Chapter 26 Phylogenies and the History of Life

Chapter 26 Phylogenies and the History of Life - Chapter...

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Chapter 26: Phylogenies and the History of Life I. Tools for studying history: phylogenies and the fossil record a. Phylogeny —evolutionary history of a group of organisms, usually shown on a phylogenic tree. (shows how organisms are related) b. Phylogenic tree (look at diagrams p 557-558)`: i. Branches —populations through time ii. Node —occurs where ancestral groups split in two iii. Tips —endpoints of the tree that represent groups living today or extinct ones iv. Polytomy —when more than 2 descendant groups emerge from a node v. Sister taxa —groups that occupy adjacent branches on a tree vi. Outgroup —taxonomic group that is known to have diverged before the rest of the taxa in the study. c. Methods for testing how closely related species are i. Phenetic approach —computes a statistic that summarizes the overall similarity among populations. 1. Ex) gene distance—summarizes the average percentage of bases in a DNA sequence that differs between 2 populations. 2. Computer clusters similar populations and places more distant populations on further branches ii. Cladistic approach —relationships among species can be reconstructed by identifying shared derived characters (synapomorphies) 1. Synamorphies identify monophyletic groups iii. Problems with these approaches: convergent evolution (traits of 2 species are similar of a similar solution to a problem, not because of a common ancestor)
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This note was uploaded on 03/30/2010 for the course BIO 1005 taught by Professor Nef during the Spring '10 term at Holy Family University.

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Chapter 26 Phylogenies and the History of Life - Chapter...

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