BIOL 123 Lecture Notes - Lecture 3: Paraphyly, Synapomorphy, Polyphyly
Document Summary
Phylogeny allows one to classify species based on evolutionary history. Taxonomic system sorted species into larger groups based on shared traits: nested hierarchy. Darwin realized a natural mechanism that could explain why nest hierarchies of species form = evolution. Monophyletic: describes a group of organisms that form a clade. Polyphyletic: describes a taxon that does not include the common ancestor of all members of the taxon. Paraphyletic: describes a group of organisms that share a common ancestor although the group does not include all the descendants of that common ancestor. We did not witness species branching so we construct phylogenetic trees as our hypothesis. Data is taken from characters: are heritable aspects of organisms that can be compared across taxa. Taxa: (singular, taxon) are groups of organisms that a taxonomist judges to be cohesive taxonomic units, such as species or order: in order to draw tree.
