15 - BIO LECTURE NOTES (2/11/09) History of life o The...

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BIO LECTURE NOTES (2/11/09) History of life o The Cambrian explosion was the rapid morphological and ecological diversification of animals that occurred during the Cambrian period o Adaptive radiations are a major pattern in the history of life. They are instances of rapid diversification associated with new ecological opportunities and new morphological innovations o Mass extinctions have occurred repeatedly throughout the history of life. They rapidly eliminate most of the species alive in a relatively random manner Cambrian explosion o The first animals-sponges, jellyfish, and simple worms-appear in the fossil record around 565 mya, at the end of the Proterozoic eon o Soon after that in geological time, by about 50 million years later, animals had diversified into almost all the major groups living today o This diversification is known as the Cambrian explosion o This period saw what was arguably the most evolutionary change in the history of life o Fossils document in the Cambrian explosion Doushantuo fossils are microscopic Small, soft-bodied animals from Ediacara Diverse, large animals with hard parts from Burgess shale Did gene duplication trigger the Cambrian explosion? o Many researchers predicted a strong association between the order in which animal lineages appeared during evolutionary history, the number of Hox genes present in each lineage, and each lineage’s morphological complexity
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This note was uploaded on 11/16/2009 for the course BIOL BIOL taught by Professor Johnson during the Spring '08 term at Aberystwyth University.

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15 - BIO LECTURE NOTES (2/11/09) History of life o The...

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