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Evolutionary Biology
Phylogenetics
Use this for “Which two of these animals are sister taxa, and is fish a clade?”
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Each branch point is the last common ancestor of everything above it.
Four traits, each gained once, need four changes: no other tree explains these traits with fewer.
Assumptions
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Each bar marks a shared derived trait (a synapomorphy), gained once on the branch into its clade.
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The lamprey is the outgroup: it split off first and roots the tree.
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A clade (monophyletic group) is one ancestor and all of its descendants.
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Turning a tree about a branch point does not change who is related to whom.
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