Taxonomy (from and ) 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 (singular taxon). A resulting taxonomy is a particular classification ("the taxonomy of ..."), arranged in a hierarchical structure or classification scheme. An example of a modern classification is the one published in 2009 by the Angiosperm Phylogeny Group for all living flowering plant families (the APG III system).

Definitions[link]

The exact definition of taxonomy varies slightly from source to source, but the core of the discipline remains: the identification, naming, and classifying of organisms. As points of reference, three recent textbook definitions 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.

Application[link]

Taxonomy is a sub-discipline of biology, and is generally practiced by scientists 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 biodiversity and conservation. Without a working taxonomy of the organisms in any given area, estimating the amount of diversity present is unrealistic, making informed conservation decisions impossible. As conservation becomes ever more politically important, taxonomic work impacts not only the scientific community, but society as a whole.

Taxonomic descriptions[link]

Taxonomic descriptions generally involve the discovery and defining of taxa, according to a strict set of rules. In zoology, the nomenclature for the more commonly used ranks (superfamily to subspecies), is regulated by the ''International Code of Zoological Nomenclature''. In the fields of botany, phycology, and mycology, the naming of taxa is governed by the ''International Code of Nomenclature for algae, fungi, and plants''.

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 reference to the attributes that make the taxon unique. #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.

Classifying organisms[link]

Biological classification is a critical step in the taxonomic process, as it informs the user as to what the relatives of the taxon are hypothesized to be. Although the discipline of taxonomy itself does not deal with the investigations of how taxa are related to one another, it does serve to communicate these results to the user. To do this, it uses taxonomic ranks, including, among others (in order from most inclusive to least inclusive): Domain, Kingdom, Phylum, Class, Order, Family, Genus, and Species.

Phylogenetics[link]

:''See full article at Phylogenetics'' Today, traditional rank-based biological classifications persist in a structure largely unchanged since the 1700s; however, how the relationships of these taxa are investigated has changed drastically in recent decades. It is now common for biologists to devise a classification based on the results of phylogenetic analyses using DNA sequence data. Although phylogenetics itself is fundamental to modern-day systematics, its use for the description of new taxa, and placement within a classification scheme, is unrequired. As a result, phylogenetics tends to have a direct impact on taxonomic classifications, even though it is not a part of taxonomy.

Numerical taxonomy[link]

:''See full article at Numerical taxonomy'' In numerical taxonomy, the taxonomy is exclusively based on cluster analysis and neighbor joining to best-fit numerical equations that characterize measurable traits of a number of organisms. It results in a measure of evolutionary "distance" between species. This method has become quite rare in modern times, having been largely superseded by cladistic analyses, as numerical taxonomy is sensitive to being misled by plesiomorphic traits.

History of taxonomy[link]

Early "taxonomists"[link]

Taxonomy has been called "the world's oldest profession", and naming and classifying our surroundings has likely 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.

In the East, one of the earliest recorded pharmacopoeias was written by Shen Nung, Emperor of China (c. 3000 BC). He wanted to spread information related to agriculture and medicine, and is said to have tasted hundreds of plants with the goal of learning their medicinal value. Records after this are difficult to interpret for some time, but 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.

Aristotle to Plinius[link]

Historical records show that informally classifying organisms took place at least back to the days of Aristotle (Greece, 384-322 BC), who was the first to begin to classify all living things. Some of the terms he gave to animals, such as "invertebrates" and "vertebrates" are still commonly used today. His student Theophrastus (Greece, 370-285 BC) carried on this tradition, and wrote a classification of 480 plants called ''Historia Plantarum''. Again, several plant groups currently still recognized can be traced back to Theophrastus, such as ''Cornus'', ''Crocus'', and ''Narcissus''. The next major turn-of-the-millennia era taxonomist came in the form of Plinius (Rome, 23-79 AD). His elaborate 160-volume work Naturalis Historia described many plants, and even gave many of them Latin binomial names. Because of this, Plinius is sometimes referred to as the "Father of Botanical Latin".

Pre-Linnaean taxonomists[link]

It was not until c. 1500 years later that taxonomic works became ambitious enough to replace the ancient texts. This is often credited to the development of sophisticated optic lenses, which allowed for the morphology of organisms to be studied in much greater detail. One of the earliest authors to take advantage of this leap in technology was Andrea Cesalpino (Italy, 1519–1603), who is often referred to as "the first taxonomist". His magnum opus De Plantis came out in 1583, and described over 1500 plant species. Two large plant families that he first recognized are still in use today: the Asteraceae and Brassicaceae. Then in the sixteenth century John Ray (England, 1627–1705) wrote many important taxonomic works. Arguably his greatest accomplishment was Methodus Plantarum Nova (1682), where he published over 18,000 plant species. At the time his classifications were perhaps the most complex yet produced by any taxonomist, as he based his taxa on many combined characters. The next major taxonomic works were produced by Joseph Pitton de Tournefort (France, 1656–1708). His work from 1700, Institutiones Rei Herbariae, included over 9000 species in 698 genera, and directly influenced Linnaeus as it was the text he used as a young student.

The Linnaean era[link]

The Swedish botanist Carl Linnaeus (1707-1778) ushered in a new era of taxonomy. With his major works ''Systema Naturae'' 1st Edition in 1735, ''Species Plantarum'' in 1753, and ''Systema Naturae'' 10th Edition, he revolutionized modern taxonomy. His works implemented a standardized binomial naming system for animal and plant species, which proved to be an elegant solution to a chaotic and disorganized taxonomic literature. As a result the Linnaean system was born, and is still used in essentially the same way today as it was in the eighteenth century. Currently, plant and animal taxonomists regard Linnaeus' work as the "starting point" for valid names (at 1753 and 1758 respectively). Names published before these dates are referred to as "pre-Linnaean", and not considered valid (with the exception of spiders published in ''Svenska Spindlar''). Even taxonomic names published by Linnaeus himself before these dates are considered pre-Linnaean.

Non-biological taxonomies[link]

Almost anything—animate objects, inanimate objects, places, concepts, events, properties, and relationships—may be classified according to some taxonomic scheme. Taxonomies of the more generic kinds of things typically stem from philosophical investigations. Starting with the work of Aristotle in his work 'Categories' several philosophers, especially ontologists, arranged generic categories (also called types or classes) in a hierarchy that more or less satisfy the criteria for being a true taxonomy.

Taxonomy, or categorization, in the human cognition has been a major area of research in psychology. Social psychologists have sought to model the manner in which the human mind categorizes social stimuli (Self-categorization theory is a prototypical example). Some have argued that the adult human mind naturally organizes its knowledge of the world into such systems. Anthropologists have observed that taxonomies are generally embedded in local cultural and social systems, and serve various social functions.

Other taxonomies, such as those analyzed by Durkheim and Lévi-Strauss, are sometimes called folk taxonomies to distinguish them from scientific taxonomies. Baraminology is a taxonomy used in creation science which in classifying form taxa resembles folk taxonomies. The phrase "enterprise taxonomy" is used in business (see economic taxonomy) to describe a very limited form of taxonomy used only within one organization. An example would be a certain method of classifying trees as "Type A", "Type B" and "Type C" used only by a certain lumber company for categorising log shipments. The military and health care/safety science fields also have their own taxonomies. In the field of modern computing, the semantic web requires formal XML extension taxonomies (like XBRL) called namespaces.

See also[link]

Alpha taxonomy

Barcode of Life

Biological classification

Evolutionary taxonomy

Identification (biology)

Nomenclature

Phylogenetics

Species description

Species problem

Systematics

Type (biology)

References[link]

External links [link]

What is taxonomy? at the ''Natural History Museum London''

What is taxonomy? at the ''European Distributed Institute of Taxonomy''

The history of taxonomy at ''Dave's Garden''

Taxonomy related articles at ''The Guardian''

Taxonomy at NCBI the ''National Center for Biotechnology Information''

Taxonomy at UniProt the ''Universal Protein Resource''

ITIS the ''Integrated Taxonomic Information System''

GTI the ''Global Taxonomic Initiative''

TRIN the ''Taxonomy Research & Information Network''

CETaF the ''Consortium of European Taxonomic Facilities''

Wikispecies ''free species directory''

Taxonomy Classification systems Category:Greek loanwords Category:Nomenclature

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