Biology 1202B Chapter 18: Phylogenetics
5 Feb 2016
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Phylogenetic trees portray the evolutionary diversi cation of lineages as a hierarchy which re ects the branching pattern of evolution. Each branch represents the descendants of a single ancestral species. Use the principle of monophyly when converting phylogenetic trees into classi cations. > try and de ne monophyletic taxa - those that have derived from a single ancestral species. Polyphyletic taxa :species from separate evolutionary lineages. Paraphyletic taxon: an ancestor and some, but not all, of its descendants (ie: Systematists strive to create parsimonious phylogenetic hypotheses where they include the fewest possible evolutionary changes to account for the diversity within a lineage. > justi cation is the assumption of parsimony : the simplest explanation must be most accurate. > it is unlikely that the same change evolved twice in one lineage. 18. 6a traditional evolutionary systematics classifies organisms according to their evolutionary history using phenotypic similarities and differences.
