PHYSICS 5A Chapter Notes - Chapter 23.2-23.4: Last Universal Common Ancestor, Phylogenetic Tree, Burgess Shale
Document Summary
The tree uses characteristics of organisms to figure out their relationships. Characters: anatomical physiological or molecular features that make up organisms. Character states: characters that have several observed conditions. Example: lungs are present in tetrapods and lungfish but absent in other vertebrate animals. Character states in different species can be similar for one of two reasons. Character state was present in the common ancestor of two groups and retained over time (common ancestry) Character state independently evolved in two groups as an adaptation to similar environments (convergent evolution) Homologous: characters that are similar because of descent from a common ancestor. Analogous: similarities due to independently adaptation from different species. Example: bats and birds have wings but not from a common ancestor. Quick check: fish and dolphins have many traits in common, including a streamlined body and fins. Analogous as a result of convergent evolution. They are only distantly related and have adapted to swimming in water independently.
