231/3 · BIOLOGY (Practical) · Paper 3 · Mar. 2022 (KCSE 2021) · 1¾ hours
Instructions: Answer all the questions in the spaces provided. Spend the first 15 minutes reading the whole paper carefully before commencing your work.
Question 1 (14 marks)
(a) You are provided with plant specimens labelled E, F, G, H and J. Use the specimens to develop a dichotomous key that can be used to identify the plants from which they were obtained, based on the following characteristics in the order given: (i) leaf form; (ii) leaf venation; (iii) leaf colour. (6 marks)
(b) Account for the likely observation if fresh specimen E was exposed to light and tested for starch. (3 marks)
(c) Explain one observable feature that adapts the plants from which specimens G and H were obtained to a dry environment. (2 marks)
(d) Besides leaf characteristics, state one other observable characteristic of the plant from which specimen F was obtained that enables it to be placed in its Class. (1 mark)
Question 2 (14 marks)
You are provided with solution M, which is a food substance.
(a) Using the reagents provided, test for the food substances present in substance M and complete the table below. (12 marks)
| Food test | Procedure | Observation | Conclusion |
|---|---|---|---|
| Starch | |||
| Vitamin C | |||
| Lipids |
(b) State two precautions one should observe while conducting the experiment in 2(a). (2 marks)
Question 3 (12 marks)
You are provided with specimens N and P, which are plants of the same species grown under different conditions.
(a) State two observable differences between the two specimens. (2 marks)
(b) (i) Name the phenomenon observed in specimen N. (1 mark) (ii) Explain how knowledge of the phenomenon named in (b)(i) is applied in agriculture. (2 marks)
(c) Account for the appearance of specimen N. (3 marks)
(d) State two environmental factors necessary for seed germination. (2 marks)
(e) State two observable features of the specimens that place them in the same Class. (2 marks)