Biology – Natural and artificial selection | e-Consult

Prior to the Industrial Revolution, light-colored peppered moths had a survival advantage because they were better camouflaged against the lichen-covered trees, reducing predation by birds. Darker-colored moths were more easily spotted and eaten. This resulted in a higher proportion of light-colored moths in the population.

The Industrial Revolution led to increased pollution, which darkened the tree bark. This changed the selective pressure. Now, the light-colored moths were more visible to predators against the dark bark, while the darker moths were better camouflaged.

As a result, the darker-colored moths had a higher survival rate and were more likely to reproduce, passing on their alleles for dark coloration to the next generation. Over time, the frequency of the dark-colored allele increased in the population, leading to a shift in the overall coloration of the peppered moth population towards darker shades.

This demonstrates how natural selection can alter allele frequencies within a population. The change in the environment (darkened trees) created a new selection pressure, favoring a previously disadvantageous trait (dark coloration). The mechanism involved is differential survival and reproduction – individuals with the advantageous trait (dark color) were more likely to survive and reproduce, increasing the frequency of the alleles associated with that trait in the population.