Question

Peppered moths come in two color variations, as shown below.

Prior to the Industrial Revolution, the majority of the population in England consisted of the light colored variation. The dark colored moth became the dominant variation by the end of the 20th century and remained so for almost 100 years. Today, the light colored variation is dominant again.

What is the best explanation for this?

A. Populations with two variations have a better chance of survival than populations with more.

B. A single variation can be beneficial under some conditions and harmful under other conditions.

C. One variation will always be harmful, and the other will always be beneficial.

D. A single variation can be beneficial in all conditions or harmful in all conditions.

Answer 1

The answer, I do believe, should be option B. Here's my reasoning...

The question doesn't ask about a bunch of other species and how the moth variations relate to the survivability of many species, so I think that rules out option A. Option C is too black-and-white, because the explanation above simply states how a moth was able to survive better on different color variations. The last option, D, is also too black-and-white. So I believe that the answer is B, because sometimes, like prior to the Industrial Revolution, the one variation is better (as seen in the upswing of dominance in different variations).