From Big Medical Encyclopedia

BIOGENETIC LAW (grech, bios life of genetikos belonging to the birth, an origin) — a complex of the theoretical generalizations describing communication between individual and historical development of live organisms.

B. z. it was formulated in 1866 it. zoologist E. Gekkel (E.N. Haeckel): «A number of forms through which there passes the individual organism at the development, beginning from an ovum and finishing quite developed state, is the short, compressed repetition of the long line of forms passed by animal ancestors of the same organism or patrimonial forms of its look since the most ancient times of so-called organic creation, up to the present», i.e. «ontogenesis is bystry and short repetition of phylogenesis».

Basis for B.'s creation z. F. Müller's work «For Darwin» served (1864), in a cut it was shown that phylogenetic new signs of adult organisms result from change of ontogenesis at descendants — lengthenings or deviations from ontogenesis of ancestors. In both cases the structure of an adult organism changes.

According to Gekkel, phylogeny happens by summing of changes of an adult organism and their shift on earlier stages of ontogenesis, i.e. phylogenesis is base for ontogenesis, the part of the reduced and distorted record of evolutionary transformations of adult organisms is assigned to Krom (see Ontogenesis, Phylogeny). From these positions Gekkel divided all signs of the developing organism into two categories: palingeneza (see) — at

signs or stages of an ontogeny, repeating, or rekapituliruyushchy stages of phylogenesis of adult ancestors, and cenogenesises in ontogenesis of descendants — any signs breaking reconciliation. Gekkel considered the reason of cenogenesises secondary devices of organisms to those conditions in which their ontogenesis proceeds. Therefore the temporary (provisional) devices which are providing survival of an individual at these or those stages of an ontogeny and absent at an adult organism, napr, embryonic membranes of a fruit (actually cenogenesises), as well as changes of laying of bodies in time (geterokhroniya) or the place (heterotopy) and secondary changes of a way of ontogenesis of this body were carried to cenogenesises. All these transformations break a paleogenesis and by that complicate use of data of embryology for reconstruction of phylogenesis for the sake of what as A. N. Severtsov (1939) showed, Gekkel formulated B. z.

At the beginning of 20 century by a number of authors it was proved that F. Muller postulating emergence of phylogenetic changes in result of transformations of processes of ontogenesis is more correct, than Gekkel, explained the ratio between individual and historical development proved in a crust, time from positions of genetics. Since evolution happens in a lineage, in it only generative mutations changing the hereditary device of gametes or a zygote matter. Only these mutations are transferred to the next generation, in Krom they change the course of ontogenesis thanks to what are shown in a phenotype of descendants. If in the next generation ontogenesis proceeds the same as in previous, then adult organisms of both generations will be identical.

On the basis of idea of primacy of ontogenetic changes And. N. Severtsov developed the theory of a filembriogenez — the description of ways (modes) of evolutionary changes of the course of ontogenesis which lead to transformation of bodies of descendants. The most widespread way of progressive evolution of bodies is the anaboly, or an extension of final stages of development. In this case to that stage, on a cut the organogeny at ancestors terminated, it is added new (lengthening of ontogenesis), and the final stage of ontogenesis of ancestors is as if shifted by the beginning of development:

Anabolies of E, F, G, H conduct to a further organogeny and cause reconciliation of ancestral states (e, f, g). Therefore, at evolution by an anaboly there is a palingenetichesky way of ontogenesis, however in this case there is not a shift of stages of ontogenesis, but a further phylogenetic organogeny which was already existing at ancestors.

The second mode of a filembriogenez — deviation, or a deviation at intermediate stages of development. In this case the organogeny of descendants begins the same as at ancestors, but then it changes the direction though additional stages and do not arise:

Deviations reconstruct ontogenesis, since intermediate stages (s1, d2, d3) that leads to change of a definitivny structure of body (E1, E2, E3). Reconciliation in ontogenesis of abc1d1E1 is traced at stages of ab, and in ontogenesis of abc1d3E3 — at stages of abc1. The third, the most rare, a mode of progressive evolution — arkhallaksis, or change of primary rudiments of bodies:

Arkhallaksis is characterized by transformation of the earliest stages of ontogenesis, since its bookmark (a1, a2, a3) that can lead to emergence of the new, being absent at ancestors bodies (E1, E2, E3) — primary arkhallaksis, or to radical reorganization of ontogenesis of body without essential changes of its definitivny structure — secondary arkhallaksis. At this way of evolution reconciliation is absent.

By means of filembriogenez there is also evolutionary reduction of bodies. Distinguish two types of a reduction: rudimentation (underdevelopment) and afaniziya (complete disappearance). At a rudimentation the body which is normally developed and functioning at ancestors loses the functional value at descendants. In this case, according to A. N. Severtsov, the reduction is carried out by a negative arkhallaksis: a bookmark at descendants is less and more weakly, than at ancestors, develops more slowly and does not reach an ancestral definitivny stage. As a result the body of descendants is underdeveloped. At an afaniziya the reduced body not only loses the functional value, but also becomes harmful to an organism. Ontogenesis of such body, as a rule, begins and a nek-swarm time proceeds the same as at ancestors, but then there is a negative anaboly — the body resolves, and process goes as it should be, the return to development, up to disappearance of the bookmark.

The theory of a filembriogenez is close to Müller's representations. However And. N. Severtsov allocated a mode of an arkhallaksis which can be observed only at evolutionary transformations of parts, but not the whole organism studied by Müller. The Soviet biologists proved that by means of filembriogenez not only bodies, but also fabrics, and cells of metaphytes evolve. There are proofs of evolution by filembriogenez not only the developed bodies, but also provisional devices (cenogenesises). It is found out also that in some cases geterokhroniya matter filembriogenez.

Thus, filembriogenez is the universal mechanism of phylogenetic transformations of a structure of organisms at all levels (from a cell to an organism) and stages of an ontonegez. At the same time filembriogeneza cannot be considered primary and elementary evolutionary changes. Mutational variability is the cornerstone of evolution, as we know. Both filembriogeneza, and generative mutations are inherited and shown during ontogenesis. However mutational variability, unlike filembriogenez, is individual (each new mutation is inherent only to that individual, at a cut it arose), and the mutational changes for the first time appearing have no adaptive character. Filembriogeneza, most likely, represent complexes of the mutations which underwent natural selection and became a genotypic norm. In that case filembriogeneza — the secondary transformations arising as result of preservation and accumulation of the mutations changing morphogenesis (see), and thereby and otroyeny adult organisms according to changes of the environment. Natural selection keeps the changes which only are building on ontogenesis more often, is more rare — the changing intermediate stages and is even more rare — transforming a morphogenesis from its very first stages. Various frequency of developing of anabolies, deviations and arkhallaksis is explained by it. Therefore, filembriogenez, being the mechanism of formation phylogenetic of new signs, at the same time represents result of mutational reorganization of an ontogeny.

Gekkel's ideas of preference of phylogenetic changes over ontogenetic and Müller about primacy of the reorganization of the course of ontogenesis leading to phylogenetic transformations of a structure of organisms are unilateral and do not reflect all complexity of evolutionary relationship of ontogenesis and phylogenesis. From modern positions communication between individual and historical development of an organism is expressed as follows: «phylogenesis is a historical number of the known ontogeneses» (I. I. Shmalgauzen, 1969) where each subsequent ontogenesis differs from previous.

See also Darwinism , Theory of evolution .

Bibliography: Lebedin S. N. Ratio onto-and phylogenesis, bibliography of a question, Izv. Nauch. in-that of Lesgaft, t. 20, No. 1, page 103, 1936; Müller F. and Gekkel E. The fundamental biogenetic law, the lane with it., M. — L., 1940; North of ts of A. N. Morphological patterns of evolution, page 453, M. — L., 1939; Severtsov A. S. To a question of evolution of ontogenesis, Zhurn. general biol., t. 31, No. 2, page 222, 1970; Sh m and l and at-zen I. I. Problems of Darwinism, page 318, L., 1969.

A.S. Severtsov.