In biological classification , TAXONOMIC RANK is the relative level of a group of organisms (a taxon ) in a taxonomic hierarchy . Examples of taxonomic ranks are species , genus , family , order , class , phylum , kingdom , domain , etc.
A given rank subsumes under it less general categories, that is, more specific descriptions of life forms. Above it, each rank is classified within more general categories of organisms and groups of organisms related to each other through inheritance of traits or features from common ancestors. The rank of any species and the description of its genus is basic; which means that to identify a particular organism, it is usually not necessary to specify ranks other than these first two.
Consider a particular species, the red fox ,
The International Code of Zoological Nomenclature defines rank as: The level, for nomenclatural purposes, of a taxon in a taxonomic hierarchy (e.g. all families are for nomenclatural purposes at the same rank, which lies between superfamily and subfamily)
* 1 Main ranks
* 2 Ranks in zoology
* 2.1 Names of zoological taxa
* 3 Ranks in botany
* 3.1 Names of botanical taxa
* 3.1.1 Outdated names for botanical ranks
* 4 Examples * 5 Terminations of names * 6 All ranks * 7 Significance and problems * 8 See also
* 9 References
* 9.1 Bibliography
In his landmark publications, such as the
MAIN TAXONOMIC RANKS
phylum phylum (in zoology )
A taxon is usually assigned a rank when it is given its formal name. The basic ranks are species and genus. When an organism is given a species name it is assigned to a genus, and the genus name is part of the species name.
The species name is also called a binomial , that is, a two-term name. For example, the zoological name for the human species is Homo sapiens. This is usually italicized in print and underlined when italics are not available. In this case, Homo is the generic name and it is capitalized; sapiens indicates the species and it is not capitalized.
RANKS IN ZOOLOGY
There are definitions of the following taxonomic ranks in the International Code of Zoological Nomenclature : superfamily, family, subfamily, tribe, subtribe, genus, subgenus, species, subspecies.
The International Code of Zoological Nomenclature divides names into "family-group names", "genus-group names" and "species-group names". The Code explicitly mentions: ------------------------- Superfamily
The rules in the Code apply to the ranks of superfamily to
subspecies, and only to some extent to those above the rank of
superfamily. In the "genus group" and "species group" no further ranks
are allowed. Among zoologists, additional terms such as species group,
species subgroup, species complex and superspecies are sometimes used
for convenience as extra, but unofficial, ranks between the subgenus
and species levels in taxa with many species (e.g. the genus
At higher ranks (family and above) a lower level may be denoted by adding the prefix "infra", meaning lower, to the rank. For example, infraorder (below suborder) or infrafamily (below subfamily).
NAMES OF ZOOLOGICAL TAXA
* A taxon above the rank of species has a scientific name in one part (a uninominal name). * A species has a name composed of two parts (a binomial name or binomen ): generic name + specific name ; for example Canis lupus. * A subspecies has a name composed of three parts (a trinomial name or trinomen ): generic name + specific name + subspecific name ; for example Canis lupus familiaris. As there is only one possible rank below that of species, no connecting term to indicate rank is needed or used.
RANKS IN BOTANY
According to Art 3.1 of the International Code of Nomenclature for algae, fungi, and plants (ICN) the most important ranks of taxa are: kingdom, division or phylum, class, order, family, genus, and species. According to Art 4.1 the secondary ranks of taxa are tribe, section, series, variety and form. There is an indeterminate number of ranks. The ICN explicitly mentions: -------------------------
PRIMARY RANKS SECONDARY RANKS FURTHER RANKS -------------------------
KINGDOM (regnum) subregnum
DIVISION or PHYLUM (divisio, phylum) subdivisio or subphylum
CLASS (classis) subclassis
ORDER (ordo) subordo -------------------------
FAMILY (familia) subfamilia TRIBE (tribus) subtribus
GENUS (genus) subgenus SECTION (sectio) subsection SERIES (series) subseries
SPECIES (species) subspecies VARIETY (varietas) subvarietas FORM (forma) subforma -------------------------
There are definitions of the following taxonomic categories in the International Code of Nomenclature for Cultivated Plants : cultivar group , cultivar , grex .
The rules in the ICN apply primarily to the ranks of family and below, and only to some extent to those above the rank of family. Also see descriptive botanical names .
NAMES OF BOTANICAL TAXA
Hybrids can be specified either by a "hybrid formula" that specifies the parentage, or may be given a name. For hybrids getting a hybrid name , the same ranks apply, prefixed with notho (Greek: 'bastard'), with nothogenus as the highest permitted rank.
Outdated Names For Botanical Ranks
If a different term for the rank was used in an old publication, but the intention is clear, botanical nomenclature specifies certain substitutions:
* If names were "intended as names of orders, but published with
their rank denoted by a term such as": "cohors" see also cohort
study for the use of the term in ecology], "nixus", "alliance", or
"Reihe" instead of "order" (Article 17.2), they are treated as names
* "Family" is substituted for "order" (ordo) or "natural order"
(ordo naturalis) under certain conditions where the modern meaning of
"order" was not intended. (Article 18.2)
Classifications of five species follow: the fruit fly so familiar in
genetics laboratories (
RANK FRUIT FLY HUMAN PEA FLY AGARIC E. COLI
SPECIES D. melanogaster H. sapiens P. sativum A. muscaria E. coli
* The ranks of higher taxa, especially intermediate ranks, are prone
to revision as new information about relationships is discovered. For
example, the flowering plants have been downgraded from a division
(Magnoliophyta) to a subclass (Magnoliidae), and the superorder has
become the rank that distinguishes the major groups of flowering
plants. The traditional classification of primates (class
Mammalia—subclass Theria—infraclass Eutheria—order Primates) has
been modified by new classifications such as McKenna and Bell (class
Mammalia—subclass Theriformes—infraclass Holotheria) with Theria
and Eutheria assigned lower ranks between infraclass and the order
Primates. See mammal classification for a discussion. These
differences arise because there are only a small number of ranks
available and a large number of branching points in the fossil record.
* Within species further units may be recognised. Animals may be
classified into subspecies (for example, Homo sapiens sapiens, modern
humans) or morphs (for example Corvus corax varius morpha leucophaeus,
the Pied Raven). Plants may be classified into subspecies (for
Pisum sativum subsp. sativum, the garden pea) or varieties
Pisum sativum var. macrocarpon, snow pea), with
cultivated plants getting a cultivar name (for example,
var. macrocarpon 'Snowbird').
TERMINATIONS OF NAMES
Pronunciations given are the most Anglicized . More Latinate pronunciations are also common, particularly /ɑː/ rather than /eɪ/ for stressed a.
RANK BACTERIA PLANTS ALGAE FUNGI ANIMALS
-phyta /ˈfaɪtə/ -phycota /ˈfaɪkoʊtə/ -mycota /maɪˈkoʊtə/
-phytina /fᵻˈtaɪnə/ -phycotina /fᵻkoʊˈtaɪnə/ -mycotina /maɪkoʊˈtaɪnə/
CLASS -ia /iə/ -opsida /ˈɒpsᵻdə/ -phyceae /ˈfaɪʃiː/ -mycetes /maɪˈsiːtiːz/
SUBCLASS -idae /ᵻdiː/ -phycidae /ˈfɪsᵻdiː/ -mycetidae /maɪˈsɛtᵻdiː/
ORDER -ales /ˈeɪliːz/
SUBORDER -ineae /ˈɪnᵻ.iː/
-acea /ˈeɪʃə/ -oidea /ˈɔɪdiə/
FAMILY -aceae /ˈeɪʃiː/ -idae /ᵻdiː/
SUBFAMILY -oideae /ˈɔɪdᵻiː/ -inae /ˈaɪniː/
TRIBE -eae /ᵻiː/ -ini /ˈaɪnaɪ/
SUBTRIBE -inae /ˈaɪniː/ -ina /ˈaɪnə/
-ad /æd/ or -iti /ˈaɪti/
* In botany and mycology names at the rank of family and below are
based on the name of a genus, sometimes called the type genus of that
taxon, with a standard ending. For example, the rose family Rosaceae
is named after the genus Rosa, with the standard ending "-aceae" for a
family. Names above the rank of family are also formed from a generic
name, or are descriptive (like Gymnospermae or Fungi ).
* For animals, there are standard suffixes for taxa only up to the
rank of superfamily.
* Forming a name based on a generic name may be not straightforward.
For example, the
There is an indeterminate number of ranks, as a taxonomist may invent a new rank at will, at any time, if they feel this is necessary. In doing so, there are some restrictions, which will vary with the nomenclature code which applies.
The following is an artificial synthesis, solely for purposes of demonstration of relative rank (but see notes), from most general to most specific:
* DOMAIN or EMPIRE
* Superphylum (or Superdivision in botany)
* PHYLUM (or DIVISION in botany)
* Subphylum (or Subdivision in botany)
* Infraphylum (or Infradivision in botany)
* Superdivision (zoology)
* Division (zoology)
* Subdivision (zoology)
* Infradivision (zoology)
* Superlegion (zoology)
* Legion (zoology)
* Sublegion (zoology)
* Infralegion (zoology)
* Supercohort (zoology)
* Cohort (zoology)
* Subcohort (zoology)
* Infracohort (zoology)
* Gigaorder (zoology)
* Magnorder or Megaorder (zoology)
* Grandorder or Capaxorder (zoology)
* Mirorder or Hyperorder (zoology)
* Series (for fish)
* Parvorder (position in some zoological classifications)
* Nanorder (zoology)
* Hypoorder (zoology)
* Minorder (zoology)
* Parvorder (usual position) or Microorder (zoology)
* Section (zoology)
* Subsection (zoology)
* Gigafamily (zoology)
* Megafamily (zoology)
* Grandfamily (zoology)
* Hyperfamily (zoology)
* Epifamily (zoology)
* Series (for Lepidoptera)
* Group (for Lepidoptera)
* Subsection (botany)
* Subseries (botany)
* Superspecies or Species-group
* Subvariety (botany)
* Subform (botany)
SIGNIFICANCE AND PROBLEMS
Ranks are assigned based on subjective dissimilarity, and do not fully reflect the gradational nature of variation within nature. In most cases, higher taxonomic groupings arise further back in time: not because the rate of diversification was higher in the past, but because each subsequent diversification event results in an increase of diversity and thus increases the taxonomic rank assigned by present-day taxonomists. Furthermore, some groups have many described species not because they are more diverse than other species, but because they are more easily sampled and studied than other group.
Of these many ranks, the most basic is species. However, this is not to say that a taxon at any other rank may not be sharply defined, or that any species is guaranteed to be sharply defined. It varies from case to case. Ideally, a taxon is intended to represent a clade , that is, the phylogeny of the organisms under discussion, but this is not a requirement.
Classification, in which all taxa have formal ranks, cannot adequately reflect knowledge about phylogeny; at the same time, if taxon names are dependent on ranks, rank-free taxa can't be supplied with names. This problem is dissolved in cladoendesis, where the specially elaborated rank-free nomenclatures are used.
There are no rules for how many species should make a genus, a family, or any other higher taxon (that is, a taxon in a category above the species level). It should be a natural group (that is, non-artificial, non-polyphyletic ), as judged by a biologist, using all the information available to them. Equally ranked higher taxa in different phyla are not necessarily equivalent (e.g., it is incorrect to assume that families of insects are in some way evolutionarily comparable to families of mollusks). For animals, at least the phylum rank is usually associated with a certain body plan , which is also, however, an arbitrary criterion.
* ^ http://www.123rf.com /clipart-vector/vulpes_vulpes.html
* ^ International Code of Nomenclature for algae, fungi, and
plants, Melbourne Code, 2012, articles 2 and 3
* ^ International Commission on Zoological Nomenclature (1999),
International Code of Zoological Nomenclature. Fourth Edition,
International Trust for Zoological Nomenclature
* ^ Moore R.T. (1974). "Proposal for the recognition of super
ranks" (PDF). Taxon. 23 (4): 650–652.
* ^ Luketa S. (2012). "New views on the megaclassification of life"
(PDF). Protistology. 7 (4): 218–237.
* ^ International Code of Nomenclature for algae, fungi, and
plants, Melbourne Code, 2012, articles 3 and 4
* ^ Stearn, W.T. 1992. Botanical Latin: History, grammar, syntax,
terminology and vocabulary, Fourth edition. David and Charles.
* ^ Chase, M.W.; Reveal, J.L. (2009), "A phylogenetic
classification of the land plants to accompany APG III", Botanical
Journal of the Linnean Society, 161 (2): 122–127, doi
* ^ Bacteriologocal Code (1990 Revision)
* ^ For example, the chelonian infrafamilies Chelodd (Gaffney &
Meylan 1988: 169) and Baenodd (ibid., 176).
* ^ ICZN article 29.2
* ^ As supplied by Gaffney & Meylan (1988).
* ^ For the general usage and coordination of zoological ranks
between the phylum and family levels, including many intercalary
ranks, see Carroll (1988). For additional intercalary ranks in
zoology, see especially Gaffney McKenna Milner (1988); Novacek (1986,
cit. in Carroll 1988: 499, 629); and
Paul Sereno 's 1986
classification of ornithischian dinosaurs as reported in Lambert
(1990: 149, 159). For botanical ranks, including many intercalary
ranks, see Willis & McElwain (2002).
* ^ A B C D These are movable ranks, most often inserted between
the class and the legion or cohort. Nevertheless, their positioning in
the zoological hierarchy may be subject to wide variation. For
examples, see the Benton classification of vertebrates (2005).
* ^ A B C D In zoological classification, the cohort and its
associated group of ranks are inserted between the class group and the
ordinal group. The cohort has also been used between infraorder and
family in saurischian dinosaurs (Benton 2005). In botanical
classification, the cohort group has sometimes been inserted between
the division (phylum) group and the class group: see Willis & McElwain
(2002: 100–101), or has sometimes been used at the rank of order,
and is now considered to be an obsolete name for order: See
International Code of Nomenclature for algae, fungi, and plants,
Melbourne Code 2012, Article 17.2.
* ^ A B C D E The supra-ordinal sequence
gigaorder-megaorder-capaxorder-hyperorder (and the microorder, in
roughly the position most often assigned to the parvorder) has been
employed in turtles at least (Gaffney & Meylan 1988), while the
parallel sequence magnorder-grandorder-mirorder figures in recently
influential classifications of mammals. It is unclear from the sources
how these two sequences are to be coordinated (or interwoven) within a
unitary zoological hierarchy of ranks. Previously, Novacek (1986) and
McKenna-Bell (1997) had inserted mirorders and grandorders between the
order and superorder, but Benton (2005) now positions both of these
ranks above the superorder.
* ^ Additionally, the terms biovar , morphovar and serovar
designate bacterial strains (genetic variants) that are
physiologically or biochemically distinctive. These are not taxonomic
ranks, but are groupings of various sorts which may define a bacterial
* ^ Gingerich, P. D. (1987). "Evolution and the fossil record:
patterns, rates, and processes". Canadian Journal of Zoology. 65 (5):
1053–1060. doi :10.1139/z87-169 .
* ^ Kluge N.J. 1999. A system of alternative nomenclatures of
supra-species taxa. Linnaean and post-Linnaean principles of
systematics. // Entomological Review 79(2): 133-147
* ^ Kluge N.J. 2010. Circumscriptional names of higher taxa in
Hexapoda. // Bionomina 1: 15–55
* ^ Stuessy, T.F. (2009).
* Benton, Michael J. 2005.
Vertebrate Palaeontology, 3rd ed. Oxford:
Blackwell Publishing. ISBN 0-632-05637-1 . ISBN 978-0-632-05637-8
* Brummitt, R.K., and C.E. Powell. 1992. Authors of
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