Explain how natural selection caused the frequency of black moths within the population to increase during the Industrial Revolution.

The concept of natural selection, as proposed by Charles Darwin, suggests that individuals within a species show wide levels of variation, and those with characteristics most suited to their environment are more likely to survive and reproduce. This process causes certain traits to become more common within a population over time.

Prior to the Industrial Revolution, the majority of peppered moths (Biston betularia) in England were of a light coloration which effectively camouflaged them against the light-colored trees and lichens upon which they rested.

However, during the Industrial Revolution, soot and pollution from factories darkened the trees and lichens, making the light-colored moths more visible to predators, and therefore more likely to be eaten before they could reproduce.

At the same time, a dark-colored variant of the peppered moth, which was previously rare in the population, now had a survival advantage. These dark-colored moths were better camouflaged against the soot-darkened trees, and so were less likely to be eaten by predators.

As a result, the dark-colored moths had a higher survival rate and could pass on their genes to their offspring. Over several generations, the frequency of dark-colored moths increased within the population - a clear demonstration of natural selection in action.

This phenomenon, known as 'industrial melanism', is one of the most famous examples of natural selection, and shows how quickly populations can evolve in response to changes in their environment.