ANT333Y1 Lecture Notes - Lecture 14: Polyphyly, Autapomorphy, Paraphyly
Document Summary
Ant333 lecture #14 cladistics & phylogenetic systematics. Method classifies taxa into groups called clades, which consist of ancestor organism and all descendants. All characters shared between taxa can be divided into three types: homologies & homoplasies, shared ancestral homologies, and, shared derived homologies. Homoplasy (bad) is a convergent character - one that is shared between species but that was not present in their common ancestor. Homology (more helpful) is character shared between species that was also present in their common ancestor. Shared ancestral homologies (symplesiomorphy - bad): found in ancestor of a group of species but only in some of its descendants. Shared derived homologies (synapomorphy - good): unique to a particular group of species (and their ancestor). Only shared derived characters gives information about phylogeny (cladistics or phylogenetic systematics. ) Taxa that share many derived characters are grouped more closely together than those that do not. Relationships are shown in branching hierarchical tree (cladogram).
