Biogenetic law of F. Muller - E

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Table of contents:
1. Biogenetic law
2. Examples of fulfillment of the biogenetic law
3. Facts that contradict the biogenetic law
4. The connection between the biogenetic law and Darwinism
5. Scientific criticism of the biogenetic law and further development of the doctrine of the connection between ontogenesis and phylogenesis
6. Criticism from creationists

Haeckel-Müller biogenetic law: every living creature in its individual development repeats to a certain extent the forms traversed by its ancestors or its species.

Germs according to Haeckel. Drawing from Remane's book, reproducing Haeckel's original illustration

It played an important role in the history of the development of science, but is currently not recognized in its original form by 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 individuals of ancestors, but of their embryos.

History of creation

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

The German anatomist and embryologist Martin Rathke in 1825 described gill slits and arches in embryos of mammals and birds - 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.

In 1828, Karl Maksimovich Baer, ​​based on Rathke’s data and the results of his own studies of the development of vertebrates, formulated the law of embryonic similarity: “Embryos successively move in their development from general characteristics of the type to more and more special characteristics. The last to develop are signs indicating that the embryo belongs to a certain genus or species, and, finally, development ends with the appearance of the characteristic features of a given individual.” Baer did not attach an evolutionary meaning to this “law,” but later this law came to be considered as “embryological proof of evolution” and evidence of the origin of animals of the same type from a common ancestor.

The “biogenetic law” as a consequence of the evolutionary development of organisms was first formulated by the English naturalist Charles Darwin in his book “The Origin of Species” in 1859: “The interest of embryology will increase significantly if we see in the embryo a more or less shaded image of the common progenitor, in the adult or his personal state, all members of the same large class"

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, 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.

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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 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 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.

  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 of the 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. Thus, the natural place of ascidians in the system of the animal kingdom was found.

  Observation of the ontogenesis of organisms by two independent biologists made it possible to formulate the Haeckel-Müller biogenetic law. The formulation was first voiced in 1866. However, the prerequisites for the formation of the law were identified back in the 1820s.

  Law and its meaning

  The essence of the law is that in the process of ontogenesis (individual development of an organism), an individual repeats the forms of its ancestors and from conception to formation goes through the stages of phylogenesis (historical development of organisms).

  Zoologist Fritz Müller's formulation was given in the book For Darwin in 1864. Müller wrote that the historical development of a species is reflected in the history of individual development.

  Two years later, the naturalist Ernst Haeckel formulated the law more briefly: ontogeny is the rapid repetition of phylogeny. In other words, every organism undergoes an evolutionary change in species during development.

  

  Rice. 1. Haeckel and Muller.

  Scientists made their conclusions by studying embryos of different species based on a number of similar characteristics. For example, gill arches form in the embryos of mammals and fish. Embryos of amphibians, reptiles and mammals go through the same stages of development and are similar in appearance. The similarity of embryos is one of the proofs of the theory of evolution and the origin of animals from one ancestor.

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  Rice. 2. Comparison of embryos of different animals.

  The founder of embryology, Karl Baer, ​​identified the similarities between embryos of different species back in 1828. He wrote that embryos are identical and only at a certain stage of embryological development do the characteristics of the genus and species appear. It is curious that, despite his observations, Baer never accepted the theory of evolution.

  Criticism

  Since the 19th century, the conclusions of Haeckel and Müller have been criticized.
  Imperfections of the basic biogenetic law were identified:

  • an individual does not repeat all stages of evolution and goes through stages of historical development in a compressed form;
  • the similarity is observed not in embryos and adults, but in two different embryos at a certain stage of development (the gills of mammals are similar to the gills of fish embryos, not adults);
  • neoteny - a phenomenon in which the adult stage resembles the larval development of the putative ancestor (preservation of infantile properties throughout life);
  • pedogenesis is a type of parthenogenesis in which reproduction occurs at the larval stage;
  • There are significant differences in the blastula and gastrula stages of vertebrates, with similarities observed in later stages.

  It has been established that the Haeckel-Muller law is never fully satisfied; there are always deviations and exceptions. Some embryologists noted that the biogenetic law is just an illusion that does not have serious premises.

  The law was revised by biologist Alexey Severtsov. Based on the biogenetic law, he developed the theory of phylembryogenesis. According to the hypothesis, changes in historical development are caused by changes at the larval or embryonic stage of development, i.e. ontogeny modifies phylogeny.

  Severtsov divided the characteristics of embryos into coenogenesis (adaptations to the larval or embryonic lifestyle) and phylembryogenesis (changes in embryos that lead to modifications in adult individuals).

  Severtsov attributed to cenogenesis:

  • embryonic membranes;
  • placenta;
  • egg tooth;
  • gills of amphibian larvae;
  • attachment organs in larvae.

  

  Rice. 3. An egg tooth is an example of cenogenesis.

  Cenogenesis “facilitated” the life of larvae and embryos during evolution. Therefore, it is difficult to trace the development of phylogeny by embryological development.

  Philembryogenesis is divided into three types:

  • archallaxis - changes in the first stages of ontogenesis, during which the further development of the organism follows a new path;
  • anabolia - increase in ontogenesis through the emergence of additional stages of embryonic development;
  • deviation - changes in the middle stages of development.

  Ontogenesis- individual development of an organism, a set of successive morphological, physiological and biochemical transformations undergone by the organism from fertilization (with sexual reproduction) or from the moment of separation from the mother (with asexual reproduction) until the end of life.

  The life cycle of development as a reflection of evolution.

  The life cycle is the result of a genetic program developed during a long process of evolutionary development.

  Fertilization (zygote is a single-celled organism).

  Embryonic development (blastula - colonial protozoa, gastrula - multicellular protozoa, fetus - full-fledged multicellular).

  Birth (vertebrates).

  Postembryonic development (mammals).

  Aging.

  2. Theory of the origin of multicellular organisms by E. Haeckel and I. I. Mechnikov

  Theory of E. Haeckel (1884):

  In constructing his hypothesis, he proceeded from embryological studies carried out by that time by A.O. Kovalevsky and other zoologists, mainly on the lancelet and a number of vertebrates. Based on the biogenetic law, Haeckel believed that each stage of ontogenesis repeats some stage passed by the ancestors of a given species during phylogenetic development. According to his ideas, the zygote stage corresponds to single-celled ancestors, the blastula stage corresponds to a spherical colony of flagellates. Further, according to this hypothesis, an invagination of one of the sides of the spherical colony occurred and a two-layer organism was formed, which Haeckel called gastrea, and Haeckel’s hypothesis was called the theory of gastrea. This theory played a big role in the history of science, as it contributed to the establishment of monophylithic ideas about the origin of multicellular organisms.

  Theory I.I. Mechnikov (1886):

  According to his ideas, in the hypothetical ancestor of multicellular organisms - a spherical colony of flagellates - cells that captured food particles temporarily lost their flagella and moved inside the colony. Then they could return to the surface and restore the flagellum. Gradually, in the spherical colony, a division of function occurred between the members of the colony. To successfully capture food, active movement is necessary, which led to polarization of the body. The anterior cells acquired specialization in relation to movement, and the posterior ones in relation to nutrition. The difficulty that arose in the transfer of food from the posterior to the anterior cells resulted in immigration phagocytoblasts into the body cavity. This hypothetical organism is similar to the larvae of many sponges and

  coelenterates. Mechnikov initially called it parenchymella. Then, due to the fact that the inner layer of the hypothetical organism is formed from phagocytoblasts, he called it phagocytella. This theory is called the phagocytella theory.

  3. Haeckel-Müller biogenetic law and its application in constructing the concept of the origin of multicellular organisms

  Biogenetic law (E. Haeckel and F. Muller): each individual in the early stages of ontogenesis repeats some basic structural features of its ancestors, in other words, ontogeny (individual development) is a brief repetition of phylogeny (evolutionary development

  Independently of each other, Haeckel and Müller formulated the biogenetic law.

  ONTOGENESIS IS A BRIEF REPEATMENT OF PHYLOGENESIS.

  In ontogenesis, Haeckel distinguished between palingenesis and cenogenesis. Palingenesis - characteristics of the embryo that repeat the characteristics of the ancestors (notochord, cartilaginous primary skull, gill arches, primary kidneys, primary single-chamber heart). But their formation can shift in time - heterochrony, and in space - heterotopia. Cenogenesis is an adaptive formation in the embryo that does not persist into adulthood. He pointed out that cenogeneses influence palingenesis and distort them. He believed that due to cenogenesis, recapitulation does not occur completely. He started from this theory when he created the theory of gastrea.

  Further research showed that the biogenetic law is valid only in general terms. There is not a single stage of development at which the embryo repeats the structure of its ancestors. It has also been established that in ontogenesis the structure of the embryos, rather than the adult stages of the ancestors, is repeated.