WAEC Biology 2021 Papers

Concept:When a predator is removed from a food chain, its prey is released from predation pressure and its population generally rises.Explanation:The food chain shown can be written as $\text{grass} \rightarrow \text{grasshopper} \rightarrow \text{lizard} \rightarrow \text{hawk}$.In this chain, grasshoppers are the prey of lizards, while lizards are the prey of hawks.If the lizard population is removed, grasshoppers will no longer be hunted by this predator.Consequently, fewer grasshoppers will be killed and eaten at that trophic level.More grasshoppers will therefore survive and reproduce successfully.This will lead to an increase in the number of grasshoppers.The hawks, however, would lose a major food source, so their population would fall instead of rising.Also, the increased grasshopper population will feed more heavily on grasses.Answer:C. grasshoppers would increase