LIFESCI 1 Lecture Notes - Lecture 2: Barracuda, Sister Group, Marsupial
21 Jan 2015
School
Department
Course
Professor
Document Summary
Taxa can be rotated around nodes and still depict the same relationships: taxa: a group of organisms; could refer to a species or something larger (like a family) Can"t tell: cladograms show relative ages of nested splits only. Taxonomic units legitimate only if they represent a clade: clades are monophyletic groups (including all that descend from one node) This phylogeny implies the species with the most characters in common are related to each other. Hash marks = synapomorphies: traits that are shared by members of a particular clade (example: cats and hyenas share trait 4 and 7) Some trees explain data better than others: can you come up with a different (worse) tree that doesn"t explain the characters as well, the original tree is more parsimonious than the alternative tree . Seals and walruses have 11 and 12, but bears and sea lions do not, so 11 and 12 had to evolve independently for seals and walruses.
