The peppered moth became darker in polluted industrial areas, providing a famous example of natural selection.
The species, Biston betularia, normally includes a pale, speckled form that blends into lichen-covered tree bark. A darker form, called carbonaria, was recorded in England during the Industrial Revolution. Soot darkened tree trunks and killed lichens, making pale moths easier for birds to see while dark moths became better camouflaged.
As air pollution declined in the 20th century, lichens returned and tree bark became lighter. In many regions, the dark form then became less common. This change in frequency was driven by differences in survival and reproduction, rather than individual moths changing color during their lifetimes.
The example is sometimes oversimplified: bird predation is important, but researchers also consider factors such as resting behavior and local habitat. The moth did not evolve because it consciously adapted; inherited color variation already existed, and selection changed its proportions in the population.