Phylogeny and Phylogenetic Trees

Vocabulary flashcards covering basic concepts of phylogeny, cladistics, taxonomic groupings, and the differentiation between homology and homoplasy as presented in BIOL&212.

Phylogeny

The evolutionary history of relationships of organisms and a history of descent from common ancestry.

Phylogenetic tree

A branched pattern representing a hypothesis about the evolutionary relationships among species.

Taxon

A group as defined by the investigator, which can be a species or a higher order taxon.

Monophyletic group (clade)

A group that includes an ancestral taxon and all of its descendants.

Paraphyletic group

A group that includes the most recent common ancestor of the group, but not all of its descendants.

Polyphyletic group

A group that does not include the most recent common ancestor of all members of the group.

Cladistics

An approach to biological classification in which organisms are categorized based on shared derived characteristics (synapomorphies).

Derived characteristic

A similarity inherited from the most recent common ancestor of an entire group.

Ancestral characteristic

A similarity that arose prior to the common ancestor of the group.

Synapomorphies

Shared derived-characteristics from the most-recent common ancestor used to inform evolutionary relationships or phylogenies.

Outgroup

A taxon related to the others but not very similar, used to root the tree in something more ancestral.

Homology

A shared trait due to common ancestry.

Homoplasy

A shared trait that was not inherited from a common ancestor, often observed in convergent evolution.

Convergent evolution

When two fairly unrelated lineages develop similar morphologies and behaviors in response to common selective pressures from the environment.

Parsimony

The principle that the simplest explanation—the one involving the fewest number of changes—is usually the correct explanation.

Maximum parsimony

The acceptance of the explanation that involves the fewest number of changes where a trait has been gained or lost.