Lecture Notes on Phylogeny and Systematics

Vocabulary flashcards based on lecture notes.

Analogy

Similarity between two species due to convergent evolution rather than descent from a common ancestor with the same trait.

Basal taxon

In a group of organisms, a taxon whose evolutionary lineage diverged early in the history of the group.

Binomial

The two-part, latinized format for naming a species, consisting of the genus and specific epithet; also called a binomen.

Branch point

The representation on a phylogenetic tree of the divergence of two or more taxa from a common ancestor.

Character

An observable heritable feature that may vary among individuals.

Clade

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

Cladistics

An approach to systematics in which organisms are placed into groups called clades based primarily on common descent.

Class

In Linnaean classification, the taxonomic category above the level of order and below phylum.

Domain

A taxonomic category above the kingdom level. The three domains are Archaea, Bacteria, and Eukarya.

Evolutionary lineage

The sequence of ancestral organisms leading to a particular taxon; represented by a branch (line) in a phylogenetic tree.

Family

In Linnaean classification, the taxonomic category above genus and below order.

Genus

A taxonomic category above the species level, designated by the first word of a species' two-part scientific name.

Horizontal gene transfer

The transfer of genes from one genome to another through mechanisms such as transposable elements, plasmid exchange, viral activity, and perhaps fusions of different organisms.

Ingroup

A species or group of species whose evolutionary relationships are being examined in a given analysis.

Kingdom

A taxonomic category, the second broadest after domain.

Maximum parsimony

A principle that states that when considering multiple explanations for an observation, one should first investigate the simplest explanation that is consistent with the facts.

Molecular clock

A method for estimating the time required for a given amount of evolutionary change, based on the observation that some regions of genomes evolve at constant rates.

Monophyletic

Pertaining to a group of taxa that consists of a common ancestor and all of its descendants. A monophyletic taxon is equivalent to a clade.

Order

In Linnaean classification, the taxonomic category above the level of family and below class.

Outgroup

A species or group of species from an evolutionary lineage that is known to have diverged before the lineage that contains the group of species being studied.

Paraphyletic

Pertaining to a group of taxa that consists of a common ancestor and some, but not all, of its descendants.

Phylogenetic tree

A branching diagram that represents a hypothesis about the evolutionary history of a group of organisms.

Phylogeny

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

Phylum

In Linnaean classification, the taxonomic category above class and below kingdom.

Polyphyletic

Pertaining to a group of taxa that includes distantly related organisms but does not include their most recent common ancestor.

Polytomy

In a phylogenetic tree, a branch point from which more than two descendant taxa emerge. A polytomy indicates that the evolutionary relationships between the descendant taxa are not yet clear.

Rooted

Describing a phylogenetic tree that contains a branch point (often, the one farthest to the left) representing the most recent common ancestor of all taxa in the tree.

Shared ancestral character

A character that is shared by members of a particular clade but that originated in an ancestor that is not a member of that clade.

Shared derived character

An evolutionary novelty that is unique to a particular clade.

Sister taxa

Groups of organisms that share an immediate common ancestor and hence are each other's closest relatives.

Synapomorphy

A characteristic present in an ancestral species and shared exclusively (in more or less modified form) by its evolutionary descendants.

Systematics

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

Taxon

A named taxonomic unit at any given level of classification.

Trait

One of two or more detectable variants in a genetic character.