Consider the evolution of protostomes (chapter 31) and deuterostomes (this chapter):
(1) compare adaptations in protostomes and deuterostomes for living on land.
(2) recall that changes in the expression patterns of tool-kit genes in arthropods such as insects enabled a dramatic diversification of their segmented appendages and bodies. design an experiment to test whether this concept applies to vertebrates.

Elephants in the savanna regions of africa dig holes in dried up river beds to reach water lying just below the surface. these holes provide drinking water for other animals as well. so, without the elephants, many animals might otherwise die from lack of water during the dry season. the location in which the elephants live is an example of a/n and the role they play in creating water holes is an example of a a) ecosystem; habitat b) community; niche c) habitat; niche d) niche; habitat