Natural selection is the process by which those organisms that are best suited to their environment and are able to reproduce well in changed environmental conditions, survive. Peppered moth, Biston betularia lives in all parts of England. Before industrialisation the bark of the tree were covered by whitish lichens. Hence,light coloured moths were majorly found over pale tree trunks as they went unnoticed from predators.

 

Due to industrialisation the pale tree trunks became more and more blackened due to industrial smoke and soot. As a result, the light moths stood out in contrast to its background, increasing the possibility of being easily detected and eaten by their predators, such as birds, in much greater number than the dark melanic variety. Decrease in the number of light winged moths was observed while increase in the number of dark variety was the ultimate result. Therefore, nature selected and evolution favoured the dark winged melanic moths to reproduce more successfully for their adaptation in the polluted areas of England. Survival of darker form in response to industrial pollution is known as industrial melanism