Biology 1001A Lecture Notes - Lecture 20: Assortative Mating, Cladistics, Disruptive Selection
Document Summary
Speciation without allopatry: adaptations to a new food type can sympatric speciation. Driving not by mutation, but by niches. Each lake has a benthic (eat at the bottom of the lake) and a limnetic (small, and eats at the surface of the lake i. e. plankton) form. Everything has been evolving for the same amount of time because we descended from the common ancestor: phylogenies are like pedigrees. Similarity verse relatedness: homology: similarity that reflects recent common ancestry inherited the arrangement of the legs from common ancestor, Different function but similar structure: homoplasy: misleading similarity, or misleading dissimilarity. Placement of the eyes for crocodile and hippo are the same, on top of their eyes, but they are not very related, they developed the placement of the eye by convergent evolution. Only some similarities are informative synapomorphy = shared traits that are derived from a common ancestor. Not all traits are informative: synapomorphy shared by two or more groups.