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

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

Answer 1

The type of selection described in the scenario is directional selection. During ice ages, larger black bears are favored, while during warmer periods, smaller bears are more prevalent. As Earth moves out of an ice age and into a warmer period, we would expect the size of black bears to shift towards the smaller end of the size spectrum.

Therefore, on a graph showing the distribution curve of black bear size, as Earth moves out of an ice age, the curve would shift to the left (representing a decrease in bear size).

So, the correct answer is: • directional; the curve would shift to the left.