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

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

Why might you go wrong? If you look “along” the top Trout Frog Lizard Mouse Human 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

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

On this tree, is a frog more closely related to a trout or a human? Mouse Lizard Frog Note one can add all sorts of info onto trees. Character changes, biogeography, chemical features, time, etc. -> The same tree depicts the same relationships

Is a gibbon more closely related to a human or a macaque? Note one can add all sorts of info onto trees. Character changes, biogeography, chemical features, time, etc. Don’t be distracted by similarity

Remember not to look “along the top” Note one can add all sorts of info onto trees. Character changes, biogeography, chemical features, time, etc.

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

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