Comparative Vertebrate Anatomy Evolutionary Relationships

A. Organisms are classified using 2 main assumptions: 1.The more similar the genes and physical traits of two species are, the more closely related they are. 2.The similarities were inherited from a most recent common ancestor (MRCA). B.Predicting Evolutionary Relationships 1.Evolutionary relationships can be predicted using diagrams. Each diagram is a hypothesis of how groups of organisms are related to one another. 2.Cladograms - Hypothesize evolutionary relationships among organisms based on significant traits and imply that time runs from the bottom of the cladogram to the top.

Cladograms Family tree that branches systematically at points (nodes) representing specific trait possessed by some groups, but not others. Phylogeny

Node: Specific trait or traits Organisms branching to right HAVE this trait. Organisms branching to left DO NOT have this trait. Branch: Name or Type of Organism How To Make a Cladogram More Complex Older Traits Newer Traits Less Complex

Brain Case and Backbone; Endoskeleton; Dorsal Nerve Cord (older traits) 4 Limbs; Lungs; Double-Loop Circulatory System; Highly Complex Digestive System Amnion; Internal Fertilization Mammary Glands; Hair 4-Chambered Heart; Endothermy; Up and Down Movement FISH AMPHIBIANS REPTILES BIRDS MAMMALS Dinosaurs? Vertebrate Cladogram