From Big Medical Encyclopedia

TAXONOMIC CATEGORIES (Greek taxis creation, an arrangement as it should be + nomos the law) — the concept from the field of systematization, to-rogo decides hierarchy of separate groups of objects (taxons) on the basis of their skhodstvenny and (or) related relations on the help. Degree of similarity or relationship reflects the taxonomical relations, and the provision of a taxon in a taxonomy (hierarchy) — its taxonomical rank (level of the organization of taxonomical system). Than more remote relations connect this taxon with others (the its situation in system is more isolated), the higher it a taxonomical rank (see. Systematics ).

Principle of hierarchical creation biol. systems and the main Since were established by K. Linney who allocated seven Since — a kingdom (Regnum), type or department (Phylum or Sectio) a class (Classis), group or an order (Ordo), a sort (Genus), a look (Species), a version (Varietas). In 19 century the family (Familia) was added to these Since. In a systematics of 20 century much more fractional hierarchical structure is accepted, in a cut the quantity Since is considerably increased. The cohort (Cohors), a tribe (Tribus) and others Since intermediate rank are added to them. Names of other taxonomic categories of an intermediate rank form by addition of a prefix over - (super-) or under - (sub-, infra-) to the name of the main taxonomic category, napr, a superorder (Superordo), a subfamily (Subfamilia). Besides, taxonomic categories can be divided into the lowest (a look and intraspecific taxons) and the highest (all nadvidovy taxons).

Since directly characterize not specific subjects to classification, and only a way of its creation, the logical principles of the solution of a problem of taxonomy. At the same time the hierarchy of taxonomical system has absolute character as it is set by two absolute levels (ranks) limiting this system from above and from below. To the top level there corresponds belonging of all of the populations inhabiting Earth to one taxon of the highest Since — to the world of live organisms; to the lowest level — ratios between intraspecific taxons. However in these borders the rank of a specific taxon is relative as the taxonomical relations have no absolute scale of measurements and are defined by relative criteria of degree of similarity and relationship. Assessment of equivalence of a rank of taxons in different systems is possible only in that case when these systems are characterized by comparable taxonomical signs. E.g., for all bisexual organisms taxons of a specific rank can be theoretically allocated by universal and absolute criterion of reproductive isolation (see the Look) that does a taxonomic category of a look in this case absolute.

Multigradualness of taxonomical hierarchy is caused by need of elimination of a contradiction between the continuous nature of evolution and discretization Since. Numerous Since intermediate ranks enter into system to reflect .maleyshy distinctions in character of the taxonomical relations between separate groups of organisms.

Nomenclature designation of the taxons relating to different Since is more or less strictly regulated. Names of the highest taxons make of one word (the unitary, uninominal nomenclature), and names of taxons of each rank have the fixed terminations determined by codes of the nomenclature (see the Taxonomist). E.g., the name of any taxon of a rank of family shall have the termination - an aseaa (in botany) or - idae (in zoology). Names of the lowest taxons make of several words: the first is the generic name, the second — a specific name (the binary, binomial nomenclature), the third — the name of an intraspecific taxon (the trinominal-ny nomenclature for infravido-vy Since).

Set of the taxons of a different rank including this terminal taxon characterizes position of the last in system of live organisms. E.g., the provision of the taxon corresponding to a look a domestic dog is described by the following hierarchical system of the coordinated taxons: animal kingdom (Regnum Animalia) — type of chordates (Phylum Chordata) — a subtype of cranial (Subphylum Craniata) — a class of mammals (Classis Mammalia) — a subclass of viviparous (Sub-classis Theria) — infraklass placental (Infraclassis Eutheria) — a cohort of predatory and hoofed (Cohors Ferungulata) — group of predatory (Ordo Carnivora) — a superfamily of canids (Superfamilia Canoidea) — family of canids (Familia Cani-dae) — a subfamily of the real canids (Subfamilia Caninae) — a genus of wolves (Genus Canis) — a subgenus of wolves and dogs (Subgenus Canis) — a look a domestic dog (Species Canis familiaris).

Thus, with the help Since the main objective — creation of natural system of animal and vegetable organisms is carried out that in addition to purely theoretical value has also especially applied character. In particular, development of a problem of identification of taxons of a specific rank, creation of universal reference books (determinants) facilitates distinguishing of separate types biol. objects (e.g., separate types of medicinal, edible or noxious plants), provides the choice of the correct strategy of fight against different types of causative agents of diseases of the person and animals.

Bibliography: See bibliogr. to St. Systematics .

I. Ya. Pavlinov.