A balanced polymorphism exist through disruptive selection in seed cracker finches from Cameroon in which small and large billed birds specialized in cracking soft and hard seeds, respectively. If long term climatic change resulted in all seeds becoming hard, what type of selection would then operate on the finch population?

a. Sexual selectionb. Stabilizing selectionc. Directional selectiond. Disruptive selection

c. Directional selection

Explanation:

There are three types of selection: stabilizing, directional and disruptive. Currently seed cracker finches show disruptive selection with respect to bills. In disruptive selection two extreme phenotypes are preferred in population over the mean phenotype. Here either, small or large bills are beneficial for birds so it is an example of disruptive selection.

If due to some climatic change all seeds would become hard, it would be more beneficial for birds to have large bills. Slowly nature will select for birds with large bills rather than birds with small bills. The selection now will shift to directional selection since only one of the extreme phenotypes is being favoured.