BIO 123 Lecture Notes - Lecture 2: Phylogenetic Tree, Monophyly, Symplesiomorphy
Document Summary
William of ockham - early 14th century. Not a scientific law, but a guide to choosing best explanations. All other things being equal, the simplest explanations is most likely to be correct. **the explanation with the fewest evolutionary steps is the simplest. Phylogenetics use ancestral and derived for character states not species. Linnaeus thought the differentia was most important. Nomenclature: a system of names, or rules for maintaining a sytem of names. The sexual system: scandalous at the time. Ex - library of congress classification of books. Natural classification: exists in nature, independent of human thought. Monophyletic group: common ancestor and all of its descendants. Recognized by synapomorphy - derived at the point you make the cut. Paraphyletic group: common ancestor and some, but not all of its descendants - one or more clades excluded make the second cut. Additional cut of branch within a monophyletic group makes it paraphyletic.
