BIOLOGY 1M03 Lecture Notes - Lecture 7: Polytomy, Homo Sapiens, Disruptive Selection
25 Jan 2018
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Document Summary
Usually happens when a geographic barrier disappears: they fuse (go back into one species: adaptive differences may be small, adaptive differences may be overwhelmed by gene ow. Hybrid offspring have low tness (incompatible alleles, disruptive selection) In these cases we expect natural selection for traits that reinforce the distinction between the two. Incompatible alleles in hybrids is an example of post zygotic mechanisms (causing offspring to be messed up) One species might eliminate the other either by competition or by success in mating: warblers competing for mates, modern humans vs neanderthals. Hybridization between related species may lead to creation of a new species. Some combination of genes that were in both ancestors. Hybrids might have incompatible alleles or disruptive selection. Phylogeny: evolutionary history of a group of organisms (represented by phylogenic tree) Based on the idea that organisms evolved via evolution. Understanding these relationships is critical to our understanding of evolution & how biological processes work.
