Light and dark forms of the peppered moth.

- The peppered moth demonstrates natural selection, where environmental changes influence which traits are advantageous for survival.
- Initially, light-colored moths with dark spots were camouflaged against lichen-covered trees, making them less visible to predators.
- A genetic mutation produced a black form of the moth, which was initially more noticeable and thus preyed upon more heavily, causing its numbers to decrease.
- During the Industrial Revolution, pollution darkened tree bark and walls, making the black moths better camouflaged while the light moths became more visible and were eaten more frequently.
- As a result, the population of black moths increased significantly while the light-colored moth population declined.
- When pollution controls were introduced, tree bark gradually lightened again, reversing the advantage: light moths regained camouflage, and black moths became more vulnerable to predation, leading to a decline in their numbers.
- This cyclical shift in moth coloration frequencies over time illustrates how natural selection acts on heritable variation in response to changing environmental conditions.