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)

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

Answer 1

The type of selection observed in this scenario is directional selection. As Earth moved out of an ice age and became warmer, the selected trait (size) shifted towards smaller individuals. Therefore, the curve representing the distribution of black bear size would shift to the left.