Right. Just to take the other side here, which is always fun, a Creationist would say that Rob just described adaption, not evolution.
Adaptation is the process by which evolution takes place. They are the baby steps towards speciation. As adaptations accumulate within an isolated strain of a species, the difference eventually becomes sufficiently great to justify classification as a different subspecies. That's speciation by evolution. Given a longer period of adaptation in isolation and the species will accumulate enough differences to justify a different genus classification, then family, order, etc. It's the gradual accumulation of alterations due to adaptation that drives the process of speciation by evolution.
For example, the genus alligator contains two subspecies, 1) the American and 2) the Chinese. The genus falls under the family alligatoridae, which contains both subspecies of alligator, plus caimans. All of them belong to the order crocodilia, including all the above, plus crocodiles and several other similar species. As you go up the ladder you find greater and greater diversity, and more distance from one another on the evolutionary tree.
