Linnaean taxonomy
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Linnaean taxonomy can mean either of two related concepts: # The particular form of
biological classification In biology, taxonomy () is the scientific study of naming, defining ( circumscribing) and classifying groups of biological organisms based on shared characteristics. Organisms are grouped into taxa (singular: taxon), and these groups are give ...
(taxonomy) set up by
Carl Linnaeus Carl Linnaeus (23 May 1707 – 10 January 1778), also known after ennoblement in 1761 as Carl von Linné,#Blunt, Blunt (2004), p. 171. was a Swedish biologist and physician who formalised binomial nomenclature, the modern system of naming o ...
, as set forth in his ''
Systema Naturae ' (originally in Latin written ' with the Orthographic ligature, ligature æ) is one of the major works of the Sweden, Swedish botanist, zoologist and physician Carl Linnaeus (1707–1778) and introduced the Linnaean taxonomy. Although the syste ...
'' (1735) and subsequent works. In the taxonomy of Linnaeus there are three kingdoms, divided into ''classes'', and the classes divided into lower ranks in a hierarchical order. # A term for rank-based classification of organisms, in general. That is, taxonomy in the traditional sense of the word: rank-based scientific classification. This term is especially used as opposed to cladistic systematics, which groups organisms into
clade In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...
s. It is attributed to Linnaeus, although he neither invented the concept of ranked classification (it goes back to
Plato Plato ( ; Greek language, Greek: , ; born  BC, died 348/347 BC) was an ancient Greek philosopher of the Classical Greece, Classical period who is considered a foundational thinker in Western philosophy and an innovator of the writte ...
and
Aristotle Aristotle (; 384–322 BC) was an Ancient Greek philosophy, Ancient Greek philosopher and polymath. His writings cover a broad range of subjects spanning the natural sciences, philosophy, linguistics, economics, politics, psychology, a ...
) nor gave it its present form. In fact, it does not have an exact present form, as "Linnaean taxonomy" as such does not really exist: it is a collective (abstracting) term for what actually are several separate fields, which use similar approaches. Linnaean name also has two meanings, depending on the context: it may either refer to a formal name given by Linnaeus (personally), such as ''Giraffa camelopardalis'' Linnaeus, 1758; or a formal name in the accepted nomenclature (as opposed to a modernistic
clade In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...
name).


The taxonomy of Linnaeus

In his ''Imperium Naturae'',
Linnaeus Carl Linnaeus (23 May 1707 – 10 January 1778), also known after ennoblement in 1761 as Carl von Linné,#Blunt, Blunt (2004), p. 171. was a Swedish biologist and physician who formalised binomial nomenclature, the modern system of naming o ...
established three kingdoms, namely ''Regnum Animale'', ''Regnum Vegetabile'' and ''Regnum Lapideum''. This approach, the Animal, Vegetable and Mineral Kingdoms, survives today in the popular mind, notably in the form of the parlour game question: "Is it animal, vegetable or mineral?". The work of Linnaeus had a huge impact on science; it was indispensable as a foundation for biological nomenclature, now regulated by the
nomenclature codes Nomenclature codes or codes of nomenclature are the various rulebooks that govern the naming of living organisms. Standardizing the scientific names of biological organisms allows researchers to discuss findings (including the discovery of new s ...
. Two of his works, the first edition of the ''
Species Plantarum ' (Latin for "The Species of Plants") is a book by Carl Linnaeus, originally published in 1753, which lists every species of plant known at the time, classified into genus, genera. It is the first work to consistently apply binomial nomenclature ...
'' (1753) for plants and the tenth edition of the ''Systema Naturae'' (1758), are accepted as part of the starting points of nomenclature; his binomials (names for species) and generic names take priority over those of others. However, the impact he had on science was not because of the value of his taxonomy. Linnaeus' kingdoms were in turn divided into '' classes'', and they, in turn, into '' orders'', '' genera'' (singular: ''genus''), and ''
species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...
'' (singular: ''species''), with an additional rank lower than species, though these do not precisely correspond to the use of these terms in modern taxonomy.


Classification of plants

In ''Systema Naturae'' (1735), his classes and orders of plants, according to his ''Systema Sexuale'', were not intended to represent natural groups (as opposed to his ''ordines naturales'' in his '' Philosophia Botanica'') but only for use in identification. However, in 1737 he published ''Genera Plantarum'' in which he claimed that his classification of genera was a natural system. His botanical classification and sexual system were used well in the nineteenth century. Within each class were several orders. This system is based on the number and arrangement of male (
stamen The stamen (: stamina or stamens) is a part consisting of the male reproductive organs of a flower. Collectively, the stamens form the androecium., p. 10 Morphology and terminology A stamen typically consists of a stalk called the filament ...
s) and female ( pistils) organs. The Linnaean classes for plants, in the Sexual System, were (page numbers refer to ''Species plantarum''): * Classis 1. Monandria: flowers with 1 stamen * Classis 2. Diandria: flowers with 2 stamens * Classis 3. Triandria: flowers with 3 stamens * Classis 4. Tetrandria: flowers with 4 stamens * Classis 5. Pentandria: flowers with 5 stamens * Classis 6. Hexandria: flowers with 6 stamens ** Hexandria monogynia pp. 285–352 ** Hexandria polygynia pp. 342–343 * Classis 7. Heptandria: flowers with 7 stamens * Classis 8. Octandria: flowers with 8 stamens * Classis 9. Enneandria: flowers with 9 stamens * Classis 10. Decandria: flowers with 10 stamens * Classis 11. Dodecandria: flowers with 11 to 19 stamens * Classis 12. Icosandria: flowers with 20 (or more) stamens, perigynous * Classis 13. Polyandria: flowers with many stamens, inserted on the receptacle * Classis 14. Didynamia: flowers with 4 stamens, 2 long and 2 short ** Gymnospermia ** Angiospermia * Classis 15. Tetradynamia: flowers with 6 stamens, 4 long and 2 short * Classis 16. Monadelphia; flowers with the anthers separate, but the filaments united, at least at the base ** Pentandria ** Decandria ** Polyandria * Classis 17. Diadelphia; flowers with the stamens united in two separate groups ** Hexandria ** Octandria ** Decandria * Classis 18. Polyadelphia; flowers with the stamens united in several separate groups ** Pentandria ** Icosandria ** Polyandria * Classis 19. Syngenesia; flowers with stamens united by their anthers ** Polygamia aequalis ** Polygamia superba ** Polygamia frustranea ** Polygamia necessaria ** Monogamia * Classis 20. Gynandria; flowers with the stamens united to the pistils * Classis 21. Monoecia: monoecious plants * Classis 22. Dioecia: dioecious plants * Classis 23. Polygamia: polygamodioecious plants * Classis 24. Cryptogamia: the "flowerless" plants, including ferns,
fungi A fungus (: fungi , , , or ; or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and mold (fungus), molds, as well as the more familiar mushrooms. These organisms are classified as one ...
,
algae Algae ( , ; : alga ) is an informal term for any organisms of a large and diverse group of photosynthesis, photosynthetic organisms that are not plants, and includes species from multiple distinct clades. Such organisms range from unicellular ...
, and bryophytes The classes based on the number of stamens were then subdivided by the number of pistils, e.g. ''Hexandria monogynia'' with six stamens and one pistil. Index to genera p. 1201 By contrast his ''ordines naturales'' numbered 69, from Piperitae to Vagae.


Classification for animals

Only in the Animal Kingdom is the higher taxonomy of Linnaeus still more or less recognizable and some of these names are still in use, but usually not quite for the same groups. He divided the Animal Kingdom into six classes. In the tenth edition, of 1758, these were: * Classis 1. Mammalia (mammals) * Classis 2. Aves (birds) * Classis 3. Amphibia (amphibians) * Classis 4. Pisces (fishes) * Classis 5. Insecta (arthropods) * Classis 6. Vermes (worms)


Classification for minerals

His taxonomy of
mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid substance with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2011): Mi ...
s has long since been dropped from use. In the tenth edition, 1758, of the ''Systema Naturae'', the Linnaean classes were: * Classis 1. Petræ * Classis 2. Mineræ * Classis 3. Fossilia * Classis 4. Vitamentra


Rank-based scientific classification

This rank-based method of classifying living organisms was originally popularized by (and much later named for) Linnaeus, although it has changed considerably since his time. The greatest innovation of Linnaeus, and still the most important aspect of this system, is the general use of binomial nomenclature, the combination of a
genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...
name and a second term, which together uniquely identify each
species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...
of organism within a kingdom. For example, the
human Humans (''Homo sapiens'') or modern humans are the most common and widespread species of primate, and the last surviving species of the genus ''Homo''. They are Hominidae, great apes characterized by their Prehistory of nakedness and clothing ...
species is uniquely identified within the animal kingdom by the name ''Homo sapiens''. No other species of animal can have this same binomen (the technical term for a binomial in the case of animals). Prior to Linnaean taxonomy, animals were classified according to their mode of movement. Linnaeus's use of binomial nomenclature was anticipated by the theory of definition used in Scholasticism. Scholastic logicians and philosophers of nature defined the species human, for example, as ''Animal rationalis'', where ''animal'' was considered a genus and ''rationalis'' (Latin for "rational") the characteristic distinguishing humans from all other animals. Treating ''animal'' as the immediate genus of the species human, horse, etc. is of little practical use to the biological taxonomist, however. Accordingly, Linnaeus's classification treats ''animal'' as a class including many genera (subordinated to the animal "kingdom" via intermediary classes such as "orders"), and treats ''homo'' as the genus of a species ''Homo sapiens'', with ''sapiens'' (Latin for "knowing" or "understanding") playing a differentiating role analogous to that played, in the Scholastic system, by ''rationalis'' (the word ''homo'', Latin for "human being", was used by the Scholastics to denote a species, not a genus). A strength of Linnaean taxonomy is that it can be used to organize the different kinds of living
organism An organism is any life, living thing that functions as an individual. Such a definition raises more problems than it solves, not least because the concept of an individual is also difficult. Many criteria, few of them widely accepted, have be ...
s, simply and practically. Every species can be given a unique (and, one hopes, stable) name, as compared with common names that are often neither unique nor consistent from place to place and language to language. This uniqueness and stability are, of course, a result of the acceptance by working systematists (biologists specializing in taxonomy), not merely of the binomial names themselves, but of the rules governing the use of these names, which are laid down in formal nomenclature codes. Species can be placed in a ranked
hierarchy A hierarchy (from Ancient Greek, Greek: , from , 'president of sacred rites') is an arrangement of items (objects, names, values, categories, etc.) that are represented as being "above", "below", or "at the same level as" one another. Hierarchy ...
, starting with either '' domains'' or ''kingdoms''. Domains are divided into kingdoms. Kingdoms are divided into '' phyla'' (singular: ''phylum'') — for
animal Animals are multicellular, eukaryotic organisms in the Biology, biological Kingdom (biology), kingdom Animalia (). With few exceptions, animals heterotroph, consume organic material, Cellular respiration#Aerobic respiration, breathe oxygen, ...
s; the term ''division'', used for
plant Plants are the eukaryotes that form the Kingdom (biology), kingdom Plantae; they are predominantly Photosynthesis, photosynthetic. This means that they obtain their energy from sunlight, using chloroplasts derived from endosymbiosis with c ...
s and
fungi A fungus (: fungi , , , or ; or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and mold (fungus), molds, as well as the more familiar mushrooms. These organisms are classified as one ...
, is equivalent to the rank of phylum (and the current International Code of Botanical Nomenclature allows the use of either term). Phyla (or divisions) are divided into '' classes'', and they, in turn, into '' orders'', '' families'', '' genera'' (singular: ''genus''), and ''
species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...
'' (singular: ''species''). There are ranks below species: in zoology, ''subspecies'' (but see '' form'' or '' morph''); in botany, ''variety'' (varietas) and ''form'' (forma), etc. Groups of organisms at any of these ranks are called ''taxa'' (singular: ''
taxon In biology, a taxon (back-formation from ''taxonomy''; : taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular name and ...
'') or ''taxonomic groups''. The Linnaean system has proven robust and it remains the only extant working classification system at present that enjoys universal scientific acceptance. However, although the number of ranks is unlimited, in practice any classification becomes more cumbersome the more ranks are added. Among the later subdivisions that have arisen are such entities as phyla, families, and tribes, as well as any number of ranks with prefixes (superfamilies, subfamilies, etc.). The use of newer taxonomic tools such as
cladistics Cladistics ( ; from Ancient Greek 'branch') is an approach to Taxonomy (biology), biological classification in which organisms are categorized in groups ("clades") based on hypotheses of most recent common ancestry. The evidence for hypothesiz ...
and phylogenetic nomenclature has led to a different way of looking at evolution (expressed in many nested
clade In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...
s) and this sometimes leads to a desire for more ranks. An example of such complexity is the scheme for mammals proposed by McKenna and Bell.


Alternatives

Over time, understanding of the relationships between living things has changed. Linnaeus could only base his scheme on the structural similarities of the different organisms. The greatest change was the widespread acceptance of
evolution Evolution is the change in the heritable Phenotypic trait, characteristics of biological populations over successive generations. It occurs when evolutionary processes such as natural selection and genetic drift act on genetic variation, re ...
as the mechanism of biological diversity and species formation, following the 1859 publication of Charles Darwin's '' On the Origin of Species''. It then became generally understood that classifications ought to reflect the phylogeny of organisms, their descent by evolution. This led to evolutionary taxonomy, where the various extant and extinct are linked together to construct a phylogeny. This is largely what is meant by the term 'Linnaean taxonomy' when used in a modern context. In
cladistics Cladistics ( ; from Ancient Greek 'branch') is an approach to Taxonomy (biology), biological classification in which organisms are categorized in groups ("clades") based on hypotheses of most recent common ancestry. The evidence for hypothesiz ...
, originating in the work of Willi Hennig, 1950 onwards, each taxon is grouped so as to include the common ancestor of the group's members (and thus to avoid phylogeny). Such taxa may be either
monophyletic In biological cladistics for the classification of organisms, monophyly is the condition of a taxonomic grouping being a clade – that is, a grouping of organisms which meets these criteria: # the grouping contains its own most recent co ...
(including all descendants) such as genus ''
Homo ''Homo'' () is a genus of great ape (family Hominidae) that emerged from the genus ''Australopithecus'' and encompasses only a single extant species, ''Homo sapiens'' (modern humans), along with a number of extinct species (collectively called ...
'', or paraphyletic (excluding some descendants), such as genus ''
Australopithecus ''Australopithecus'' (, ; or (, ) is a genus of early hominins that existed in Africa during the Pliocene and Early Pleistocene. The genera ''Homo'' (which includes modern humans), ''Paranthropus'', and ''Kenyanthropus'' evolved from some ''Aus ...
''. Originally, Linnaeus established three kingdoms in his scheme, namely for
Plant Plants are the eukaryotes that form the Kingdom (biology), kingdom Plantae; they are predominantly Photosynthesis, photosynthetic. This means that they obtain their energy from sunlight, using chloroplasts derived from endosymbiosis with c ...
s,
Animal Animals are multicellular, eukaryotic organisms in the Biology, biological Kingdom (biology), kingdom Animalia (). With few exceptions, animals heterotroph, consume organic material, Cellular respiration#Aerobic respiration, breathe oxygen, ...
s and an additional group for minerals, which has long since been abandoned. Since then, various life forms have been moved into three new kingdoms: Monera, for
prokaryote A prokaryote (; less commonly spelled procaryote) is a unicellular organism, single-celled organism whose cell (biology), cell lacks a cell nucleus, nucleus and other membrane-bound organelles. The word ''prokaryote'' comes from the Ancient Gree ...
s (i.e., bacteria);
Protist A protist ( ) or protoctist is any eukaryotic organism that is not an animal, land plant, or fungus. Protists do not form a natural group, or clade, but are a paraphyletic grouping of all descendants of the last eukaryotic common ancest ...
a, for protozoans and most algae; and
Fungi A fungus (: fungi , , , or ; or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and mold (fungus), molds, as well as the more familiar mushrooms. These organisms are classified as one ...
. This five-kingdom scheme is still far from the phylogenetic ideal and has largely been supplanted in modern taxonomic work by a division into three domains:
Bacteria Bacteria (; : bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of Prokaryote, prokaryotic microorganisms. Typically a few micr ...
and
Archaea Archaea ( ) is a Domain (biology), domain of organisms. Traditionally, Archaea only included its Prokaryote, prokaryotic members, but this has since been found to be paraphyletic, as eukaryotes are known to have evolved from archaea. Even thou ...
, which contain the prokaryotes, and
Eukaryota The eukaryotes ( ) constitute the Domain (biology), domain of Eukaryota or Eukarya, organisms whose Cell (biology), cells have a membrane-bound cell nucleus, nucleus. All animals, plants, Fungus, fungi, seaweeds, and many unicellular organisms ...
, comprising the remaining forms. These arrangements should not be seen as definitive. They are based on the genomes of the organisms; as knowledge on this increases, classifications will change. Representing presumptive evolutionary relationships within the framework of Linnaean taxonomy is sometimes seen as problematic, especially given the wide acceptance of cladistic methodology and numerous molecular phylogenies that have challenged long-accepted classifications. Therefore, some systematists have proposed a PhyloCode to replace it.


See also

* History of plant systematics * Linnaean Herbarium * Phylogenetic tree – a way to express insights into evolutionary relationships * Zoology mnemonic for a list of mnemonic sentences used to help people remember the list of Linnaean ranks.


References


Bibliography

;Books * * * * * Dawkins, Richard. 2004. '' The Ancestor's Tale: A Pilgrimage to the Dawn of Life''. Boston: Houghton Mifflin. * Ereshefsky, Marc. 2000. ''The Poverty of the Linnaean Hierarchy: A Philosophical Study of Biological Taxonomy''. Cambridge: Cambridge University Press. * Gould, Stephen Jay. 1989. '' Wonderful Life: The Burgess Shale and the Nature of History''. W. W. Norton & Co. * Pavord, Anna. ''The Naming of Names: The Search for Order in the World of Plants''. Bloomsbury. ;Articles * * ;Websites *


External links


International Code of Botanical Nomenclature
(Saint Louis Code), Electronic version
International Code of Nomenclature for algae, fungi, and plants
(Melbourne Code, 2011), Electronic version
ICZN website
for zoological nomenclature
Text of the ICZN
Electronic version
ZooBank: The World Register of Animal Names

International Committee on Systematics of Prokaryotes
for bacteria
International Code of Zoological Nomenclature. 4th Edition. By the International Union of Biological Sciences

ICTVdB website
for virus nomenclature by the International Union of Microbiological Societies
Tree of Life

European Species Names in Linnaean, Czech, English, German and French
{{Carl Linnaeus
Taxonomy image:Hierarchical clustering diagram.png, 280px, Generalized scheme of taxonomy Taxonomy is a practice and science concerned with classification or categorization. Typically, there are two parts to it: the development of an underlying scheme o ...
Taxonomy (biology) Biological nomenclature Botanical nomenclature Zoological nomenclature Swedish inventions