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32 convergent evolution character similarity

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32 convergent evolution: character similarity resulting from independent responses to a similar environment Homoplasy: similarities that result from factors other than common ancestry Morelia viridis Corallus caninus Green tree boa and Green tree python. both arboreal Homoplasy: similarities that result from factors other than common ancestry convergent evolution: character similarity resulting from independent responses to a similar environment
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33 Homoplasy: similarities that result from factors other than common ancestry convergent evolution: character similarity resulting from independent responses to a similar environment Meadowlark • N. America Longclaw • Africa Reversals: character similarity in distantly related taxa resulting from reversal to an original state Homoplasy: similarities that result from factors other than common ancestry
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34 Homoplasy in Phylogenetics Without homoplasy all characters would support the same tree But with homoplasy, different trees are supported by different characters! How to decide among possibilities? The PARSIMONY principle Occam s Razor: Pluralitas non est ponenda sine necessitate (complexity should not be posited without necessity) William of Ockham 14th-century English logician and Franciscan friar The simplest answer is always best!
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35 Applied to phylogenetics: The evolutionary tree that requires the least amount of change is the most likely. Put simply: the least complicated tree wins. The PARSIMONY principle Occam s Razor: Pluralitas non est ponenda sine necessitate (complexity should not be posited without necessity) The PARSIMONY principle Two characters: Viviparity (live birth) Hair
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36 lizard platypus kangaroo dog human hair viviparity Tree length = 2 changes The PARSIMONY principle Tree length = 3 changes hair viviparity viviparity The PARSIMONY principle lizard platypus kangaroo dog human
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37 Tree length = 3 changes hair viviparity loss of viviparity The PARSIMONY principle lizard platypus kangaroo dog human hair viviparity Tree length = 2 changes The MOST PARSIMONIOUS TREE The PARSIMONY principle lizard platypus kangaroo dog human
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38 Did a dentist spread HIV to his patients?
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39 Next we will map a relevant character on the tree Next we will map a relevant character on the tree
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40 Next we will map a relevant character on the tree Next we will map a relevant character on the tree
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32 convergent evolution character similarity resulting from...

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