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[[Image:Biological classification L Pengo.svg|right|150px]]
'''Scientific classification''' or '''biological classification''' is a method by which [[biologist]]s group and categorize [[species]] of [[organism]]s. Scientific classification can also be called scientific taxonomy, but should be distinguished from [[folk taxonomy]], which lacks scientific basis. Modern classification has its root in the work of [[Carolus Linnaeus]], who grouped species according to shared physical characteristics. These groupings have since been revised to improve consistency with the [[Charles Darwin|Darwinian]] principle of [[common descent]]. [[Molecular systematics]], which uses [[DNA sequences]] as data, has driven many recent revisions and is likely to continue to do so. Scientific classification belongs to the science of [[taxonomy]] or [[systematics|biological systematics]].
== Early systems ==
The earliest known system of classifying forms of life comes from the Greek philosopher [[Aristotle]], who classified all living organisms known at that time as either a plant or an animal. He further classified animals based on their means of transportation (air, land, or water).
In 1172 Ibn Rushd ([[Averroes]]), who was a judge ([[Qadi]]) in [[Seville]], translated and abridged Aristotle's book ''de Anima'' (''[[On the Soul]]'') into Arabic. His original commentary is now lost, but its translation into Latin by [[Michael Scot]] survives.
An important advance was made by the Swiss professor, [[Conrad von Gesner]] (1516–1565). Gesner's work was a critical compilation of life known at the time.
The exploration of parts of the [[New World]] next brought to hand descriptions and specimens of many novel forms of animal life. In the latter part of the 16th century and the beginning of the 17th, careful study of animals commenced, which, directed first to familiar kinds, was gradually extended until it formed a sufficient body of knowledge to serve as an anatomical basis for classification. Advances in using this knowledge to classify living beings bear a debt to the research of medical anatomists, such as [[Hieronymus Fabricius|Fabricius]] (1537–1619), [[Petrus Severinus]] (1580–1656), [[William Harvey]] (1578–1657), and [[Edward Tyson]] (1649–1708). Advances in classification due to the work of [[entomologist]]s and the first microscopists is due to the research of people like [[Marcello Malpighi]] (1628–1694), [[Jan Swammerdam]] (1637–1680), and [[Robert Hooke]] (1635–1702). [[Lord Monboddo]] (1714-1799) was one of the early abstract thinkers whose works illustrate knowledge of species relationships and who foreshadowed the theory of [[evolution]]. Successive developments in the history of insect classification may be followed on the website<ref name="">{{cite web|url = http://www.bio.pu.ru/win/entomol/KLUGE/nom/-nom-F.htm | accessdate = 2006-09-09 | title = NOMINA CIRCUMSCRIBENTIA INSECTORUM}}</ref> by clicking on succeeding works in chronological order.
=== Early methodists ===
Since late in the 15th century, a number of authors had become concerned with what they called ''methodus,'' or method. By method they meant an arrangement of minerals, plants, and animals according to the principles of logical division. The term ''methodists'' was coined by [[Carolus Linnaeus]] in his ''Bibliotheca Botanica'' to denote the authors who care about the principles of classification (in contrast to the mere ''collectors'' who are concerned primarily with the description of plants paying little or no attention to their arrangement into genera, etc). Important early methodists were an Italian philosopher, physician, and botanist [[Andrea Caesalpino]], an English naturalist [[John Ray]], a German physician and botanist [[Augustus Quirinus Rivinus]], and a French physician, botanist, and traveller [[Joseph Pitton de Tournefort]].
[[Andrea Caesalpino]] ([[1519]]–[[1603]]) in his ''De plantis libri XVI'' ([[1583]]) proposed the first methodical arrangement of plants. On the basis of the structure of [[Trunk (botany)|trunk]] and [[fructification]] he divided plants into fifteen "higher genera".
[[John Ray]] ([[1627]]–[[1705]]) was an English naturalist who published important works on plants, animals, and natural theology. The approach he took to the classification of plants in his [[Historia Plantarum]] was an important step towards modern taxonomy. Ray rejected the system of dichotomous division by which species were classified according to a pre-conceived, either/or type system, and instead classified plants according to similarities and differences that emerged from observation.
Both Caesalpino and Ray used traditional plant names and thus, the name of a plant did not reflect its taxonomic position (e.g. even though the [[apple]] and the [[peach]] belonged to different "higher genera" of John Ray's ''methodus'', both retained their traditional names ''Malus'' and ''Malus Persica'' respectively). A further step was taken by Rivinus and Pitton de Tournefort who made [[genus]] a distinct rank within taxonomic hierarchy and introduced the practice of naming the plants according to their genera.
[[Augustus Quirinus Rivinus]] ([[1652]]–[[1723]]), in his classification of plants based on the characters of the [[flower]], introduced the category of [[Order (biology)|order]] (corresponding to the "higher" genera of John Ray and Andrea Caesalpino). He was the first to abolish the ancient division of plants into [[herb]]s and [[tree]]s and insisted that the true method of division should be based on the parts of the [[fructification]] alone. Rivinus extensively used [[dichotomous key]]s to define both orders and genera. His method of naming plant species resembled that of Joseph Pitton de Tournefort. The names of all plants belonging to the same genus should begin with the same word (generic name). In the genera containing more than one species the first species was named with generic name only, while the second, etc were named with a combination of the generic name and a modifier (''differentia specifica'').
[[Joseph Pitton de Tournefort]] ([[1656]]–[[1708]]) introduced an even more sophisticated hierarchy of class, section, genus, and species. He was the first to use consistently the uniformly composed species names which consisted of a generic name and a many-worded diagnostic phrase ''differentia specifica.'' Unlike Rivinus, he used ''differentiae'' with all species of polytypic genera.
===Linnaeus===
Two years after John Ray's death, [[Carolus Linnaeus]] ([[1707]]–[[1778]]) was born. His great work, the ''[[Systema Naturae]]'', ran through twelve editions during his lifetime (1st ed. [[1735]]). In this work, nature was divided into three kingdoms: mineral, vegetable and animal. Linnaeus used five ranks: class, order, genus, species, and variety.
He abandoned long descriptive names of classes and orders and two-word generic names (e. g. ''Bursa pastoris'') still used by his immediate predecessors (Rivinus and Pitton de Tournefort) and replaced them with single-word names, provided genera with detailed diagnoses (''characteres naturales''), and reduced numerous varieties to their species, thus saving botany from the chaos of new forms produced by [[horticulturalist]]s.
Linnaeus is best known for his introduction of the method still used to formulate the [[scientific name]] of every species. Before Linnaeus, long many-worded names (composed of a generic name and a ''differentia specifica'') had been used, but as these names gave a description of the species, they were not fixed. In his ''Philosophia Botanica'' (1751) Linnaeus took every effort to improve the composition and reduce the length of the many-worded names by abolishing unnecessary rhetorics, introducing new descriptive terms and defining their meaning with an unprecedented precision. In the late 1740s Linnaeus began to use a parallel system of naming species with ''nomina trivialia.'' ''Nomen triviale'', a trivial name, was a single- or two-word epithet placed on the margin of the page next to the many-worded "scientific" name. The only rules Linnaeus applied to them was that the trivial names should be short, unique within a given genus, and that they should not be changed. Linnaeus consistently applied ''nomina trivialia'' to the species of plants in ''[[Species Plantarum]]'' (1st edn. 1753) and to the species of animals in the 10th edition of ''[[Systema Naturae]]'' (1758).
By consistently using these specific epithets, Linnaeus separated nomenclature from taxonomy. Even though the parallel use of ''nomina trivialia'' and many-worded descriptive names continued until late in the eighteenth century, it was gradually replaced by the practice of using shorter proper names combined of the generic name and the trivial name of the species. In the nineteenth century, this new practice was codified in the first Rules and Laws of Nomenclature, and the 1st edn. of ''[[Species Plantarum]]'' and the 10th edn. of ''[[Systema Naturae]]'' were chosen as starting points for the Botanical and Zoological Nomenclature respectively. This convention for naming species is referred to as [[binomial nomenclature]].
Today, nomenclature is regulated by [[Nomenclature Codes]], which allows names divided into ranks; see [[rank (botany)]] and [[rank (zoology)]].
== Modern developments ==
Whereas Linnaeus classified for ease of identification, it is now generally accepted that classification should reflect the Darwinian principle of [[common descent]].
Since the 1960s a trend called [[Cladistics|cladistic]] taxonomy (or [[cladistics]] or cladism) has emerged, arranging taxa in an [[evolutionary tree]]. If a [[taxon]] includes all the descendants of some ancestral form, it is called [[monophyletic]], as opposed to [[paraphyletic]]. Other groups are called [[polyphyletic]].
A new formal code of nomenclature, the [[PhyloCode]], is currently under development, intended to deal with clades rather than taxa. It is unclear, should this be implemented, how the different codes will coexist.
[[Domain (biology)|Domains]] are a relatively new grouping. The [[three-domain system]] was first invented in 1990, but not generally accepted until later. Now, the majority of biologists accept the domain system, but a large minority use the five-kingdom method. One main characteristic of the three-domain method is the separation of Archaea and Bacteria, previously grouped into the single kingdom Bacteria (sometimes Monera). A small minority of scientists add Archaea as a sixth kingdom but do not accept the domain method.
== Examples ==
The usual classifications of five species follow: the [[Drosophila melanogaster|fruit fly]] so familiar in genetics laboratories (''Drosophila melanogaster''), [[human]]s (''Homo sapiens''), the [[pea]]s used by [[Gregor Mendel]] in his discovery of [[genetics]] (''Pisum sativum''), the "fly agaric" mushroom ''[[Amanita muscaria]]'', and the bacterium ''[[Escherichia coli]]''. The eight major ranks are given in bold; a selection of minor ranks are given as well.
{| border="1" cellpadding="4" cellspacing="0" style="margin: 0.5em 1em 0.5em 0; background: #f9f9f9; border: 1px #aaa solid; border-collapse: collapse;"
|- style="background:palegrey; border: 1px;"
!style="width:16%; background:#f3f3f3;"|Rank
!style="width:16%; background:#f3f3f3;"|[[Drosophila melanogaster|Fruit fly]]
!style="width:16%; background:#f3f3f3;"|[[Human]]
!style="width:16%; background:#f3f3f3;"|[[Pea]]
!style="width:16%; background:#f3f3f3;"|[[Fly Agaric]]
!style="width:16%; background:#f3f3f3;"|''[[Escherichia coli|E. coli]]''
|-
|style="background:#f2f2f2;"|'''[[Domain (biology)|Domain]]'''
|[[Eukaryota]]
|[[Eukaryota]]
|[[Eukaryota]]
|[[Eukaryota]]
|[[Bacteria]]
|-
|style="background:#f2f2f2;"|'''[[Kingdom (biology)|Kingdom]]'''
|[[Animal]]ia
|[[Animal]]ia
|[[Plant]]ae
|[[Fungi]]
|[[Monera]]
|-
|style="background:#f2f2f2;"|'''[[Phylum]]''' or '''[[Division (biology)|Division]]'''
|[[Arthropod]]a
|[[Chordate|Chordata]]
|[[Flowering plant|Magnoliophyta]]
|[[Basidiomycota]]
|[[Proteobacteria]]
|-
|style="background:#f2f2f2;"|[[Subphylum]] or subdivision
|[[Hexapoda]]
|[[Vertebrate|Vertebrata]]
|[[Magnoliophytina]]
|[[Hymenomycotina]]
|
|-
|style="background:#f2f2f2;"|'''[[Class (biology)|Class]]'''
|[[Insect]]a
|[[Mammal]]ia
|[[Magnoliopsida]]
|[[Homobasidiomycetae]]
|[[Proteobacteria]]
|-
|style="background:#f2f2f2;"|Subclass
|[[Pterygota]]
|[[Eutheria]]
|[[Magnoliidae]]
|[[Hymenomycetes]]
|[[Gammaproteobacteria]]
|-
|style="background:#f2f2f2;"|'''[[Order (biology)|Order]]'''
|[[Diptera]]
|[[Primate]]s
|[[Fabales]]
|[[Agaricales]]
|[[Enterobacteriaceae|Enterobacteriales]]
|-
|style="background:#f2f2f2;"|Suborder
|[[Brachycera]]
|[[Haplorrhini]]
|[[Fabineae]]
|[[Agaricineae]]
|
|-
|style="background:#f2f2f2;"|'''[[Family (biology)|Family]]'''
|[[Drosophilidae]]
|[[Hominidae]]
|[[Fabaceae]]
|[[Amanitaceae]]
|[[Enterobacteriaceae]]
|-
|style="background:#f2f2f2;"|Subfamily
|[[Drosophilinae]]
|[[Homininae]]
|[[Faboideae]]
|[[Amanitoideae]]
|
|-
|style="background:#f2f2f2;"|'''[[Genus]]'''
|''[[Drosophila]]''
|''[[Homo (genus)|Homo]]''
|''[[Pisum]]''
|''[[Amanita]]''
|''[[Escherichia]]''
|-
|style="background:#f2f2f2;"|'''[[Species]]'''
|''[[Drosophila melanogaster|D. melanogaster]]''
|''[[Homo sapiens|H. sapiens]]''
|''[[Pisum sativum|P. sativum]]''
|''[[Amanita muscaria|A. muscaria]]''
|''[[Escherichia coli|E. coli]]''
|}
Notes:
*Higher taxa and especially intermediate taxa are prone to revision as new information about relationships is discovered. For example, the traditional classification of primates (class Mammalia — subclass Theria — infraclass Eutheria — order Primates) is challenged by new classifications such as McKenna and Bell (class Mammalia — subclass Theriformes — infraclass Holotheria — 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 [[morph (zoology)|morph]]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]] name (for example, ''Pisum sativum'' var. ''macrocarpon'' 'Snowbird'). Bacteria may be classified by [[strain (biology)|strains]] (for example [[Escherichia coli O157:H7|''Escherichia coli'' O157:H7]], a strain that can cause [[food poisoning]]).
*A popular mnemonic to remember the taxa is ''"King Philip can only find [[girl scout]]s"'' (Kingdom, Phylum, Class, Order, Family, Genus, Species).
==Terminations of names==
[[Taxon|Taxa]] above the genus level are often given names based on the [[type genus]], 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.
{| border="1" cellpadding="4" cellspacing="0" style="margin: 0.5em 1em 0.5em 0; background: #f9f9f9; border: 1px #aaa solid; border-collapse: collapse;"
|-
!style="background:#f3f3f3;"|Rank
!style="background:#f3f3f3;"|[[Plant]]s
!style="background:#f3f3f3;"|[[Alga]]e
!style="background:#f3f3f3;"|[[Fungi]]
!style="background:#f3f3f3;"|[[Animal]]s
!style="background:#f3f3f3;"|[[Bacteria]]<ref>[http://www.bacterio.cict.fr/classificationgenera.html Bacteriologocal Code (1990 Revision)]</ref>
|-
|style="background:#f2f2f2;"|'''Division/Phylum'''
| align="center" colspan="2" | -phyta
| -mycota
|
|
|-
|style="background:#f2f2f2;"|'''Subdivision/Subphylum'''
| align="center" colspan="2" | -phytina
| -mycotina
|
|
|-
|style="background:#f2f2f2;"|'''Class'''
| -opsida
| -phyceae
| -mycetes
|
| -ia
|-
|style="background:#f2f2f2;"|'''Subclass'''
| -idae
| -phycidae
| -mycetidae
|
| -idae
|-
|style="background:#f2f2f2;"|'''Superorder'''
|align="center" colspan="3"| -anae
|
|
|-
|style="background:#f2f2f2;"|'''Order'''
|align="center" colspan="3"| -ales
|
| -ales
|-
|style="background:#f2f2f2;"|'''Suborder'''
|align="center" colspan="3"| -ineae
|
| -ineae
|-
|style="background:#f2f2f2;"|'''Infraorder'''
|align="center" colspan="3"| -aria
|
|
|-
|style="background:#f2f2f2;"|'''Superfamily'''
|align="center" colspan="3"| -acea
| -oidea
|
|-
|style="background:#f2f2f2;"|'''Family'''
|align="center" colspan="3"| -aceae
| -idae
| -aceae
|-
|style="background:#f2f2f2;"|'''Subfamily'''
|align="center" colspan="3"| -oideae
| -inae
| -oideae
|-
|style="background:#f2f2f2;"|'''Tribe/Infrafamily'''
|align="center" colspan="3"| -eae
| -ini
| -eae
|-
|style="background:#f2f2f2;"|'''Subtribe'''
|align="center" colspan="3"| -inae
| -ina
| -inae
|}
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]] 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 formed from a family name, or are descriptive (like [[Gymnospermae]] or [[Fungi]]).
* For animals, there are standard suffixes for taxa only up to the rank of superfamily (ICZN article 27.2).
* Forming a name based on a generic name may be not straightforward. For example, the [[Latin]] "''homo''" has the genitive "''hominis''", thus the genus "''Homo''" (human) is in the [[Hominidae]], not "Homidae".
==Authorities (author citation)==
The name of any taxon may be followed by the "authority" for the name, that is, the name of the author who first published a valid description of it. These names are frequently abbreviated: the abbreviation "L." is universally accepted for Linnaeus, and in botany there is a regulated list of standard abbreviations (see [[list of botanists by author abbreviation]]). The system for assigning authorities is slightly different in different branches of biology: see [[author citation (botany)]] and [[author citation (zoology)]]. However, it is standard that if a name or placement has been changed since the original description, the first authority's name is placed in parentheses and the authority for the new name or placement may be placed after it (usually only in botany).
==Bibliography==
<references />
===History===
*Atran, S. ''Cognitive foundations of natural history: towards an anthropology of science.'' Cambridge: Cambridge Univ. Press. 1990. xii+360 p. ISBN [http://www.amazon.com/gp/product/0521372933 0521372933]
*Larson, J. L. ''Reason and experience. The representation of Natural Order in the work of Carl von Linne.'' Berkeley: Univ. of California Press. 1971. VII+171 p.
*Stafleau, F. A. ''Linnaeus and the Linnaeans. The spreading of their ideas in systematic botany, 1753-1789.'' Utrecht: Oosthoek. 1971. xvi+386 p.
==See also==
*[[Binomial nomenclature]]
*[[Trinomial nomenclature]]
*[[Linnaean taxonomy|Taxonomy]]
*[[International Code of Botanical Nomenclature]]
*[[International Code of Zoological Nomenclature]]
*[[List of chordate orders]]
*[[List of Latin and Greek words commonly used in systematic names]]
*[[Phylogenetic tree]]
*[[Virus classification]]
*[[Set]]
*[[Species Problem]]
==External links==
*[http://en.wikiquote.org/wiki/Biology_mnemonics Wikiquote: Biology Mnemonics]
*[http://tolweb.org/tree/ The Tree of Life Web]
*[http://www.iczn.org/iczn/ International Code of the Zoological Nomenclature (4th Edition) 2000]
*[http://www.bgbm.fu-berlin.de/iapt/nomenclature/code/SaintLouis/0000St.Luistitle.htm International Code of the Botanical Nomenclature (St. Louis Code) 2000]
*[http://www.ohiou.edu/phylocode/ Phylocode]
*[http://www.omne-vivum.com Classification of all living things, with many pictures]
*[http://species.wikipedia.org Wikispecies: a directory of life]
*For a cladistic approach to animal classification: [http://anthro.palomar.edu/animal/default.htm Classification of living things]
*For details about the history of insect classification, see [http://www.bio.pu.ru/win/entomol/KLUGE/nom/-nom-F.htm Nomina Circumscribentia Insectorum].
<!--Categories-->
[[Category:Classification systems]]
[[Category:Cognition]]
[[Category:Knowledge]]
[[Category:Scientific classification| ]]
'''Scientific classification''' or '''biological classification''' is a method by which [[biologist]]s group and categorize [[species]] of [[organism]]s. Scientific classification can also be called scientific taxonomy, but should be distinguished from [[folk taxonomy]], which lacks scientific basis. Modern classification has its root in the work of [[Carolus Linnaeus]], who grouped species according to shared physical characteristics. These groupings have since been revised to improve consistency with the [[Charles Darwin|Darwinian]] principle of [[common descent]]. [[Molecular systematics]], which uses [[DNA sequences]] as data, has driven many recent revisions and is likely to continue to do so. Scientific classification belongs to the science of [[taxonomy]] or [[systematics|biological systematics]].
== Early systems ==
The earliest known system of classifying forms of life comes from the Greek philosopher [[Aristotle]], who classified all living organisms known at that time as either a plant or an animal. He further classified animals based on their means of transportation (air, land, or water).
In 1172 Ibn Rushd ([[Averroes]]), who was a judge ([[Qadi]]) in [[Seville]], translated and abridged Aristotle's book ''de Anima'' (''[[On the Soul]]'') into Arabic. His original commentary is now lost, but its translation into Latin by [[Michael Scot]] survives.
An important advance was made by the Swiss professor, [[Conrad von Gesner]] (1516–1565). Gesner's work was a critical compilation of life known at the time.
The exploration of parts of the [[New World]] next brought to hand descriptions and specimens of many novel forms of animal life. In the latter part of the 16th century and the beginning of the 17th, careful study of animals commenced, which, directed first to familiar kinds, was gradually extended until it formed a sufficient body of knowledge to serve as an anatomical basis for classification. Advances in using this knowledge to classify living beings bear a debt to the research of medical anatomists, such as [[Hieronymus Fabricius|Fabricius]] (1537–1619), [[Petrus Severinus]] (1580–1656), [[William Harvey]] (1578–1657), and [[Edward Tyson]] (1649–1708). Advances in classification due to the work of [[entomologist]]s and the first microscopists is due to the research of people like [[Marcello Malpighi]] (1628–1694), [[Jan Swammerdam]] (1637–1680), and [[Robert Hooke]] (1635–1702). [[Lord Monboddo]] (1714-1799) was one of the early abstract thinkers whose works illustrate knowledge of species relationships and who foreshadowed the theory of [[evolution]]. Successive developments in the history of insect classification may be followed on the website<ref name="">{{cite web|url = http://www.bio.pu.ru/win/entomol/KLUGE/nom/-nom-F.htm | accessdate = 2006-09-09 | title = NOMINA CIRCUMSCRIBENTIA INSECTORUM}}</ref> by clicking on succeeding works in chronological order.
=== Early methodists ===
Since late in the 15th century, a number of authors had become concerned with what they called ''methodus,'' or method. By method they meant an arrangement of minerals, plants, and animals according to the principles of logical division. The term ''methodists'' was coined by [[Carolus Linnaeus]] in his ''Bibliotheca Botanica'' to denote the authors who care about the principles of classification (in contrast to the mere ''collectors'' who are concerned primarily with the description of plants paying little or no attention to their arrangement into genera, etc). Important early methodists were an Italian philosopher, physician, and botanist [[Andrea Caesalpino]], an English naturalist [[John Ray]], a German physician and botanist [[Augustus Quirinus Rivinus]], and a French physician, botanist, and traveller [[Joseph Pitton de Tournefort]].
[[Andrea Caesalpino]] ([[1519]]–[[1603]]) in his ''De plantis libri XVI'' ([[1583]]) proposed the first methodical arrangement of plants. On the basis of the structure of [[Trunk (botany)|trunk]] and [[fructification]] he divided plants into fifteen "higher genera".
[[John Ray]] ([[1627]]–[[1705]]) was an English naturalist who published important works on plants, animals, and natural theology. The approach he took to the classification of plants in his [[Historia Plantarum]] was an important step towards modern taxonomy. Ray rejected the system of dichotomous division by which species were classified according to a pre-conceived, either/or type system, and instead classified plants according to similarities and differences that emerged from observation.
Both Caesalpino and Ray used traditional plant names and thus, the name of a plant did not reflect its taxonomic position (e.g. even though the [[apple]] and the [[peach]] belonged to different "higher genera" of John Ray's ''methodus'', both retained their traditional names ''Malus'' and ''Malus Persica'' respectively). A further step was taken by Rivinus and Pitton de Tournefort who made [[genus]] a distinct rank within taxonomic hierarchy and introduced the practice of naming the plants according to their genera.
[[Augustus Quirinus Rivinus]] ([[1652]]–[[1723]]), in his classification of plants based on the characters of the [[flower]], introduced the category of [[Order (biology)|order]] (corresponding to the "higher" genera of John Ray and Andrea Caesalpino). He was the first to abolish the ancient division of plants into [[herb]]s and [[tree]]s and insisted that the true method of division should be based on the parts of the [[fructification]] alone. Rivinus extensively used [[dichotomous key]]s to define both orders and genera. His method of naming plant species resembled that of Joseph Pitton de Tournefort. The names of all plants belonging to the same genus should begin with the same word (generic name). In the genera containing more than one species the first species was named with generic name only, while the second, etc were named with a combination of the generic name and a modifier (''differentia specifica'').
[[Joseph Pitton de Tournefort]] ([[1656]]–[[1708]]) introduced an even more sophisticated hierarchy of class, section, genus, and species. He was the first to use consistently the uniformly composed species names which consisted of a generic name and a many-worded diagnostic phrase ''differentia specifica.'' Unlike Rivinus, he used ''differentiae'' with all species of polytypic genera.
===Linnaeus===
Two years after John Ray's death, [[Carolus Linnaeus]] ([[1707]]–[[1778]]) was born. His great work, the ''[[Systema Naturae]]'', ran through twelve editions during his lifetime (1st ed. [[1735]]). In this work, nature was divided into three kingdoms: mineral, vegetable and animal. Linnaeus used five ranks: class, order, genus, species, and variety.
He abandoned long descriptive names of classes and orders and two-word generic names (e. g. ''Bursa pastoris'') still used by his immediate predecessors (Rivinus and Pitton de Tournefort) and replaced them with single-word names, provided genera with detailed diagnoses (''characteres naturales''), and reduced numerous varieties to their species, thus saving botany from the chaos of new forms produced by [[horticulturalist]]s.
Linnaeus is best known for his introduction of the method still used to formulate the [[scientific name]] of every species. Before Linnaeus, long many-worded names (composed of a generic name and a ''differentia specifica'') had been used, but as these names gave a description of the species, they were not fixed. In his ''Philosophia Botanica'' (1751) Linnaeus took every effort to improve the composition and reduce the length of the many-worded names by abolishing unnecessary rhetorics, introducing new descriptive terms and defining their meaning with an unprecedented precision. In the late 1740s Linnaeus began to use a parallel system of naming species with ''nomina trivialia.'' ''Nomen triviale'', a trivial name, was a single- or two-word epithet placed on the margin of the page next to the many-worded "scientific" name. The only rules Linnaeus applied to them was that the trivial names should be short, unique within a given genus, and that they should not be changed. Linnaeus consistently applied ''nomina trivialia'' to the species of plants in ''[[Species Plantarum]]'' (1st edn. 1753) and to the species of animals in the 10th edition of ''[[Systema Naturae]]'' (1758).
By consistently using these specific epithets, Linnaeus separated nomenclature from taxonomy. Even though the parallel use of ''nomina trivialia'' and many-worded descriptive names continued until late in the eighteenth century, it was gradually replaced by the practice of using shorter proper names combined of the generic name and the trivial name of the species. In the nineteenth century, this new practice was codified in the first Rules and Laws of Nomenclature, and the 1st edn. of ''[[Species Plantarum]]'' and the 10th edn. of ''[[Systema Naturae]]'' were chosen as starting points for the Botanical and Zoological Nomenclature respectively. This convention for naming species is referred to as [[binomial nomenclature]].
Today, nomenclature is regulated by [[Nomenclature Codes]], which allows names divided into ranks; see [[rank (botany)]] and [[rank (zoology)]].
== Modern developments ==
Whereas Linnaeus classified for ease of identification, it is now generally accepted that classification should reflect the Darwinian principle of [[common descent]].
Since the 1960s a trend called [[Cladistics|cladistic]] taxonomy (or [[cladistics]] or cladism) has emerged, arranging taxa in an [[evolutionary tree]]. If a [[taxon]] includes all the descendants of some ancestral form, it is called [[monophyletic]], as opposed to [[paraphyletic]]. Other groups are called [[polyphyletic]].
A new formal code of nomenclature, the [[PhyloCode]], is currently under development, intended to deal with clades rather than taxa. It is unclear, should this be implemented, how the different codes will coexist.
[[Domain (biology)|Domains]] are a relatively new grouping. The [[three-domain system]] was first invented in 1990, but not generally accepted until later. Now, the majority of biologists accept the domain system, but a large minority use the five-kingdom method. One main characteristic of the three-domain method is the separation of Archaea and Bacteria, previously grouped into the single kingdom Bacteria (sometimes Monera). A small minority of scientists add Archaea as a sixth kingdom but do not accept the domain method.
== Examples ==
The usual classifications of five species follow: the [[Drosophila melanogaster|fruit fly]] so familiar in genetics laboratories (''Drosophila melanogaster''), [[human]]s (''Homo sapiens''), the [[pea]]s used by [[Gregor Mendel]] in his discovery of [[genetics]] (''Pisum sativum''), the "fly agaric" mushroom ''[[Amanita muscaria]]'', and the bacterium ''[[Escherichia coli]]''. The eight major ranks are given in bold; a selection of minor ranks are given as well.
{| border="1" cellpadding="4" cellspacing="0" style="margin: 0.5em 1em 0.5em 0; background: #f9f9f9; border: 1px #aaa solid; border-collapse: collapse;"
|- style="background:palegrey; border: 1px;"
!style="width:16%; background:#f3f3f3;"|Rank
!style="width:16%; background:#f3f3f3;"|[[Drosophila melanogaster|Fruit fly]]
!style="width:16%; background:#f3f3f3;"|[[Human]]
!style="width:16%; background:#f3f3f3;"|[[Pea]]
!style="width:16%; background:#f3f3f3;"|[[Fly Agaric]]
!style="width:16%; background:#f3f3f3;"|''[[Escherichia coli|E. coli]]''
|-
|style="background:#f2f2f2;"|'''[[Domain (biology)|Domain]]'''
|[[Eukaryota]]
|[[Eukaryota]]
|[[Eukaryota]]
|[[Eukaryota]]
|[[Bacteria]]
|-
|style="background:#f2f2f2;"|'''[[Kingdom (biology)|Kingdom]]'''
|[[Animal]]ia
|[[Animal]]ia
|[[Plant]]ae
|[[Fungi]]
|[[Monera]]
|-
|style="background:#f2f2f2;"|'''[[Phylum]]''' or '''[[Division (biology)|Division]]'''
|[[Arthropod]]a
|[[Chordate|Chordata]]
|[[Flowering plant|Magnoliophyta]]
|[[Basidiomycota]]
|[[Proteobacteria]]
|-
|style="background:#f2f2f2;"|[[Subphylum]] or subdivision
|[[Hexapoda]]
|[[Vertebrate|Vertebrata]]
|[[Magnoliophytina]]
|[[Hymenomycotina]]
|
|-
|style="background:#f2f2f2;"|'''[[Class (biology)|Class]]'''
|[[Insect]]a
|[[Mammal]]ia
|[[Magnoliopsida]]
|[[Homobasidiomycetae]]
|[[Proteobacteria]]
|-
|style="background:#f2f2f2;"|Subclass
|[[Pterygota]]
|[[Eutheria]]
|[[Magnoliidae]]
|[[Hymenomycetes]]
|[[Gammaproteobacteria]]
|-
|style="background:#f2f2f2;"|'''[[Order (biology)|Order]]'''
|[[Diptera]]
|[[Primate]]s
|[[Fabales]]
|[[Agaricales]]
|[[Enterobacteriaceae|Enterobacteriales]]
|-
|style="background:#f2f2f2;"|Suborder
|[[Brachycera]]
|[[Haplorrhini]]
|[[Fabineae]]
|[[Agaricineae]]
|
|-
|style="background:#f2f2f2;"|'''[[Family (biology)|Family]]'''
|[[Drosophilidae]]
|[[Hominidae]]
|[[Fabaceae]]
|[[Amanitaceae]]
|[[Enterobacteriaceae]]
|-
|style="background:#f2f2f2;"|Subfamily
|[[Drosophilinae]]
|[[Homininae]]
|[[Faboideae]]
|[[Amanitoideae]]
|
|-
|style="background:#f2f2f2;"|'''[[Genus]]'''
|''[[Drosophila]]''
|''[[Homo (genus)|Homo]]''
|''[[Pisum]]''
|''[[Amanita]]''
|''[[Escherichia]]''
|-
|style="background:#f2f2f2;"|'''[[Species]]'''
|''[[Drosophila melanogaster|D. melanogaster]]''
|''[[Homo sapiens|H. sapiens]]''
|''[[Pisum sativum|P. sativum]]''
|''[[Amanita muscaria|A. muscaria]]''
|''[[Escherichia coli|E. coli]]''
|}
Notes:
*Higher taxa and especially intermediate taxa are prone to revision as new information about relationships is discovered. For example, the traditional classification of primates (class Mammalia — subclass Theria — infraclass Eutheria — order Primates) is challenged by new classifications such as McKenna and Bell (class Mammalia — subclass Theriformes — infraclass Holotheria — 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 [[morph (zoology)|morph]]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]] name (for example, ''Pisum sativum'' var. ''macrocarpon'' 'Snowbird'). Bacteria may be classified by [[strain (biology)|strains]] (for example [[Escherichia coli O157:H7|''Escherichia coli'' O157:H7]], a strain that can cause [[food poisoning]]).
*A popular mnemonic to remember the taxa is ''"King Philip can only find [[girl scout]]s"'' (Kingdom, Phylum, Class, Order, Family, Genus, Species).
==Terminations of names==
[[Taxon|Taxa]] above the genus level are often given names based on the [[type genus]], 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.
{| border="1" cellpadding="4" cellspacing="0" style="margin: 0.5em 1em 0.5em 0; background: #f9f9f9; border: 1px #aaa solid; border-collapse: collapse;"
|-
!style="background:#f3f3f3;"|Rank
!style="background:#f3f3f3;"|[[Plant]]s
!style="background:#f3f3f3;"|[[Alga]]e
!style="background:#f3f3f3;"|[[Fungi]]
!style="background:#f3f3f3;"|[[Animal]]s
!style="background:#f3f3f3;"|[[Bacteria]]<ref>[http://www.bacterio.cict.fr/classificationgenera.html Bacteriologocal Code (1990 Revision)]</ref>
|-
|style="background:#f2f2f2;"|'''Division/Phylum'''
| align="center" colspan="2" | -phyta
| -mycota
|
|
|-
|style="background:#f2f2f2;"|'''Subdivision/Subphylum'''
| align="center" colspan="2" | -phytina
| -mycotina
|
|
|-
|style="background:#f2f2f2;"|'''Class'''
| -opsida
| -phyceae
| -mycetes
|
| -ia
|-
|style="background:#f2f2f2;"|'''Subclass'''
| -idae
| -phycidae
| -mycetidae
|
| -idae
|-
|style="background:#f2f2f2;"|'''Superorder'''
|align="center" colspan="3"| -anae
|
|
|-
|style="background:#f2f2f2;"|'''Order'''
|align="center" colspan="3"| -ales
|
| -ales
|-
|style="background:#f2f2f2;"|'''Suborder'''
|align="center" colspan="3"| -ineae
|
| -ineae
|-
|style="background:#f2f2f2;"|'''Infraorder'''
|align="center" colspan="3"| -aria
|
|
|-
|style="background:#f2f2f2;"|'''Superfamily'''
|align="center" colspan="3"| -acea
| -oidea
|
|-
|style="background:#f2f2f2;"|'''Family'''
|align="center" colspan="3"| -aceae
| -idae
| -aceae
|-
|style="background:#f2f2f2;"|'''Subfamily'''
|align="center" colspan="3"| -oideae
| -inae
| -oideae
|-
|style="background:#f2f2f2;"|'''Tribe/Infrafamily'''
|align="center" colspan="3"| -eae
| -ini
| -eae
|-
|style="background:#f2f2f2;"|'''Subtribe'''
|align="center" colspan="3"| -inae
| -ina
| -inae
|}
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]] 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 formed from a family name, or are descriptive (like [[Gymnospermae]] or [[Fungi]]).
* For animals, there are standard suffixes for taxa only up to the rank of superfamily (ICZN article 27.2).
* Forming a name based on a generic name may be not straightforward. For example, the [[Latin]] "''homo''" has the genitive "''hominis''", thus the genus "''Homo''" (human) is in the [[Hominidae]], not "Homidae".
==Authorities (author citation)==
The name of any taxon may be followed by the "authority" for the name, that is, the name of the author who first published a valid description of it. These names are frequently abbreviated: the abbreviation "L." is universally accepted for Linnaeus, and in botany there is a regulated list of standard abbreviations (see [[list of botanists by author abbreviation]]). The system for assigning authorities is slightly different in different branches of biology: see [[author citation (botany)]] and [[author citation (zoology)]]. However, it is standard that if a name or placement has been changed since the original description, the first authority's name is placed in parentheses and the authority for the new name or placement may be placed after it (usually only in botany).
==Bibliography==
<references />
===History===
*Atran, S. ''Cognitive foundations of natural history: towards an anthropology of science.'' Cambridge: Cambridge Univ. Press. 1990. xii+360 p. ISBN [http://www.amazon.com/gp/product/0521372933 0521372933]
*Larson, J. L. ''Reason and experience. The representation of Natural Order in the work of Carl von Linne.'' Berkeley: Univ. of California Press. 1971. VII+171 p.
*Stafleau, F. A. ''Linnaeus and the Linnaeans. The spreading of their ideas in systematic botany, 1753-1789.'' Utrecht: Oosthoek. 1971. xvi+386 p.
==See also==
*[[Binomial nomenclature]]
*[[Trinomial nomenclature]]
*[[Linnaean taxonomy|Taxonomy]]
*[[International Code of Botanical Nomenclature]]
*[[International Code of Zoological Nomenclature]]
*[[List of chordate orders]]
*[[List of Latin and Greek words commonly used in systematic names]]
*[[Phylogenetic tree]]
*[[Virus classification]]
*[[Set]]
*[[Species Problem]]
==External links==
*[http://en.wikiquote.org/wiki/Biology_mnemonics Wikiquote: Biology Mnemonics]
*[http://tolweb.org/tree/ The Tree of Life Web]
*[http://www.iczn.org/iczn/ International Code of the Zoological Nomenclature (4th Edition) 2000]
*[http://www.bgbm.fu-berlin.de/iapt/nomenclature/code/SaintLouis/0000St.Luistitle.htm International Code of the Botanical Nomenclature (St. Louis Code) 2000]
*[http://www.ohiou.edu/phylocode/ Phylocode]
*[http://www.omne-vivum.com Classification of all living things, with many pictures]
*[http://species.wikipedia.org Wikispecies: a directory of life]
*For a cladistic approach to animal classification: [http://anthro.palomar.edu/animal/default.htm Classification of living things]
*For details about the history of insect classification, see [http://www.bio.pu.ru/win/entomol/KLUGE/nom/-nom-F.htm Nomina Circumscribentia Insectorum].
<!--Categories-->
[[Category:Classification systems]]
[[Category:Cognition]]
[[Category:Knowledge]]
[[Category:Scientific classification| ]]
