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

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)

Item 2
• disruptive; the curve would break into two peaks with a dip in the middle
• directional; the curve would shift to the left
• directional; the curve would shift to the right
• stabilizing: the curve would become taller in the middle and shorter on each side

Answer 1

The type of selection being described is directional selection. During warmer periods, smaller black bears were favored, and during ice ages, larger black bears were favored.

As Earth moved out of an ice age, the graph of the distribution curve of black bear size would shift to the left. This means that the average size of black bears would decrease, and there would be fewer individuals of larger sizes.