10/6 & 10/8 Phylogenies

What is a phylogeny?

the evolutionary history of a group of organisms, representing how species diverged from common ancestors over time.

What are the parts of a phylogeny?

Branches, Tips, Nodes, Root

Branches

Connects species to ancestors

Tips

organisms (taxa)

Nodes

divergence from one species into two (or more)

Root

hypothetical common ancestor of all organisms on the tree

How to we read and interpret phylogenies?

identify the root and read it from it to the tips

What happens to the relationships a phylogeny displays when we rotate sections of the phylogeny at the nodes?

It does not change the relationships the tree displays.

What are sister taxa?

two groups that share the most recent common ancestor and are each other’s closest relative.

Do phylogenetic trees reflect relative time or absolute time?

(usually) relative time

What are the three phylogenetic groupings?

Monophyletic, paraphyletic, and polyphyletic

Monophyletic group

a common ancestor and all of its descendants

Paraphyletic group

includes a common ancestor and some, but not all of its descendants

Polyphyletic group

does not include the common ancestor (unites traits that didn’t come from a common ancestor); only includes ends of branches and tips

Analogous characters/traits

characters that arose because of similar selective environments, NOT from a common ancestor

Homologous characters

characters that are present in groups that descended from a common ancestor

Synapomorphy

a special case of homologous trait that defines a monophyletic group (trait evolved once and is in all descendants)