Industrial Melanism in Biston Betularia

Industrial melanism is a phenomenon observed in certain species where the frequency of dark-colored individuals increases dramatically in response to environmental changes. One of the most well-known examples of industrial melanism is seen in the moth species Biston betularia.

Background
Before the industrial revolution, Biston betularia moths in England were predominantly light-colored, with a small proportion of dark-colored individuals. These light-colored moths were able to blend in with the lichen-covered tree trunks, which provided camouflage against predation by birds. However, with the advent of industrialization, the landscape underwent significant changes due to pollution.

Impact of Pollution
Industrial pollution led to the accumulation of soot and other dark particles on tree trunks and other surfaces. As a result, the lichen cover on the trees decreased, exposing the darkened bark. This change in the environment created a selective pressure favoring dark-colored individuals of Biston betularia.

Natural Selection
Dark-colored moths had a better chance of survival in the polluted environment as they were able to blend in with the darkened tree trunks, making them less visible to predatory birds. On the other hand, the light-colored moths stood out against the dark background and became more vulnerable to predation. Consequently, the frequency of dark-colored individuals increased significantly over time.

Observations and Studies
The phenomenon of industrial melanism in Biston betularia was first observed and documented by British geneticist Bernard Kettlewell in the 1950s. Kettlewell conducted experiments to investigate the role of natural selection in the evolution of moth coloration. He released moths in both polluted and unpolluted environments and observed that the survival rates of the moths were influenced by their coloration, with dark-colored moths faring better in polluted areas.

Conclusion
The case of industrial melanism in Biston betularia serves as a remarkable example of natural selection in response to environmental changes. It demonstrates how human activities, such as industrialization and pollution, can exert selective pressures on organisms, leading to evolutionary changes within relatively short periods of time. This phenomenon has been extensively studied and has contributed to our understanding of adaptation and evolution.