In a species of snail, dark-shelled individuals are better hidden from bird predators in the shady forest, while light-shelled individuals are better hidden in well-lit brushy edge areas. If there were no areas of intermediate brightness in this habitat, which type of selection would act on shell color in these snails?

Disruptive selection

Explanation:

In the given question, the dark-snails and the light-snails are protected from the predator in the shady and the brushy edge areas respectively while the areas with intermediate colour will not prove beneficial to the snails and will increase the chances of the predation.

Therefore nature will select the snails which could be either the dark coloured or light coloured but not the intermediate colour of the snail. This shows that the intermediate colour will not survive whereas the extreme colour of the snail is favoured and will reproduce.

Thus, Disruptive selection is correct.