From Big Medical Encyclopedia

PHYLOGENESIS (Greek phylon the tribe, a sort, a look + genesis origin, an origin) — process of historical development of signs of organisms or systematic groups (taxons) from their emergence to the present, i.e. history of process of evolution.

The term is entered in 1866 is mute. scientist Gekkel (E. Haeckel) as pair to the term «ontogenesis» designating an ontogeny of an individual (see Ontogenesis). In such value the term «phylogenesis» («genealogy») on the volume and value almost did not differ from the term «evolution».

More strict definition of the term «phylogenesis» is given by I. I. Shmalga-uzen (1946), according to Krom phylogenesis is a historical number of ontogeneses which underwent natural selection, i.e. the sequence of the survivors and the individuals who left posterity connected by a ratio parents — children — grandsons etc. Such interpretation of the term «phylogenesis» follows from developed by I. I. Shmalgauzen and T. G. Dobr-zhanskpm concepts of mesh relationship of individuals in population, on a cut evolution of population — the elementary evolving unit (see Population, Theory of evolution) it is possible to submit as a space lattice, in a cut each small knot is a stage of crossing of the individuals who underwent selection, and each line — ontogenesis survived, i.e. undergone natural selection, individuals. Studying the historical sequence of ontogeneses, it is possible to track development of the new organization of individuals of this population. As evolution is continuous, theoretically in such way it is possible to track F. a taxon of any rank (see the Taxonomist, Taxonomic categories). Practically it cannot be carried out, first, because of incompleteness of the paleontologic chronicle (a rarity of stay in layers of crust of the dead of organisms and detection of their remains) and, secondly, because of impossibility rather fully to investigate the organization even of extant forms. Therefore F. always reconstruct, using for this purpose the separate signs reflecting transformations of the organization in the course of historical development of this taxon.

The «method of triple parallelism» based on comparison of data of a comparative anatomy, embryology and paleontology and been the basis for the special section of biology — phylogenetics was developed for reconstruction of phylogenesis by E. Gekkel.

So, data of a comparative anatomy allow to construct a comparative number of forms which is more or less precisely reflecting the directions of evolution of the studied signs. The embryological signs reflecting stages F. this taxon (see. Biogenetic law), and also paleontologic data, give the chance to estimate the sequence and a heating-up period of the studied signs. Thus, by means of phylogenetics historical development of animals and plants was reconstructed; T. prokariot (see Prokariotny organisms) and protozoa it is investigated not enough. At the same time F. ancestors of the person — anthropogenesis (see) treats the most in details developed sections of phylogenetics.

The big contribution to development of phylogenetics was made by domestic biologists. So, I. I. Mechnikov created the theory of an origin of a fagotsitella — the two-layer ancestor multicellular. A. O. Kowalewski showed unity of an origin of all animals. V. O. Kowalewski laid the foundation of evolutionary paleontology; modern representations about F. invertebrates were created substantially thanks to V. N. Beklemishev and A. V. Ivanov's works who created the most perfect theory of an origin of multicellularity. However the problem of an origin of types of an animal kingdom still is up to the end not solved. Under the influence of A. N. Severtsov and I. I. Shmalga-uzen's researches there were modern representations about F. vertebrate animals, to-rye J1 continues to develop. P. Tatarinov. Genealogy of plants is developed by A. JI. Takhtad-zhyan. The big contribution to studying of anthropogenesis was made by Ya. Ya. Rogin-sky and V. V. Bunak.

In process of development of phylogenetics, a cut the hl depends. obr. from accumulation of paleontologic data, need of detailing of phylogenetic reconstruction and increase in their reliability increases. A major step in development of methods of phylogenetics was creation of an ekologo-morfo-logical reconstruction method by K. A. Yudin (1974) F., the main requirement to-rogo consists in need of establishment of adaptive value of observed transformations. The last substantially depends on the choice of signs and attraction of these other fields of biology — molecular biology, biochemistry, physiology, biogeography, functional anatomy, etc.

Patterns F., coming to light at synthesis of data on phylogenesis of specific systematic groups, represent the section of the theory of evolution (see Darwinism, Theory of evolution).

Bibliography: Beklemishev V. N.

Bases of a comparative anatomy of invertebrates, t. 1 — 2, M., 1964; Dogel V. A. Zoology of invertebrates, M., 1981; R about-ginek and y Ya. Ya. Problems of anthropogenesis, M., 1977; Severtsov A. S. Introduction to the theory of evolution, M., 1981; Takhtadzhyan A. JI. System and genealogy of flowering plants, M. — L., 1966; Theoretical questions of systematization and genealogy of animals, under the editorship of B. E. Bykhov-sky, page 5, L., 1974; Sh m and l and at -

zen I. I. Problema of Darwinism, L., 1969. A.S. Severtsov.