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 in this, and how would a graph of the distribution curve of black bear size change as Earth moved out of an ice age?

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 in this, and how would a graph of the distribution curve of black bear size change as Earth moved out of an ice age?

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

Answer 1

B. directional; the curve would shift to the left

During ice ages, larger black bears would have a higher chance of survival and reproduction due to their ability to retain heat and hunt larger prey. This would lead to a shift in the distribution curve towards larger sizes. As the Earth moved out of an ice age and temperatures warmed, smaller black bears would have a higher chance of survival and reproduction due to their ability to dissipate heat more efficiently. This would lead to a shift in the distribution curve towards smaller sizes.