Why did dark moths become more common on soot-darkened tree trunks?

The increase in dark-colored moths on soot-darkened tree trunks is a classic example of natural selection driven by industrial melanism.

Before the Industrial Revolution, the peppered moth population consisted primarily of a light-colored morph that blended into lichen-covered trees, protecting it from bird predators. As coal soot from industrial activity covered trees and killed the light-colored lichens, the environment changed significantly.

In this new, soot-darkened landscape, the light-colored moths became highly visible and were more easily preyed upon. Conversely, the dark morph—which existed as a rare genetic mutation—became less conspicuous against the darkened bark. This camouflage provided a survival advantage, leading to reduced predation of the dark moths and a rapid shift in the population's genetic composition as the dark morph became the dominant form.12