Name ……………………………….………….. Class …………………….………………….
Adm. No. …………………………..…………… Index No. ……………………..……………
231/2 BIOLOGY
Theory
Paper 2
March 2025
2 hours
Instructions to candidates
This paper consists of two sections, A and B.
Answer all the questions in section A in the spaces provided.
In section B answer question 6(compulsory) and either question 7 or 8 in the spaces provided
after question 8.
This paper consists of 12 printed pages.
For Examiner’s use only
Section Question Maximum score Candidate’s score
1 8
2 8
A 3 8
4 8
5 8
6 20
B 7 20
8 20
Total score 80
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Section A (40 marks)
1. Study the diagram below and answer the questions that follow
F G
(a) Name two processes carried out by the structures labelled F to allow the opening of the
stoma. (2 marks)
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(b) State three characteristics of the structures labelled G. (3 marks)
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(c) Explain how uptake of water enables the structures labelled F to function. (3 marks)
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2. The diagram below show cell division in an organism. Study the diagrams and answer the
questions that follow.
(a) (i)Identify the type of cell division illustrated above. (1 mark)
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(ii) Give two reasons for your answer in (a)(i) above. (2 marks)
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(b) Name two parts in a plant where the type of cell division named in (a)(i) occurs. (2 marks)
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(c) State the significance of this type of cell division in organisms. (2 marks)
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(d) Name the hormone that promotes cell division in plants. (1 mark)
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3. Form 3 students went to the school farm nursery bed. They found out that some seeds sprout
and the hypocotyl bulged first out of the soil pulling the cotyledons above the ground.
(a)(i) Name the type of germination exhibited by the above seedlings. (1 mark)
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(ii) (ii) State the functions of the cotyledons. (3 marks)
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(c) Explain how the following conditions are necessary in breaking seed dormancy
(i)Temperature (1mark)
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(ii) Water (2 marks)
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(iii) Oxygen (1 mark)
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4. The diagram below represents part of a human nephron.
(a)(i) Describe the changes that occur on the blood flowing as shown by the arrow up to the
proximal convoluted tubule. (3 marks)
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(ii) Explain two structural adaptation of proximal convoluted tubule to its function (2 marks)
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(iii) Give a reason why blood glucose appears in the urine of a patient. (1 mark)
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(b) Name two diseases of the liver. (2 marks)
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5. (a) In humans, the ability to taste phenylthiocarbamide (PTC) is controlled by a single
dominant gene represented by letter T. A heterozygous female taster married a non – taster male.
Work out the genotypic ratio of their offspring. (5 marks)
(b) Name Mendel’s second law of inheritance. (1 mark)
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(c) What is meant by the following terms? (2 marks)
Allele,
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Hybrid vigour.
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SECTION B (40 Marks)
Answer question 6 (Compulsory) and either question 7 or 8 in the spaces provided after
question 8.
6. A group of students carried out a study of the population growth of flour weevils. They put 16
grams of maize flour into two equal boxes K and L respectively. They then introduced equal
numbers of weevils into the boxes. The boxes were kept under similar environmental conditions.
The weevils were counted at intervals and the results recorded in the table below
No. of days after Approximate No. of weevils present.
introduction of weevils K L
0 10 10
20 10 10
40 10 10
60 100 150
80 190 400
100 280 650
120 320 820
140 280 820
160 300 850
(a) Using a suitable scale, draw two graphs of number of weevils against time, on the same axes.
(8 marks)
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(b) What was the approximate number of weevils present in the two boxes on the 90th day?
(2 marks)
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(c)(i)On what day was the population of weevils in L 580? (1 mark)
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(ii)Between which days was the population difference greatest in box L? (1 mark)
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(d) Account for the shape of graph L between day 40 and day 120. (4 marks)
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(e) In a natural ecosystem, name two abiotic and biotic factors that affect distribution of
organisms. (4 marks)
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7. (a) Describe the ways in which prey are adapted for survival against predators. (10 marks)
(b) Outline five measures that can be employed to prevent spread of schistosoma parasite.
(10 marks)
8. How is the mammalian skin suited to its function? (20 marks)
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