TAXONOMY (from Ancient Greek τάξις _(taxis )_, meaning 'arrangement', and -νομία _(-nomia)_, meaning 'method ') is the science of defining and naming groups of biological organisms on the basis of shared characteristics. Organisms are grouped together into taxa (singular: taxon) and these groups are given a taxonomic rank ; groups of a given rank can be aggregated to form a super group of higher rank, thus creating a taxonomic hierarchy. The principal ranks in modern use are kingdom, phylum, class, order, family, genus and species. The Swedish botanist Carl Linnaeus is regarded as the father of taxonomy, as he developed a system known as Linnaean taxonomy for categorization of organisms and binomial nomenclature for naming organisms.
With the advent of such fields of study as phylogenetics , cladistics , and systematics , the Linnaean system has progressed to a system of modern biological classification based on the evolutionary relationships between organisms, both living and extinct.
* 1 Definition
* 1.1 Alpha and beta taxonomy * 1.2 Microtaxonomy and macrotaxonomy
* 2 History
* 2.1 Pre-Linnaean
* 2.1.1 Early taxonomists
* 2.1.2 _Bhagavata Purana_
* 2.1.3 Ancient times
* 2.1.4 Medieval
* 2.2 The Linnaean era
* 3 Modern system of classification
* 3.1 Kingdoms and domains * 3.2 Recent comprehensive classifications
* 4 Application
* 4.1 Classifying organisms * 4.2 Taxonomic descriptions * 4.3 Author citation
* 5 Phenetics * 6 Databases * 7 See also * 8 Notes * 9 References * 10 Bibliography * 11 External links
The exact definition of taxonomy varies from source to source, but the core of the discipline remains: the conception, naming, and classification of groups of organisms. As points of reference, recent definitions of taxonomy are presented below:
* Theory and practice of grouping individuals into species, arranging species into larger groups, and giving those groups names, thus producing a classification * A field of science (and major component of systematics ) that encompasses description, identification, nomenclature, and classification * The science of classification, in biology the arrangement of organisms into a classification * "The science of classification as applied to living organisms, including study of means of formation of species, etc." * "The analysis of an organism's characteristics for the purpose of classification" * " studies phylogeny to provide a pattern that can be translated into the classification and names of the more inclusive field of taxonomy" (listed as a desirable but unusual definition)
The varied definitions either place taxonomy as a sub-area of systematics (definition 2), invert that relationship (definition 6), or appear to consider the two terms synonymous. There is some disagreement as to whether biological nomenclature is considered a part of taxonomy (definitions 1 and 2), or a part of systematics outside taxonomy. For example, definition 6 is paired with the following definition of systematics that places nomenclature outside taxonomy:
* _Systematics_: "The study of the identification, taxonomy and nomenclature of organisms, including the classification of living things with regard to their natural relationships and the study of variation and the evolution of taxa".
A whole set of terms including taxonomy, systematic biology , systematics, biosystematics , scientific classification, biological classification, and phylogenetics have at times had overlapping meanings – sometimes the same, sometimes slightly different, but always related and intersecting. The broadest meaning of "taxonomy" is used here. The term itself was introduced in 1813 by de Candolle , in his _Théorie élémentaire de la botanique_.
ALPHA AND BETA TAXONOMY
Not to be confused with Alpha diversity .
The term "ALPHA TAXONOMY" is primarily used today to refer to the discipline of finding, describing, and naming taxa , particularly species. In earlier literature, the term had a different meaning, referring to morphological taxonomy, and the products of research through the end of the 19th century.
William Bertram Turrill introduced the term "alpha taxonomy" in a series of papers published in 1935 and 1937 in which he discussed the philosophy and possible future directions of the discipline of taxonomy.
… there is an increasing desire amongst taxonomists to consider their problems from wider view-points, to investigate the possibilities of closer co-operation with their cytological, ecological and genetical colleagues and to acknowledge that some revision or expansion, perhaps of a drastic nature, of their aims and methods may be desirable … Turrill (1935) has suggested that while accepting the older invaluable taxonomy, based on structure, and conveniently designated "alpha", it is possible to glimpse a far-distant taxonomy built up on as wide a basis of morphological and physiological facts as possible, and one in which "place is found for all observational and experimental data relating, even if indirectly, to the constitution, subdivision, origin and behaviour of species and other taxonomic groups". Ideals can, it may be said, never be completely realized. They have, however, a great value of acting as permanent stimulants, and if we have some, even vague, ideal of an "omega" taxonomy we may progress a little way down the Greek alphabet. Some of us please ourselves by thinking we are now groping in a "beta" taxonomy.
Turrill thus explicitly excludes from alpha taxonomy various areas of study that he includes within taxonomy as a whole, such as ecology, physiology, genetics, and cytology. He further excludes phylogenetic reconstruction from alpha taxonomy (pages 365–366).
Later authors have used the term in a different sense, to mean the delimitation of species (not subspecies or taxa of other ranks), using whatever investigative techniques are available, and including sophisticated computational or laboratory techniques. Thus, Ernst Mayr in 1968 defined BETA TAXONOMY as the classification of ranks higher than species.
An understanding of the biological meaning of variation and of the evolutionary origin of groups of related species is even more important for the second stage of taxonomic activity, the sorting of species into groups of relatives ("taxa") and their arrangement in a hierarchy of higher categories. This activity is what the term classification denotes; it is also referred to as BETA TAXONOMY.
MICROTAXONOMY AND MACROTAXONOMY
Main article: Species problem
How species should be defined in a particular group of organisms gives rise to practical and theoretical problems that are referred to as the species problem . The scientific work of deciding how to define species has been called microtaxonomy. By extension, macrotaxonomy is the study of groups at higher taxonomic ranks , from subgenus and above only, than species.
While some descriptions of taxonomic history attempt to date taxonomy
to ancient civilizations, a truly scientific attempt to classify
organisms did not occur until the 18th century. Earlier works were
primarily descriptive, and focused on plants that were useful in
agriculture or medicine. There are a number of stages in this
scientific thinking. Early taxonomy was based on arbitrary criteria,
the so-called "artificial systems", including Linnaeus's system of
sexual classification. Later came systems based on a more complete
consideration of the characteristics of taxa, referred to as "natural
systems", such as those of de Jussieu (1789), de Candolle (1813) and
Bentham and Hooker (1862–1863). These were pre-evolutionary in
thinking. The publication of
Naming and classifying our surroundings has probably been taking place as long as mankind has been able to communicate. It would always have been important to know the names of poisonous and edible plants and animals in order to communicate this information to other members of the family or group.
Medicinal plant illustrations show up in Egyptian wall paintings from c. 1500 BC. The paintings clearly show that these societies valued and communicated the uses of different species, and therefore had a basic taxonomy in place.
In Canto 3, chapter 10 of _
* _Vanaspatis_ – large trees that grow fruits without flowering. * _Drumas_ – large trees that bloom and give fruits. * _Osadhis_ – trees that die soon after they give fruits. * _Latas_ – creepers and tiny plants. * _Viruts_ – plants that grow as bushes. * _Tvaksaras_ – plants hollow inside with strong barks like bamboos.
Further information: Aristotle\'s biology § Classification
Organisms were first classified by
Taxonomy in the
THE LINNAEAN ERA
Main article: Linnaean taxonomy _ Title page of Systema Naturae _, Leiden, 1735
The Swedish botanist
Carl Linnaeus (1707–1778) ushered in a new
era of taxonomy. With his major works _
Systema Naturae _ 1st Edition
in 1735, _
MODERN SYSTEM OF CLASSIFICATION
Evolutionary taxonomy and
Whereas Linnaeus classified for ease of identification, the idea of
Linnaean taxonomy as translating into a sort of dendrogram of the
With Darwin's theory, a general acceptance quickly appeared that a classification should reflect the Darwinian principle of common descent . Tree of Life representations became popular in scientific works, with known fossil groups incorporated. One of the first modern groups tied to fossil ancestors was birds . Using the then newly discovered fossils of _ Archaeopteryx _ and _ Hesperornis _, Thomas Henry Huxley pronounced that they had evolved from dinosaurs, a group formally named by Richard Owen in 1842. The resulting description, that of dinosaurs "giving rise to" or being "the ancestors of" birds, is the essential hallmark of evolutionary taxonomic thinking. As more and more fossil groups were found and recognized in the late 19th and early 20th centuries, palaeontologists worked to understand the history of animals through the ages by linking together known groups. With the modern evolutionary synthesis of the early 1940s, an essentially modern understanding of the evolution of the major groups was in place. As evolutionary taxonomy is based on Linnaean taxonomic ranks, the two terms are largely interchangeable in modern use.
The cladistic method (or cladism) has emerged since the 1960s. In
Julian Huxley used the term clade. Later, in 1960, Cain and
Harrison introduced the term cladistic. The salient feature is
arranging taxa in a hierarchical evolutionary tree , ignoring ranks.
A taxon is called monophyletic, if it includes all the descendants of
an ancestral form. Groups that have descendant groups removed from
them (e.g. dinosaurs , with birds as offspring group) are termed
paraphyletic , while groups representing more than one branch from
the tree of life are called polyphyletic . The _International Code
KINGDOMS AND DOMAINS
The basic scheme of modern classification. Many other levels can be used; the highest level, domain, is both new and disputed. Main article: Kingdom (biology)
Well before Linnaeus, plants and animals were considered separate Kingdoms. Linnaeus used this as the top rank, dividing the physical world into the plant, animal and mineral kingdoms. As advances in microscopy made classification of microorganisms possible, the number of kingdoms increased, five and six-kingdom systems being the most common.
Domains are a relatively new grouping. First proposed in 1977, Carl
Woese 's three-domain system was not generally accepted until later.
One main characteristic of the three-domain method is the separation
Thomas Cavalier-Smith , who has published extensively on the classification of protists , has recently proposed that the Neomura , the clade that groups together the Archaea and Eucarya , would have evolved from Bacteria, more precisely from Actinobacteria . His 2004 classification treated the archaeobacteria as part of a subkingdom of the Kingdom Bacteria, i.e. he rejected the three-domain system entirely. Stefan Luketa in 2012 proposed a five "dominion" system, adding Prionobiota (acellular and without nucleic acid) and Virusobiota (acellular but with nucleic acid) to the traditional three domains.
Linnaeus 1735 Haeckel 1866 Chatton 1925 Copeland 1938 Whittaker 1969 Woese et al. 1990 Cavalier-Smith 1998
2 kingdoms 3 kingdoms 2 empires 4 kingdoms 5 kingdoms 3 domains 6 kingdoms
Vegetabilia Plantae Plantae Plantae Plantae
Animalia Animalia Animalia Animalia Animalia
Main article: Kingdom (biology) § Summary
RECENT COMPREHENSIVE CLASSIFICATIONS
Partial classifications exist for many individual groups of organisms and are revised and replaced as new information becomes available, however comprehensive treatments of most or all life are rarer; two recent examples are that of Adl et al., 2012, which covers eukaryotes only with an emphasis on protists, and Ruggiero et al., 2015, covering both eukaryotes and prokaryotes to the rank of Order, although both exclude fossil representatives.
Biological taxonomy is a sub-discipline of biology , and is generally practiced by biologists known as "taxonomists", though enthusiastic naturalists are also frequently involved in the publication of new taxa. The work carried out by taxonomists is crucial for the understanding of biology in general. Two fields of applied biology in which taxonomic work is of fundamental importance are the studies of biodiversity and conservation . Without a working classification of the organisms in any given area, estimating the amount of diversity present is unrealistic, making informed conservation decisions impossible.
Main article: Taxonomic rank
Biological classification is a critical component of the taxonomic
process. As a result, it informs the user as to what the relatives of
the taxon are hypothesized to be.
Biological classification uses
taxonomic ranks, including among others (in order from most inclusive
to least inclusive): Domain , Kingdom,
Phylum , Class , Order , Family
The "definition" of a taxon is encapsulated by its description or its
diagnosis or by both combined. There are no set rules governing the
definition of taxa, but the naming and publication of new taxa is
governed by sets of rules. In zoology , the nomenclature for the more
commonly used ranks (superfamily to subspecies ), is regulated by the
_International Code of Zoological
The initial description of a taxon involves five main requirements:
* The taxon must be given a name based on the 26 letters in the Latin alphabet (a binomial for new species, or uninomial for other ranks). * The name must be unique (i.e. not a homonym ). * The description must be based on at least one name-bearing type specimen. * It should include statements about appropriate attributes either to describe (define) the taxon, or to differentiate it from other taxa (the diagnosis, _ICZN Code_, Article 13.1.1, _ICN_, Article 38). Both codes deliberately separate defining the content of a taxon (its circumscription ) from defining its name. * These first four requirements must be published in a work that is obtainable in numerous identical copies, as a permanent scientific record.
However, often much more information is included, like the geographic range of the taxon, ecological notes, chemistry, behavior, etc. How researchers arrive at their taxa varies: depending on the available data, and resources, methods vary from simple quantitative or qualitative comparisons of striking features, to elaborate computer analyses of large amounts of DNA sequence data.
Main articles: Author citation (botany) and Author citation (zoology)
An "authority" may be placed after a scientific name. The authority is the name of the scientist or scientists who first validly published the name. For example, in 1758 Linnaeus gave the Asian elephant the scientific name _Elephas maximus_, so the name is sometimes written as "_Elephas maximus_ Linnaeus, 1758". The names of authors are frequently abbreviated: the abbreviation _L., for Linnaeus,_ is commonly used. In botany, there is, in fact, a regulated list of standard abbreviations (see list of botanists by author abbreviation ). The system for assigning authorities differs slightly between botany and zoology . However, it is standard that if a species' name or placement has been changed since the original description, the original authority's name is placed in parentheses.
Main article: Phenetics
In phenetics, also known as taximetrics, or numerical taxonomy, organisms are classified based on overall similarity, regardless of their phylogeny or evolutionary relationships. It results in a measure of evolutionary "distance" between taxa. Phenetic methods have become relatively rare in modern times, largely superseded by cladistic analyses, as phenetic methods do not distinguish plesiomorphic from apomorphic traits. However, certain phenetic methods, such as neighbor joining , have found their way into cladistics, as a reasonable approximation of phylogeny when more advanced methods (such as Bayesian inference ) are too computationally expensive.
Main article: Taxonomic database
Modern taxonomy uses database technologies to search and catalogue classifications and their documentation. While there is no commonly used database, there are comprehensive databases such as the _ Catalogue of Life _, which attempts to list every documented species. The catalogue listed 1.64 million species for all kingdoms as of April 2016, claiming coverage of more than three quarters of the estimated species known to modern science.
* Automated species identification * Consortium for the Barcode of Life * Genetypes * Glossary of scientific naming * Identification (biology) * _ Incertae sedis _, or "of uncertain placement", a term used for a taxonomic group where its broader relationships are unknown or undefined * Taxonomy (general) * Type (biology)
* ^ This ranking system can be remembered by the mnemonic "Do Kings Play Chess On Fine Glass Sets?"
* ^ _A_ _B_ Wilkins, J. S. (5 February 2011). "What is systematics
and what is taxonomy?". Retrieved 21 August 2016.
* ^ Judd, W.S., Campbell, C.S., Kellogg, E.A., Stevens, P.F.,
Donoghue, M.J. (2007) Taxonomy. In _
* Stace, Clive A. (1989) . _
_ Look up TAXONOMY _ in Wiktionary, the free dictionary.
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