Taxa

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Information about Taxa

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A taxon (plural taxa), or taxonomic unit, is a name designating an organism or group of organisms. A taxon is assigned a rank and can be placed at a particular level in a systematic hierarchy reflecting evolutionary relationships.

A distinction is to be made between taxa/taxonomy and classification/systematics. The former refers to biological names and the rules of naming. The latter refers to rank ordering of taxa according to presumptive evolutionary (phylogenetic) relationships.

A broad scheme of ranks in hierarchical order:

Phylum or Division

Note: "Phylum" applies formally to any biological domain but traditionally it was always used of animals whereas "Division" was traditionally often used of plants, fungi etc.

A simple mnemonic phrase to remember the order is "Dignified Kings Play Chess On Fine Green Silk"; another, highly expedient example is "King Philip's Class Orders the Family Genius to Speak".

A prefix is used to indicate a ranking of lesser importance. The prefix super- indicates a rank above, the prefix sub- indicates a rank below. In zoology the prefix infra- indicates a rank below sub-. For instance:

Rank is relative, and restricted to a particular systematic schema. For example, liverworts have been grouped, in various systems of classification, as a family, order, or a class. The use of a narrow set of ranks is challenged by users of cladistics; for example, the mere 10 ranks traditionally used between animal families (governed by the ICZN) and animal phyla (usually the highest relevant rank in taxonomic work) often cannot adequately represent the evolutionary history as more about a lineage's phylogeny becomes known. In addition, the class rank is quite often not an evolutionary but a phenetical and paraphyletic group and as opposed to those ranks governed by the ICZN, can usually not be made monophyletic by exchanging the taxa contained therein. This has given rise to phylogenetic taxonomy and the ongoing development of the PhyloCode, which is to govern the application of taxa to clades.

See also

Plantae

Chromalveolata

Heterokontophyta

Haptophyta

Cryptophyta

Alveolata

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domain (also superregnum, superkingdom, or empire) is a taxon in the highest rank of organisms, higher than a kingdom. Domain (or its synonyms) is the most inclusive of these biological groupings.
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kingdom or regnum is a taxon in either (historically) the highest rank, or (in the new three-domain system) the rank below domain. Each kingdom is divided into smaller groups called phyla (or in some contexts these are called "divisions").
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phylum (Greek Φῦλον plural: Φῦλα phyla) is a taxon in the rank below kingdom and above class.
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division.

The main plant divisions, in the order in which they probably evolved, are the liverworts (Division Marchantiophyta), the hornworts (Division Anthocerophyta), the mosses (Division Bryophyta), the ferns (Division Filicophyta), the horsetails (Division Sphenophyta),
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class is the rank in the scientific classification of organisms in biology below Phylum and above Order.

For example, Mammalia is the class used in the classification of dogs, whose phylum is Chordata (animals with notochords) and order is Carnivora (mammals that eat meat).
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order (Latin: ordo, plural ordines) is a rank between class and family (termed a taxon at that rank). The superorder is a rank between class and order. Exact details of formal nomenclature depend on the Nomenclature Code which applies.
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family (Latin: familia, plural familiae) is a rank, or a taxon in that rank. Exact details of formal nomenclature depend on the Nomenclature Code which applies.
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genus (plural: genera) is part of the Latinized name for an organism. It is a name which reflects the classification of the organism by grouping it with other closely similar organisms.
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species is one of the basic units of biological classification. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring.
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Domain has several meanings:

General

some kind of territory, such as (for example) a demesne or a realm
synonymous with a metaphorical field, e.g. "the domain of computer science"

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Plantae
Haeckel, 1866^[1]

Divisions

Green algae

Chlorophyta
Charophyta

Land plants (embryophytes)

Non-vascular land plants (bryophytes)

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Eukarya
Whittaker & Margulis, 1978
(unranked) Opisthokonta

Kingdom: Fungi
(L., 1753) R.T. Moore, 1980^[1]

Subkingdom/Phyla

Chytridiomycota

Blastocladiomycota

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Not to be confused with pneumonic.

A mnemonic (pronounced IPA: /niːˈmɒnɪk/ in RP, /nɨˈmɑnɨk/
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Chess is a recreational and competitive game for two players. Sometimes called Western Chess or International Chess to distinguish it from its predecessors and other chess variants, the current form of the game emerged in Southern Europe in the second half of the 15th
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class is the rank in the scientific classification of organisms in biology below Phylum and above Order.

For example, Mammalia is the class used in the classification of dogs, whose phylum is Chordata (animals with notochords) and order is Carnivora (mammals that eat meat).
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class is the rank in the scientific classification of organisms in biology below Phylum and above Order.

For example, Mammalia is the class used in the classification of dogs, whose phylum is Chordata (animals with notochords) and order is Carnivora (mammals that eat meat).
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class is the rank in the scientific classification of organisms in biology below Phylum and above Order.

For example, Mammalia is the class used in the classification of dogs, whose phylum is Chordata (animals with notochords) and order is Carnivora (mammals that eat meat).
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In zoology, an infraclass is a further subdivision of a subclass, but it is rarely used. The next rank below the infraclass would be the Order or Superorder. For example:

Phylum Arthropoda

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Liverwort may refer to either

Marchantiophyta, a division of non-vascular plants.
Hepatica, a genus of spring flowers.

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Cladistics is a philosophy of classification that arranges organisms only by their order of branching in an evolutionary tree and not by their morphological similarity, in the words of Luria et al. (1981).
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phylogenetics (Greek: phyle = tribe, race and genetikos = relative to birth, from genesis = birth) is the study of evolutionary relatedness among various groups of organisms (e.g., species, populations).
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phenetics, also known as numerical taxonomy, is an attempt to classify organisms based on overall similarity, usually in morphology or other observable traits, regardless of their phylogeny or evolutionary relation.
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In phylogenetics, a group of organisms is said to be paraphyletic (Greek para = near and phyle = race) if the group contains its most recent common ancestor, but does not contain all the descendants of that ancestor.
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Phylogenetic nomenclature is an alternative to rank-based nomenclature. Its two defining features are the use of phylogenetic definitions of biological taxon names, and the lack of obligatory ranks.
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The International Code of Phylogenetic Nomenclature, known for short as the PhyloCode, is a developing draft for a formal set of rules governing phylogenetic nomenclature.
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This article has been tagged since July 2007.
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Taxonomy, sometimes alpha taxonomy, is the science of finding, describing and categorising organisms, thus giving rise to taxonomic groups or taxa, which may then be named.
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Cladistics is a philosophy of classification that arranges organisms only by their order of branching in an evolutionary tree and not by their morphological similarity, in the words of Luria et al. (1981).
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In botanical nomenclature, a taxon is usually assigned to a rank in a hierarchy. The basic rank is that of species, and if an organism is named it most often will receive a species name.
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