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Published byMarylou Cannon Modified over 8 years ago
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“Evolutionary speculation constitutes a kind of metascience, which has the same intellectual fascination for some biologists that metaphysical speculation possessed for some mediaeval scholastics. It can be considered a relatively harmless habit, like eating peanuts, unless it assumes the form of an obsession; then it becomes a vice” (Stanier, 1970)
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Linnaean classification Defining characteristics –Binomial (Genus species) –Hierarchical KingdomAnimalia PhylumChordata ClassMammalia OrderPrimates FamilyHominidae Genus Homo Speciessapiens
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Tree of Life: primary divisions Haeckel’s three categories Five kingdoms
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Tree of Life: primary divisions Haeckel’s three categories Five kingdoms Procaryote/eucaryote
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Tree of Life: three “domains” Based on 16S rRNA (Woese, 1987):
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Tree of Life: three “domains” Based on 16S rRNA (Pace, 1997): environmental sequence endosymbiosis
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Tree basics: meaning
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Tree basics: nodes
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Tree basics: rotation
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Tree basics: shape
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Tree basics: lengths, unrooted cladograms vs. phylograms
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Tree basics: character change
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Key phylogenetic terms Clade, sister taxa Cladogenesis vs. anagenesis Homology Monophyletic vs. polyphyletic vs. paraphyletic
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Key phylogenetic terms Clade, sister taxa Cladogenesis vs. anagenesis Homology Monophyletic vs. polyphyletic vs. paraphyletic
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Key phylogenetic terms Clade, sister taxa Cladogenesis vs. anagenesis Homology Monophyletic vs. polyphyletic vs. paraphyletic
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Overall similarity vs. number of derived characters –Shared ancestral traits & homoplasies (or convergent evolution) Lysozyme amino acid changes in unrelated ruminants Phenetics vs. cladistics
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Overall similarity vs. number of derived characters –Shared ancestral traits & homoplasies (or convergent evolution)
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Phenetics vs. cladistics Overall similarity vs. number of derived characters –Shared ancestral traits & homoplasies (or convergent evolution) –Why does this difference matter?
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Maximum Parsimony Parsimony – shortest tree (fewest homoplasies) –Assume: ancestral state is that most common outside clade
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Microbial systematics Phenotypic traits for microbes GC% T m for genomic hybridizations Formerly Pseudomonas (partial list): –Ralstonia, Burkholderia, Hydrogenophaga, Sphingomonas, Methylobacterium, Cellvibrio, Xanthomonas, Acidovorax, Hydrogenophillus, Brevundimonas, Pandoraea
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Molecular phylogenetics Zuckerkandl & Pauling. 1965. Molecules as documents of evolutionary history. J Theor Biol. 8:357-366. Neutral theory (Motoo Kimura, 1968) –Many differences neutral (synonomous) –Neutral differences rise in frequency due to drift –Rate of fixation proportional to mutation rate Molecular clock?
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16S rRNA as phylogenetic marker How pick good molecule? –Clocklike –Phylogenetic range –Size/accuracy –Changes “neutral” (p.255) Variants that fix are functionally equivalent
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