01:119:115 Lecture Notes - Lecture 18: Branch Point, Polyphyly, Convergent Evolution
15 Mar 2016
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Document Summary
Above species level there are several other levers in hierarchy. A taxon is grouping of organisms at any one level in hierarchy. Each taxonomic level is more inclusive (has more species) than you know. Phylogenetic trees are branching diagrams representing evolutionary history of species groups. Relationships are series of dichotomies (2 way branch points) A rooted tree includes a branch to represent the last common ancestor of all taxa in the tree. Extant species: currently living: tips of branches. Ancestral lineage common ancestor of taxa a-g. Basal taxon: diverges early in history of group; originates near common ancestor of group. Sister taxa: groups that share an immediate common ancestor. Represent evolutionary history of a group of organisms from a common ancestor. Degree of relationship between species based on similarity of characters. Character is a heritable trait possessed by organism; described in terms of its state: e. g. hair present vs. hair absent .
