BIOL 1500 Chapter Notes -Genetic Drift, Barcode System, Shocked Quartz
4 May 2014
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Document Summary
Phylogeny: the evolutionary history of a group of organisms. Phylogenies are usually depicted in a form of a phylogenetic tree which shows ancestor- descendant relationships among populations or species. Node: the point where two branches diverge and represents the point in time when an ancestral species split into 2 or more descendant species. Tip: (or terminal node) is the endpoint of a branch and represents a group that is living today or is extinct. Phylogenetic trees are an extremely effective way of summarizing data on the evolutionary history of a group of organisms. Two general strategies used to estimate trees: Phenetic approach: computing a statistic that summarizes the overall similarity among populations based on the data. Researchers use gene sequences to compute an overall genetic distance between two populations into computers which then organizes the most similar genes onto one branch and the more divergent ones onto another branch. The cladistic approach: uses synapomorphies in order to estimate trees.
