In This Chapter

^ Developing an understanding of development ^ Discovering how a little change can make a big difference ^ Finding the deep similarities between very different animals species with one particular form can give rise to a species with another form. Take humans and fruit flies, for example. They have a common ancestor somewhere in the distant past. This common ancestor gave rise to two very different organisms. The question is how. What process is at work that results in such different creatures?

The answer has to do with the interplay between evolution and development, which is one of the hottest areas of current evolutionary research and one in which today's scientists are able to learn lots of things that people back in Charles Darwin's time didn't have a clue about.

This chapter talks primarily about the development of animals because animal development is for the most part deterministic — that is, all the members of the species end up looking pretty much identical, at least structurally. Humans have two arms, two legs, one heart, one head, and so on, and all these parts need to be in the right places. Compare this structure with that of a maple tree; branches can go every which way, and their reproductive structures (flowers) can be all over the place. Lop off one of the branches, and another one may grow and produce its own flowers — definitely not the way that human structures work! All this doesn't mean that plants don't have development; they're just a little bit more free-form about it.

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