BIOLOGY 1M03 Chapter Notes - Chapter 27: Cambrian Explosion, Hox Gene, Even-Toed Ungulate
15 May 2017
School
Department
Course
Professor
Document Summary
Chapter 27: phylogenies and the history of life. The evolutionary history of a group of organisms is called its phylogeny. Phylogenies are usually summarized and depicted in the form of a phylogenetic tree. A phylogenetic tree shows the ancestor-descendant relationships among populations or species and clarifies who is related to whom. In a phylogenetic tree, a branch represents a population through time. The point where two branches diverge, called a node, represents the point in time when an ancestral group split into two or more descendant groups. A tip, the endpoint of a branch, represents a group living today or one that ended in extinction. Fur and lactation are synapomorphies that identify mammals as a monophyletic group: synapomorphies are characteristics that are shared because they are derived from traits that existed in their common ancestor. In many cases, homology and homoplasy are much more difficult to distinguish than in the previous example: ex.
