Question

In British land snails, snails with darker shells and snails with lighter shells are both more successful in their environments than snails that are more intermediate in color. This is an example of _____ selection.

Answer 1

British land snails with darker and lighter shells, being more successful than intermediate-colored snails, are an example of diversifying selection, where multiple phenotypes have advantages in natural selection.

Step-by-step explanation:

In British land snails, snails with darker shells and snails with lighter shells being more successful than snails with intermediate color is an example of diversifying selection. Diversifying selection occurs when two or more distinct phenotypes each have their advantages for natural selection, while intermediate phenotypes are less fit. This pattern is similar to what has occurred in a hypothetical mouse population living in a beach environment, where light and dark-colored mice are favored over medium-colored mice due to better camouflage.

Furthermore, the situation with the British land snails mirrors the historical case of the evolution of the peppered moth in England during the Industrial Revolution. Before the Industrial Revolution, light-colored moths were well-camouflaged against predators. As the environment changed due to pollution, dark-colored moths became more camouflaged, leading to an increase in their survival rates. This scenario is an example of directional selection. However, the snails in the question are not undergoing a shift towards one extreme, but rather, both extremes are favored which is indicative of diversifying selection.