The answer is; The moths will evolve due to selective pressure.
The allele for dark colored moths will be favored by natural selection over the allele for light-colored moths. This is because of the selective pressure of predation. Black moths are able to camouflage in their environment while light-colored moths stand out to their predators. More black moths are therefore able to pass down their genes than light-colored moths. Successive generation will, therefore, have more and more black moths.
