Chapter 26

Phylogeny

The evolutionary history of a species or group of related species.

Systematics

A discipline focused on classifying organisms and determining their evolutionary relationships.

Binomial nomenclature

A two-part naming system attributed to Carolus Linnaeus, consisting of genus and specific epithet.

Hierarchical classification

A system for grouping species in increasingly inclusive groups, from domain to species.

Sister taxa

Groups that share a common ancestor not shared by any other group.

Homology

Similarity due to shared ancestry—organisms with similar morphology or DNA sequences are likely more closely related.

Analogy

Similarity due to convergent evolution—unrelated species evolve superficial similarities through adaptation.

Shared ancestral characteristics

A character that originated in an ancestor of the taxon and is present in broader taxonomic groups.

Shared derived characteristics

An evolutionary novelty unique to a particular clade, often core for building cladograms.

Monophyletic group (clade)

A group consisting of an ancestor and all of its descendants.

Paraphyletic group

A group consisting of an ancestor species and some but not all of the descendants.

Polyphyletic group

A group that includes distantly related species but not their most recent common ancestor.

In-group

The group of species being studied in a cladistic analysis.

Out-group

A species or group closely related to the in-group but not part of it.

Maximum parsimony

An analytical principle that assumes the most likely tree requires the fewest evolutionary events.

Maximum likelihood

Method identifying the tree most likely to have produced a given set of DNA data, based on probability rules.

Phylogenetic bracketing

A method to predict that features shared by two closely related groups will also be present in their ancestor and all descendants.