BIS+2C+W2012Lect5OUT - BIS$2C$W2012$ $ $ $ $ $...

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BIS 2C W2012 Lecture 5 (Jan 18, 2012) Today’s lecture: •How many times has life evolved on Earth? –Do all organisms trace their origin to a single common ancestor? –How many “trees of life” are there? •What are the major branches on the tree(s) of life? –How many major groupings are there? –What were the early “events” in the evolutionary history of species? •Rooting the tree(s) of life –The Outgroup problem –The solution How do we distinguish two hypotheses? –1. a single origin (and thus a single tree of life) –2. multiple origins (and thus multiple separate trees)? •What data might support one hypothesis versus the other? The concept of Universal Homologies •Characters that are found in the same state an all organisms are considered universal ” (remember “ presence ” can be a state) •Characters that are inherited from a common ancestor are homologous •Homologous characters that are found in the same state in all organisms are universal homologies
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BIS+2C+W2012Lect5OUT - BIS$2C$W2012$ $ $ $ $ $...

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