Kenya Certificate of Secondary Education 2020
231/2 - BIOLOGY -Paper 2
(THEORY)
2 hours
INSTRUCTIONS TO CANDIDATES
- This paper consists of two sections; A and B
- Answer all the questions in section A in spaces provided
- In section B, answer question 6 (compulsory) and either question 7 or 8 in the spaces provided after question 8.
- Candidates should answer all the questions in English.
SECTION A (40marks)
Answer all the questions in this section in the spaces provided
- The diagrams below show simplified structures of kidneys from two different animals.
- State any two differences between kidneys A and B (2marks)
- What is the likely habitat for animal having kidney A? Explain your answer. (4marks)
- Explain the importance of having wider afferent arteriole than efferent arteriole in kidney nephron. (2marks)
- The table below shows the rate of inspiration and blood flow to the gut for some groups of students which were measured at rest and during strenuous exercise.
Average rate of blood flow to the gut (dm2/minutes) Average number of inspiration per minutes At rest 1.6 12 During Strenous exercise 0.23 20 -
- Account for the average number of inspiration during strenuous exercise (3marks)
- Explain the increase in blood flow to the gut at rest. (2marks)
- Explain the role of muscles in inspiration (3marks)
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- The diagram below represents chromosomes arrangement in somatic cells of a female suffering from a certain genetic disorder.
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- Name the disorder (1mark)
- Name the type of chromosomal mutation that causes the above disorder. (1mark)
- State two symptoms of a female with above disorder (2marks)
- Explain why there are no males with above genetic disorder. (2marks)
- State two advantages of cross breeding as a method of artificial selection (2marks)
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- The set ups below were carried out by a group of students to investigate an aspect in transpiration. Both potometers were placed under same environmental conditions and observation done at the same time after six hours.
- State the aim of experiment (1mark)
- State the expected observations in potometers A and B. (2marks)
A…………………………………………………………………………………….
B……………………………………………………………………………………. - Explain the expected observation in potometer B. (2marks)
- Account for what would happen if leaves on both set ups were smeared with Vaseline jelly on their upper and lower surfaces. (3marks)
- The diagram below illustrates an experiment to demonstrate certain aspect of respiration.
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- State the aim of experiment. (1mark)
- What is the role of soda lime in the set up? (1mark)
- State observations made in vessels A and B (2marks)
A………………………………………………………………………
B……………………………………………………………………….. - Why is it necessary to enclose the pot with polythene bag? (1mark)
- State the role of black cotton cloth covering bell jar. (1mark)
- During aerobic respiration involving lipid as a respiratory substrate, 102 cm3 of carbon (iv) oxide was produced. Determine the volume of oxygen that was used. (2marks)
- Explain how locomotion in animals is dependent on respiration (2marks)
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SECTION B (40 marks)
Answer question 6 (compulsory) and either question 7 or 8 in the spaces provided after question
- The table below shows changes in human hormonal levels in blood during 40 weeks of pregnancy
TIME(WEEKS) HORMONAL LEVELS (UNITS × 1000) Progesterone Human Chorionic Gonadotropin Oestrogen 5 10 00 00 10 15 45 02 15 15 60 02 20 20 15 02 25 40 04 04 30 75 14 10 35 85 20 18 40 84 20 18 - On the same axis, plot graphs of concentrations of hormones against time. (8marks)
- Account for the changes in levels of the following hormones during 40 weeks period.
- Progesterone (2marks)
- Oestrogen (2marks)
- Explain the following.
- Injection of an expectant mother with high levels of Luteinizing hormone after 4th month of pregnancy could cause an abortion. (2marks)
- At 4th month of pregnancy, surgical removal of ovaries of an expectant mother does not affect pregnancy. (2marks)
- xplain the role of oxytocin hormone during parturition. (2marks)
- State two ways in which oviduct is adapted to reproductive function. (2marks)
- On the same axis, plot graphs of concentrations of hormones against time. (8marks)
- A student while on his way to sleep saw a python snake. He immediately changed direction and ran away. Explain how the nervous and endocrine systems coordinate to bring about response shown by the student. (20marks)
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- Explain the role of skin in thermoregulation (12marks)
- Describe how red blood cell is adapted to its function (8marks).
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