Biology 1001A Lecture Notes - Lecture 21: Synapomorphy, Cladistics, Ingroups And Outgroups
14 Feb 2018
School
Department
Course
Document Summary
Synapomorphy (shared, derived traits) reveal relationships between taxa. A characteristic present in an ancestral species and shared exclusively (in more or less modified form) by its evolutionary descendants. Traits that unite groups of populations, taxa, higher levels of organization. Synapomorphies- first that was present/ they are nested first present and then hidden. They also have other synapomorphy present before that branches (nested) Shared vs unique is easy to determine. Find outgroup (close-ish relative known to have branched off earlier than any of the groups of interest) Out group is more distantly related to any of the in-group. In-groups are more closely related to one another than any of them are to the outgroup. Looking at state of outgroup we can determine if it is derived or ancestral. If the character is present in every group, it is more likely (ancestral) Present in outgroup and some of the groups (ancestral) Absent in outgroup, present in some of ingroup (derived)
