MOKASA II EXAMINATIONS

Kenya Certificate of Secondary Education

231/1 BIOLOGY Paper 1

July/August, 2025 Exam – 2 hours

Name: Index no:

School: Sign: Date:

Instructions to candidates
 Write your name, class and Admission number in the spaces provided above.
 Append your signature and write the date of examination in the spaces provided above.
 Spelling errors especially of Biological terms shall be penalized.
 Answer ALL questions in the spaces provided.

For Examiner’s Use Only:

Question Maximum Candidate’s
Score Score

1 – 31 80

TOTAL

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

1|Page
 1. (a)Define the term cell specialization (1mark)
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(b) Name the cell organelles that would be most abundant in (2marks)

a. Skeletal muscle cells ………………………………………………………………………………

b. Palisade cells ……………………………………………………………………………………….
2. Given a temporary slide of onion cells, a microscope and a ruler, describe how you can
estimate the size of each cell. (3 marks)
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3. Give two characteristics of living organisms that involve direct movement of substances
into the body of a living organism (2 marks)
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4. The diagram below illustrates a structure found in a cell, Study it and answer the
questions that follow.

(a) Identify the organelle shown above (1mark)

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(b) Identify the structures 2 and 8 (2marks)
2. …………………………………………………………………………………………………………………
8. …………………………………………………………………………………………………………………..
(c) Give the role of the structure 3. (1mark)
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2|Page
 5. Is diffusion an energy driven process? Explain. (2marks)
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6. Define the term binomial nomenclature (1mark)
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7. State the causative agents for the following diseases. (2marks)

(i) Gonorrhea
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(ii) Amoebic dysentery
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8. Oxygen, Glucose and amino acids are some of the products of photosynthesis. What is
the fate of each of these products? (3 marks)

Oxygen
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Glucose
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Amino acids
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9. The diagram below represents a muscle found in an organ of a mammal:

a) Identify the type of muscle (1mark)

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b) Name the parts labeled A and C. (2mark)
A ………………………………………………………………………………………………………………….
C …………………………………………………………………………………………………………………..

3|Page
 c) State one adaptation of the muscle indicated above. (1mark)

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10. Other than turgor pressure, suggest two other ways in which herbaceous stems obtain
mechanical support. (2mk)
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11. Study the diagram below of a neuron in human being.

Effectors
Myelin
dendrites
A sheath

Cell body
Nucleu
s

a. Identify the neuron. (1mk)

………………………………………………………………………………………
b. Name the parts labeled
A ……………………………………………………………………………. (1mk)
B …………………………………………………………………………… (1mk)
c. Using an arrow indicate the direction of movement of a nerve impulse along the
neuron. (1mk)

12. The paddles of a whale and the fins of a fish adapt these organisms to aquatic habitats.
a. Name the evolutionary process that may have given rise to these structures.
(1mk)

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b. What is the name given to such structures? (1mk)

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4|Page
 c. Identify two evidences that support organic evolution. (2mk)
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13. Name the type of response shown by:
a. Leaves of Mimosa pudica when they fold after being touched. (1mk)

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b. Euglena when it swims towards the source of light. (1mk)

…………………………………………………………………………………………………………………….

c. Maggots moving from the lit chamber to the chamber painted black. (1mk)

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d. Roots of plants when they grow downwards. (1mk)

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14. Below is a section of nuclei acid strand. Study it and then answer questions that follow:

T–G–C–A–G–A–T–C

a. Identify the type of nucleic acid strand. (1mk)

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b. Give reason for your answer in (b) (i) above. (1mk)
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c. Write down the base sequence of the complimentary strand. (1mk)
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15. Distinguish between the following terms:
a. Genotype and phenotype. (1mk)

5|Page
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b. Dominant and recessive alleles. (1mk)
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16. After an ecological study of nutritional relationships in an ecosystem, a student
constructed the following food web.

Large bird

Bird J Bird K Bird L

Small Fish

mussels
Zooplanton
algae

a) Name the ecosystem in which the ecological study was done. (1mk)
…………………………………………………………………………………………………………………………
b) State one short term effect of the eradication of all zooplankton from this ecosystem.
(1mk)
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c) What trophic level is the large bird? (1mk)
…………………………………………………………………………………………………………………………….

6|Page
 17. The diagram below shows the structure a cell during a certain stage of cell division.

a) Identify the stage shown. (1mark)

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b) Give two reasons for your answer in (a) above. (2marks)
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18. The diagram below represents a certain plant species.

a) Name the division to which the plant belongs. (1mk)

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b) State two differences between members of sub- division Gymnospermaphyta and
Angiospermaphyta. (2mk)
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c) Name division in which plants show alternation of generations. (1mk)

7|Page
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19. a) What are the advantages of fruit and seed dispersal? (2mk)
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b) State two characteristics of fruits and seeds dispersed by animals. (2mk)

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20. (a) State two roles of water in seed germination (2 marks)

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(b) Explain the difference in germination rate between seedlings at 5℃ and 35℃
(1mark)
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21. The table below shows blood components and how they become modified in the
process of urine formation.

Blood plasma Glomerular filtrate Urine

Component
g/100cm3 g/100cm3 g/100cm3
Glucose 0.15 0.15 0.00
Proteins 7.89 0.00 0.00
Mineral salts 0.68 0.68 0.50
Urea 0.10 0.10 1.50

State one possible reason for each of the following observations.

(i) No protein in the glomerular filtrate. (1 mark)
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8|Page
 (ii) No glucose in urine. (1 mark)
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(iii) Increased level of urea in urine. (1 mark)
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22. State any two adaptations of the polar mammals to their environment (2 marks)
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23. Name the hormone involved in ionic balance in the kidney (1mark)
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24. The diagram below shows part of a mammalian respiratory system.

T
S

(a) Explain two ways in which the part labeled T is adapted to its functions.(2 marks)
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(b) How does the part labeled S facilitates breathing in? (1 mark)
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25. State a characteristic of an efficient respiratory surface which is absent in amoeba

(1mark)
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9|Page
 26. State the function of spiral bands of chitin in the trachea of terrestrial insects

(1mark)
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27. What is the role of the following in a germinating seed? (2 marks)
(a) Oxygen
……………………………………………………………………………………………………………………………

(b) Cotyledon
…………………………………………………………………………………………………………………………..

28. (a) Why would you give an athlete glucose and not sucrose after a race? (1mark)

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29. State any two differences between open and closed circulatory systems (2 marks)

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30. In blood test, a few drops of anti-B serum were added to two samples of blood. It was
noted that agglutination occurred. What were the possible blood groups of the two
blood samples? (2 marks)

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31. State an adaptation of blood to high altitude (1 mark)

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10 | P a g e
11 | P a g e