The peppered moth provides a well-known example of natural selection. The light-coloured form of the moth was predominant in England before the Industrial Revolution. In the mid-19th century, a dark-coloured form appeared. The difference is produced by a dominant allele of one gene. By about 1900, approximately 90% of the moths around industrial areas were dark coloured, whereas light-coloured moths were still abundant elsewhere. Apparently, birds could readily find the light moths against the soot-darkened background in industrial areas and, therefore, were eating more light moths. Recently, use of cleaner fuels has greatly reduced soot in the landscape, and the dark-coloured moths have been disappearing. Should the two forms of moths be considered separate species?
A) Yes; natural selection has affected the frequency of the two different forms.
B) Yes; they have completely different colouration.
C) Yes; they are reproductively isolated based on habitat.
D) No; they still can interbreed.

Question

Quizplus · Accepted Answer

The two forms of moths should not be considered separate species because they can still interbreed. The difference in coloration is produced by a single dominant allele, and there is no evidence of reproductive isolation between the two forms based on habitat. The change in frequency of the two forms is due to natural selection acting on the moths' camouflage against their environment.

The Peppered Moth Provides a Well-Known Example of Natural Selection