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Evolution Notes

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Western University
Biology 3466B
Yolanda Morbey

Evolution NotesOct 2011 Humans are located at two places in the phylogenetic tree because we are eukaryotic and prokaryotic Mitochondria are some kind of bacteria that have become part of eukaryotic cells through symbiosis Principles of phylogeneticsObservation All species are related by common ancestry Implication A classification base on evolutionary history will be informative and permanentObservation As species change through time anagenesis differences accumulate within species microevolution As species split cladogenesis differences accumulate between species macroevolution The only difference between macro and micro is that they occur at different branchesApplication The current character states can be used to reconstruct that history In phylogenetic classification taxa should be monophyletic which means that they are all derived from a single lineage all taxa are nested sets Reptiles without the birds are paraphyletic which means a subset of lineage members is excluded This is not good and should be avoided Polyphyletic is a grouping that is made up of selected taxa from diverse lineages An example is coldblooded tetrapods which excludes mammals and birds This is not good because it puts the animals together based on characteristics that do not reflect evolutionary history Taxa should be monophyletic because it includes an ancestor and all of its descendants However ancestors are hardly ever available for study because they are extinct Only extant species ones that arent extinct are included in classifications Divergence increases as evolutionary time increases The genome changes over time In a tree anagenesis is the branch and cladogenesis is the fork Species diverge and become different and will never become identical again The molecular clock says that the rate at which mutations take place in genomes
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