When heavily armored marine sticklebacks have invaded freshwater lakes where there are no predatory fish, their populations have evolved lighter body armor. Given what you've learned about evolution, which of the following explanations for why this happens is most plausible? A. Young sticklebacks only grow heavy armor when they see predatory fish in their environment. B. When sticklebacks don't use their armor, it shrinks. Then they pass lighter armor to their offspring. C. Concentrated pollutants in freshwater lakes disrupt the sticklebacks' ability to grow armor. D. Heavily armored fish grow more slowly and breed later, making armor dis-advantageous in these lakes.

B

Explanation:

The correct answer would be that when sticklebacks don't use their armor, it shrinks. Then they pass lighter armor to their offspring.

According to the theory of natural selection, adaptive traits that enable organisms to survive in an environment are selected by the forces of natural selection.

When a particular trait is not needed for survival in an environment, the trait gradually degenerates within the population as natural selection ignores the existence of such trait. The degenerated trait is inherited by the subsequent generations of the population.

The mechanism is also consistent with the law of use and disuse of organs by Jean Larmack.

The correct option is B.