Biology 1001A Lecture Notes - Lecture 20: Synapomorphy, Ingroups And Outgroups, Adaptive Radiation
Document Summary
Thursday, november 20, 2014. Whether a particular trait is probably ancestral or derived, given a phylogeny and a suitable out-group. Out-group has characteristics separate from in-group ->furthest in phylogenetic tree, has least in common with the rest of the organisms. Ex: the shark is the out-group in this phyla tree because it is the furthest branch from the tree and has the least in common with the other organisms. Present in out-group and all of in-group = ancestral. Might have evolved independently of in-group (not informative - Present in out-group and some of in-group = ancestral. Common ancestor had the trait but somewhere along the line some animals did not acquire the trait but all other members of in-group ended up having the trait. Present in out-group but none of in-group = cannot tell if derived or ancestral (equally likely of being either ancestral or derived) Trait has been gained or lost over evolutionary time.
