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Name…………………………………… …………………………..………… Index No: ……………………….

231/1
BIOLOGY
PAPER 1
(THEORY)
TIME: 2 HOURS

BIOLOGY PAPER 1
Kenya Certificate of Secondary Education (K.C.S.E.)

231/1
Biology
Paper 1

INSTRUCTIONS TO CANDIDATES

 Write your name and index number in the spaces provided above
 Sign and write the date of examination in the spaces provided.
 Answer all the questions in the spaces provided.

For Examiners Use Only

Question Maximum score Candidate’s score

1- 30 80

This paper consists of 11printed pages. Candidates should check to ascertain that all pages are printed as indicated and that no questions are
missing.

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1. Give three examples of continuous variations in human beings (3mks)

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2. (i) Name the main product of the dark stage of photosynthesis (1mk)
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(ii) State the importance of chlorophyll in photosynthesis (1mk)
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3. (a) Define the term balanced diet (1mk)
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(b) State the importance of roughage in a diet (1mk)
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4. (a) How is the fovea centralis adapted for its function in human eye (1mk)
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(b) A person was not able to see far objects clearly but could view near objects clearly. Name the
eye-defect the person had (1mk)
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(c) How can the defect be corrected (1mk)
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5. (a) What is fertilization ? (2mks)
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(b) Explain how double fertilization takes place in plants (2mks)
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6. In an experiment, the pituitary gland of a rat was removed
(a) State the effect this will have on the quantity of urine produced by the rat. (1mk)
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(b) Give a reason for your answer in (a) above (1mk)
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7. State two importance of sexual reproduction (2mks)
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8. The diagram below show part of a food relationship in an ecosystem

Fox Dog Leopard

Rabbit

(a) Name the food relationship shown in the diagram (1mk)

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(b) Name the trophic level occupied by organism A (1mk)
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(c) What is the main source of energy in the ecosystem shown in the diagram above? (1mk)
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9. State the function of the diaghragm in the light microscope (1mk)
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10. Explain the role of antidiuretic hormone when there is less water in the human body (3mks)
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11. State the function of each of the following organelles
(a) Centrioles (1mk)
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(b) Golgi body (1mk)
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12. The graph below shows action of heat on enzyme reaction

Rate of Enzyme
B

ratio
C

A
Temperature (oC)

(a) What is the effect of temperature on the rate of enzyme reaction ? (2mks)
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(b) State the relationship between temperature and enzyme activity (2mks)
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13. Distinguish between divergent and convergent evolution (2mks)
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14. State three distinguishing features for members of pylum chordate (3mks)
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15. (a) State the reasons for the following adaptations of the xylem vessels (2mks)
(i) Narrow lumen:
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(ii) Lack of cross walls
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(b) State two distinguishing features of the phloem sieve tubes (2mks)
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16. State the economic importance of the following plant excretory products
(a) Caffeine (2mks)
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(b) Quinine (1mk)
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17. Explain why a baby loses more heat per unit weight than an adult when exposed to the same
environmental conditions (2mks)
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18. During oxidation of certain food substances, the respiratory quotient was found to be 0.718
(i) Name the type of food substance being oxidized (1mk)
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(ii) State two advantages of using the food substances named (2mks)
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19. The diagram below shows various types of gene mutations

Mutation 1: A B C D E F G A B C F G

Mutation 2: A B C D E F G A B C F G E D G
(c) Identify the type of gene mutation shown above (2mks)
Mutation 1
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Mutation 2
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(d) Distinguish between gene and chromosomal mutations (2mks)
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20. The diagram below shows dentition of a dog
X

(a) (i) Name the part labeled X (1mk)

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(ii) Give a reason for your answer in a (i) above (1mk)

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(b) State how part labeled Y is adapted to its function (1mk)

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21. The diagrams below represents a nerve cell

Cell body
(a) Identify the nerve cell (1mk)
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(b)(i) Give a reason for your answer in (a) above (1mk)
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(iii) Show by use of an arrow the direction of flow of the nerve impulses
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22. (a) State the importance of the following features in gaseous exchange
(i) Cartilage in the trachea (1mk)
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(ii) Moisture on the surface of alveoli. (1mk)
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(b) Name two sites where gaseous exchange takes place in terrestrial plants (2mks)
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23. During germination and early growth, the dry weight of endosperm decreases while that of the
embryo increases. Explain (2mks)
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24. The table below shows the percentage composition of blood plasma and urine for four substances

Component substance Blood plasma % Urine %

Urea 0.03 2.0
Water 90 90
Plasma proteins 8.0 0
Glucose 0.1 0

(a) Account for the absence of plasma proteins in urine (1mk)

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(b) Urea concentration being greater in the urine than in the blood plasma (1mk)
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25. State three advantages of asexual reproduction in organisms (3mks)
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26. Explain how the human eye accommodates an image from a far distant object (2mks)
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27. The diagram below represents a stage of growth in two different seeds

Seedling A Seedling B
(a)Identify the type of germination exhibited by seedlings A and B (2mks)
Seedling A
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Seedling B
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(f) State the role of oxygen in germination (1mk)
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28. In view of modern genetics explain why Lamarckian theory is unacceptable. (2mks)
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29. Define the following terms used in ecology (4mks)
(i) Biosphere
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(ii) Population
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(iii) Synecology
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(iv) Carrying capacity
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