BIOL 2P05 Lecture Notes - Lecture 7: Symplesiomorphy, Autapomorphy, Lactation
28 Mar 2016
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Document Summary
Shared derived characters (synapomorphies) are the most informative! Focusing on homologous structures, we need to determine when that character arose. Newer characters tell us more: derived characters are more important. Backbone all vertebrates have a backbone. Shared by much more than the clade under consideration: therefore, shared primitive character. A shared derived character is a new evolutionary feature, unique to a particular group: ex. All mammals have hair, and no other animals have hair: these are the features that are most useful for determining evolutionary relationships, newer than the common ancestor. Primitive: with respect to the primates. Apomorphy: a character state different than the ancestral state, therefore. Therefore, one of the limbs that can grasp is a plesiomorphy. Autapomorphy: a uniquely derived character state (because it became the fin: 1 species has this trait, particular case of apomorphy. Plesiomorphy: refers to the ancestral character state.
