CAPE Biology Unit 1 · 2008 (Rest of Region) · Paper 1 · Question Q26

Item 26 refers to the graph which shows the effect of a pesticide on houseflies. A fixed amount of chemical was used each year during the rainy season, and the data were collected over a number of years. Which of the following statements BEST explains the effect of the pesticide?

1. (A)A few resistant flies reproduced more successfully and the resistance allele increased in frequency.
2. (B)At every generation an increasing predation of flies caused them to become more resistant.
3. (C)Repeated exposure to the pesticide caused the flies to become more resistant.
4. (D)The allele for resistance mutated from the recessive form to the dominant form.

This question uses a figure or table from the paper — you'll see it when you practise.