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Biol 121- 2010.03.26- Evolution- Phylogeny, History of Life on Earth (Ch. 27).docx

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BIOL 121
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Biol 121 225 Freeman 543556Mar 26 10 Evolution Phylogeny and History of Lifevariation is the key to natural selection species divergence is the outcome of selection and evolution How do biologists study the history of 1 Construct phylogenies life on earth 2 2 Fossil record Phylogeny is the evolutionary history of a group of organisms phylogenies are usually summarized and depicted in the form of a phylogenetic tree Phylogenetic tree shows the ancestordescendant relationships among populations or species and clarifies who is related to whom in a phylogenetic tree a branch represents a population through time the point where two branches diverge is a node that represents the time when an ancestral group split into 2 descent groups the endpoint of a branch represents a group a species or larger taxon living today or one that went extinct dead endphylogenetic trees are an extremely effective way of summarizing data on the evolutionary history of a group of organisms however the genealogical relationships among species cannot be known with absolute certainty but are instead estimated from given data How do researchers estimate make inferences by looking at morphological or genetic characteristics or both phylogenies clo
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