From Big Medical Encyclopedia

SYSTEMATICS (the Greek systematikos arranged, relating to system) — the division of science (e.g., botanists, zoology), the main objective to-rogo is streamlining of this or that set of objects in uniform structural system.

The purpose C. in biology — creation of natural system of animal and vegetable organisms. The most general concepts C. — a taxon, the taxonomical relations, a taxonomical rank, a taxonomical sign. The taxon is main unit of taxonomical system; it reflects a community a nek-swarm of set of live organisms on the basis of their skhodstvenny and (or) related relations; the taxon is designated according to the existing rules of the nomenclature (see. Taxonomic categories ). Both forms of relationship (skhodstvenny and related) make the taxonomical relations. The taxonomical rank reflects the provision of a taxon in a taxonomy (hierarchy) of taxonomical system. A taxonomical sign — the characteristic of live organisms allowing to estimate their taxonomical relations. The most important parameter of a taxonomical sign — its «weight» — specifies probability of adequate reflection by this sign of all taxonomical relations of this taxon.

The first attempt of systematization of basic groups of animals belongs to Aristotle. The founder S. consider K. Linney who developed philosophy of taxonomy, rules of the nomenclature which are the cornerstone modern of Page. It possesses the first arranged hierarchical system of classification of animals and plants. The main achievement of S. of the linnean period — the statement of the general principle, according to Krom a variety of live organisms is arranged in natural groups. The theory of evolution of Ch. Darvin theoretically proved this principle (see. Theory of evolution ). Formation of the synthetic theory of evolution, first of all doctrines was of great importance for modern S.'s development about populations (see). Judgment of the general principles of biological S., use of the ideas and methods of the general theory classifications (see) and theories recognitions of images (see) led to creation of own theory

of S. Sovremennaya S. is divided by character of solvable tasks on theoretical, practical and applied. Theoretical S. (taxonomy) considers the purposes, the general principles and specific methods S. Prakticheskaya S. represents the taxonomical analysis of specific groups of live organisms, clarification of the taxonomical relations between them. The important sphere of practical S. — definition of the rules regulating classification (so-called codes of the nomenclature). Applied S. is expressed in drawing up attributive tables, in work on taxonomical identification biol. objects etc.

Theoretical S. is divided by the general principles of allocation of taxons and interpretation of the taxonomical relations on fenetichesky, phylogenetic and evolutionary. Fe-neticheskaya S. is historically primary and unlike the phylogenetic and evolutionary directions reduces the taxonomical relations only (or it is preferential) to skhodstvenny, without considering the related relations. The problem of «weight» of taxonomical signs or is excluded from the analysis (to all signs identical «weight» is attributed), or is solved formally, proceeding from the nature of distribution of values of signs to sets of organisms (taxons). Need of the analysis is anyway postulated as it is possible bigger number of taxonomical signs. Similarity of organisms (taxons) on all set of signs serves as a direct measure of their taxonomical proximity. Therefore the taxonomical systems designed within fe-netichesky S. are purely skhodstvenny.

In modern S. this direction is presented by the so-called numerical taxonomy which is quantitatively expressing all skhodstvenny taxonomical relations that shall eliminate an element of subjectivity in assessment of the status and a rank of taxons. For this purpose in numerical taxonomy two groups of methods of multivariate statistics — dendrografiche-sky (cluster analysis) and ordinates-nye are used preferential (factor analysis). The numerical taxonomy is based on creation enough formal taxonomical systems and quite often replaces traditional taxonomical concepts, using new: phenon instead of a taxon, the fenetichesky relations instead of taxonomical, digital coding instead of the traditional nomenclature. Despite many shortcomings caused by formalistic approach, the numerical taxonomy is capable to provide the proof of reality of not hierarchical taxonomical systems, definition of optimum number of the taxonomic categories which are adequately reflecting the taxonomical relations of a final set of taxons, etc. Nek-ry methods of numerical taxonomy are successfully used in other directions C.

Two other directions of modern S. — phylogenetic and evolutionary — unlike hair dryer-tichesky S. in a varying degree focus attention on the related relations, considering them as the leader components of the taxonomical relations or at least equivalent from skhodstvenny; degree of taxonomical proximity in many respects (or it is exclusive) is defined by degree of relationship. Therefore they are forced to solve the common fundamental problem of transition from observed purely skhodstvenny relations to not observed related. It finds the reflection in a problem of assessment of phylogenetic «weight» of taxonomical signs: «weight» of a sign is considered that big, than big information is born by a sign about the related relations; at creation of systems only those signs which have largest phylogenetic «weight» are used.

Phylogenetic (kladistiches-ky) S. considers the related (genealogical) relations as an exclusive basis for creation of taxonomical systems. Therefore phylogenetic S.'s problem is definition of degree of relationship, edges is directly proportional to time of division of groups of organisms in the course of evolution. Those signs have largest «weight», to-rye allow to define the specified time most precisely. Among them special significance is attached to signs, changes to-rykh are minimum connected with adaptation of organisms to specific conditions of existence or are at least minimum subject to the modifying influence of the environment. Therefore in phylogenetic S. biochemical methods (chemo - a systematics), from to-rykh especially zhazhna methods of «molecular clock» and molecular hybridization of DNA (a so-called genosistematik) are most widely applied. The phylogenetic system represents direct interpretation of a family tree of taxons: the quantity of taxonomic categories in system is defined by number of branching points of this tree, and the taxons dispersing from one branching points (i.e. sisterly groups), receive an identical rank. Phylogenetic S.'s lack consists in underestimation of value of degree and character of evolutionary divergence of taxons, their evolutionary specifics.

Evolutionary S. in the analysis of the taxonomical relations equally considers both the skhodstvenny, and related relations. Related a component in this case that is identical in phylogenetic S.; skhodstvenny a component is considered not formally and as a basis of assessment of evolutionary specifics of taxons. The last means that a necessary element of creation of taxonomical system is search of the so-called decisive gaps between taxons indicating that each taxon is characterized by a certain evolutionary tendency and that members of this taxon in the evolutionary changes entirely submit to this tendency. Therefore in evolutionary S. the analysis of «weight» of taxonomical signs is always specific and considers features of each separate taxon. In the natural system designed within evolutionary S., the number of taxonomic categories and a rank of taxons are defined generally by number and scale of decisive gaps. A lack of such approach — lack of the accurate formalized criteria of exarticulation of taxons and assessment of their rank.

Practical S. represents use of the principles of taxonomy during the studying of specific groups of live organisms, creation of separate, private, taxonomical systems — skhodstvenny, phylogenetic or approaching to natural. Classification as the procedure begins with the analysis of the signs chosen for the characteristic of all studied set of organisms, allocation taxonomical essential, determination of «weight» of each of them. Creation of taxonomical system is carried out or as consecutive association of the lowest taxons in taxons of higher rank or as a consecutive partition of a taxon of higher rank on the coordinated taxons. The subsequent stage of classification provides the taxonomical characteristic of system, in a cut for each taxon the main diagnostic characters are specified: allocation of type — a taxon of more low rank or (in case of a taxon of the lowest rank) a standard copy; nomenclature designation, or assignment to a taxon of the suitable Latin name. All procedure of the taxonomical characteristic is regulated by the rules consolidated in codes of the zoological nomenclature (1964), the botanical nomenclature (1975) and the nomenclature of bacteria (1975).

Applied S. is directed to simplification of taxonomical identification of live organisms, their remains and traces of life activity for nonspecialists. For this purpose identification tables in the form of the attributive keys added with drawings and lists of distinguishing characters are formed. The taxonomical system constructed as a result of classification supplied with identification tables is that universal reference book, the Crimea also scientists at the indication of taxonomical accessory are guided practical investigated biol. objects.

In the medical practice connected with use of achievements in the field of biology the applied S.'s value developing questions of identification of taxons of a specific rank is especially big. As a rule, planning of strategy of fight against causative agents of diseases, dangerous to the person, or uses medicinal plants (see) in many respects depends on ability to distinguish these types. Insufficient development of S. of such types can cause mistakes in carrying out practical medicobiological works.

In medical practice more and more widely the principles C. are used during the development of nomenclatures of diseases, viruses, microbes, preparation of thesauruses, in projects of informatsionnopoiskovy systems etc.

See also Nomenclature and classification of diseases , System , Thesaurus .

Bibliography: Jaffray Ch. The biological nomenclature, the lane with English, M., 1980; Zarenkov N. A. Lectures on the theory of a systematics, M., 1976; Mayr E. The principles of a zoological systematics, the lane with English, M., 1971; H e n n i g W. Phylogenetic systematlcs, Urbana and. lake, 1966; H e at w about about d V. N of Plant taxonomy, L., 1976; Simpson G. G. Principles of animal taxonomy, N. Y., 1961; S n e-a t h P. H. A. a. S o k a 1 R. R. Numerical taxonomy, principles and practice of numerical classification, San Francisco, 1973.

I. Ya. Pavlinov.