Chapter 17

Segmented animals occur in multiple phyla. How might segmentation benefit an animal? If segmentation is adaptive, why do unsegmented animals still exist?

Create lists of animal phyla that (a) are cephalized, (b) have an incomplete digestive tract, (c) have segmented bodies, and (d) have a coelom.

Both amniotes and insects do very well on land. What characteristics are found in both groups that facilitate their success in terrestrial environments?

Explain how a sessile or slow-moving lifestyle, such as that of sponges sea cucumbers, and tunicates, might select for bright colors and an arsenal of toxic chemicals.

What can scientists learn by comparing the fossilized skeletons of extinct primates with the bones of modern species?

At one time, several species of Homo coexisted. Propose at least two hypotheses that might explain why only Homo sapiens remains.