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Published byGervais Goodman Modified over 9 years ago
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Understanding Trees
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Pre-test Which mammal is the pig more closely related to, cow or camel? Which mammal here is the most primitive? Fig. 4.8b
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Common ancestor Root of the tree Nodes Terminal taxa (tips) Branches
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Phylograms and Cladograms
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Trees can be built for extinct organisms…
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Trees can include lineage “persistence”
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Some trees show timing of events
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Most trees today are built for extant organisms only…
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Tree Rules 1. Read the nodes, remember they swivel 2. Bifurcation rule 3. Monophyly snip rule 4. Sibling ≠ Ancestor 5. Sister lineage snip rule and ages
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1. Read the nodes, remember they swivel! Don’t read left to right or top to bottom Read the nodes, and the nodes swivel
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Read the nodes ABCD e f g For cladograms, some information about timing (e and f after g)
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For phylograms, a little more information about timing
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This tree is ladderized right… Swivel the nodes to make it ladderized left Redraw it with lungfish at the top
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Assignment
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2. Bifurcation Rule Can only have one divergence event at a time. Can’t have two divergence events at the same time (snap two fingers at once)
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Breaking the Bifurcation Rule: Hard polytomies and Soft polytomies Cichlids
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