Biogenetic law: history, essence, application. What does “biogenetic law” mean? Examples of implementation of the biogenetic law

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In fact, the “biogenetic law” was formulated long before the advent of Darwinism.
The German anatomist and embryologist Martin Rathke (1793-1860) described gill slits and arches in embryos of mammals and birds in 1825 - one of the most striking examples of recapitulation.
In 1824-1826, Etienne Serra formulated the “Meckel-Serre law of parallelism”: each organism in its embryonic development repeats the adult forms of more primitive animals [ ] .

Facts that contradict the biogenetic law

Already in the 19th century, enough facts were known that contradicted the biogenetic law. Thus, numerous examples of neoteny were known, in which during evolution there is a shortening of ontogenesis and the loss of its final stages. In the case of neoteny, the adult stage of the descendant species resembles the larval stage of the ancestor species, and not vice versa, as would be expected with complete recapitulation.
It was also well known that, contrary to the “law of germinal similarity” and the “biogenetic law”, the most early stages development of vertebrate embryos - blastula and gastrula - and only at later stages of development is a “node of similarity” observed - the stage at which the structural plan characteristic of vertebrates is laid down, and embryos of all classes are truly similar to each other. Differences in the early stages are associated with different amounts of yolk in the eggs: as it increases, crushing becomes first uneven and then (in fish, birds and reptiles) incomplete and superficial. As a result, the structure of the blastula also changes - coeloblastula is present in species with a small amount of yolk, amphiblastula - with a medium amount, and discoblastula - with a large amount. In addition, the course of development in the early stages changes dramatically in terrestrial vertebrates due to the appearance of embryonic membranes.

The connection between biogenetic law and Darwinism

The biogenetic law is often seen as a confirmation of Darwin's theory of evolution, although it does not follow from classical evolutionary teaching.
For example, if the view A3 arose by evolution from an older species A1 through a series of transitional forms (A1 => A2 => A3), then, in accordance with the biogenetic law (in its modified version), the reverse process is also possible, in which the species A3 turns into A2 by shortening development and eliminating its final stages (neoteny or pedogenesis).
R. Raff and T. Coffman speak out equally sharply: “The secondary discovery and development of Mendelian genetics at the turn of two centuries will show that, in essence, the biogenetic law is just an illusion” (p. 30), “The final blow to the biogenetic law was dealt then when it became clear that... morphological adaptations are important... for all stages of ontogenesis” (p. 31).
", proposed by Haeckel, Severtsov interpreted differently; for Haeckel, cenogenesis (any new characteristics that distorted recapitulation) was the opposite of palingenesis (preservation in development of unchanged characteristics that were also present in the ancestors). Severtsov used the term “coenogenesis” to designate characteristics that serve as adaptations to the embryonic or larval way of life and are not found in adult forms, since they cannot have adaptive significance for them. Severtsov included, for example, the embryonic membranes of amniotes (amnion, chorion, allantois), the placenta of mammals, the egg tooth of bird and reptile embryos, etc., as cenogenesis.
Phylembryogeneses are changes in ontogenesis that, during evolution, lead to changes in the characteristics of adult individuals. Severtsov divided phylembryogenesis into anabolism, deviation and archallaxis. Anabolia is an extension of ontogenesis, accompanied by an increase in stages. Only with this method of evolution is recapitulation observed - the characteristics of the embryos or larvae of the descendants resemble the characteristics of the adult ancestors. With deviation, changes occur in the middle stages of development, which lead to more dramatic changes in the structure of the adult body than with anabolia. With this method of evolution of ontogenesis, only the early stages of descendants can recapitulate the characteristics of ancestral forms. With archallaxis, changes occur at the earliest stages of ontogenesis, changes in the structure of the adult organism are most often significant, and recapitulations are impossible.

Biogenetic law
Biogenetic law Haeckel-Müller (also known as “Haeckel’s law”, “Müller-Haeckel’s law”, “Darwin-Müller-Haeckel’s law”, “basic biogenetic law”): every living creature in its individual development (ontogenesis) repeats to a certain extent forms traversed by its ancestors or its species (phylogeny).
Germs according to Haeckel. Drawing from Remane's book (1892), reproducing Haeckel's original illustration
Played an important role in the history of the development of science, but currently in its original form not recognized as modern biological science. According to the modern interpretation of the biogenetic law, proposed by the Russian biologist A. N. Severtsov at the beginning of the 20th century, in ontogenesis there is a repetition of the characteristics not of adult ancestors, but of their embryos.

History of creation

In fact, the “biogenetic law” was formulated long before the advent of Darwinism.

The German anatomist and embryologist Martin Rathke (1793-1860) described gill slits and arches in embryos of mammals and birds in 1825 - one of the most striking examples of recapitulation.

In 1824-1826, Etienne Serra formulated the “Meckel-Serre law of parallelism”: each organism in its embryonic development repeats the adult forms of more primitive animals.

2 years before Ernst Haeckel formulated the biogenetic law, a similar formulation was proposed by the German zoologist Fritz Müller, who worked in Brazil, based on his studies of the development of crustaceans. In his book For Darwin (Für Darwin), published in 1864, he italicizes the idea: “the historical development of a species will be reflected in the history of its individual development.”

A brief aphoristic formulation of this law was given by the German naturalist Ernst Haeckel in 1866. The brief formulation of the law is as follows: Ontogenesis is the recapitulation of phylogeny(in many translations - “Ontogenesis is a quick and brief repetition of phylogeny”).

Examples of implementation of the biogenetic law

A striking example of the implementation of the biogenetic law is the development of the frog, which includes the tadpole stage, which in its structure is much more similar to fish than to amphibians:

In the tadpole, as in lower fish and fish fry, the basis of the skeleton is the notochord, only later becoming overgrown with cartilaginous vertebrae in the body part. The tadpole's skull is cartilaginous, and well-developed cartilaginous arches adjoin it; gill breathing. The circulatory system is also built according to the fish type: the atrium has not yet divided into right and left halves, only venous blood enters the heart, and from there it goes through the arterial trunk to the gills. If the development of the tadpole stopped at this stage and did not go further, we should, without any hesitation, classify such an animal as a superclass of fish.

The embryos of not only amphibians, but also all vertebrates without exception, also have gill slits, a two-chambered heart, and other features characteristic of fish in the early stages of development. For example, a bird embryo in the first days of incubation is also a tailed fish-like creature with gill slits. At this stage, the future chick reveals similarities with lower fish, and with amphibian larvae, and with the early stages of development of other vertebrates (including humans). At subsequent stages of development, the bird embryo becomes similar to reptiles:

And while the chicken embryo, by the end of the first week, has both the hind and forelimbs looking like identical legs, while the tail has not yet disappeared, and feathers have not yet formed from the papillae, in all its characteristics it is closer to reptiles than to adult birds.

The human embryo goes through similar stages during embryogenesis. Then, during the period between approximately the fourth and sixth weeks of development, it changes from a fish-like organism to an organism indistinguishable from a monkey embryo, and only then acquires human characteristics.

Haeckel called this repetition of the characteristics of ancestors during the individual development of an individual recapitulation.

There are many other examples of recapitulations that confirm the fulfillment of the “biogenetic law” in some cases. Thus, when the terrestrial hermit crab palm thief reproduces, its females, before hatching the larvae, go into the sea, and there the planktonic shrimp-like zoea larvae emerge from the eggs, having a completely symmetrical abdomen. Then they turn into glaucotoe and settle to the bottom, where they find suitable shells gastropods. For some time they lead a lifestyle characteristic of most hermit crabs, and at this stage they have a soft spiral abdomen with asymmetrical limbs, characteristic of this group, and breathe with gills. Having grown to a certain size, palm thieves leave the shell, go onto land, acquire a hard, shortened abdomen, similar to the abdomen of crabs, and forever lose the ability to breathe in water.

Such complete fulfillment of the biogenetic law is possible in cases where the evolution of ontogenesis occurs through its lengthening - “adding stages”:
1. a1 - a2
2. a1" - a2" - a3"
3. a1" - a2" - a3" - a4"
(In this diagram, ancestral and descendant species are located from top to bottom, and from left to right - the stages of their ontogenesis.)

Facts that contradict the biogenetic law

Already in the 19th century, enough facts were known that contradicted the biogenetic law. Thus, numerous examples of neoteny were known, in which during evolution there is a shortening of ontogenesis and the loss of its final stages. In the case of neoteny, the adult stage of the descendant species resembles the larval stage of the ancestor species, and not vice versa, as would be expected with complete recapitulation.

It was also well known that, contrary to the “law of embryonic similarity” and the “biogenetic law”, the earliest stages of development of vertebrate embryos - blastula and gastrula - differ very sharply in structure, and only at later stages of development is a “node of similarity” observed - the stage on which the structural plan characteristic of vertebrates is laid down, and the embryos of all classes are really similar to each other. Differences in the early stages are associated with different amounts of yolk in the eggs: as it increases, crushing becomes first uneven and then (in fish, birds and reptiles) incomplete and superficial. As a result, the structure of the blastula also changes - coeloblastula is present in species with a small amount of yolk, amphiblastula - with a medium amount, and discoblastula - with a large amount. In addition, the course of development in the early stages changes dramatically in terrestrial vertebrates due to the appearance of embryonic membranes.

The connection between biogenetic law and Darwinism

The biogenetic law is often seen as a confirmation of Darwin's theory of evolution, although it does not at all follow from classical evolutionary teaching.

For example, if the view A3 arose by evolution from an older species A1 through a series of transitional forms (A1 =>A2 => A3), then, in accordance with the biogenetic law (in its modified version), the reverse process is also possible, in which the species A3 turns into A2 by shortening development and eliminating its final stages (neoteny or pedogenesis).

R. Raff and T. Coffman speak equally sharply: “The secondary discovery and development of Mendelian genetics at the turn of two centuries will show that, in essence, the biogenetic law is just an illusion” (p. 30), “The final blow to the biogenetic law was dealt then , when it became clear that ... morphological adaptations are important ... for all stages of ontogenesis” (p. 31).

In a sense, cause and effect are confused in the biogenetic law. Phylogenesis is a sequence of ontogenies; therefore, changes in adult forms during phylogenesis can only be based on changes in ontogenesis. This understanding of the relationship between ontogenesis and phylogeny was reached, in particular, by A. N. Severtsov, who in 1912-1939 developed the theory of phylembryogenesis. According to Severtsov, all embryonic and larval characters are divided into coenogenesis and phylembryogenesis. The term “coenogenesis”, proposed by Haeckel, was interpreted differently by Severtsov; for Haeckel, cenogenesis (any new characteristics that distorted recapitulation) was the opposite of palingenesis (preservation in development of unchanged characteristics that were also present in the ancestors). Severtsov used the term “coenogenesis” to designate characteristics that serve as adaptations to the embryonic or larval way of life and are not found in adult forms, since they cannot have adaptive significance for them. Severtsov included, for example, the embryonic membranes of amniotes (amnion, chorion, allantois), the placenta of mammals, the egg tooth of bird and reptile embryos, etc., as cenogenesis.

Phylembryogeneses are changes in ontogenesis that, during evolution, lead to changes in the characteristics of adult individuals. Severtsov divided phylembryogenesis into anabolism, deviation and archallaxis. Anabolia is an extension of ontogenesis, accompanied by an increase in stages. Only with this method of evolution is recapitulation observed - the characteristics of the embryos or larvae of the descendants resemble the characteristics of the adult ancestors. With deviation, changes occur in the middle stages of development, which lead to more dramatic changes in the structure of the adult body than with anabolia. With this method of evolution of ontogenesis, only the early stages of descendants can recapitulate the characteristics of ancestral forms. With archallaxis, changes occur at the earliest stages of ontogenesis, changes in the structure of the adult organism are most often significant, and recapitulations are impossible.

Literature
- Darwin Ch., Origin of species..., Soch., vol. 3, M., 1939
- Muller F. and Haeckel E., Basic biogenetic law, M.-L., 1940
- Kozo-Polyansky B. M., Basic biogenetic law from a botanical point of view, Voronezh, 1937
- Severtsov A.N., Morphological patterns of evolution, M.-L., 1939
- Shmalgauzen I.I., The organism as a whole in individual and historical development, M.-L., 1942
- Mirzoyan E. N., Individual development and evolution, M., 1963.
Notes

see also
- The principle of oligomerization of homologous organs
Links

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Question 1.
All multicellular organisms develop from a fertilized egg. The processes of embryo development in animals belonging to the same type are largely similar. In all chordates, in the embryonic period, an axial skeleton is formed - the notochord, a neural tube appears, and gill slits are formed in the anterior part of the pharynx. During the embryonic development of vertebrates, gill slits and corresponding septa are formed in the pharynx, but in reptiles, birds and mammals they do not develop into gills. The fact of the formation of the gill apparatus in the embryos of terrestrial vertebrates is explained by their origin from fish-like ancestors that breathed with gills.
The structure of the heart of a human embryo in the early period of formation resembles the structure of this organ in fish, namely, it has one atrium and one ventricle. In toothless whales, teeth are formed during the embryonic period. Subsequently, they are destroyed and dissolved.
The structural plan of chordates is also the same.
These facts confirm the validity of the law of embryonic similarity formulated by K. Baer: “Embryos exhibit, already from the earliest stages, a certain general similarity within the limits of type.”

Question 2.
In the early stages of development, vertebrate embryos are extremely similar. Subsequently, the structure of the embryos reveals characteristics of class, genus, species, and, finally, characteristics characteristic of a given individual. The similarity of the embryos serves as evidence of their common origin.
The divergence of characteristics of embryos during development is called embryonic divergence and is explained by the history of a given species, reflecting the evolution of one or another systematic group of animals.

Question 3.
This phenomenon is explained biogenetic law Muller-Haeckel:
Ontogenesis (individual development) of each individual is a short and rapid repetition of the phylogeny (historical development) of the species to which this individual belongs.
Therefore, in all vertebrates, including their higher representatives, a notochord is formed, which is later replaced by a spine. During the embryonic development of vertebrates, gill slits and corresponding septa are formed in the pharynx, but in reptiles, birds and mammals they do not develop into gills. The fact of the formation of the gill apparatus in the embryos of terrestrial vertebrates is explained by their origin from fish-like ancestors that breathed with gills.

Question 4.
Biogenetic law played an outstanding role in the development of evolutionary ideas. Many scientists in their works subjected it to further development. The contribution to deepening the understanding of the evolutionary role of embryonic transformations of our domestic scientist A. N. Severtsov was especially great. He established that in individual development the characteristics are repeated not of adult ancestors, but of their embryos. For example, in the embryos of birds and mammals, gill slits are formed. Their structure is similar to the structure of the gill slits of fish embryos, and not the gills of adult fish.

In some cases, changes that distinguish the structure of adult organisms from the structure of their ancestors appear in the embryonic period. Sometimes these changes are superimposed on an already completed general process formation of an organ, prolonging its development. This is how the wing of a bird develops - by transforming the almost formed rudiment of the horny scales of reptiles.
In some cases, changes occur in the middle stages of organ development. Finally, changes can affect the organ rudiment itself, and development will follow a path different from the path of development of this rudiment in the ancestor. Thus, in the process of hair formation in mammals, the stage of formation of scales completely disappears, as was the case with their ancestors - fish and reptiles. The stages inherent in the ancestors also drop out when the vertebrae are formed in snakes, teeth in mammals, etc. In case of deviation from the stages of development of the ancestors or changes in the rudiments themselves, the biogenetic law is not observed and the characteristics of the ancestors are not repeated.
If new characters are hereditary, that is, they are the result of mutations of the corresponding genes and have adaptive significance for adult organisms, then they are preserved by selection.
Thus, phylogeny is based on changes occurring in the ontogeny of individual individuals.
The repetition of structures characteristic of ancestors in the embryogenesis of descendants is called recapitulation. Recapitulate not only morphological characters - notochord, gill slits and gill arches - in all chordates, but also features of biochemical organization and physiology. Thus, in the evolution of vertebrates, there is a gradual loss of enzymes necessary for the breakdown of uric acid, a product of purine metabolism. In most invertebrates, the final product of the breakdown of uric acid is ammonia, in amphibians and fish it is urea, in many reptiles it is allantoin, and in some mammals uric acid is not broken down at all and is excreted in the urine. In the embryogenesis of mammals and humans, biochemical and physiological recapitulations are noted: the release of ammonia by early embryos, later urea, then allantoin, and in the last stages of development - uric acid.
However, in the ontogenesis of highly organized organisms, a strict repetition of the stages of historical development is not always observed, as follows from the biogenetic law. Thus, the human embryo never repeats the adult stages of fish, amphibians, reptiles and mammals, but is similar in a number of features only to their embryos. The early stages of development remain the most conservative, due to which they recapitulate more completely than the later ones. This is due to the fact that one of the most important mechanisms for integrating the early stages of embryogenesis is embryonic induction, and the structures of the embryo that form first, such as the notochord, neural tube, pharynx, gut and somites, represent the organizational centers of the embryo, from which depends on the entire course of development.
The genetic basis of recapitulation lies in the unity of the mechanisms of genetic control of development, which is preserved on the basis of common genes for the regulation of ontogenesis, which are inherited by related groups of organisms from common ancestors.

The biogenetic law was formulated by E. Haeckel: “Ontogenesis is a quick and brief repetition of phylogeny (the historical development of a species).” Haeckel argued that phylogeny is the cause of ontogenesis: individual development is completely determined by the history of the development of the species. Subsequently, these views were partially rejected by science, and partially modified and supplemented.
German scientists F. Müller and E. Haeckel in the second half of the 19th century. established the law of the relationship between ontogenesis and phylogenesis, which was called the biogenetic law. According to this law, each individual in individual development (ontogenesis) repeats the history of the development of its species (phylogeny), or, in short, ontogenesis is a repetition of phylogeny.
However, in a short period of individual development, an individual cannot repeat all the stages of evolution that took place over thousands or millions of years. Therefore, the repetition of the stages of the historical development of a species in the individual development of an individual occurs in a compressed form, with the loss of a number of stages. In addition, embryos resemble not the adult forms of their ancestors, but their embryos. Thus, in the ontogenesis of mammals there is a stage at which gill arches are formed in the embryos. In the fish embryo, on the basis of these arches, a respiratory organ is formed - the gill apparatus. In the ontogeny of mammals, it is not the structure of the gill apparatus of adult fish that is repeated, but the structure of the anlage of the gill apparatus of the embryo, on the basis of which completely different organs develop in mammals.
In the development of the theory of ontogenesis, the research of Academician A.N. played an outstanding role. Severtsova. He proved that changes in historical development are caused by changes in the course of embryonic development. Hereditary changes affect all stages life cycle, including the embryonic period. Mutations that arise during the development of the embryo, as a rule, disrupt interactions in the body and lead to its death. However, small mutations may turn out to be beneficial and will then be preserved by natural selection. They will be passed on to posterity and will be included in historical development, influencing its course.
Typically, embryonic stages of development do not change as significantly during evolution as adult animals. Therefore, when comparing embryos and larvae of even animals distant from each other, great similarities are often discovered between them, indicating kinship.
Of particular interest for evolutionary zoology are recapitulations, i.e. repetition in the course of individual development of characteristic structural features of more or less distant ancestors. Let's give just one classic example. The systematic position and origin of ascidiae (Ascidiae), leading a sedentary lifestyle, were completely unclear for a long time, and only the famous study of A. O. Kovalevsky (1866) on the development of these animals finally resolved the issue. A free-swimming tailed larva emerges from the ascidian egg, similar in structure to chordates (Chordata). During the metamorphosis of the larva that has settled to the bottom, the tail with notochord and muscles and sensory organs disappear, the neural tube is reduced to the level of a small neural node, the ventral surface of the body grows intensively, siphons are formed, etc., i.e. organizational features associated with a sedentary lifestyle appear. The formed young sea squirt has almost nothing in common with other chordates. In this example, the larva, with its organization, recapitulates (repeats) the main structural features of the free-swimming ancestor. So it was found natural place ascidians in the system of the animal kingdom.

BIOGENETIC LAW(Greek bios life, genetikos relating to birth, origin) - a set of theoretical generalizations that describe the relationship between the individual and historical development living organisms.
B. z. was formulated in 1866 by German. zoologist E. Haeckel: “A series of forms through which individual organism during its development, starting from the egg and ending with a fully developed state, it is a short, compressed repetition of a long series of forms traversed by the animal ancestors of the same organism or the generic forms of its species, starting from ancient times, the so-called. organic creation, up to the present time,” i.e., “ontogenesis is a quick and brief repetition of phylogeny.”
The basis for creating B. z. was the work of F. Müller “For Darwin” (1864), in which it was shown that phylogenetically new characters of adult organisms arise as a result of changes in ontogenesis in descendants - lengthening or deviation from the ontogenesis of ancestors. In both cases, the structure of the adult organism changes.
According to Haeckel, phylogeny occurs by summing up the changes in an adult organism and shifting them to earlier stages of ontogenesis, i.e. phylogeny is the basis for ontogeny, which plays the role of an abbreviated and distorted record of evolutionary transformations of adult organisms (see Ontogenesis, Phylogeny) . From these positions, Haeckel divided all the signs of a developing organism into two categories: palingenesis (see) - signs or stages of individual development that repeat or recapitulate in the ontogenesis of descendants the stages of the phylogeny of adult ancestors, and cenogeneses - any signs that violate recapitulation. Haeckel considered the cause of cenogenesis to be secondary adaptations of organisms to the conditions in which their ontogenesis occurs. Therefore, cenogenesis included temporary (provisional) adaptations that ensure the survival of an individual at certain stages of individual development and are absent in an adult organism, for example, the embryonic membranes of the fetus (cenogenesis proper), as well as changes in the anlage of organs in time (heterochrony) or place (heterotopia) and secondary changes in the path of ontogenesis of a given organ. All these transformations disrupt palingenesis and thereby complicate the use of embryological data for the reconstruction of phylogeny, for the sake of which, as A. N. Severtsov showed (1939), Haeckel formulated the B. z.
At the beginning of the 20th century. a number of authors have proven that F. Muller, who postulated the emergence of phylogenetic changes as a result of transformations in ontogenesis processes, more correctly than Haeckel, explained the relationship between individual and historical development, substantiated in modern times, from the standpoint of genetics. Since evolution occurs over a number of generations, only generative mutations that change the hereditary apparatus of gametes or zygotes are significant. Only these mutations are transmitted to the next generation, in which they change the course of ontogenesis, due to which they manifest themselves in the phenotype of the descendants. If in the next generation ontogenesis proceeds in the same way as in the previous one, then the adult organisms of both generations will be the same.
Based on the idea of the primacy of ontogenetic changes, A. N. Severtsov developed the theory of phylembryogenesis - a description of the methods (modes) of evolutionary changes in the course of ontogenesis, which lead to the transformation of the organs of descendants. The most common method of progressive evolution of organs is anabolia, or the addition of the final stages of development. In this case, to the stage at which the development of the organ in the ancestors ended, a new one is added (extension of ontogenesis), and the final stage of the ontogenesis of the ancestors appears to be shifted to the beginning of development:

Anabolisms E, F, G, H lead to further development organ and determine the recapitulation of ancestral states (e, f, g). Consequently, it is during evolution through anabolism that the palingenetic path of ontogenesis arises, but in this case there is not a shift in the stages of ontogenesis, but a further phylogenetic development of an organ that already existed in the ancestors.
The second mode of phylembryogenesis is deviation, or deviation at intermediate stages of development. In this case, the development of the organ of the descendants begins in the same way as in the ancestors, but then it changes direction, although additional stages do not arise:

Deviations rearrange ontogeny, starting from intermediate stages (c1, d2, d3), which leads to a change in the definitive structure of the organ (E1, E2, E3). Recapitulation in abc1d1E1 ontogenesis can be traced at ab stages, and in abc1d3E3 ontogenesis - at abc1 stages. The third, most rare, mode of progressive evolution is archallaxis, or a change in the primary rudiments of organs:

Archallaxis is characterized by a transformation of the earliest stages of ontogenesis, starting from its origin (a1, a2, a3), which can lead to the emergence of new organs that were absent in the ancestors (E1, E2, E3) - primary archallaxis, or to a radical restructuring of the ontogenesis of an organ without significant changes in its definitive structure - secondary archallaxis. With this method of evolution, there is no recapitulation.
Through phylembryogenesis, the evolutionary reduction of organs also occurs. There are two types of reduction: rudimentation (underdevelopment) and aphanisia (disappearance without a trace). With rudimentation, an organ that was normally developed and functioning in the ancestors loses its functional significance in the descendants. In this case, according to A.N. Severtsov, reduction is carried out through negative archallaxis: the anlage in the descendants is smaller and weaker than in the ancestors, develops more slowly and does not reach the ancestral definitive stage. As a result, the organ of the descendants turns out to be underdeveloped. With aphania, the reduced organ not only loses its functional significance, but also becomes harmful to the body. The ontogenesis of such an organ, as a rule, begins and for a certain time proceeds in the same way as in the ancestors, but then negative anabolia occurs - the organ resolves, and the process proceeds in the reverse order of development, until the disappearance of the anlage itself.
The theory of phylembryogenesis is close to Muller's ideas. However, A. N. Severtsov identified a mode of archallaxis, which can only be observed during evolutionary transformations of parts, and not of the whole organism studied by Muller. Soviet biologists proved that not only organs, but also tissues and cells of multicellular organisms evolve through phylembryogenesis. There is evidence of evolution through phylembryogenesis not only of developed organs, but also of provisional adaptations (coenogenesis). It was also found out that in a number of cases heterochronies have the significance of phylembryogenesis.
Thus, phylembryogenesis is a universal mechanism of phylogenetic transformations of the structure of organisms at all levels (from cell to organism) and stages of ontogeny. At the same time, phylembryogenesis cannot be considered primary and elementary evolutionary changes. As is known, evolution is based on mutational variability. Both phylembryogenesis and generative mutations are inherited and manifest themselves during ontogenesis. However, mutational variability, unlike phylembryogenesis, is individual (each new mutation is characteristic only of the individual in which it arose), and mutational changes that appear for the first time are not adaptive in nature. Phylembryogenesis, in all likelihood, represents complexes of mutations that have undergone natural selection and become the genotypic norm. In this case, phylembryogenesis is a secondary transformation that occurs as a result of the preservation and accumulation of mutations that change morphogenesis (see), and thereby the formation of adult organisms in accordance with the changes environment. Natural selection more often preserves changes that only build ontogenesis, less often - changing intermediate stages, and even less often - transforming morphogenesis from its very first stages. This explains the different incidence of anabolia, deviations and archallaxis. Consequently, phylembryogenesis, being a mechanism for the formation of phylogenetically new characters, at the same time is the result of mutational restructuring of individual development.
Haeckel’s ideas about the primacy of phylogenetic changes over ontogenetic ones and Müller’s ideas about the primacy of restructuring the course of ontogenesis, leading to phylogenetic transformations in the structure of organisms, are one-sided and do not reflect the full complexity of the evolutionary relationships between ontogenesis and phylogeny. From a modern point of view, the connection between the individual and historical development of an organism is expressed as follows: “phylogeny is a historical series of known ontogenies” (I. I. Shmalgauzen, 1969), where each subsequent ontogenesis differs from the previous one.
Bibliography: Lebedin S.N. Correlation of onto- and phylogeny, bibliography of the issue, Izv. Scientific Institute named after Lesgafta, t. 20, no. 1, p. 103, 1936; Muller F. and Haeckel E. Basic biogenetic law, trans. from German, M.-L., 1940; Severtsov A. N. Morphological patterns of evolution, p. 453, M.-L., 1939; Severtsov A. S. On the question of the evolution of ontogenesis, Zhurn. total biol., t. 31, no. 2, p. 222, 1970; Sh m a l g a u-zen I. I. Problems of Darwinism, p. 318, L., 1969.
A. S. Severtsov.

Biogenetic law: history, essence, application. What does “biogenetic law” mean? Examples of implementation of the biogenetic law

Encyclopedic YouTube

Facts that contradict the biogenetic law

The connection between biogenetic law and Darwinism

History of creation

Examples of implementation of the biogenetic law

Facts that contradict the biogenetic law

The connection between biogenetic law and Darwinism

Literature

Notes

see also

Links

See what the “Biogenetic Law” is in other dictionaries: