Answer:
Natural Selection is an evolutionary process that caused the increment of dark-coloured Biston betularia moths in England. It happened due to increase of air pollution in the industries. The bark of the trees became darker because of the deposition of pollutants.
In order to save itself from predators, the species of Biston betularia evolved itself to a dark coloured species so that the predators gets confused between the bark of the tree and the Biston betularia.