Biology 1001A Lecture Notes - Lecture 19: Cladistics, Monophyly, Dicotyledon
Document Summary
Branching points represent speciation events and mrca: nodes = speciation events, internodes = ancestors. Time progresses from root (base) to tips. Some phylogenies convey more information than branching over: branch lengths can indicate time, ex. Longer branch = more rapid evolution in species: not covered in biology 1001a. To find closest relative, trace evolutionary history and figure how far we have to go back in time to find mrca: ex. Even though fighting fish and sharks are both considered fish, fighting fish are more related to frogs and humans than sharks. Scientific names are not always indicative of evolutionary relationships: ex. If group names reflect evolutionary relationships, then all members are closer related to each other than to anything outside the group: this idea used in cladistics systematics. Cladistics emphasized these monophyletic groups (clades: monophyletic group includes all descendants of mrca. Many traditionally-recognized groups are not monophyletic: ex. Reptiles groups lizards and crocodiles, but ignores birds: ex.
