Question

Small fish eat algae, medium fish eat small fish, and large fish eat medium fish. If pollution kills most of the algae, what will likely happen to fish populations?
Question 5 options:

Only large fish populations will be significantly affected

Medium and large fish will benefit from reduced competition

Fish will easily switch to alternative food sources

All fish populations will decline due to food web disruption

Answer 1

All fish populations will decline due to food web disruption.

Explanation: algae are the base of this food chain. If algae die off, small fish lose their food and decline, which reduces food for medium fish, which in turn reduces food for large fish — a bottom-up cascade.