7.9: Phylogeny

Phylogeny

The study of evolutionary relationships among biological entities.

Cladogram

A diagram that depicts evolutionary relationships but does not indicate time or amount of difference.

Phylogenetic tree

A diagram that shows evolutionary relationships and indicates time spans between branching points.

Taxon

The species of interest in a phylogenetic study.

Branch

Represents the evolutionary history of a taxon.

Node

Represents the most recent common ancestor (MRCA) between two species.

Root

The oldest common ancestor of the species on a phylogenetic tree.

Ancestral character

A trait shared among all descendants from the root.

Derived character

A trait shared among specific descendants, not all.

Outgroup

The least closely related organism used for comparison in phylogenetic studies.

Monophyletic taxon (clade)

Defined by shared characteristics inherited from a common ancestor, includes all descendants of that ancestor.

Polyphyletic taxon

Defined by shared characteristics that arise through convergent evolution, and do not share a very recent common ancestor.

Paraphyletic taxon

Includes some, but not all, descendants of a common ancestor and is defined by shared ancestral characteristics.

Classification in phylogeny

Organisms grouped in smaller, more specific classifications are more closely related.