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Lecture 7

Lecture 7

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Biology 3466B
Yolanda Morbey

Handout 7 – inferring phylogenies A more recent phylogenetic tree The oldest phylogenetic tree based on whole genome sequence analysis  Principles of phylogenetic Reptiles without the birds are paraphyletic o observation: all species are related by a common ancestry o implication: a classification based on evolutionary history will be informative and permanent o observation: Reptiitlliia Aves  as species change through time (anagenesis) differences accumulate within species  as species spilt (cladogensis) differences accumulate between species A more recent phylogenetic tree  the current character states can be used to reconstruct that history 9/26/2012  in a phylogenetic classification taxa should be monophyletic o monophyletic: derived from single lineages Paraphyletic = a subset of lineage members is excluded  reptilReptiles without the birds aretic o a subset of lineages with members excluded (a group that contains some taxa that are related but some that are not) Reptiitlliia Aves “Cold-blooded tetrapods” would be polyphyletic based on whole genome sequence analysis Warm-blooded tetrapods Cold-blooded tetrapods Paraphyletic 2  cold blooded tetra pods would be polyphyleticis excluded o made up of selected taxa from diverse lineages (doesn’t follow that high achy [doesn’t follow the ancestor patterns])  Every time there is a cladogenesis event the species diverge Polyphyletic =from diverse lineagestaxa from “Cold-blooded tetrapods” would o the more species are a part in time the more different be polyphyletic they become o We know today sequences and we use them to try and predict Cold-blooded tetrapods o Methods are often based on the principle of parsimony AAAAAA The molecular clock  The simplest explanation is the one that happens, don’t add stuff that makes it more complicated  “one should not add things that are not necessary” “the path to the truth is the shortest 9/26/2012 path” But we only know extant sequences o but we only know the extant species  GCAGCT CCCGAT CGTATT CGCATT e GCAGAT CCAGAT CGAATT This tree is a hypothesis that  the be parsimonious, classifications should be based on r ACAGAT CAAATT requires 6 steps synapomorphies : shnred, derivedAAAGATlogousAAAATTcteristics o shared: found tn members of the same group l o derived: more vecent evolved conditionT 9/26/2012 o homologous: similar due to comm
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