What is the Industrial Melanism in evolution?

A classic example of Darwin's theory at work in an actual real-life situation lies in the case of the peppered moth during the industrial revolution in the mid-1800's that took place . Prior to the industrial revolution, most peppered moths (Biston betularia) were light-colored. Most of the trees upon which they usually rested were also light colored, and therefore offered camouflage protection from birds that fed upon them.

The industrial revolution was made possible by the use of coal, which was burned to produce the power to drive the machinery in the factories that popped up all over the landscape. Coal isn't a clean burning fuel, in fact, it is downright filthy, giving off noxious fumes and huge clouds of dirty black soot. The soot soon covered the tree trunks, and the polluted air killed off many of the trees, turning them black.

The light-colored moths soon began to stand out against the black background of the trees, and became easy targets for the birds, who now had no trouble identifying food. However, a small percentage of the moths had always been darker than average because of genetic variation. These darker moths did not present as easy a target for the birds, and therefore had a higher rate of survival. Over time, a larger and larger percentage of the darker moths survived were able to successfully reproduce. Their offspring was more likely to be dark, and so the population around these industrial centers began to change, since fewer and fewer light-colored moths survived to reproduce.

In this way, a light-colored population gradually evolved to become dark-colored because of natural selection. This process of evolution has been named industrial melanism.