BI111 Lecture Notes - Lecture 13: Polyphyly, Cladistics, Paraphyly
Document Summary
Combination of ancestral and derived characters in evolutionary liniage. Derived characters: determines what it looks like, modification to ancestral traits, determines from fossils and embryos, appear later in development. Principle of monophly: all groups in the clade include a common ancestor and all of its, simplest explanation most likely to be correct, all phylogenic trees are hypotheses that attempt to accurately reflect historical events. Because species have answers, any clade used to describe that particular group should include that ancestor. Errors: polyphyletic taxon (sharks & dolphins, paraphyletic taxon. Saying two species are related when they actually aren"t. Does not include an ancestral species and only records some of its descendants. States we want to strive for the most simplistic explanation which is most likely correct. Unless other data suggest more complicated explanation. Evolutionary change is an unlikely event: evolution of character teice is extremely unlikely. Conclusion: phylogenic tree is a hypothesis.
