BIOL321 Lecture Notes - Lecture 3: Archaea, Consistency, Eukaryote

• School: University of Alberta
• Department: Biology (Biological Sciences)
• Course: BIOL321
• Professor: Heather Proctor

Document Summary

Worked on determining phylogenetic relationships, before hennig, most people just argued over who had more authority and then decided arbitrarily which organisms were more closely related. Cladistics: relationships among taxa: follows a dichotomous branching pattern, synapomorphies are a shared, derived feature, the most parsimonious, least branching tree is preferred, should be logically consistent with the phylogenetic tree. To do this: find variable characteristics (number of toes, presence of a trait etc) Identify one or more taxa that are believed to have arisen before all taxa in question :the outgroup: list variable features and either derived = 1 (different from the outgroup) or ancestral =0 (same as the outgroup) Derived traits in only one taxon are autapomorphies. William of ockham (occam) > if you have many explanations, choose the one that requires the fewest assumptions. Homology - traits that are present in more than one taxon and are present in the common ancestor.