BIOL 243 Lecture Notes - Lecture 16: Paraphyly, Molecular Clock, Ingroups And Outgroups
17 May 2016
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Document Summary
Phylogeny is the history of decent - as species proliferate and their evolutionary relationships branch out, evolutionary and genetic relationships between organisms. The last common ancestor is identified as a node. If two or more species share a common ancestor not shared by any other species, they are considered closest relatives. , or sister groups. They usually emphasize monophyletic groups in which all individuals share a common ancestor. In contrast, a group such as reptiles, which excludes birds (whom do share the same ancestor), is simply a paraphyletic group. Finally, polyphyletic groups do not include the last common ancestor of all members (ex/ birds and bats). For birds and bats, they are grouped together because of their wings (which is an example of a character state). However, birds wings and bat wings developed independently of eachother and are therefore analogous. If a character trait were to be similar because of descent from a common ancestor, it is homologous.
