The evolutionary history of a species or group of related species.
a scientific discipline focused on classifying organisms and determining their evolutionary relationships.
the science of describing, naming, and classifying organisms.
The two-part latinized name of a species, consisting of genus and specific epithet.
A taxonomic category above the species level, designated by the first word of a species' binomial scientific name.
a taxonomic group containing one or more genera.
In classification, the taxonomic category above family.
In classification, the taxonomic category above order.
In classification, the taxonomic category above class.
A taxonomic category, the second broadest after domain.
a taxonomic category above the kingdom level; the three domains of life are Archaea, Bacteria, and Eukarya.
a named taxonomic unit at any given level of classification.
a branching diagram that represents a hypothesis about the evolutionary history of a group of organisms.
System of classification of organisms based on evolutionary relationships: Only groups that include a common ancestor and all of its descendents are named.
The representation on a phylogenetic tree of the divergence of two or more taxa from a common ancestor.
Groups of organisms that share an immediate common ancestor and hence are each other's closest relatives.
describing a phylogenetic tree that contains a branch point representing the last common ancestor of all taxa in the tree.
In a phylogenetic tree, a branch point from which more than two descendant taxa emerge. A polytomy indicates that the evolutionary relationships among the descendant taxa are not yet clear.
similarity of structure between two species that are not closely related; attributable to convergent evolution.
similar structure or molecular sequence that has evolved independently in two species.
a scientific discipline that uses nucleic acids or other molecules in different species to infer evolutionary relationships.
An approach to systematics in which organisms are placed into groups called clades based primarily on common descent.
a group of species that includes an ancestral species and all its descendants.
pertaining to a grouping of species consisting of an ancestral species and all its descendants.
pertaining to a grouping of species that consists of an ancestral species and some, but not all, of its descendants.
pertaining to a group of taxa derived from two or more different ancestors.
shared ancestral character
A character, shared by members of a particular clade, that originated in an ancestor that is not a member of that clade.
shared derived character
an evolutionary novelty unique to a particular clade.
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.
a species or group of species whose evolutionary relationships we seek to determine.
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.
as applied to systematics, a principle that states that when considering multiple phylogenetic hypotheses, one should take into account the hypothesis that reflects the most likely sequence of evolutionary events, given certain rules about how DNA changes over time.
an approach in which features shared by two groups of organisms are predicted (by parsimony) to be present in their common ancestor and all of its descendants.
homologous genes that are found in different species because of speciation.
homologous genes that are found in the same genome due to gene duplication.
a method for estimating the time required for a given amount of evolutionary change, based on the observation that some regions of genomes appear to evolve at constant rates.
the hypothesis that much evolutionary change in genes and proteins has no effect on fitness and therefore is not influenced by Darwinian natural selection.
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.