If a population of short-lived, annually reproducing fish is exposed for several years in a row to a chemical toxin that kills 5% of them each year, what might you expect to happen if the population is re-exposed to the chemical several years later?
A) much higher death rate.
B) lower death rate.
C) about the same death rate.
D) no mortality-they will be immune to the toxin.

Question

Quizplus · Accepted Answer

Fewer fish would die upon re-exposure. The population will have evolved resistance to the toxin. Natural selection (appearing in the form of the toxin) would have selected individuals that are naturally resistant to the toxin, allowing them to persist and reproduce, passing the resistant trait on within the next generation of fish.

If a Population of Short-Lived, Annually Reproducing Fish Is Exposed