Over evolutionary time, many cave-dwelling organisms have lost their eyes. Tapeworms have lost their digestive systems. Whales have lost their hind limbs. How can natural selection account for these losses?
A) Natural selection cannot account for losses, only for innovations.
B) Natural selection accounts for these losses by the principle of use and disuse.
C) Under particular circumstances that persisted for long periods, each of these structures presented greater costs than benefits.
D) The ancestors of these organisms experienced harmful mutations that forced them to find new habitats that these species had not previously used.

Question

Quizplus · Accepted Answer

Natural selection accounts for these losses when under particular circumstances that persisted for long periods, each of these structures presented greater costs than benefits. In the case of cave-dwelling organisms, eyes were no longer useful because they were in complete darkness, and the energy required to maintain them was not worth it. In tapeworms, the digestive system became unnecessary because they infect the intestines of their hosts, allowing them to directly absorb nutrients, thus making digestion useless. In the case of whales, hind limbs were no longer needed because evolution favored the development of streamlined bodies for efficient swimming in the water, and hind limbs would have only created drag and slowed them down.

Over Evolutionary Time, Many Cave-Dwelling Organisms Have Lost Their Eyes