2019 mokasa biology paper 2

1. (a) Explain how dichogamy prevents self-fertilization in flowering plants. (2 marks)

2. (a) Explain how convergent evolution may occur. (3 marks)

b) The diagrams below show some organism structures that have been used as evidence of the process

of evolution

Name the type of evidence and explain it provides evidence to proof that the process of evolution may

be taking place. (3 marks)

(c) Outline two evolutionary characteristics that adapt man to his environment. (2 marks)

Below is a diagram, use it to answer the questions that follow:

(i) Name the chemical compound labelled X and state its function. (2 marks)

(ii) What changes would you expect to observe in the level of the coloured water in the capillary tube after the experiment has run for 10 minutes? (1 mark)

(iii) Explain the changes you have stated in (b) (ii) above. (3 marks)

(c) Why was it necessary to place the flask in a water bath? (1 mark)

4.Use the experiment below to answer the questions that follow:

After 30 minutes, the starch suspension had turned blue-black while iodine solution retained its colour.

d) Define cell physiology. (1 mark)

5. In a plant breeding research, a certain plant species was developed and found to be normally green

in colour. A recessive gene for colour (g) causes these plants to be white in the homozygous state. In this

state, the gene is lethal causing white plants to die at an early age soon after germination. In the

heterozygous state, these plants are pale green in colour and grow to maturity.

(a) Suggest a reason for the early death of the plants with homozygous recessive genes. (1 marks)

(d) Give an explanation for the occurrence of the pale green colour in heterozygous plants. (1 mark)

SECTION B (40 MARKS)

(ii) In a related exercise, students caught 240 grasshoppers, marked them with ink and then released

them. After five days, they caught 160 grasshoppers and found that 40 were marked. Work out the

estimated population of grasshoppers in the school compound. (3 marks)

b) (i) Identify the method described in (a)(ii) above. (1 mark)

(ii) Identify the instrument the students might have used to get the grasshoppers. (1 mark)

(iii) State three factors that would influence the results in the method above. (3 marks)

(c) Outline the adaptable observations the students would make on the grasshopper regarding;

(i) Locomotion.

(ii) Protection. (2 marks)

(iii) Feeding. (2 marks)

(a) Name the tissues in flowering plants responsible for secondary thickening (2 marks).(b) Describe an experiment you would carry out to demonstrate the region of growth in the root of a bean seedling. (8 marks).

(c) Explain the role of growth hormones in metamorphosis of a housefly (10 marks).

8. What is the role of a liver in:

(a) Blood sugar regulation. (10 marks)

(b) Thermoregulation. (5 marks)

2019 mokasa agriculture paper 2