18 determine the phylogenetic relationships among

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18 Determine the phylogenetic relationships among turtles, crocodiles, birds, and lizards. Use amphibians as an outgroup Attention! Do not memorize characters. Understand the principle!
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19 Cladistic estimation of phylogeny Character Birds Crocs Lizards Turtles Frog Feathers + - - - - Amniotic egg + + + + - Parental care + + - - - Four chambered heart + + - - - Bilateral symmetry - - - - - Ancestral (-) vs derived (+) To reconstruct a tree we need characters. But not any old character! We need: Homologous characters and synapomorphies !
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20 Cladistic estimation of phylogeny Feathers Character Birds Crocs Lizards Turtles Frog Feathers + - - - - Amniotic egg + + + + - Parental care + + - - - Four chambered heart + + - - - Bilateral symmetry - - - - - Ancestral (-) vs derived (+) To reconstruct a tree we need characters. But not any old character! We need: Homologous characters and synapomorphies !
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21 Cladistic estimation of phylogeny Amniotic egg Feathers Character Birds Crocs Lizards Turtles Frog Feathers + - - - - Amniotic egg + + + + - Parental care + + - - - Four chambered heart + + - - - Bilateral symmetry - - - - - Ancestral (-) vs derived (+) To reconstruct a tree we need characters. But not any old character! We need: Homologous characters and synapomorphies !
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22 Cladistic estimation of phylogeny Parental care Feathers Amniotic egg Character Birds Crocs Lizards Turtles Frog Feathers + - - - - Amniotic egg + + + + - Parental care + + - - - Four chambered heart + + - - - Bilateral symmetry - - - - - Ancestral (-) vs derived (+) To reconstruct a tree we need characters. But not any old character! We need: Homologous characters and synapomorphies !
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23 Cladistic estimation of phylogeny Parental care Feathers Amniotic egg 4-chambered heart Character Birds Crocs Lizards Turtles Frog Feathers + - - - - Amniotic egg + + + + - Parental care + + - - - Four chambered heart + + - - - Bilateral symmetry - - - - - Ancestral (-) vs derived (+) To reconstruct a tree we need characters. But not any old character! We need: Homologous characters and synapomorphies !
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24 Cladistic estimation of phylogeny Parental care Feathers Amniotic egg 4-chambered heart Bilateral symmetry Cladistic estimation of phylogeny Parental care Feathers Amniotic egg 4-chambered heart To resolve polytomy, need a character shared by lizards/ turtles or birds/crocs/lizards or birds/crocs/turtles Bilateral symmetry
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31 Only position 7 is phylogenetically informative Potential problems inferring phylogenies Some similarities can be confounding Evolutionary reversals Convergent evolution This is HOMOPLASY
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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.
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