Question

Paleontologists observed changes in the sizes of black bears as their environment changed. During warmer periods between ice ages, most black bears were small. During ice ages, most black bears were large. Which type of selection is this, and how would a graph of the distribution curve of black bear size change as Earth moved out of an ice age?(1 point)
Responses

directional; the curve would shift to the right
directional; the curve would shift to the right

disruptive; the curve would break into two peaks with a dip in the middle
disruptive; the curve would break into two peaks with a dip in the middle

stabilizing; the curve would become taller in the middle and shorter on each side
stabilizing; the curve would become taller in the middle and shorter on each side

directional; the curve would shift to the left

Answer 1

This is an example of directional selection. As the environment changed, one extreme of the bear size (either small or large) became more favorable than the other, causing the population to shift towards that extreme.

If Earth moved out of an ice age, and the environment became warmer again, the bear population would likely shift back towards smaller sizes. Therefore, the distribution curve would shift to the right.