In cod fishing, older and larger fish are more likely to be retained in nets than younger and smaller fish. Despite the removal of these large breeders, the population is still reproducing. How do you think cod characteristics have changed due to the selection pressure from over-fishing?

A. Selection has led to increased growth rates. B. Selection has led to decreased growth rates. C. Selection has led to increases in the age of fish at the age of reproductive maturity. D. Selection has led to decreases in the size of fish at the age of reproductive maturity.

The correct answer is - option d.

Explanation:

Selective pressure is the process or phenomenon that leads to the change or alteration in the behavior in a specific environment. It is the basis of the natural selection based on genetic variation.

In selection pressure population will decrease and adapt the size of the fish at the age of reproductive maturity, However the offspring in such condition would be less.

Thus, the correct answer is - option D.

D. Selection has led to decreases in the size of fish at the age of reproductive maturity.

Explanation:

The larger body size of the fishes is not an adaptive trait as it reduces the survival chances of these fishes. The process of natural selection tends to increase the frequency of the traits that increase the survival fitness of the organisms. Here, the fishes with smaller body size at the reproductive age have greater chances of survival and would reproduce more to leave more progeny. Over the generations, the selection pressure would increase the proportion of fishes that are smaller during reproductive age.