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The analytical study of the diversity and relationships of organisms, both present-day and extinct.
The comparison of nucleic acids or other molecules in different species to infer relatedness.
The chronicle of evolution over millions of years of geologic time engraved in the order in which fossils appear in rock strata.
Similarity between two species that is due to convergent evolution rather than to descent from a common ancestor with the same trait.
Similar (analogous) structure or molecular sequence that has evolved independently in two species.
Ordered division of organisms into categories based on a set of characteristics used to assess similarities and differences, leading to a classification scheme; the branch of biology concerned with naming and classifying the diverse forms of life.
A taxonomic category above the species level, designated by the first word of a species′ two-part scientific name.
A branching diagram that represents a hypothesis about evolutionary relationships.
Pertaining to a grouping of species consisting of an ancestral species and all its descendants; a clade. Made up of an ancestral species and all of its descendant species.
Pertaining to a grouping of species that consists of an ancestral species and some, but not all, of its descendants.
Pertaining to a grouping of species derived from two or more different ancestral forms.
Used to differentiate between shared derived characters and shared primitive characters.
A species or group of species that is closely related to the group of species being studied, but clearly not as closely related as any study-group members are to each other
In a cladistic study of evolutionary relationships among taxa of organisms, the group of taxa that is actually being analyzed
A phylogenetic tree in which the lengths of the branches reflect the number of genetic changes that have taken place in a particular DNA or RNA sequence in the various lineages
A phylogenetic tree in which the lengths of the branches reflect measurements of geologic time.
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.
A principle that states that when considering multiple phylogenetic hypotheses, one should take into account the one that reflects the most likely sequence of evolutionary events, given certain rules about how DNA changes over time.
Homologous genes that are passed in a straight line from one generation to the next, but have ended up in different gene pools because of speciation.
An evolutionary timing method based on the observation that at least some regions of genomes evolve at constant rates.
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