The Peppered Moth

The color form with higher fitness depends on the environment. In non-polluted environments, the tree trunks upon which the moths rest during the day are covered with lichen, and are gray. Gray moths are better camouflaged in these non-polluted environments, and are less likely to be seen and eaten by birds, so in non-polluted environments gray moths survive better than do black moths. In polluted environments, the tree trunks are black. Black moths are better camouflaged, and survive better, than do gray moths.

For this exercise, assume that in non-polluted environments black moths survive to reproduce only 40% as well as do gray moths. In polluted environments, gray moths survive to reproduce only 40% as well as do black moths.

Do you want to model this situation as genetic drift or as natural selection?