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Relatedness = recency of common ancestry

Relatedness = recency of common ancestry. You are more closely related to your first cousins than your second cousins because…. You are more closely related to a chimpanzee than to a worm because…. grandparents vs. great-grandparents ≈ 6 Million years ago (Ma) vs. ≈ 600 Ma.

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Relatedness = recency of common ancestry

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  1. Relatedness = recency of common ancestry • You are more closely related to your first cousins than your second cousins because…. • You are more closely related to a chimpanzee than to a worm because…. • grandparents vs. great-grandparents • ≈ 6 Million years ago (Ma) vs. ≈ 600 Ma

  2. Is a frog more closely related to a trout or a human?

  3. Why might you go wrong?If you look “along” the top Human Trout Frog Lizard Mouse • But this is not how evolution happened • All these species are alive today: A living trout is not an ancestor of a frog • The order “along the top” can change without changing the content of the tree

  4. Fish Fish Frog Lizard Mouse Human Human Mouse Lizard Frog You can change the order without changing the tree

  5. On this tree, is a frog more closely related to a trout or a human? Trout Human Mouse Lizard Frog -> The same tree depicts the same relationships

  6. Is a gibbon more closely related to a human or a macaque? Don’t be distracted by similarity

  7. Remember not to look “along the top”

  8. Non-monophyletic group Some members are more closely related to organisms outside the group Monophyletic group (clade) Members are more closely related to each other than to any organisms outside the group

  9. Biological classifications should reflect evolutionary relationships • They should mirror phylogenetic trees • Only clades should be named • Most named groups you know of are clades • But there are a few exceptions: Fish, invertebrata, reptiles, protista, prokaryota

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