Speaker: Douglas H. Erwin
Senior Scientist, Department of Paleobiology, National Museum of Natural History, Smithsonian Institution
Abstract: Diversity and Repetition
Repetition without variation is sterile and uninteresting, but repetition coupled to variation has been a source of great diversity in fields as disparate as biology, music and transmission networks. Among animals, arthropods (insects, spiders and their kin) and annelids (earthworms and the like) both contain large numbers of species, and both have a modular architecture involving segmentation. Although some have argued that such repetition, seen both in the shape of organisms and in their underlying developmental systems, is the source of their taxic diversity, the diversity reflects patterns of interaction among genes during development, and among the various segments of an animal. In arthropods, for example, their morphologic diversity is built upon the extraordinary variety of limbs between different segments of the same animal, as well as between different groups of arthropods, much as classical music or jazz employ variations upon a theme. In any system it appears that interesting diversity arises from the opportunities which repetition opens up to produce diversity.
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