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)

Question

Responses

directional; the curve would shift to the left
directional; the curve would shift to the left

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

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

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

Answer 1

The observed changes in the sizes of black bears as their environment changed from ice ages to warmer periods indicate that this is an example of directional selection. Specifically, during warmer periods, the smaller black bears had a survival advantage, while during ice ages, larger bears were favored.

As Earth moved out of an ice age and environmental conditions became warmer, we would expect the distribution curve of black bear sizes to shift towards the smaller size range, leading to the graph reflecting a directional selection toward smaller sizes.

Therefore, the correct response is:

directional; the curve would shift to the left.