Linnaean taxonomy - AbsoluteAstronomy.com

Linnaean taxonomy can mean either of two related concepts:

the particular form of biological classification
Biological classification
Biological classification, or scientific classification in biology, is a method to group and categorize organisms by biological type, such as genus or species. Biological classification is part of scientific taxonomy....

(taxonomy) set up by Carl Linnaeus, as set forth in his Systema Naturæ (1735) and subsequent works. In the taxonomy
Taxonomy
Taxonomy is the science of identifying and naming species, and arranging them into a classification. The field of taxonomy, sometimes referred to as "biological taxonomy", revolves around the description and use of taxonomic units, known as taxa...

of Linnaeus there are three kingdoms, divided into classes, and they, in turn, into orders, families, genera (singular: genus), and species (singular: species), with an additional rank lower than species.
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
Cladistics
Cladistics is a method of classifying species of organisms into groups called clades, which consist of an ancestor organism and all its descendants . For example, birds, dinosaurs, crocodiles, and all descendants of their most recent common ancestor form a clade...

systematics, which groups organisms into clade
Clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...

s. It is attributed to Linnaeus, although he neither invented the concept of ranked classification (it goes back to Plato
Plato
Plato , was a Classical Greek philosopher, mathematician, student of Socrates, writer of philosophical dialogues, and founder of the Academy in Athens, the first institution of higher learning in the Western world. Along with his mentor, Socrates, and his student, Aristotle, Plato helped to lay the...

and Aristotle
Aristotle
Aristotle was a Greek philosopher and polymath, a student of Plato and teacher of Alexander the Great. His writings cover many subjects, including physics, metaphysics, poetry, theater, music, logic, rhetoric, linguistics, politics, government, ethics, biology, and zoology...

) 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.

The same applies to "Linnaean name": depending on the context this may either be 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 name).

The taxonomy of Linnaeus

In his Imperium Naturae, Linnaeus 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

Nomenclature codes or codes of nomenclature are the various rulebooks that govern biological taxonomic nomenclature, each in their own broad field of organisms...

. Two of his works, the first edition of the Species Plantarum
Species Plantarum
Species Plantarum was first published in 1753, as a two-volume work by Carl Linnaeus. Its prime importance is perhaps that it is the primary starting point of plant nomenclature as it exists today. This means that the first names to be considered validly published in botany are those that appear...

(1753) for plants and the tenth edition of the Systema Naturae (1758), are accepted as among the starting points of nomenclature; his binomials (names for species) and his generic names take priority over those of others. However, the impact he had on science was not because of the value of his taxonomy.

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 as used by Linnaeus. He divided the Animal Kingdom into six classes, in the tenth edition, of 1758, these were:

Classis 1. Mammalia
Mammalia in the 10th edition of Systema Naturae
In the 10th edition of Systema Naturae, Carl Linnaeus described the Mammalia as:Animals that suckle their young by means of lactiferous teats. In external and internal structure they resemble man: most of them are quadrupeds; and with man, their natural enemy, inhabit the surface of the Earth...
Classis 2. Aves
Aves in the 10th edition of Systema Naturae
In the 10th edition of Systema Naturae, Carl Linnaeus listed the 564 species of bird from around the world which were known to him at the time. There are now believed to be around 10,000 extant species...
Classis 3. Amphibia
Amphibia in the 10th edition of Systema Naturae
In the 10th edition of Systema Naturae, Carl Linnaeus described the Amphibia as:Animals that are distinguished by a body cold and generally naked; stern and expressive countenance; harsh voice; mostly lurid color; filthy odor; a few are furnished with a horrid poison; all have cartilaginous bones,...
Classis 4. Pisces
Pisces in the 10th edition of Systema Naturae
In the 10th edition of Systema Naturae, Carl Linnaeus described the Pisces as:Always inhabiting the waters; are swift in their motion and voracious in their appetites. They breathe by means of gills, which are generally united by a bony arch; swim by means of radiate fins, and are mostly covered...
Classis 5. Insecta
Insecta in the 10th edition of Systema Naturae
In the 10th edition of Systema Naturae, Carl Linnaeus classified the arthropods, including insects, arachnids and crustaceans, among his class "Insecta"...
Classis 6. Vermes
Vermes in the 10th edition of Systema Naturae
In 1758, in the 10th edition of Systema Naturae, the Swedish scientist and taxonomist Carl Linnaeus described the class "Vermes" as:Animals of slow motion, soft substance, able to increase their bulk and restore parts which have been destroyed, extremely tenatious of life, and the inhabitants of...

For plants

His classes and orders of plants, according to his Systema Sexuale, were never intended to represent natural groups (as opposed to his ordines naturales

Ordo naturalis

In botany, the phrase ordo naturalis, "natural order", was once used for what today is a family. Its origins lie with Carolus Linnaeus who used the word when he referred to natural units of plants...

in his Philosophia Botanica) but only for use in identification. They were used for that purpose well into the nineteenth century. Within each class were several orders; the names of the orders .

The Linnaean classes for plants, in the Sexual System, were:

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
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 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
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
Classis 17. Diadelphia; flowers with the stamens united in two separate groups
Classis 18. Polyadelphia; flowers with the stamens united in several separate groups
Classis 19. Syngenesia; flowers with 5 stamens, the anthers united at their edges
Classis 20. Gynandria; flowers with the stamens united to the pistils
Classis 21. Monoecia: monoecious plants
Classis 22. Dioecia: dioecious
Dioecious
Dioecy is the property of a group of biological organisms that have males and females, but not members that have organs of both sexes at the same time. I.e., those whose individual members can usually produce only one type of gamete; each individual organism is thus distinctly female or male...

plants
Classis 23. Polygamia: polygamodioecious plants
Classis 24. Cryptogamia: the "flowerless" plants, including fern
Fern
A fern is any one of a group of about 12,000 species of plants belonging to the botanical group known as Pteridophyta. Unlike mosses, they have xylem and phloem . They have stems, leaves, and roots like other vascular plants...

s, fungi
Fungus
A fungus is a member of a large group of eukaryotic organisms that includes microorganisms such as yeasts and molds , as well as the more familiar mushrooms. These organisms are classified as a kingdom, Fungi, which is separate from plants, animals, and bacteria...

, algae
Algae
Algae are a large and diverse group of simple, typically autotrophic organisms, ranging from unicellular to multicellular forms, such as the giant kelps that grow to 65 meters in length. They are photosynthetic like plants, and "simple" because their tissues are not organized into the many...

, and bryophyte
Bryophyte
Bryophyte is a traditional name used to refer to all embryophytes that do not have true vascular tissue and are therefore called 'non-vascular plants'. Some bryophytes do have specialized tissues for the transport of water; however since these do not contain lignin, they are not considered to be...

s

For minerals

His taxonomy of minerals has dropped long since from use. In the tenth edition, 1758, of the Systema Naturæ, 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

Binomial nomenclature

Binomial nomenclature is a formal system of naming species of living things by giving each a name composed of two parts, both of which use Latin grammatical forms, although they can be based on words from other languages...

, the combination of a genus

Genus

In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

name and a second term, which together uniquely identify each species

Species

In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

of organism. For example, the human

Human

Humans are the only living species in the Homo genus...

species is uniquely identified by the name Homo sapiens. No other species of organism can have this same binomen

Binomen

In zoological nomenclature, a binomen , is the two-part name of a species. The term was introduced in 1953, abolishing the previously used "binomial name" . A binomen consists of a generic name and a specific epithet...

(the technical term for a binomial in the case of animals). Prior to Linnaean taxonomy, animals were classified according to their mode of movement.

A strength of Linnaean taxonomy is that it can be used to organize the different kinds of living organism

Organism

In biology, an organism is any contiguous living system . In at least some form, all organisms are capable of response to stimuli, reproduction, growth and development, and maintenance of homoeostasis as a stable whole.An organism may either be unicellular or, as in the case of humans, comprise...

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

Nomenclature Codes

Nomenclature codes or codes of nomenclature are the various rulebooks that govern biological taxonomic nomenclature, each in their own broad field of organisms...

.

Species can be placed in a ranked

Taxonomic rank

In biological classification, rank is the level in a taxonomic hierarchy. Examples of taxonomic ranks are species, genus, family, and class. Each rank subsumes under it a number of less general categories...

hierarchy

Hierarchy

A hierarchy is an arrangement of items in which the items are represented as being "above," "below," or "at the same level as" one another...

, starting with either domains
Domain (biology)
In biological taxonomy, a domain is the highest taxonomic rank of organisms, higher than a kingdom. According to the three-domain system of Carl Woese, introduced in 1990, the Tree of Life consists of three domains: Archaea, Bacteria and Eukarya...

or kingdoms. Domains are divided into kingdoms

Kingdom (biology)

In biology, kingdom is a taxonomic rank, which is either the highest rank or in the more recent three-domain system, the rank below domain. Kingdoms are divided into smaller groups called phyla or divisions in botany...

. Kingdoms are divided into phyla
Phylum
In biology, a phylum The term was coined by Georges Cuvier from Greek φῦλον phylon, "race, stock," related to φυλή phyle, "tribe, clan." is a taxonomic rank below kingdom and above class. "Phylum" is equivalent to the botanical term division....

(singular: phylum) — for animal

Animal

Animals are a major group of multicellular, eukaryotic organisms of the kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life. Most animals are motile, meaning they can move spontaneously and...

s; the term division, used for plant

Plant

Plants are living organisms belonging to the kingdom Plantae. Precise definitions of the kingdom vary, but as the term is used here, plants include familiar organisms such as trees, flowers, herbs, bushes, grasses, vines, ferns, mosses, and green algae. The group is also called green plants or...

s and fungi, 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
Class (biology)
In biological classification, class is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, order, family, genus, and species, with class fitting between phylum and order...

, and they, in turn, into orders
Order (biology)
In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...

, families
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...

, genera
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

(singular: genus), and species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

(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
Taxon
|thumb|270px|[[African elephants]] form a widely-accepted taxon, the [[genus]] LoxodontaA taxon is a group of organisms, which a taxonomist adjudges to be a unit. Usually a taxon is given a name and a rank, although neither is a requirement...

) 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

Cladistics is a method of classifying species of organisms into groups called clades, which consist of an ancestor organism and all its descendants . For example, birds, dinosaurs, crocodiles, and all descendants of their most recent common ancestor form a clade...

and phylogenetic nomenclature

Phylogenetic nomenclature

Phylogenetic nomenclature or phylogenetic taxonomy is an alternative to rank-based nomenclature, applying definitions from cladistics . Its two defining features are the use of phylogenetic definitions of biological taxon names, and the lack of obligatory ranks...

has led to a different way of looking at evolution (expressed in many nested clade

Clade

A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...

s) and this sometimes leads to a desire for more ranks.

The alternative

Over time, the 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

Evolution is any change across successive generations in the heritable characteristics of biological populations. Evolutionary processes give rise to diversity at every level of biological organisation, including species, individual organisms and molecules such as DNA and proteins.Life on Earth...

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

Evolutionary taxonomy

Evolutionary taxonomy, evolutionary systematics or Darwinian classification is a branch of biological classification that seeks to classify organisms using a combination of phylogenetic relationship and overall similarity. This type of taxonomy considers taxa rather than single species, so that...

, 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

, originating in the work of Willi Hennig

Willi Hennig

Emil Hans Willi Hennig was a German biologist who is considered the founder of phylogenetic systematics, also known as cladistics. With his works on evolution and systematics he revolutionised the view of the natural order of beings...

, 1950 onwards, each taxon is grouped so as to include the common ancestor of the group's members (and thus to avoid polyphyly

Polyphyly

A polyphyletic group is one whose members' last common ancestor is not a member of the group.For example, the group consisting of warm-blooded animals is polyphyletic, because it contains both mammals and birds, but the most recent common ancestor of mammals and birds was cold-blooded...

). Such taxa may be either monophyletic (including all descendants) such as genus Homo
Homo (genus)
Homo is the genus that includes modern humans and species closely related to them. The genus is estimated to be about 2.3 to 2.4 million years old, evolving from australopithecine ancestors with the appearance of Homo habilis....

, or paraphyletic (excluding some descendants), such as genus Australopithecus
Australopithecus
Australopithecus is a genus of hominids that is now extinct. From the evidence gathered by palaeontologists and archaeologists, it appears that the Australopithecus genus evolved in eastern Africa around 4 million years ago before spreading throughout the continent and eventually becoming extinct...

.

Originally, Linnaeus established three kingdoms in his scheme, namely for Plant

Plant

s, Animal

Animal

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

Monera

Monera is a superseded kingdom that contains unicellular organisms without a nucleus , such as bacteria....

, for prokaryote

Prokaryote

The prokaryotes are a group of organisms that lack a cell nucleus , or any other membrane-bound organelles. The organisms that have a cell nucleus are called eukaryotes. Most prokaryotes are unicellular, but a few such as myxobacteria have multicellular stages in their life cycles...

s (i.e., bacteria); Protist

Protist

Protists are a diverse group of eukaryotic microorganisms. Historically, protists were treated as the kingdom Protista, which includes mostly unicellular organisms that do not fit into the other kingdoms, but this group is contested in modern taxonomy...

a, for protozoans and most algae; and Fungi

Fungus

A fungus is a member of a large group of eukaryotic organisms that includes microorganisms such as yeasts and molds , as well as the more familiar mushrooms. These organisms are classified as a kingdom, Fungi, which is separate from plants, animals, and bacteria...

. 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 and Archaea

Archaea

The Archaea are a group of single-celled microorganisms. A single individual or species from this domain is called an archaeon...

, which contain the prokaryotes, and Eukaryota

Eukaryote

A eukaryote is an organism whose cells contain complex structures enclosed within membranes. Eukaryotes may more formally be referred to as the taxon Eukarya or Eukaryota. The defining membrane-bound structure that sets eukaryotic cells apart from prokaryotic cells is the nucleus, or nuclear...

, comprising the remaining forms. These arrangements should not be seen as definitive. They are based on the genome

Genome

In modern molecular biology and genetics, the genome is the entirety of an organism's hereditary information. It is encoded either in DNA or, for many types of virus, in RNA. The genome includes both the genes and the non-coding sequences of the DNA/RNA....

s of the organisms; as knowledge on this increases, so will classifications change.

Representing presumptive evolutionary relationships, especially given the wide acceptance of cladistic methodology and numerous molecular phylogenies that have challenged long-accepted classifications, within the framework of Linnaean taxonomy, is sometimes seen as problematic. Therefore, some systematists have proposed a PhyloCode

PhyloCode

The International Code of Phylogenetic Nomenclature, known as the PhyloCode for short, is a developing draft for a formal set of rules governing phylogenetic nomenclature...

to replace it.

External links

Wikispecies
International Code of Botanical Nomenclature (Saint Louis Code), 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

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