In the industrial regions of England during the nineteenth and twentieth centuries, the number of birch moth butterflies with

In the industrial regions of England during the nineteenth and twentieth centuries, the number of birch moth butterflies with dark colored wings increased, compared with light colored ones. Explain this phenomenon from the perspective of evolutionary doctrine and determine the form of selection.

1) in the offspring of the butterfly population, both light and dark forms are born;
2) light individuals are eliminated from the darkened trunks in birds polluted with soot in industrial areas; therefore, after a number of generations, butterflies with a dark color became the dominant form in the populations;
3) color change in butterfly populations – the emergence of a moving form of natural selection