Disruptive selection maintains a bimodal distribution of bill size in the West African seedcracker because
A) bills of intermediate shapes are difficult to form.
B) the birds' two major food sources differ markedly in size and hardness.
C) males use their large bills in displays.
D) migrants introduce different bill sizes into the population each year.
E) older birds need larger bills than younger birds.

Question

Quizplus · Accepted Answer

Disruptive selection occurs when extreme traits are favored over intermediate traits, leading to the maintenance of two separate subgroups in a population. In the case of the West African seedcracker, the two major food sources for the birds differ markedly in size and hardness. This means that birds with larger bills are better suited to crack larger, harder seeds, while birds with smaller bills are better suited to crack smaller, softer seeds. As a result, birds with intermediate bill sizes are at a disadvantage and are less likely to survive and reproduce, leading to the maintenance of a bimodal distribution of bill sizes in the population.

Disruptive Selection Maintains a Bimodal Distribution of Bill Size in the West