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Lecture 20

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Biology 1001A

Lecture 20  Speciation without allopatry?  o Adaptations to a new food type can o  sympatric speciation   driving not by mutation, but by niches  Hawthorn maggot introduced to North America  Subset of maggots began feeding (and mating) only on apples  these two never see each other because one only mate on apples and the other on hawthorn o Competition, disruptive selection and assortative mating o  sympatric speciation  stickleback speciies pairs  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  closely related but no longer interbreed  Phylogeny  Reading phylogenies  o it can tell us the most recent common ancestors, see which species is more closely related to each other o time passes from root to tips o How much time? We don't know... no scale bar o D/E and C/F splits did not necessarily happen at the same time (refer to slide) o we can only infer the sequential of the species but we cannot tell time on the phylogenic tree o Some phylogenies convey more information than branching other o  some has scale bars o Rotating nodes changes nothing o Higher and lower life forms? Highly evolved and less highly evolved? o  humans seems to be the most evolved thus we put it on the end o Which group is the most highly evolved? o  everything has been evolving for the same amount of time because we descended from the common ancestor o Phylogenies are like pedigrees
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