. (1 mark)

7. State the difference between glycolysis and Kreb’s cycle based on the following: a. Where they occur (1 mark)

b. Amount of energy produced (1 mark)

8.a. Distinguish between gaseous exchange and respiration. (2 marks)

b. Explain the importance of algae in a pond(2 marks)

9. State two advantages of an insect undergoing a complete metamorphosis process. (2 marks)

10. Complete the table below, outlining the differences between members of Class Diplopoda and Chilopoda based on the characteristics given. (3 marks)

Body shape
Body segmentation
Number of legs per segment

First row is a table header 11.a. State two reasons why the snake is classified as a reptile. (2 marks)

b. Name the structure which enables Paramecium to move. (1 mark)

12. The diagram below represents an apparatus used to collect specimens for study.

a. Identify the apparatus. (1 mark)

b. State why it is advisable to have the apparatus illustrated above made of glass. (1 mark)

13.a. State two activities that take place in the ovule of a flowering plant during fertilisation. (2 marks)

b. State two functions of the seminal fluid in reproduction. (2 marks)

c. Name the hormone that stimulates the contraction of muscles of the uterine wall during birth (1 mark)

14.a. Giving an example in each case, state the difference between internal and external fertilisation. (2 marks)

b. State the agent of pollination in a maize plant. (1 mark)

15. Identify the response and receptor from the following list of sensory structures and processes:salivary gland smell of fried eggs olfactory cells salivation.

a. Response (1 mark)

b. Receptor (1 mark)

16. Explain how the knowledge of apical dominance is applied in agriculture, (2 marks)

17.a. Explain why the population of people with sickle-cell anaemia is higher in malaria-prone areas. (2 marks)

b. Explain why it is not advisable to put a patient on a drip of distilled water for rehydration (3 marks)