Biology 1001A Lecture Notes - Lecture 19: Convergent Evolution, Polyphyly, Paraphyly
3 Apr 2016
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Document Summary
Phylogenies show evolutionary history of a group of organisms. Phylogenic trees are formal hypotheses identifying likely relationships among groups of organisms. The relative positions of the nodes (branching points) define how recently sister clades diverged. Clades that emerge from a recent common node (near the tips of the branches) are more closely related to each other than clades that emerged from an older node (closer to the root of the tree). Useful systematic characters must be genetically independent, reflecting different parts of organisms" genomes: different organismal characters can have the same genetic basis. Outgroup comparison is used to distinguish between ancestral and derived characteristics. Phylogenetic trees portray the evolutionary diversification of lineages as a hierarchy that reflects the branching pattern of evolution. Each branch represents the descendants of a single ancestral species. Homologous traits: shared with common ancestor let us examine evolutionary relationships. Chromosomal anatomy, physiology patterns of behaviors and traits: meanings of mosaic evolution, ancestral character, derived character.
