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In
biological classification In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mecha ...
, taxonomic rank is the relative level of a group of organisms (a
taxon In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechani ...
) in a
taxonomic Taxonomy (general) is the practice and science of classification of things or concepts, including the principles that underlie such classification. The term may also refer to a specific classification scheme. Originally used only about biological ...
hierarchy A hierarchy (from the Greek: , from , 'president of sacred rites') is an arrangement of items (objects, names, values, categories, etc.) in which the items are represented as being "above", "below", or "at the same level as" one another. Hierarch ...

hierarchy
. Examples of taxonomic ranks are
species In biology, a species is the basic unit of biological classification, classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individu ...

species
,
genus Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank In biological classification In biology, taxonomy () is the scientific study of naming, defining (Circumscription (taxonomy), circumscribing) and classifying gr ...
,
family In human society A society is a Social group, group of individuals involved in persistent Social relation, social interaction, or a large social group sharing the same spatial or social territory, typically subject to the same Politic ...
,
order Order, ORDER or Orders may refer to: * Orderliness Orderliness is a quality that is characterized by a person’s interest in keeping their surroundings and themselves well organized, and is associated with other qualities such as cleanliness a ...
,
class Class or The Class may refer to: Common uses not otherwise categorized * Class (biology), a taxonomic rank * Class (knowledge representation), a collection of individuals or objects * Class (philosophy), an analytical concept used differently f ...
,
phylum In biology, a phylum (; plural The plural (sometimes list of glossing abbreviations, abbreviated ), in many languages, is one of the values of the grammatical number, grammatical category of number. The plural of a noun typically denotes a q ...
,
kingdom Kingdom may refer to: Monarchy * A type of monarchy * A realm ruled by: **A king, during the reign of a male monarch **A queen regnant, during the reign of a female monarch Taxonomy * Kingdom (biology), a category in biological taxonomy Arts an ...
,
domain Domain may refer to: Mathematics *Domain of a function In mathematics, the domain of a Function (mathematics), function is the Set (mathematics), set of inputs accepted by the function. It is sometimes denoted by \operatorname(f), where is th ...
, 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 Trait may refer to: * Phenotypic trait in biology, which involve genes and characteristics of organisms * Trait (computer programming), a model for structuring object-oriented programs (a template class in the C++ programming language) * Trait the ...
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 red fox (''Vulpes vulpes'') is the largest of the true foxes and one of the most widely distributed members of the order Order or ORDER or Orders may refer to: * Orderliness Orderliness is associated with other qualities such as cleanli ...

red fox
, ''Vulpes vulpes'': the next rank above, the genus ''
Vulpes '' Vulpes '' is a genus Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank In biological classification In biology, taxonomy () is the scientific study of naming, defining (Circumscription (taxonomy), circu ...
'', comprises all the "true" foxes. Their closest relatives are in the immediately higher rank, the family
Canidae Canidae (; from Latin, ''canis'', "dog") is a biological family Family ( la, familia, plural ') is one of the eight major hierarchical taxonomic ranks in Linnaean taxonomy; it is classified between order (biology), order and genus. A famil ...
, which includes dogs, wolves, jackals, and all foxes; the next higher rank, the order
Carnivora Carnivora is an order of placental Placentalia is one of the three extant subdivisions of the class of animals Mammalia Mammals (from Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch ...
, includes
caniforms Caniformia is a within the order consisting of "dog-like" carnivorans. They include dogs, bears, wolves, foxes, raccoons, badgers, and mustelids. The (, es and ) are also assigned to this group. The center of diversification for the Caniformia ...
(bears, seals, weasels, skunks, raccoons and all those mentioned above), and
feliforms Feliformia is a suborder within the order Carnivora consisting of "cat-like" carnivorans, including Felidae, cats (large and small), hyenas, mongooses, viverrids, and related taxa. Feliformia stands in contrast to the other suborder of Carnivora, ...
(cats, civets, hyenas, mongooses). Carnivorans are one group of the hairy, warm-blooded, nursing members of the class
Mammalia Mammals (from Latin language, Latin , 'breast') are a group of vertebrate animals constituting the class (biology), class Mammalia (), and characterized by the presence of mammary glands which in Female#Mammalian female, females produce milk ...

Mammalia
, which are classified among animals with backbones in the phylum
Chordata
Chordata
, and with them among all animals in the kingdom
Animalia Animals (also called Metazoa) are multicellular A multicellular organism is an organism In biology, an organism () is any organic, life, living system that functions as an individual entity. All organisms are composed of cells ...

Animalia
. Finally, at the highest rank all of these are grouped together with all other organisms possessing
cell nuclei In cell biology Cell biology (also cellular biology or cytology) is a branch of biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical process ...
in the domain
Eukarya Eukaryotes () are organism In biology, an organism () is any organic, life, living system that functions as an individual entity. All organisms are composed of cells (cell theory). Organisms are classified by taxonomy (biology), tax ...
. The ''
International Code of Zoological Nomenclature The International Code of Zoological Nomenclature (ICZN) is a widely accepted convention Convention may refer to: * Convention (norm), a custom or tradition, a standard of presentation or conduct ** Treaty, an agreement in international law * C ...
'' defines ''rank'' as: "The level, for nomenclatural purposes, of a
taxon In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechani ...
in a taxonomic hierarchy (e.g. all families are for nomenclatural purposes at the same rank, which lies between superfamily and subfamily)."


Main ranks

In his landmark publications, such as the ''
Systema Naturae ' (originally in Latin Latin (, or , ) is a classical language A classical language is a language A language is a structured system of communication Communication (from Latin ''communicare'', meaning "to share" or "to be in ...
'',
Carl Linnaeus Carl Linnaeus (; 23 May 1707 – 10 January 1778), also known after his ennoblement Ennoblement is the conferring of nobility—the induction of an individual into the noble social class, class. Currently only a few kingdoms still grant nob ...

Carl Linnaeus
used a ranking scale limited to: kingdom, class, order, genus, species, and one rank below species. Today, nomenclature is regulated by the
nomenclature codes Nomenclature codes or codes of nomenclature are the various rulebooks that govern biological taxonomic Taxonomy (general) is the practice and science of classification of things or concepts, including the principles that underlie such classifica ...
. There are seven main taxonomic ranks: kingdom, phylum or division, class, order, family, genus, species. In addition, ''domain'' (proposed by
Carl Woese Carl Richard Woese (; July 15, 1928 – December 30, 2012) was an American microbiologist A microbiologist (from Greek ) is a scientist A scientist is a person who conducts Scientific method, scientific research to advance knowledge in an B ...

Carl Woese
) is now widely used as a fundamental rank, although it is not mentioned in any of the nomenclature codes, and is a synonym for dominion (lat. dominium), introduced by Moore in 1974. 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, or 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 The International Code of Zoological Nomenclature (ICZN) is a widely accepted convention Convention may refer to: * Convention (norm), a custom or tradition, a standard of presentation or conduct ** Treaty, an agreement in international law * C ...
: 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 the following ranks for these categories: ---- :Superfamily ''
Family In human society A society is a Social group, group of individuals involved in persistent Social relation, social interaction, or a large social group sharing the same spatial or social territory, typically subject to the same Politic ...
'' :
Subfamily In biological classification In biology, taxonomy () is the scientific study of naming, defining (Circumscription (taxonomy), circumscribing) and classifying groups of biological organisms based on shared characteristics. Organisms are grou ...
:
Tribe The term tribe is used in many different contexts to refer to a category of human social group. The predominant usage of the term is in the discipline of anthropology. The definition is contested, in part due to conflicting theoretical understa ...
: Subtribe ---- ''
Genus Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank In biological classification In biology, taxonomy () is the scientific study of naming, defining (Circumscription (taxonomy), circumscribing) and classifying gr ...
'' :
Subgenus In biology, a subgenus (plural: subgenera) is a taxonomic rank directly below genus. In the International Code of Zoological Nomenclature, a subgeneric name can be used independently or included in a binomen, species name, in parentheses, placed ...
---- ''
Species In biology, a species is the basic unit of biological classification, classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individu ...

Species
'' :
Subspecies In biological classification In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interacti ...
---- 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. Among "genus-group names" and "species-group names" no further ranks are officially allowed. Zoologists sometimes use additional terms such as ''species group'', ''species subgroup'', ''species complex'' and ''superspecies'' for convenience as extra, but unofficial, ranks between the subgenus and species levels in
taxa In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechani ...
with many species, e.g. the genus ''
Drosophila ''Drosophila'' () is a genus of fly, flies, belonging to the family (biology), family Drosophilidae, whose members are often called "small fruit flies" or (less frequently) pomace flies, vinegar flies, or wine flies, a reference to the character ...

Drosophila
''. (Note the potentially confusing use of "species group" as both a category of ranks as well as an unofficial rank itself.) At higher ranks (family and above) a lower level may be denoted by adding the prefix "''infra''", meaning ''lower'', to the rank. For example, ''infra''order (below suborder) or ''infra''family (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 In taxonomy, binomial nomenclature ("two-term naming system"), also called nomenclature ("two-name naming system") or binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, bot ...
): generic name +
specific nameSpecific name may refer to: * in Database management systems, a system-assigned name that is unique within a particular database In Taxonomy (biology), taxonomy, either of these two meanings, each with its own set of rules: * Specific name (botany), ...
; for example ''Canis lupus''. * A subspecies has a name composed of three parts (a trinomial name or
trinomen In zoological nomenclature The International Code of Zoological Nomenclature (ICZN) is a widely accepted Convention (norm), convention in zoology that rules the formal scientific name, scientific naming of organisms treated as animals. It is a ...
): generic name + specific name +
subspecific name In zoological nomenclature, a subspecific name is the third part of a trinomen. In zoology Zoology ()The pronunciation of zoology as is typically regarded as nonstandard, though it is not uncommon. is the branch of biology that studies the an ...
; for example ''Canis lupus italicus''. 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 The ''International Code of Nomenclature for algae, fungi, and plants'' (ICN) is the set of rules and recommendations dealing with the formal botanical name A botanical name is a formal scientific name Science (from the Latin Latin (, ...
(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 The ''International Code of Nomenclature for Cultivated Plants'' (ICNCP), also known as the Cultivated Plant Code, is a guide to the rules and regulations for naming cultigens, plants whose origin or selection is primarily due to intentional huma ...
:
cultivar groupA Group (previously cultivar-groupInternational Code of Nomenclature for Cultivated Plants, 4th edition (1969), 5th edition (1980) and 6th edition (1995)) is a formal category in the ''International Code of Nomenclature for Cultivated Plants The ' ...
,
cultivar A cultivar is a type of plant that people have bred for desired traits, which are reproduced in each new generation by a method such as grafting, tissue culture or carefully controlled seed production. Most cultivars arise from purposeful human ...
, 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 name.


Names of botanical taxa

Taxa at the rank of genus and above have a
botanical name A botanical name is a formal scientific name In taxonomy Taxonomy (general) is the practice and science of classification of things or concepts, including the principles that underlie such classification. The term may also refer to a specif ...
in one part (unitary name); those at the rank of species and above (but below genus) have a botanical name in two parts ( binary name); all taxa below the rank of species have a botanical name in three parts (an
infraspecific name In botany Botany, also called , plant biology or phytology, is the science Science (from the Latin word ''scientia'', meaning "knowledge") is a systematic enterprise that Scientific method, builds and Taxonomy (general), organizes kno ...
). To indicate the rank of the infraspecific name, a "connecting term" is needed. Thus ''Poa secunda'' subsp. ''juncifolia'', where "subsp." is an abbreviation for "subspecies", is the name of a subspecies of ''
Poa secunda ''Poa secunda'' (variously known by the common names of Sandberg bluegrass, alkali bluegrass, big bluegrass, Canby's bluegrass, Nevada bluegrass, one-sided bluegrass, Pacific bluegrass, pine blugrass, slender bluegrass, wild bluegrass, and curly ...
''. Hybrids can be specified either by a "hybrid formula" that specifies the parentage, or may be given a name. For hybrids receiving 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.html" ;"title="atin for "cohort"; see also cohort study">atin for "cohort"; 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 of orders. * "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) * "Subfamily is substituted for "suborder" (subordo) under certain conditions where the modern meaning of "suborder" was not intended. (Article 19.2) * In a publication prior to 1 January 1890, if only one infraspecific rank is used, it is considered to be that of variety. (Article 37.4) This commonly applies to publications that labelled infraspecific taxa with Greek letters, α, β, γ, ...


Examples

Classifications of five species follow: the
fruit fly
fruit fly
familiar in genetics laboratories (''Drosophila melanogaster''),
human Humans (''Homo sapiens'') are the most abundant and widespread species In biology, a species is the basic unit of biological classification, classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A speci ...

human
s (''Homo sapiens''), the
pea The pea is most commonly the small spherical seed A seed is an embryonic plant enclosed in a protective outer covering. The formation of the seed is part of the process of reproduction Reproduction (or procreation or breeding) is ...

pea
s used by
Gregor Mendel Gregor Johann Mendel (; cs, Řehoř Jan Mendel; 20 July 1822 – 6 January 1884) was a meteorologist, mathematician, biologist, AugustinianAugustinian may refer to: *Augustinians Augustinians are members of Christian religious orders th ...

Gregor Mendel
in his discovery of
genetics Genetics is a branch of biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, ...

genetics
(''Pisum sativum''), the "fly agaric" mushroom ''
Amanita muscaria ''Amanita muscaria'', commonly known as the fly agaric or fly amanita, is a basidiomycete of the genus ''Amanita''. It is also a muscimol mushroom. Native throughout the temperate and boreal ecosystem, boreal regions of the Northern Hemisphere, ...

Amanita muscaria
'', and the bacterium ''
Escherichia coli ''Escherichia coli'' (),Wells, J. C. (2000) Longman Pronunciation Dictionary. Harlow ngland Pearson Education Ltd. also known as ''E. coli'' (), is a Gram-negative bacteria, Gram-negative, Facultative anaerobic organism, facultative anaer ...

Escherichia coli
''. The eight major ranks are given in bold; a selection of minor ranks are given as well. ;Table notes *In order to keep the table compact and avoid disputed technicalities, some common and uncommon intermediate ranks are omitted. For example, the
mammals Mammals (from Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the power of the R ...
of Europe, Africa, and upper North America are in class
Mammalia Mammals (from Latin language, Latin , 'breast') are a group of vertebrate animals constituting the class (biology), class Mammalia (), and characterized by the presence of mammary glands which in Female#Mammalian female, females produce milk ...

Mammalia
, legion
Cladotheria Cladotheria is a group ( legion) of mammals that includes the ancestor of Dryolestida, Amphitheriida, Peramuridae and Zatheria (living therians plus all of its ancestors). Phylogeny Below is a cladogram from Rowe (1988) and Malcolm McKenna, McK ...
, sublegion
Zatheria Zatheria is a group (sublegion) of mammal Mammals (from Latin language, Latin , 'breast') are a group of vertebrate animals constituting the class (biology), class Mammalia (), and characterized by the presence of mammary glands which in F ...
, infralegion
Tribosphenida Tribosphenida is a group (infralegion) of mammals that includes the ancestor of ''Hypomylos'', Aegialodontia and Theria (the last common ancestor of marsupials and placentals plus all of its descendants). Its current definition is more or less syn ...
, subclass
Theria Theria (; Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is approximatel ...
, clade
Eutheria Eutheria (; from Greek , 'good, right' and , 'beast'; ) is the clade consisting of all Theria, therian mammals that are more closely related to Placentalia, placentals than to Marsupial, marsupials. Eutherians are distinguished from noneuther ...

Eutheria
, clade
Placentalia The infraclass Placentalia is one of the three extant subdivisions of the class of animals Mammalia; the other two are Monotremata and Marsupialia. Placentalia contains the vast majority of extant mammals. Placentals are partly distinguished fro ...

Placentalia
– but only Mammalia and Theria are in the table. Legitimate arguments might arise if the commonly used clades Eutheria and Placentalia were both included, over which is the rank "infraclass" and what the other's rank should be, or whether the two names are synonyms. *The ranks of higher taxa, especially intermediate ranks, are prone to revision as new information about relationships is discovered. For example, the
flowering plant Flowering plants include multiple members of the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greec ...

flowering plant
s 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 Mammalia is a class of animal within the phylum Chordata. Mammal classification has been through several iterations since Carl Linnaeus initially defined the class. No classification system is universally accepted; McKenna & Bell (1997) and Wilson ...
for a discussion. These differences arise because there are few available ranks and many 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
morph Morph may refer to: Astronomy * Morphs collaboration, a collaboration that studied the evolution of spiral galaxies using the Magellan and the Hubble Space Telescope Biology * Morph (zoology), a visual or behavioral difference between organi ...
s (for example ''Corvus corax varius'' morpha ''leucophaeus'', the pied raven). Plants may be classified into subspecies (for example, ''Pisum sativum'' subsp. ''sativum'', the garden pea) or varieties (for example, ''Pisum sativum'' var. ''macrocarpon'', snow pea), with cultivated plants getting a
cultivar A cultivar is a type of plant that people have bred for desired traits, which are reproduced in each new generation by a method such as grafting, tissue culture or carefully controlled seed production. Most cultivars arise from purposeful human ...
name (for example, ''Pisum sativum'' var. ''macrocarpon'' 'Snowbird'). Bacteria may be classified by strains (for example ''Escherichia coli'' O157:H7, a strain that can cause
food poisoning Foodborne illness (also foodborne disease and colloquially referred to as food poisoning) is any Disease, illness resulting from the spoilage of food contaminant, contaminated food, pathogenic bacteria, viruses, or parasites that contaminate food, ...
).


Terminations of names

Taxa In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechani ...
above the genus level are often given names based on the
type genus In biological taxonomy the type genus is the genus Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank In biological classification In biology, taxonomy () is the scientific study of naming, defining (Circumsc ...
, with a standard termination. The terminations used in forming these names depend on the kingdom (and sometimes the phylum and class) as set out in the table below. Pronunciations given are the most Anglicized. More Latinate pronunciations are also common, particularly rather than for stressed ''a''. ;Table notes: * 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 In biological taxonomy the type genus is the genus Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank In biological classification In biology, taxonomy () is the scientific study of naming, defining (Circumsc ...
of that taxon, with a standard ending. For example, the rose family,
Rosaceae Rosaceae , the rose family, is a medium-sized family In , family (from la, familia) is a of people related either by (by recognized birth) or (by marriage or other relationship). The purpose of families is to maintain the well-being ...
, 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
Gymnosperm The gymnosperms ( lit. revealed seeds) are a group of seed-producing plants that includes conifers Conifers are a group of cone-bearing seed plants, a subset of gymnosperms. Scientifically, they make up the division Pinophyta (), also ...
ae or
Fungi A fungus (plural The plural (sometimes abbreviated An abbreviation (from Latin ''brevis'', meaning ''short'') is a shortened form of a word or phrase, by any method. It may consist of a group of letters, or words taken from the full ...

Fungi
). * For animals, there are standard suffixes for taxa only up to the rank of superfamily. Uniform suffix has been suggested (but not recommended) in AAAS as ''-ida'' for orders, for example; protozoologists seem to adopt this system. Many metazoan (higher animals) orders also have such suffix, e.g.
Hyolithida The Hyolithida are lophophorates, one of the two orders of hyolithid, the other being the Orthothecida. Most of our knowledge of the hyolithids comes from studies on the Hyolithida. Both orders had an operculum (gastropod), operculum that was not ...
and Nectaspida (Naraoiida). * Forming a name based on a generic name may be not straightforward. For example, the has the genitive , thus the genus ''Homo'' (human) is in the
Hominidae The Hominidae (), whose members are known as great apes or hominids (), are a taxonomic family In , family (from la, familia) is a of people related either by (by recognized birth) or (by marriage or other relationship). The purpose ...
, not "Homidae". * The ranks of epifamily, infrafamily and infratribe (in animals) are used where the complexities of phyletic branching require finer-than-usual distinctions. Although they fall below the rank of superfamily, they are not regulated under the International Code of Zoological Nomenclature and hence do not have formal standard endings. The suffixes listed here are regular, but informal. * In virology, the formal endings for taxa of
viroid Viroids are small single-stranded, circular RNA Circular RNA (or circRNA) is a type of single-stranded RNA which, unlike linear RNA, forms a covalently closed continuous loop. In circular RNA, the 3' and 5' ends normally present in an RNA molec ...
s and of satellite nucleic acids are similar to viruses, only -vir- is replaced by -viroid-, -satellit-.


All ranks

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 Nomenclature codes or codes of nomenclature are the various rulebooks that govern biological taxonomic Taxonomy (general) is the practice and science of classification of things or concepts, including the principles that underlie such classifica ...
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 Domain may refer to: Mathematics *Domain of a function In mathematics, the domain of a Function (mathematics), function is the Set (mathematics), set of inputs accepted by the function. It is sometimes denoted by \operatorname(f), where is th ...
or Empire ** Subdomain (biology) *
Realm A realm is a community or territory over which a sovereign Sovereign is a title which can be applied to the highest leader in various categories. The word is borrowed from Old French ''souverain'', which is ultimately derived from the Latin ...
(in virology) ** Subrealm (in virology) *
Hyperkingdom In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechanisms, ...
** Superkingdom ***
Kingdom Kingdom may refer to: Monarchy * A type of monarchy * A realm ruled by: **A king, during the reign of a male monarch **A queen regnant, during the reign of a female monarch Taxonomy * Kingdom (biology), a category in biological taxonomy Arts an ...
****
Subkingdom In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechanisms, ...
***** Infrakingdom ****** Parvkingdom *
Superphylum In biology, a phylum (; plural The plural (sometimes abbreviated An abbreviation (from Latin ''brevis'', meaning ''short'') is a shortened form of a word or phrase, by any method. It may consist of a group of letters, or words taken fr ...
, or superdivision (in botany) **
Phylum In biology, a phylum (; plural The plural (sometimes list of glossing abbreviations, abbreviated ), in many languages, is one of the values of the grammatical number, grammatical category of number. The plural of a noun typically denotes a q ...
, or
division Division or divider may refer to: Mathematics *Division (mathematics), the inverse of multiplication *Division algorithm, a method for computing the result of mathematical division Military *Division (military), a formation typically consisting o ...
(in botany) ***
Subphylum In zoological nomenclature The International Code of Zoological Nomenclature (ICZN) is a widely accepted Convention (norm), convention in zoology that rules the formal scientific name, scientific naming of organisms treated as animals. It is als ...
, or subdivision (in botany) **** Infraphylum, or infradivision (in botany) ***** Microphylum * Superclass **
Class Class or The Class may refer to: Common uses not otherwise categorized * Class (biology), a taxonomic rank * Class (knowledge representation), a collection of individuals or objects * Class (philosophy), an analytical concept used differently f ...
*** Subclass ****
Infraclass In biological classification In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, ...
***** Subterclass ****** Parvclass * Superdivision (in zoology) ** Division (biology), Division (in zoology)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 th
Benton classification of vertebrates
(2005).
*** Subdivision (in zoology) **** Infradivision (in zoology) * Superlegion (in zoology) ** Legion (taxonomy), Legion (in zoology) *** Sublegion (in zoology) **** Infralegion (in zoology) * Supercohort (in zoology)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.
** Cohort (in zoology) *** Subcohort (in zoology) **** Infracohort (in zoology) * Gigaorder (in zoology) ** Magnorder or megaorder (in zoology)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. *** Grandorder or capaxorder (in zoology) **** Mirorder or hyperorder (in zoology) ***** Superorder ****** Series (for fish) ******* Order (biology), Order ******** Parvorder (position in some zoological classifications) ********* Nanorder (in zoology) ********** Hypoorder (in zoology) *********** Minorder (in zoology) ************ Suborder ************* Infraorder ************** Parvorder (usual position), or microorder (in zoology) * Section (in zoology) ** Subsection (in zoology) * Gigafamily (in zoology) ** Megafamily (in zoology) *** Grandfamily (in zoology) **** Hyperfamily (in zoology) ***** Superfamily ****** Epifamily (in zoology) ******* Series (for Lepidoptera) ******** Group (for Lepidoptera) *********
Family In human society A society is a Social group, group of individuals involved in persistent Social relation, social interaction, or a large social group sharing the same spatial or social territory, typically subject to the same Politic ...
**********
Subfamily In biological classification In biology, taxonomy () is the scientific study of naming, defining (Circumscription (taxonomy), circumscribing) and classifying groups of biological organisms based on shared characteristics. Organisms are grou ...
*********** Infrafamily * Supertribe **
Tribe The term tribe is used in many different contexts to refer to a category of human social group. The predominant usage of the term is in the discipline of anthropology. The definition is contested, in part due to conflicting theoretical understa ...
*** Subtribe **** Infratribe * Supergenus **
Genus Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank In biological classification In biology, taxonomy () is the scientific study of naming, defining (Circumscription (taxonomy), circumscribing) and classifying gr ...
***
Subgenus In biology, a subgenus (plural: subgenera) is a taxonomic rank directly below genus. In the International Code of Zoological Nomenclature, a subgeneric name can be used independently or included in a binomen, species name, in parentheses, placed ...
**** Section (botany), Section (in botany) ***** Subsection (in botany) ****** Series (botany), Series (in botany) ******* Subseries (in botany) * Superspecies or Cryptic species complex, Species-group **
Species In biology, a species is the basic unit of biological classification, classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individu ...

Species
***
Subspecies In biological classification In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interacti ...
, or ''forma specialis'' (for fungi), or pathovar (for bacteria)) **** Variety (botany), Variety or ''varietas'' (in botany); or Form (zoology), form or Morph (zoology), morph (in zoology) or form (zoology), aberration (in lepidopterology) ***** Subvariety (in botany) ****** Form (botany), Form or ''forma'' (in botany) ******* Subform (in 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 groups. 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 phylogenetics, phylogeny of the organisms under discussion, but this is not a requirement. A classification in which all taxa have formal ranks cannot adequately reflect knowledge about phylogeny. Since taxon names are dependent on ranks in traditional Linnaean systems of classification, taxa without ranks cannot be given names. Alternative approaches, such as using circumscriptional names, avoid this problem. The theoretical difficulty with superimposing taxonomic ranks over evolutionary trees is manifested as the Taxonomic boundary paradox, boundary paradox which may be illustrated by Darwinian evolutionary models. 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).Stuessy, T.F. (2009). ''Plant Taxonomy: The Systematic Evaluation of Comparative Data.'' 2nd ed. Columbia University Press, p. 175.Brusca, R.C. & Brusca, G.J. (2003). ''Invertebrates''. 2nd ed. Sunderland, Massachusetts: Sinauer Associates, pp. 26–27. 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.


Mnemonic

There are several acronyms intended to help memorise the taxonomic hierarchy, such as "King PhillipPhilip II of Spain came over for great spaghetti". See taxonomy mnemonic.


See also

* Breed * Catalogue of Life (a database) * Cladistics * Landrace * Tree of life (biology)


Footnotes


References


Bibliography

* * Michael J. Benton, Benton, Michael J. 2005. ''Vertebrate Palaeontology'', 3rd ed. Oxford: Blackwell Publishing. . * Brummitt, R.K., and C.E. Powell. 1992. ''Authors of Plant Names''. Royal Botanic Gardens, Kew. * Robert L. Carroll, Carroll, Robert L. 1988. ''Vertebrate Paleontology and Evolution''. New York: W.H. Freeman & Co. * Eugene S. Gaffney, Gaffney, Eugene S., and Peter A. Meylan. 1988. "A phylogeny of turtles". In M.J. Benton (ed.), ''The Phylogeny and Classification of the Tetrapods, Volume 1: Amphibians, Reptiles, Birds'', 157–219. Oxford: Clarendon Press. * Haris Abba Kabara. 2001. ''Karmos hand book for botanical names''. * Lambert, David. 1990. ''Dinosaur Data Book''. Oxford: Facts on File & British Museum (Natural History). * McKenna, Malcolm C., and Susan K. Bell (editors). 1997. ''Classification of Mammals Above the Species Level''. New York: Columbia University Press. * Milner, Andrew. 1988. "The relationships and origin of living amphibians". In M.J. Benton (ed.), ''The Phylogeny and Classification of the Tetrapods, Volume 1: Amphibians, Reptiles, Birds'', 59–102. Oxford: Clarendon Press. * Novacek, Michael J. 1986. "The skull of leptictid insectivorans and the higher-level classification of eutherian mammals". ''Bulletin of the American Museum of Natural History'' 183: 1–112. * Sereno, Paul C. 1986. "Phylogeny of the bird-hipped dinosaurs (Order Ornithischia)". ''National Geographic Research'' 2: 234–56. * Willis, K.J., and J.C. McElwain. 2002. ''The Evolution of Plants''. Oxford University Press. {{Taxonomic ranks Botanical nomenclature Plant taxonomy, 1rank40 Zoological nomenclature, R Biology terminology