The bell-shaped curve at the top of the figure below shows the distribution of a phenotype in a population at the start of an experiment. The three graphs (lettered A-C)beneath predict what the distribution will look like if a certain type of selection occurs. Which graph represents what the phenotypic distribution will look like if the population undergoes stabilizing selection?
A)Graph A
B)Graph B
C)Graph C
D)These graphs all show natural selection, but none show stabilizing selection.

Question

The bell-shaped curve at the top of the figure below shows the distribution of a phenotype in a population at the start of an experiment. The three graphs (lettered A-C)beneath predict what the distribution will look like if a certain type of selection occurs. Which graph represents what the phenotypic distribution will look like if the population undergoes stabilizing selection? 
A)Graph A 
B)Graph B 
C)Graph C 
D)These graphs all show natural selection, but none show stabilizing selection.

Quizplus · Accepted Answer

Stabilizing selection favors intermediate phenotypes and reduces variation, causing the peak of the bell curve to become narrower and taller. This is shown in graph B, where the peak of the curve is higher and narrower compared to the original distribution in the top graph. Graph A shows directional selection, where one extreme phenotype is favored over the others, while graph C shows disruptive selection, where both extreme phenotypes are favored over the intermediate ones.

The Bell-Shaped Curve at the Top of the Figure Below