BIO 311D Lecture Notes - Lecture 33: Allopatric Speciation, Lactose Intolerance, Divergent Evolution
Document Summary
Bio 311d, dr. donald levin, lecture #33, 17 april 2017 (all images are taken from dr. levin"s lecture slides, which are available on his website http://www. sbs. utexas. edu/levin/bio311d/) Review over last lecture: mutations are the ultimate source of evolution but not the only source. Migration also plays a role: examples of recent human evolution. Most adults had this in the past but with the rise of agriculture and domesticated cows, many are now able to drink it because of its health benefits. Responses: differences in lung capacity, different blood cell counts, etc: prezygotic barriers prevent formation of f1 hybrids. Divergence occurs due to geographical isolation: makes for not genetically based divergence. Post zygotic barriers prevent backcrossing: hybrid sterility may be because reproductive structures don"t develop normally. But an individual can still be duplicated by asexual reproduction done by human interference. Failure of chromosomes to pair normally: hybrid breakdown deals with next generation"s issues. Models of allopatric speciation: dumbbell model.
