Genus

genus, in taxonomy: see classification.

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genus

Biological classification. It ranks below family and above species, consisting of structurally or phylogenetically (see phylogenetic tree) related species or a single species exhibiting unusual differences. For example, the species of roses collectively form the genus Rosa and those of horses, donkeys, and zebras form the genus Equus. The genus name, capitalized and usually italicized, is the first word of a scientific name in the system of binomial nomenclature.

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genus

1. Biology any of the taxonomic groups into which a family is divided and which contains one or more species. For example, Vulpes (foxes) is a genus of the dog family (Canidae)

2. Logic a class of objects or individuals that can be divided into two or more groups or species

3. Maths a number characterizing a closed surface in topology equal to the number of handles added to a sphere to form the surface. A sphere has genus 0, a torus, genus 1, etc.

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genus [′jē·nəs]

(mathematics)

An integer associated to a surface which measures the number of holes in the surface.

(systematics)

A taxonomic category that includes groups of closely related species; the principal subdivision of a family.

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Genus 

a major taxonomic category that phylogenetically unites closely related species. For example, various cat species (European wildcat, jungle cat, leopard cat) are united in the genus Felis. Various pine species (Scotch pine, Siberian pine) form the genus Pinus. The scientific name of a genus is designated by a single Latin word.

Genera may consist of many species. For example, some insect and plant genera contain hundreds or thousands of species. Some genera comprise only one or a few species.

Genera having only one species, such as Desmana or Welwitschia, are called monotypic. Genera with several species are often divided into subgenera, which unite especially closely related species. Each genus belongs to a family, but between these two taxonomic categories there are often intermediate ones. For example, tribes are grouped in subfamilies, which in turn are grouped in families.

In paleobotany there also are organ genera and formal genera.

V. G. GEPTNER and M. E. KIRPICHNIKOV