Individual and historical development. Law of germinal similarity

Chapter 40 Law of time. The Law of Purity of Thoughts - The Law says: The Universe is abundant! Or, in other words: God has a lot of everything! The universe has everything for everyone. Each of us is part of the whole. The world was created for us, and we are for it. In order to become

BIOGENETIC LAW (Greek bios - life and genesis - origin) the theoretical assumption formulated by F. Müller and Haeckel that the totality of adjacent forms that a living being passes through in the process of its individual evolution from an egg to

Prohibition of Haeckel's book in Tsarist Russia

Prohibition of Haeckel's book in tsarist Russia On October 28, 1908, the chairman of the St. Petersburg committee for the press, A. Katenin, ordered the prosecutor of the court chamber to seize E. Haeckel's book "World Riddles":

BIOGENETIC LAW(Greek, bios life genetikos referring to birth, origin) - a set of theoretical generalizations describing the relationship between the individual and historical development of living organisms.

B. h. was formulated in 1866 by him. zoologist E. Haeckel (E.N. Haeckel): “The series of forms through which the individual organism passes during its development, starting from the egg and ending with the fully developed state, is a brief, compressed repetition of the long series of forms passed by the animal ancestors of the same organism or generic forms of its species, starting from ancient times, the so-called. organic creation, up to the present time”, i.e. “ontogeny is a quick and short repetition of phylogeny”.

The basis for the creation of B. h. the work of F. Muller "For Darwin" (1864) served, in which it was shown that phylogenetically new signs of adult organisms arise as a result of a change 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, phylogenesis occurs by summing up the changes in an adult organism and shifting them to earlier stages of ontogenesis, i.e. phylogenesis is the basis for ontogenesis, which plays the role of an abbreviated and distorted record of the evolutionary transformations of adult organisms (see Ontogeny, Phylogeny) . From these positions, Haeckel divided all the signs of a developing organism into two categories: palingenesis (see) - with

signs or stages of individual development that repeat or recapitulate in the ontogenesis of descendants the stages of phylogenesis of adult ancestors, and coenogenesis - any signs that violate recapitulation. Haeckel considered the cause of cenogenesis to be the secondary adaptations of organisms to the conditions in which their ontogenesis proceeds. Therefore, temporary (provisional) devices 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 (coenogenesis proper), as well as changes in the laying of organs in time (heterochrony) or place (heterotopias) and secondary changes in the path of ontogenesis of this organ. All these transformations disrupt palingenesis and thus make it difficult to use embryological data for the reconstruction of phylogenesis, for which, as A. N. Severtsov (1939) has shown, Haeckel formulated B. z.

At the beginning of the 20th century A number of authors have proved that Muller (F. Muller), who postulated the occurrence of phylogenetic changes as a result of transformations in the processes of ontogenesis, more correctly than Haeckel explained the relationship between individual and historical development, justified at the present time from the standpoint of genetics. Since evolution occurs in a number of generations, only generative mutations that change the hereditary apparatus of gametes or zygotes matter in it. Only these mutations are transmitted to the next generation, in which they change the course of ontogeny, due to which they appear in the phenotype of 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.

On the basis of 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 way of progressive evolution of organs is anabolism, or the superimposition 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 (lengthening of ontogenesis) is added, 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 of the organ and cause recapitulation of ancestral states (e, f, g). Consequently, it is during evolution through anabolism that the palingenetic path of ontogenesis arises, however, in this case, there is not a shift in the stages of ontogenesis, but a further phylogenetic development of the 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 descendant organ begins in the same way as in the ancestors, but then it changes direction, although additional stages do not arise:

Deviations rebuild 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 is traced at ab stages, and in abc1d3E3 ontogeny, at abc1 stages. The third, rarest, mode of progressive evolution is archallaxis, or a change in the primary rudiments of organs:

Archallaxis is characterized by the transformation of the earliest stages of ontogenesis, starting from its initiation (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 ontogeny of an organ without significant changes in its definitive structure - secondary archallaxis. With this mode of evolution, there is no recapitulation.

Through phylembryogenesis, the evolutionary reduction of organs also occurs. There are two types of reduction: rudimentation (underdevelopment) and aphasia (without a trace). During rudimentation, an organ that was normally developed and functioned in the ancestors loses its functional significance in the descendants. In this case, according to A. N. Severtsov, the reduction is carried out by means of negative archallaxis: the priming of the descendants is smaller and weaker than that of the ancestors, develops more slowly and does not reach the ancestral definitive stage. As a result, the organ of the descendants is underdeveloped. With aphasia, the reducing 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 some time proceeds in the same way as in the ancestors, but then negative anabolism occurs - the organ resolves, and the process proceeds in the reverse order of development, up to the disappearance of the bookmark itself.

The theory of phylembryogenesis is close to Muller's ideas. However, A. N. Severtsov singled out the modus of archallaxis, which can be observed only during evolutionary transformations of parts, and not 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 has also been found that in a number of cases heterochronies play the role of phylembryogenesis.

Thus, phylembryogenesis is a universal mechanism of phylogenetic transformations in the structure of organisms at all levels (from cell to organism) and stages of ontogenesis. 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 during ontogenesis. However, mutational variability, unlike phylembryogenesis, is individual (each new mutation is characteristic only of the individual in which it arose), and the mutational changes that appear for the first time are not of an adaptive nature. Phylembryogenesis, in all likelihood, is a complex of mutations that have passed 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 thus the development of adult organisms in accordance with environmental changes. Natural selection more often preserves changes that only build ontogenesis, less often - changing intermediate stages, and even more rarely - transforming morphogenesis from its very first stages. This explains the different frequency of occurrence of anabolism, deviations and archallaxis. Consequently, phylembryogenesis, being a mechanism for the formation of phylogenetically new characters, is at the same time the result of a mutational rearrangement of individual development.

Haeckel's ideas about the predominance of phylogenetic changes over ontogenetic ones and Muller's ideas about the primacy of the restructuring of the course of ontogenesis, leading to phylogenetic transformations in the structure of organisms, are one-sided and do not reflect the complexity of the evolutionary relationship between ontogenesis and phylogenesis. From modern positions, the relationship between the individual and historical development of an organism is expressed as follows: “phylogenesis is a historical series of known ontogenesis” (I. I. Shmalgauzen, 1969), where each subsequent ontogenesis differs from the previous one.

Bibliography: Lebedin S. N. Correlation of onto- and phylogenesis, bibliography of the question, Izv. Scientific in-ta im. Lesgaft, vol. 20, no. 1, p. 103, 1936; Müller 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. To the question of the evolution of ontogenesis, Zhurn. total biol., t. 31, no. 2, p. 222, 1970; Shmalga u-zen I. I. Problems of Darwinism, p. 318, L., 1969.

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Biogenetic law [Haeckel-Muller]

Haeckel-Muller biogenetic law speaks of a brief repetition of phylogeny in ontogeny. This law was discovered in the second half of the 19th century. German scientists E. Haeckel and F. Müller.

The biogenetic law is reflected in the development of many representatives of the animal world. So, the tadpole repeats the stage of development of fish, which are the ancestors of amphibians. The biogenetic law is also valid in relation to plants. For example, seedlings of cultivars of cotton first appear complete lamellar leaves, from which two-, three-, four-, five-lobed leaves then develop. In the wild cotton species G. raimondii and G. klotzschianum, the leaves on the stem are a single plate. Consequently, cultivars of cotton, in the process of their individual development, briefly repeat the historical development of their ancestors.

However, in the process of individual development, not all, but only some stages of the historical development of ancestors are repeated, while the rest fall out. This is explained by the fact that the historical development of ancestors lasts millions of years, and individual development - a short time. In addition, it is not the stages of adult forms of ancestors that are repeated in ontogeny, but their embryonic stages of development.

Theory of phylembryogenesis

Naturally, the question arises: if phylogeny influences ontogeny, then can ontogeny influence phylogeny? It should be emphasized that in ontogeny not only certain stages in the development of ancestors drop out, but also changes occur that were not observed in phylogeny. This was proved by the Russian scientist A.N. Severtsov with his theory of phylembryogenesis. Material from the site http://wikiwhat.ru

It is known that mutational variability occurs at different stages of the embryonic development of an individual. Organisms with beneficial mutations survive in the struggle for existence and natural selection, passing beneficial mutations from generation to generation, and, in the end, change the course of phylogenesis. For example, in reptiles, the epithelial cells of the skin, and under it the connective tissue, develop and form scales. And in mammals, derivatives of epithelial and connective tissue, changing, form a hair bag under the skin.

biogenetic law

biogenetic law Haeckel-Muller (also known as "Haeckel's law", "Muller-Haeckel's law", "Darwin-Muller-Haeckel's law", "basic biogenetic law"): every living being in its individual development (ontogenesis) repeats to a certain extent forms passed by its ancestors or its species (phylogeny).

He played an important role in the history of the development of science, but at present in his original form not recognized 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 signs not of adult individuals of the 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) in 1825 described gill slits and arches in mammalian and bird embryos - one of the most striking examples of recapitulation [ source unspecified 469 days] .

In 1824-1826, Etienne Serra formulated the "Meckel-Serra law of parallelism": each organism in its embryonic development repeats the adult forms of more primitive animals [ source unspecified 469 days] .

In 1828, Karl Maksimovich Baer, ​​based on Rathke's data and on the results of his own studies of the development of vertebrates, formulated the law of germline similarity: “Embryos successively move in their development from general type traits to more and more special traits. Last of all, signs develop that indicate that the embryo belongs to a certain genus, species, and, finally, development ends with the appearance of the characteristic features of this individual. Baer did not attach evolutionary meaning to this "law" (he did not accept the evolutionary teachings of Darwin until the end of his life), but later this law began to be considered as "embryological proof of evolution" (see Macroevolution) 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 (rather vaguely) by the English naturalist Charles Darwin in his book On the Origin of Species in 1859: , in its adult or personal state, all members of the same large class ”(Darwin Ch. Soch. M.-L., 1939, vol. 3, p. 636.)

2 years before the formulation of the biogenetic law by Ernst Haeckel, a similar formulation was proposed by the German zoologist Fritz Müller, who worked in Brazil, on the basis of his studies of the development of crustaceans. In his book "For Darwin" (Für Darwin), published in 1864, he emphasizes in italics the idea: "the historical development of the 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: Ontogeny is the recapitulation of phylogeny(in many translations - "Ontogeny is a quick and short repetition of phylogenesis").

Examples of the fulfillment of the biogenetic law

A vivid example of the fulfillment of the biogenetic law is the development of a frog, which includes the stage of a tadpole, 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, which only later becomes overgrown with cartilaginous vertebrae in the trunk part. The skull of the tadpole 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 the 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 any further, we should have no hesitation in classifying 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 shows 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 embryo of a bird becomes similar to reptiles:

And while in the chicken embryo, until the end of the first week, both the hind and forelimbs look like the same 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, between approximately the fourth and sixth weeks of development, it transforms from a fish-like organism to an organism indistinguishable from an ape fetus, and only then acquires human features.

Haeckel called this repetition of ancestral traits 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. So, during the reproduction of the terrestrial hermit crab of the palm thief, its females enter the sea before hatching the larvae, and there planktonic zoea shrimp-like larvae emerge from the eggs, having a completely symmetrical abdomen. Then they turn into glaucotoe and settle to the bottom, where they find suitable gastropod shells. For some time they lead a lifestyle characteristic of most hermit crabs, and at this stage they have a soft spiral abdomen characteristic of this group with asymmetrical limbs and breathe through gills. Having grown to a certain size, palm thieves leave the shell, go to land, acquire a rigid shortened abdomen, similar to the abdomen of crabs, and forever lose the ability to breathe in water.

Such a complete fulfillment of the biogenetic law is possible in those cases when the evolution of ontogeny occurs by its lengthening - "extension of stages":

(In this diagram, from top to bottom, ancestor and descendant species are located, and from left to right, the stages of their ontogeny.)

Facts contrary to 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, in the course of evolution, ontogenesis shortens and its final stages fall out. 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 earliest stages of development of vertebrate embryos - blastula and gastrula - differ very sharply in structure, and only at later stages of development is a "knot of similarity" observed - the stage on which the structural plan characteristic of vertebrates is laid, and the embryos of all classes are really similar to each other. Differences in the early stages are associated with a different amount of yolk in the eggs: with its increase, fragmentation becomes first uneven, and then (in fish, birds and reptiles) incomplete superficial. As a result, the structure of the blastula also changes - the 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.

Relationship of biogenetic law with Darwinism

The biogenetic law is often regarded as a confirmation of Darwin's theory of evolution, although it does not follow at all 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 loss of its final stages (neoteny or pedogenesis).

Darwinism and the synthetic theory of evolution, on the contrary, deny the possibility of a complete return to ancestral forms (Dollo's Law of Irreversibility of Evolution). The reason for this, in particular, is the rearrangement of embryonic development at its early stages (archallaxis according to A.N. Severtsov), in which the genetic programs of development change so significantly that their complete restoration in the course of further evolution becomes almost unbelievable.

Scientific criticism of the biogenetic law and further development of the doctrine of the relationship between ontogenesis and phylogenesis

The accumulation of facts and theoretical developments have shown that the biogenetic law in the formulation of Haeckel in its pure form is never fulfilled. Recapitulation can only be partial.

These facts have led many embryologists to completely reject the biogenetic law in Haeckel's formulations. So, S. Gilbert writes: “Such a point of view ( on the repetition of phylogenesis by ontogeny) was scientifically discredited even before it was proposed ... Therefore, it spread into biology and the social sciences ... before it was shown that it was based on false premises.

R. Raff and T. Kofman speak just as 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 last 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 mixed up in the biogenetic law. Phylogeny is a sequence of ontogenies, therefore, changes in adult forms in the course of phylogenesis can be based only on changes in ontogeny. This understanding of the relationship between ontogenesis and phylogenesis came, in particular, A. N. Severtsov, who in 1912-1939 developed the theory of phylembryogenesis. According to Severtsov, all embryonic and larval characters are divided into cenogenesis and phylembryogenesis. The term "coenogenesis", proposed by Haeckel, was interpreted differently by Severtsov; for Haeckel, cenogenesis (any new traits that distorted recapitulation) was the opposite of palingenesis (preservation in development of unchanged traits that were also present in ancestors). Severtsov used the term "coenogenesis" to designate traits that serve as adaptations to the embryonic or larval lifestyle and are not found in adult forms, since they cannot have an adaptive value for them. Severtsov referred to coenogenesis, for example, the embryonic membranes of amniotes (amnion, chorion, allantois), the placenta of mammals, the egg tooth of the embryos of birds and reptiles, etc.

Phylembryogenesis is such changes in ontogeny that in the course of evolution lead to a change in the characteristics of adults. Severtsov divided phylembryogenesis into anabolism, deviation and archallaxis. Anabolia is the lengthening of ontogenesis, accompanied by an extension of stages. Only with this method of evolution is recapitulation observed - signs of embryos or larvae of descendants resemble signs of adult ancestors. With deviation, changes occur at the middle stages of development, which lead to more dramatic changes in the structure of the adult organism than with anabolism. With this method of evolution of ontogeny, only the early stages of descendants can recapitulate the traits of ancestral forms. In archallaxis, changes occur at the earliest stages of ontogenesis, changes in the structure of an adult organism are most often significant, and recapitulations are impossible.

Biogenetic law of Müller and Haeckel. Ontogeny of plants and animals.

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Topic: Muller and Haeckel's biogenetic law. Plant ontogeny. Animal ontogeny.

Target: To formulate knowledge about the essence and manifestation of the biogenetic law, to continue deepening knowledge about the material unity of living nature. Develop the ability to work with the text of the textbook, compare, generalize and draw appropriate conclusions. To form general educational logical UUD - the ability to analyze, synthesize, draw certain conclusions. Foster a culture of learning and communication.

From the standpoint of the competence approach: to form general educational, informational and communicative competences.

Updating knowledge on the topic "Ontogeny"

What does the concept of ontogeny mean? (Individual development of the organism, from the moment of fertilization to death)

- Each organism belongs to a certain species, class, type, which have undergone a certain development.

— What is the name of the historical development of a species or any other taxonomic unit? (phylogenesis)

Our task today in the lesson is to establish a connection between ontogenesis and phylogeny.

Let's repeat and remember the studied material during the intellectual warm-up. The task 1. - Establish the correct sequence of stages of the embryonic period. (blastula, gastrula, neurula, zygote)

The task 2. What are the types of the postembryonic period, the name of the stages. (developmental stages of the cockchafer and grasshopper)

The task 3. Set the right term and definition

1. Amnion - the embryonic membrane, filled with liquid, is an aqueous medium, protects from drying out and damage.

2. Chorion - outer shell. Serves for the exchange of the embryo with the environment, participates in respiration, nutrition

3. Allantois - the shell of the embryo, in which metabolic products accumulate

4. Placenta-allantois, together with the chorion, forms the placenta, only in mammals. What concepts are causing you trouble?

3. Learning new material.

What does the name R. Hook tell you? K. Baer? M. Schleiden and T. Schwann? (The names of these scientists are associated with the study of cells) Think about how Schleiden and Schwann were able to create a cell theory? (They collected all the available information about the cell, double-checked it and formulated their cell theory)

Guys, it is very important to be able to analyze, summarize information and come to a certain conclusion. Today we will find ourselves in the middle of the 19th century, together with the German scientists E. Haeckel and F. Müller, and, based on a generalization of known facts, we will try to establish a certain pattern. (Moss ontogeny, development of moss from spores)

Are mosses the first plants on Earth or do they have ancestors? Prove that the ancestors of mosses were algae (At the beginning of development, moss looks like a green filamentous algae and is called - protonema) Write it down in your notebook. In the ontogeny of moss, signs of their ancestors are observed.

2. Study the pattern of butterfly development. What type are butterflies? (Type Arthropods) Can you tell who was the ancestor of arthropods? (The ancestors of butterflies may have been worms) Why did you decide that the ancestors were annelids? (A caterpillar butterfly larva is very similar to a worm) Write it down in a notebook. Butterflies in their development, at the larval stage, repeat the signs of worms.

3. Frog development. Tell us about how the frog develops.

(The frog tadpole looks more like a fish. It lives in water, breathes with gills, it has a 2-chambered heart and one circle of blood circulation, there is a lateral line. All these signs are characteristic of fish).

As evidenced by the fact that the tadpole is very similar to a fish. (The ancestors of amphibians were fish)

Can all these facts be called a coincidence? What are common facts called? (pattern)

Guys, so what pattern have you discovered now? ( organisms in their development repeat the characteristics of their ancestors ) Students write down– biogenetic law .(Each organism in its development repeats the development of its species. ) Who discovered and how to read. We have now repeated what Muller and Haeckel did in 1864, we have identified a pattern.

Who discovered the law of germline similarity? (in 1828 K. Baer)

What can you say? (the embryos of different vertebrate organisms are very similar in the early stages)

What does this indicate? (On the unity of the origin of living organisms)

Work with the textbook is organized. In the textbook, find what stages of development the embryos of different organisms go through (The zygote stage corresponds to a unicellular organism, a chord appears, gill slits),

Find the answer why in the early stages the embryos are very similar, and in the later stages they begin to differ? (All stages of development are subject to variability .. But the structures that arise in early embryos play a very important role. If they change, the embryo dies. And changes in the later stages of development can be beneficial for the body).

Our Russian scientists, biologists A.N. Severtsev and I.I. Shmalgauzen, contributed greatly to the deepening and refinement of the biogenetic law. Find information in the textbook, what clarifications were made to the content of the law by Russian scientists. (Severtsev A.N. found that in individual development, animals repeat the signs not of adult ancestors, but of their embryos)

Guys, what pattern did we discover in the lesson? Ontogeny is a brief repetition of phylogenesis. But not all stages are repeated in ontogeny.

Emphasis: BIOGENETIC LAW

BIOGENETIC LAW (from the Greek βιος - life and γενεσις - origin), the main biogenetic law, is the pattern of living nature, which consists in the fact that organisms during their embryonic (intrauterine) development repeat the main stages of development of their kind, i.e., their ancestral forms. As a result, in the early stages of development, the embryos of various animals are largely similar in shape. An example of repetition is the developmental sequence of a mammalian embryo. At the first stage, it resembles primary unicellular creatures, in the process of further development it acquires a resemblance to a worm-like creature, then to a fish-like creature, etc. Such parallelism confirms that the process of development of living nature went from lower forms to higher ones, from simple ones to complex ones. Repeatability is also observed in the development of individual organs. So, for example, in the process of development of the embryo of a modern horse, its limbs undergo changes similar to those observed in the evolution of a number of horses.

Formulated by B. z. German zoologist E. Haeckel (1866). However, even before him, Charles Darwin drew attention to the fact that the embryo is often a kind of obscured image of ancestral forms and that the similarity in the development of animal embryos is associated with the commonality of their origin. Value B. z. F. Engels emphasized for the theory of development. B. h. at one time served as a means of promoting the theory of organic development. peace and weapons of struggle against anti-Darwinists, who denied the variability of species and the continuity between them. However B. z. reveals only one of the aspects of the relationship between phylogenesis (genus development) and ontogenesis (individual development) - the influence of phylogenesis on ontogeny, while they must be considered in their inseparable unity and interdependence.

In the beginning. 20th century A number of bourgeois psychologists and educators (Amer. psychologists S. Hall, J. Baldwin, and others) made an illegitimate attempt to transfer B. z. from natural science to psychology and pedagogy. According to the views of supporters of B. z. in psychology and pedagogy, there is supposedly an analogy between the development of the child and the development of mankind. So, for example, the early age of children was compared by nek-ry authors with the period of initial gathering and digging up of roots, age 5 — 12 years — with the period of hunting, the senior age — with the period of industrial production. According to another classification, preschool age (3-7 years old) allegedly corresponds to the era of myths, primary school age (7-10 years old) to antiquity, middle school age (11-14 years old) to the era of Christianity. Even youth was viewed from this point of view as "the discoverer of the past races" (Hall).

Similar interpretations, which completely distorted the true natural-scientific meaning of biological science, were also given to individual features of the psyche of children at different stages of their development. So, the initial forms of a child's fear of strangers for him, people allegedly reproduce the features of animal instinctive fear, and the positive attitude towards people that appears, as if only in the future, supposedly resurrects the "stage of feelings of the ancient patriarchs" (Baldwin).

Also unfounded is the striving of bourgeois authors to seek from the point of view of B. z. similar features in children's drawings and images of ancient peoples. On this basis, attempts were made even to create a special "theory" of drawing performed for children, which planted extreme formalism among children's illustrators. primitive.

An attempt to mechanically transfer B. h. in psychology and pedagogy is one of the expressions of the idealistic. and a reactionary view of the development of the psyche as a process, allegedly fatalistically and one-sidedly determined by some kind of "from within" going "maturing" of properties and abilities inherited in the child; this does not take into account the determining influence of the social environment on the development of the psyche. Harmful and anti-scientific are also ped. conclusions, to-rye follow from attempts to transfer B. h. in the theory of development of the child's psyche: if mental. development is determined entirely by the history of the development of mankind, the main stages of which it must fatally repeat, then education and training are forced only to obediently follow the change of these stages and adapt to them; they seem to be unable to play any active role.

B. h. was widely involved in pedology to substantiate its main position - fatalistic. the conditionality of the fate of children by the influence of heredity and the unchanging environment. Owls. psychology and pedagogy resolutely reject attempts to endure B. h. in the theory of mental development. child's life, upbringing and education. The fact that in the process of mental development of the child, as well as in the process of historical. development of the psyche, there is a transition from a less developed to a more developed psyche, by no means can serve as a basis for the assertion that the development of the human psyche in ontogenesis is fatally predetermined by the development of the psyche in phylogeny.

Owls. psychology recognizes that the problem of the relationship between the properties of the species and the individual at the stage of man remains, but it acquires a completely different content. A person realizes in the ontogenetic process. development of the achievement of its kind, including those accumulated over the course of the socio-historical. development. However, the form of inheritance of social and historical achievements. human development is fundamentally different from the biological. forms of inheritance of phylogenetically established properties. Accordingly, the form of transferring historical achievements is also fundamentally different. human development for the individual. Psych. human properties are not the identification of certain biologically inherent special properties in him, but are formed in the process of mastering the socio-historical experience of mankind, embodied in language, science and technology, in works of art and moral norms.

A truly scientific understanding of the development of the psyche of children, without denying the role of heredity (see Heredity and upbringing) and the innate characteristics of the organism, reveals the uniqueness of the development of the psyche of each child, which is closely dependent on those specific socio-historical. the conditions in which it is carried out, as well as the main, leading role, which belongs to the development of the psyche of children, their upbringing and education.

Lit .: Engels F., Anti-Dühring, M., 1957, p. 70; Darwin Ch., Origin of species by means of natural selection, Soch., v. 3, M.-L., 1939; Müller F., Gekkel E., Basic biogenetic law, M.-L., 1940; Chamberlain A.F., Child. Essays on human evolution, trans. from English, part 1 - 2, M., 1911; Leontiev A.N., On the historical approach to the study of the human psyche, in the book: Psychological science in the USSR, vol. 1, M., 1959; Hall G.S., Adolescence, its psychology. v. 1 - 2, N. Y., 1904 - 08.

A. N. Leontiev. Moscow.

1. Pedagogical encyclopedia. Volume 1. Ch. editor - A.I. Kairov and F.N. Petrov. M., 'Soviet Encyclopedia', 1964. 832 column. with illustrations, 7 sheets. ill.
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Ontogenesis - the realization of genetic information occurring at all stages.

Ontogeny is a genetically controlled process. During ontogenesis, the genotype is realized and the phenotype is formed.

Ontogeny is the individual development of an organism, a set of successive morphological, physiological and biochemical transformations that an organism undergoes from the moment of its inception to the end of life. O. includes growth, i.e., an increase in body weight, its size, differentiation. The term "Oh." introduced by E. Haeckel(1866) when he formulated biogenetic law.

The first attempt at a historical substantiation of O. was made by I. f. Meckel. The problem of the relationship between O. and phylogenesis was posed by Ch. Darwin and developed by F. Muller,E. Haeckel, and others. All evolutionally new traits associated with changes in heredity arise in O., but only those that contribute to a better adaptation of the organism to the conditions of existence are preserved in the process. natural selection and are passed on to subsequent generations, that is, they are fixed in evolution. Knowledge of the patterns, causes, and factors of naturalization serves as the scientific basis for finding means of influencing the development of plants, animals, and humans, which is of great importance for the practice of crop and animal husbandry, as well as for medicine.

Phylogeny is the historical development of organisms. The term was introduced by evolutionist E. Haeckel in 1866. The main task in the study of F. is the reconstruction of the evolutionary transformations of animals, plants, microorganisms, establishing on this basis their origin and family ties between the taxa to which the studied organisms belong. For this purpose, E. Haeckel developed the method of "triple parallelism", which allows, by comparing the data of three sciences - morphology, embryology and paleontology - to restore the course of the historical development of the studied systematic group.

Law of germinal similarity

Researchers in the early 19th century For the first time, attention began to be paid to the similarity of the stages of development of the embryos of higher animals with the stages of complication of organization, leading from low-organized forms to progressive ones. Comparing the stages of development of embryos of different species and classes of chordates, K. Baer made the following conclusions.

1. Embryos of animals of the same type in the early stages of development are similar.

2. They successively move in their development from more general features of the type to more and more particular ones. Lastly, signs develop that indicate that the embryo belongs to a particular genus, species, and, finally, individual traits.

3. Embryos of different representatives of the same type gradually separate from each other.

K. Baer, ​​not being an evolutionist, could not connect the patterns of individual development discovered by him with the process of phylogenesis. Therefore, the generalizations he made had the value of no more than empirical rules.

The development of the evolutionary idea subsequently made it possible to explain the similarity of early embryos by their historical relationship, and the acquisition of more and more particular features by them with a gradual separation from each other - the actual isolation of the corresponding classes, orders, families, genera and species in the process of evolution.

Soon after the discovery of the law of germline similarity, Charles Darwin showed that this law testifies to the common origin and unity of the initial stages of evolution within a type.

biogenetic law Haeckel-Muller: every living being in its individual development ( ontogenesis) repeats to a certain extent the form passed by its ancestors or its species ( phylogenesis).

Ontogeny - repetition of phylogenesis

Comparing the ontogenesis of crustaceans with the morphology of their extinct ancestors, F. Müller concluded that living crustaceans in their development repeat the path traveled by their ancestors. The transformation of ontogeny into evolution, according to F. Muller, is carried out due to its elongation by adding additional stages or extensions to it. Based on these observations, as well as studying the development of chordates, E. Haeckel (1866) formulated the basic biogenetic law, according to which ontogeny is a brief and rapid repetition of phylogenesis.

The repetition of structures characteristic of ancestors in the embryogenesis of descendants is called recapitulations. Recapitulate not only morphological features - the notochord, gill slit and gill arch anlages in all chordates, but also the features of the 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 end 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 were noted: the release of ammonia by early embryos, later urea, then allantoin, and, at the last stages of development, uric acid.

However, in the ontogeny 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 retain the greatest conservatism, due to which they recapitulate more completely than the later ones. This is due to the fact that one of the most important mechanisms of integration of the early stages of embryogenesis is embryonic induction, and the structures of the embryo that form in the first place, such as the notochord, neural tube, pharynx, intestine and somites, are the organizational centers of the embryo, from which the whole course of development depends.

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.

Recapitulation(from Latin recapitulatio - repetition) - a concept used in biology to denote the repetition in individual development of features characteristic of an earlier stage of evolutionary development.

Ontogeny as the basis of phylogeny. Cenogenesis. Autonomization of ontogeny. Philembryogenesis. Teachings of A.N. Severtsov about phylembryogenesis. Mechanisms of their occurrence. Heterochrony and heterotopy of biological structures in the evolution of ontogeny.

Relying only on the basic biogenetic law, it is impossible to explain the process of evolution: the endless repetition of the past does not in itself give rise to a new one. Since life exists on Earth due to the change of generations of specific organisms, its evolution proceeds due to changes occurring in their ontogenies. These changes boil down to the fact that specific ontogenies deviate from the path laid by ancestral forms and acquire new features.

Such deviations include, for example, coenogenesis - adaptations that arise in embryos or larvae and adapt them to the characteristics of their habitat. In adult organisms, coenogenesis is not preserved. Examples of coenogenesis are horny formations in the mouth of tailless amphibian larvae, which make it easier for them to feed on plant foods. In the process of metamorphosis in the frog, they disappear and the digestive system is rebuilt to feed on insects and worms. The cenogenesis in amniotes includes the embryonic membranes, the yolk sac and allantois, and in placental mammals and humans, it also includes the placenta with the umbilical cord.

Cenogenesis, manifesting itself only in the early stages of ontogenesis, does not change the type of organization of the adult organism, but provides a higher probability of survival of the offspring. At the same time, they may be accompanied by a decrease in fertility and a lengthening of the embryonic or larval period, due to which the organism in the postembryonic or postlarval period of development is more mature and active. Having arisen and turned out to be useful, coenogenesis will be reproduced in subsequent generations. Thus, the amnion, which first appeared in the ancestors of reptiles in the Carboniferous period of the Paleozoic era, is reproduced in all vertebrates that develop on land, both in egg-laying reptiles and birds, and in placental mammals.

Another type of phylogenetically significant transformations of phylogeny is phylembryogenesis. They represent deviations from the ontogeny characteristic of ancestors, manifested in embryogenesis, but having an adaptive significance in adult forms. Thus, the anlage of the hairline appears in mammals at very early stages of embryonic development, but the hairline itself is important only in adult organisms.

Such changes in ontogeny, being useful, are fixed by natural selection and reproduced in subsequent generations. These changes are based on the same mechanisms that cause congenital malformations: a violation of cell proliferation, their movement, adhesion, death or differentiation (see § 8.2 and 9.3). However, they, like cenogenesis, are distinguished from malformations by adaptive value, i.e. usefulness and fixation by natural selection in phylogenesis.

Depending on the stages of embryogenesis and morphogenesis of specific structures, developmental changes that have the significance of phylembryogenesis occur, three types of them are distinguished.

1.Anabolia, or extensions, appear after the organ has almost completed its development, and are expressed in the addition of additional stages that change the final result.

Anabolisms include such phenomena as the acquisition of a specific body shape by a flounder only after a fry hatches from an egg, indistinguishable from other fish, as well as the appearance of spine bends, fusion of sutures in the brain skull, the final redistribution of blood vessels in the body of mammals and humans.

2.Deviations - deviations arising in the process of organ morphogenesis. An example is the development of the heart in the ontogeny of mammals, in which it recapitulates the tube stage, two-chamber and three-chamber structure, but the stage of formation of an incomplete septum, characteristic of reptiles, is supplanted by the development of a septum, built and located differently and characteristic only of mammals (see § 14.4) .In the development of the lungs in mammals, recapitulation of the early stages of ancestors is also found, later morphogenesis proceeds in a new way (see Section 14.3.4).

Rice. 13.9. Transformations of onto- and phylogenesis in connection with emerging phylembryogenesis

The letters indicate the stages of ontogenesis, the numbers indicate phylembryogenetic transformations.

3.Archallaxis - changes that are found at the level of rudiments and are expressed in a violation of their division, early differentiation, or in the appearance of fundamentally new anlages. A classic example of archallaxis is

the development of hair in mammals, the anlage of which occurs at a very early stage of development and differs from the very beginning from the anlage of other vertebrate skin appendages (see § 14.1).

According to the type of archallaxis, a notochord arises in primitive non-cranial animals, a cartilaginous spine in cartilaginous fish (see section 14.2.1.1), nephrons of the secondary kidney develop in reptiles (see section 14.5.1).

It is clear that during evolution due to anabolism, the main biogenetic law is fully realized in the ontogenies of descendants, i.e. recapitulations of all ancestral stages of development occur. In deviations, the early ancestral stages recapitulate, while the later ones are replaced by development in a new direction. Archallaxis completely prevent recapitulation in the development of these structures, changing their very beginnings.

If we compare the diagram of phylembryogenesis with the table of K. Baer (Fig. 13.9), illustrating the law of germline similarity, it will become clear that Baer was already very close to the discovery of phylembryogenesis, but the absence of an evolutionary idea in his reasoning did not allow him to be more than 100 years ahead of scientific thought .

In the evolution of ontogeny, anabolisms are most often encountered as phylembryogenesis, which only to a small extent change the integral process of development. Deviations as violations of the morphogenetic process in embryogenesis are often swept aside by natural selection and therefore occur much less frequently. Archallaxis appear most rarely in evolution due to the fact that they change the entire course of embryogenesis, and if such changes affect the rudiments of vital organs or organs that are important as embryonic organizational centers (see Section 8.2.6), then they often turn out to be incompatible with life.

In the same phylogenetic group, evolution in different organ systems can occur due to different phylembryogenesis.

Thus, in the ontogeny of mammals, all stages of the development of the axial skeleton in the subtype of vertebrates (anabolism) are traced, in the development of the heart, only early stages recapitulate (deviation), and in the development of skin appendages there are no recapitulations at all (archallaxis). Knowledge of the types of phylembryogenesis in the evolution of chordate organ systems is necessary for a doctor to predict the possibility of atavistic birth defects in fetuses and newborns (see Section 13.3.4). Indeed, if atavistic malformations are possible in an organ system that evolves through anabolism and deviations due to the recapitulation of ancestral states, then in the case of archallaxis this is completely excluded.

In addition to cenogenesis and phylembryogenesis, in the evolution of ontogenesis, deviations in the time of laying organs can also be detected - heterochrony - and places of their development - heterotopias. Both the first and the second lead to a change in the relationship of developing structures and are subject to strict control of natural selection. Only those heterochronies and heterotopias are preserved that are useful. Examples of such adaptive heterochrony are shifts in time of the anlage of the most vital organs in groups evolving according to the type of arogenesis. Thus, in mammals, and especially in humans, the differentiation of the forebrain significantly outstrips the development of its other departments.

Heterotopies lead to the formation of new spatial and functional relationships between organs, ensuring their joint evolution in the future. So, the heart, located in fish under the pharynx, provides an effective supply of blood to the gill arteries for gas exchange. Moving to the retrosternal region in terrestrial vertebrates, it develops and functions already in a single complex with new respiratory organs - the lungs, performing here, first of all, the function of delivering blood to the respiratory system for gas exchange.

Heterochronies and heterotopies, depending on the stages of embryogenesis and morphogenesis of organs, can be regarded as different types of phylembryogenesis. Thus, the movement of the rudiments of the brain, leading to its bending, characteristic of amniotes, and manifesting itself at the initial stages of its differentiation, is archallaxis, and heterotopia of the testis in humans from the abdominal cavity through the inguinal canal to the scrotum, observed at the end of embryogenesis after its final formation, - typical anabolic.

Sometimes processes of heterotopy, identical in results, can be phylembryogenesis of different types. For example, in various classes of vertebrates, movement of the limb belts is very common. In many groups of fish leading a benthic lifestyle, the ventral fins (hind limbs) are located anterior to the pectorals, while in mammals and humans, the shoulder girdle and forelimbs in the definitive state are much caudal to the place of their initial laying. In this regard, the innervation of the shoulder girdle in them is carried out by nerves associated not with the thoracic, but with the cervical segments of the spinal cord. In the fish mentioned above, the ventral fins are innervated not by the nerves of the posterior trunk, but by the anterior segments located anterior to the centers of innervation of the pectoral fins. This indicates the heterotopy of the fin anlage already at the stage of the earliest rudiments, while the movement of the anterior girdle of the limbs in humans occurs at later stages, when their innervation is already fully realized. Obviously, in the first case, heterotopy is archallaxis, while in the second, it is anabolic.

Cenogenesis, phylembryogenesis, as well as heterotopy and heterochrony, having proved useful, are fixed in the offspring and reproduced in subsequent generations until new adaptive changes in ontogenesis displace them, replacing them. Due to this, ontogeny not only briefly repeats the evolutionary path traversed by the ancestors, but also paves the way for new directions of phylogenesis in the future.

Cenogenesis

(from Greek kainós - new and ... genesis (See ... genesis)

adaptation of an organism that occurs at the stage of the embryo (fetus) or larva and is not preserved in an adult. Examples C. - the placenta of mammals, providing the fetus with respiration, nutrition and excretion; external gills of amphibian larvae; an egg tooth in birds, which serves to chicks to break through the egg shell; attachment organs in the larva of ascidians, a swimming tail in the larva of trematodes - cercaria, etc. The term "C." introduced in 1866 by E. Haeckel to designate those characters that, by violating the manifestations of palingenesis (See. Palingenesis), i.e. repetitions of distant stages of phylogenesis in the process of embryonic development of an individual do not allow us to trace the sequence of stages of phylogenesis of their ancestors during the ontogenesis of modern forms, i.e. violate biogenetic law. At the end of the 19th century C. began to be called any change in the course of ontogenesis characteristic of ancestors (German scientists E. Mehnert, F. Keibel, and others). The modern understanding of the term "C." was formed as a result of the work of A. N. Severtsov, who retained for this concept only the meaning of provisional adaptations, or embryo-adaptation. see also Philembryogenesis.

Cenogenesis(Greek kainos new + genesis birth, formation) - the appearance in the embryo or larva of adaptations to the conditions of existence that are not characteristic of adult stages, for example. the formation of membranes in the embryos of higher animals.

Philembryogenesis

(from the Greek phýlon - tribe, genus, species and Embryogenesis

FILEMBRIOGENESIS (from Greek phylon - genus, tribe, embryon - embryo and genesis - origin), evolutionary change ontogeny organs, tissues and cells, associated with both progressive development and reduction. The doctrine of phylembryogenesis was developed by a Russian evolutionary biologist A.N. Severtsov. The modes (methods) of phylembryogenesis differ in the time of occurrence in the process of development of these structures.

If the development of a certain organ in the descendants continues after the stage at which it ended in the ancestors, anabolism occurs (from the Greek anabole - rise) - an extension of the final stage of development. An example is the formation of a four-chambered heart in mammals. Amphibians have a three-chambered heart: two atria and one ventricle. In reptiles, a septum develops in the ventricle (the first anabolism), but this septum is incomplete in most of them - it only reduces the mixing of arterial and venous blood. In crocodiles and mammals, the development of the septum continues until the complete separation of the right and left ventricles (second anabolism). In children, sometimes as an atavism, the interventricular septum is underdeveloped, which leads to a serious illness requiring surgical intervention.

Prolongation of the development of an organ does not require profound changes in the previous stages of its ontogenesis; therefore, anabolism is the most common method of phylembryogenesis. The stages of organ development preceding anabolism remain comparable to the stages phylogenesis ancestors (i.e. are recapitulations) and can serve for its reconstruction (see Fig. biogenetic law). If the development of an organ at intermediate stages deviates from the path along which its ontogeny went in its ancestors, a deviation occurs (from late Latin deviatio - deviation). For example, in fish and reptiles, scales appear as thickenings of the epidermis and the underlying connective tissue layer of the skin - the corium. Gradually thickening, this bookmark bends outward. Then, in fish, the corium ossifies, the forming bony scale pierces the epidermis and extends to the surface of the body. In reptiles, on the contrary, the bone does not form, but the epidermis becomes keratinized, forming the horny scales of lizards and snakes. In crocodilians, the corium can ossify, forming the bony base of the horny scales. Deviations lead to a deeper restructuring of ontogeny than anabolism, so they are less common.

Least of all, changes in the primary rudiments of organs occur - archallaxis (from the Greek arche - beginning and allaxis - change). With deviation, recapitulation can be traced from the laying of the organ to the moment of deviation of development. With archallaxis, there is no recapitulation. An example is the development of the vertebral bodies in amphibians. In fossil amphibians - stegocephals and in modern tailless amphibians, the vertebral bodies form around a chord of several, usually three on each side of the body, separate anlages, which then merge to form the vertebral body. In tailed amphibians, these bookmarks do not occur. The ossification grows from above and below, covering the chord, so that a bone tube is immediately formed, which, thickening, becomes the body of the vertebra. This archallaxis is the cause of the still debated question of the origin of the tailed amphibians. Some scientists believe that they descended directly from lobe-finned fish, independently of other terrestrial vertebrates. Others - that the tailed amphibians very early diverged from the rest of the amphibians. Still others, neglecting the development of the vertebrae, prove the close relationship of the caudate and anuran amphibians.

Organ reduction, which have lost their adaptive significance, also occurs through phylembryogenesis, mainly through negative anabolism - the loss of the final stages of development. In this case, the organ either underdeveloped and becomes rudiment, or undergoes a reverse development and completely disappears. An example of a rudiment is the human appendix - an underdeveloped caecum, an example of complete disappearance - the tail of frog tadpoles. Throughout life, the tail grows in water, new vertebrae and muscle segments are added at its end. During metamorphosis, when the tadpole turns into a frog, the tail dissolves, and the process goes in the reverse order - from the end to the base. Phylembryogenesis is the main way of adaptive changes in the structure of organisms during phylogenesis.

Principles (methods) of phylogenetic transformations of organs and functions. Correspondence of structure and function in living systems. Polyfunctionality. Quantitative and qualitative changes in the functions of biological structures.

GENERAL REGULARITIES

THE EVOLUTION OF ORGANS

An organism, or an individual, is a separate living being, in the process of ontogenesis, showing all the properties of a living thing. The constant interaction of an individual with the environment in the form of organized flows of energy and matter maintains its integrity and development. Structurally, the body is an integrated hierarchical system built from cells, tissues, organs and systems that ensure its vital activity. Let us dwell on the organs and life support systems in more detail.

Authority called a historically established specialized system of tissues, characterized by delimitation, constancy of shape, localization, internal structure of the blood circulation and innervation pathways, development in ontogenesis and specific functions. The structure of organs is often very complex. Most of them are polyfunctional, i.e. performs several functions at the same time. At the same time, various organs may be involved in the implementation of any complex function.

A group of organs of similar origin that combine to perform a complex function is called system(circulatory, excretory, etc.).

If the same function is performed by a group of organs of different origin, it is called apparatus. An example is the respiratory apparatus, consisting of both the respiratory organs themselves and the elements of the skeleton and muscular system that provide respiratory movements.

In the process of ontogenesis, development occurs, and often the replacement of some organs by others. The organs of a mature organism are called definitive; organs that develop and function only in embryonic or larval development, - provisional. Examples of provisional organs are the gills of amphibian larvae, the primary kidney, and the embryonic membranes of higher vertebrates (amniotes).

In historical development, transformations of organs may be progressive or regressive. In the first case, the organs increase in size and become more complex in structure, in the second, they decrease in size, and their structure is simplified.

If two organisms at different levels of organization have organs that are built according to a single plan, located in the same place and develop in a similar way from the same embryonic rudiments, then this indicates the relationship of these organisms. Such bodies are called homologous. Homologous organs often perform the same function (for example, the heart of fish, amphibian, reptile and mammal), but in the process of evolution, functions may change (for example, the forelimbs of fish and amphibians, reptiles and birds).

When unrelated organisms live in the same environment, they may develop similar adaptations, which manifest themselves in the appearance similar organs. Similar organs perform the same functions, but their structure, location and development are sharply different. Examples of such organs are the wings of insects and birds, the limbs and jaw apparatus of arthropods and vertebrates.

The structure of organs strictly corresponds to the functions they perform. At the same time, in the historical transformations of organs, a change in functions is invariably accompanied by a change in the morphological characteristics of the organ.

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

Haeckel and Müller independently formulated the biogenetic law.

ONTOGENESIS IS A BRIEF REPETITION OF PHYLOGENESIS.

In ontogeny, Haeckel distinguished between palingenesis and cenogenesis. Palingenesis - signs of the embryo, repeating the signs of ancestors (chord, cartilaginous primary skull, gill arches, primary kidneys, primary single-chamber heart). But their formation can shift in time - heterochrony, and in space - heterotopia. Cenogeneses are adaptive formations in the embryo that do not persist in adulthood. He pointed out that cenogenesis influences palingenesis and distorts them. He believed that due to coenogenesis, recapitulation does not occur completely. He started from this theory when he created the theory of gastrea.

Further studies have shown that the biogenetic law is valid only in general terms. There is not a single stage of development at which the embryo would repeat the structure of its ancestors. It has also been established that in ontogenesis the structure is repeated not of the adult stages of the ancestors, but of the embryos.

113. The main provisions of the evolutionary theory of Ch. Darwin.
biological evolution- this is an irreversible directed historical development of living nature,
accompanied by a change in the genetic composition of populations, the formation of adaptations,
formation and extinction of species, transformations of biogeocenoses and the biosphere as a whole. Other
In other words, biological evolution should be understood as a process of adaptive historical
development of living forms at all levels of organization of the living.

The theory of evolution was developed by C. Darwin (1809-1882) and presented by him in the book The Origin of Species by Means of Natural Selection, or the Preservation of Favored Breeds in the Struggle for Life (1859).
The main provisions of the evolutionary theory of Ch. Darwin. Darwin's evolutionary theory
is a holistic doctrine of the historical development of the organic world. She covers
a wide range of problems, the most important of which are evidence of evolution, identification
driving forces of evolution, determination of the ways and patterns of the evolutionary process and
others The essence of evolutionary teaching lies in the following basic provisions:
1. All kinds of living beings inhabiting the Earth have never been created by someone.
2. Having arisen naturally, organic forms were slowly and gradually transformed
and improved according to the environment.
3. The transformation of species in nature is based on such properties of organisms as heredity and variability, as well as natural selection constantly occurring in nature. Natural selection is carried out through the complex interaction of organisms with each other and with factors of inanimate nature; Darwin called this relationship the struggle for existence. 4. The result of evolution is the adaptability of organisms to their conditions
habitat and diversity of species in nature.

114. The first evolutionary theory of Sh. B. Lamarck.
Jean-Baptiste Lamarck outlined the foundations of his concept in his most famous work "Philosophy
zoology" (1809). Lamarck drew attention to the existence of varieties that look like
intermediate forms between different species, and on changes in organisms as a result of processes
domestication, and the differences between fossil forms of organisms from modern ones.
Lamarck's general conclusion from these observations was the recognition of historical variability, the transformation of organisms in time, that is, their evolution.
The doctrine of gradation. The originality of Lamarck's concept was given by the unification of the idea of ​​variability
organic world with ideas about gradation - a gradual increase in the level of organization from
the simplest to the most complex and perfect organisms. From this Lamarck made the most important
the conclusion that changes in organisms are not random, but regular, directed:
the development of the organic world is in the direction of gradual improvement and complication
organizations. On this path, life arose from inanimate matter by spontaneous generation, and after
long evolution of organisms, a man appeared, descended from the "four-armed", i.e. from
primates. driving force gradation Lamarck considered "nature's desire for progress", which
originally inherent in all living beings, being invested in them by the Creator, i.e. God. progressive
The development of living nature, according to Lamarck, is a process of self-development - autogenesis. IN
implementation of this process (gradation), organisms are completely independent of the external world, from
environment.
Influence on organisms of external conditions. The second part of Lamarck's theory is about changes in organisms
under the influence of changing external conditions - in later times received significantly
greater fame than the first (the doctrine of gradation). Plants perceive changes in conditions, so
say, directly - through your metabolism with the external environment (with digestible mineral
compounds, water, gases and light).
In this and other similar examples, Lamarck takes the modification non-hereditary variability of organisms, which is the reaction of a given individual to various environmental conditions, for hereditary changes. In reality, such modification changes, as such, are not inherited.
2 Lamarck's laws
I. In every animal that has not reached the limit of its development, a more frequent and constant
the use of any organ leads to an increased development of the latter, while the constant
disuse of the organ weakens it and eventually causes it to disappear.
II. Everything that organisms acquire under the influence of prevailing use or lose
under the influence of the constant disuse of any organs, is subsequently preserved in the offspring,
unless the acquired changes are common to both parents.
As examples illustrating these provisions, Lamarck called the loss of the ability to fly in
poultry, loss of teeth in whales, elongation of the neck and forelimbs in giraffes (as a result of
constant stretching of these organs when plucking high-growing leaves), lengthening of the neck in
waterfowl (due to its constant stretching when extracting prey from under the water), etc.

The main provisions of the theory of evolution Zh.B. Lamarck:

1. Organisms are changeable. Species change extremely slowly, and therefore not noticeably

2. Causes of changes (driving forces)

b) The influence of the external environment. It violates the gradual complication of organisms (gradation), so there are organisms with different levels of development

3. Any change is inherited

115. Linnean period of development of biology.
The very idea of ​​evolution is as old as time. The era of the great geographical discoveries introduced
Europeans with an amazing variety of life in the tropics, led to the emergence of the first herbariums (Rome, Florence, Bologna) already in the 16th century, botanical gardens (England, France), cabinets of curiosities and zoological museums (Netherlands, England, Sweden). By the end of the XVII century. The variety of newly described forms was so great that botanists and zoologists of that time literally began to drown in a sea of ​​accumulated and constantly arriving material.
It took the painstaking genius of the great Swedish biologist Carl Linnaeus (1707-1778) to bring order to these piles of material. K. Linnaeus was a creationist (he wrote that "there are as many species as they were created by the Infinite Being"). The historical significance of K. Linnaeus lies in the fact that he put forward the principle of hierarchy of systematic categories (taxa): species are combined into genera, genera into families, families into orders, orders into classes, etc. K. Linnaeus was the first to place man among the order of primates. At the same time, Linnaeus did not claim that man descended from an ape, he only emphasized an undeniable external resemblance. The principle of hierarchy was summarized by Linnaeus in the main work of his life, The System of Nature.

116. Modern system of the organic world.
1. Diversity of species on Earth: 1.5-2 million animal species, 350-500 thousand plant species,
about 100 thousand species of mushrooms. Systematics - the science of diversity and classification
organisms. Carl Linnaeus is the founder of taxonomy. The principle of binary nomenclature:
double Latin names of each species (creeping clover, warty birch, field sparrow,
cabbage white, etc.).
2. The division of the organic world into two kingdoms: nuclear (eukaryotes) and non-nuclear (pre-nuclear,
or prokaryotes) and four kingdoms: Plants, Fungi, Animals, Bacteria and cyanobacteria.
3. Bacteria and blue-green, or cyanobacteria - single-celled, simply organized
non-nuclear organisms, autotrophs or heterotrophs, intermediaries between inorganic nature
and over-the kingdom of nuclear. Bacteria - destroyers of organic substances, their role in decomposition
organic matter to minerals. The role of cyanobacteria in the biosphere - the colonization of barren
substrates (stones, rocks, etc.) and preparing them for colonization by various organisms.
4. Mushrooms are unicellular and multicellular organisms that live both on land and in water.
Heterotrophs. The role of fungi in the cycle of substances in nature, in the transformation of organic substances into
mineral, in soil-forming processes.
5. Plants are unicellular and multicellular organisms, most of which are in cells
contains the pigment chlorophyll, which gives the plant its green color. Plants are autotrophs
synthesize organic substances from inorganic substances using the energy of sunlight.
Plants are the basis for the existence of all other groups of organisms, except for blue-green and a number of
bacteria, as plants supply them with food, energy, oxygen.
6. Animals - the kingdom of organisms that actively move in space (exception
make up some polyps, etc.). Heterotrophs. Role in the cycle of substances in nature -
consumers of organic matter. Transport function of animals in the biosphere - transfer
matter and energy.
7. Kinship, common origin of organisms - the basis of their classification

117 . Origin of life on earth.
The nature of life, its origin, the diversity of living beings and the structural and
functional proximity occupy one of the central places in biology. According to the theory
"stationary state" the Universe has existed forever, i.e. always. According to other hypotheses
The universe could have arisen from a bunch of neutrons, as a result of the "big bang" or was born in
one of the "black holes", or even was created by the "creator, the Almighty".

Among the main theories of the origin of life on Earth, the following should be mentioned..:
1. Theory of creationism: life was created at a certain time by a supernatural being.
2. The theory of spontaneous infection: life arose repeatedly from inanimate matter.
3. The theory of "stationary state": life has always existed, regardless of our consciousness.
4. The theory of panspermia: life is brought to our Planet from the outside.
5. Theory of biochemical evolution: life arose as a result of those processes that are subject to chemical. and physical laws. More or less scientific.

Even Darwin realized that life can arise only in the absence of life. At first omnipresent
microorganisms that are now common on Earth would “eat up” the newly formed
organic substances, therefore, the appearance of life, in our usual terrestrial conditions, is not
maybe.
The second condition under which life can arise is the absence of free O2 in the atmosphere, i.e.
the absence of conditions when organic matter can accumulate without being oxidized. On our planet
they accumulate only in anoxic conditions (peat, oil, coal).
This may have been the discovery made by Oparin and Haldane. Later they formed a hypothesis,
considering the emergence of life as the result of a long evolution of carbon
connections. It formed the basis of scientific ideas about the origin of life.
For the first time, signs of life appeared on it about 3.8 billion years ago.

There are 4 stages in the development of life:
Stage 1: Synthesis of low molecular weight organic compounds from gas in the primary atmosphere.
In the primary atmosphere, which probably had a restorative character, under the influence of various
types of energy (radioactive and ultraviolet radiation, electrical discharges, volcanic
processes, heat, etc.) molecules of amino acids, sugars,
fatty acids, nitrogenous bases, etc. This stage is subject to a number of model experiments. IN
1912 american biol. J. Loeb was the first to obtain from a mixture of gases under the action of an electric discharge
leucine (amino acid).
Stage 2: Polymerization of monomers with the formation of protein chains and nucleic acids. High
concentration of molecules of amino acids, fatty acids in solutions led to the formation
biopolymers: primitive proteins and nucleic acids.
Stage 3: Formation of phase-separated systems of organic substances, separated from the external environment
membranes. This stage of the formation of life is often called. protocell. It is possible that the resulting
polymers were combined into multimolecular complexes according to the principle of the so-called. non-specific
self-assembly. The resulting phase-separated systems are able to interact with
external environment by the type of open systems.
Stage 4: The emergence of the simplest cells with the properties of the living, including
reproductive apparatus, which guarantees the transfer of all chemical and
metabolic properties of parent cells.
The evolution of protobionts ended with the appearance of primitive organisms with
genetic and protein-synthesizing apparatus and inherited metabolism in-in.
The first living organisms were heterotrophs, feeding on abiogenic organic
molecules.

118 questions no!!!

119. Emergence and disappearance of biological structures in phylogenesis .

In the process of evolution, it is natural as occurrence new structures and their disappearance. It is based on the principle of differentiation, which manifests itself against the background of primary polyfunctionality and the ability of functions to change quantitatively. Any structure in this case arises on the basis of previous structures, regardless of at what level of organization of the living the process of phylogenesis is carried out. So, it is known that about 1 billion years ago, the original globin protein, following the duplication of the original gene, differentiated into myo- and hemoglobin - proteins that are part of muscle and blood cells, respectively, and differentiated in connection with this by functions. In the same way, new biological species are formed in the form of isolated populations of the original species, and new biogeocenoses are formed due to the differentiation of pre-existing ones.
An example occurrence organs is the origin of the uterus of placental mammals from paired oviducts. With the lengthening of the embryonic development of mammals, the need arises for a longer retention of the embryo in the mother's body. This can only be done in the caudal sections of the oviducts, the cavity of which increases in this case, and the wall is differentiated in such a way that the placenta is attached to it, which ensures the relationship between the mother and the fetus. As a result, a new organ appeared - the uterus, which provides the embryo with optimal conditions for intrauterine development and increases the survival rate of the corresponding species. In the emergence of such a more complex and specialized organ as the eye, the same patterns are observed.
disappearance, or reduction, body in phylogeny can be associated with three different causes and has different mechanisms. First, an organ that previously performed important functions may turn out to be harmful in the new conditions. Natural selection works against it, and the organ can quite quickly disappear completely. There are few examples of such direct disappearance of organs. Thus, many insects of small oceanic islands are wingless due to the constant elimination of flying individuals from their populations by the wind. The disappearance of organs is more often observed due to their substitution by new structures that perform the same functions with greater intensity. Thus, for example, in reptiles and mammals, the pronephros and primary kidneys disappear, being functionally replaced by secondary kidneys. In the same way, in fish and amphibians, the notochord is forced out by the spine.
The most common route to organ failure is across gradual weakening of their functions. Such situations usually arise when the conditions of existence change. Due to this, such an organ often becomes harmful and natural selection begins to act against it.
In medical practice, it is widely known that rudimentary organs in humans are also characterized by wide variability. Third large molars, or "wisdom teeth", for example, are characterized not only by a significant variability in structure and size, but also by different eruption periods, as well as a particular susceptibility to caries. Sometimes they do not erupt at all, and often, having erupted, they are completely destroyed over the next few years. The same applies to the appendix of the caecum (appendix), which normally can have a length of 2 to 20 cm and be located in different ways (behind the peritoneum, on the long mesentery, behind the cecum, etc.). In addition, inflammation of the appendix (appendicitis) is much more common than inflammatory processes in other parts of the intestine.
Underdeveloped organs are name of rudimentary or vestiges . To the rudiments in humans, they include, firstly, structures that have lost their functions in postnatal ontogenesis, but persist after birth (hairline, muscles of the auricle, coccyx, appendix as a digestive organ), and, secondly, organs that remain only in the embryonic period of ontogenesis (chord, cartilaginous gill arches, right aortic arch, cervical ribs, etc.).

In 1864, a German zoologist working in Brazil Fritz Müller in his book he wrote: "... the historical development of the species will be reflected in the history of its individual development."

In two years Ernst Haeckel gave a more generalized formulation:

“Ontogeny (E. Haeckel’s term) is a recapitulation of phylogeny (in many translations, “Ontogeny is a quick and short repetition of phylogeny”).

Or: those stages through which a living organism passes in the process of its development, in a compressed form, repeat the evolutionary history of its species.

Repeated attempts have been made to extend the biogenetic law to the development of the human psyche...

Modern addition:

“At present, according to most scientists, the law does not have absolute significance, and the structure of the embryo does not correspond in all details to the structure of the ancestor.

The earlier the hereditary change deviates the path of development from the normal, parental one, the more significantly the structure of the adult organism will change, the less likely it is that this change will be adaptive and will be preserved in the selection process. Therefore, changes in the final stages of development (superstructures or anabolism) occur in evolution more often than deviations (changes in the middle stages) and archallaxis (changes in the initial stages).

The initial stages of development are more conservative and therefore, in many cases, they can be evidence of kinship and indicate the stages passed in the process of evolution.

Dictionary of genetic terms / Comp.: M.V. Supotnitsky, M., "University book", 2007, p.180.

biogenetic law

1. Law and its meaning
2. Criticism
3. What have we learned?

• Topic quiz

Law and its meaning

The essence of the law lies in the fact 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).

The formulation of the zoologist Fritz Müller was given in 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 concisely: ontogeny is the rapid repetition of phylogeny. In other words, each organism undergoes an evolutionary change of species in the process of development.

Rice. 1. Haeckel and Müller.

Scientists made their conclusions when studying embryos of different species based on a number of similar features. For example, in the embryos of mammals and fish, gill arches are formed. 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.

Rice. 2. Comparison of embryos of different animals.

The founder of embryology, Karl Baer, ​​already in 1828 revealed the similarity of embryos of different species. He wrote that the embryos are identical, and only at a certain stage of embryological development, signs of the genus and species appear. Curiously, despite his observations, Baer never accepted the theory of evolution.

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

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

It has been established that the Haeckel-Muller law is never completely fulfilled, there are always deviations and exceptions. Some embryologists noted that the biogenetic law is just an illusion with no serious prerequisites.

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

Severtsov divided the signs of embryos into coenogenesis (adaptation to a larval or embryonic way of life) and phylembryogenesis (changes in embryos that lead to the modification of adults).

Severtsov attributed to cenogenesis:

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

Rice. 3. Egg tooth is an example of cenogenesis.

Cenogenesis "facilitated" the life of larvae and embryos in the course of evolution. Therefore, it is difficult to trace the development of phylogenesis by embryological development.

Philembryogenesis is divided into three types:

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

What have we learned?

From the 9th grade biology lesson, we learned about the Haeckel-Muller law, according to which each individual goes through the stages of phylogenesis during ontogenesis. The law does not work in its "pure" form and has a lot of assumptions. The biologist Severtsov developed a more complete theory of individual development.

Haeckel-Muller biogenetic law

The formulation of the Haeckel-Muller biogenetic law, its connection with Darwinism and contradictory facts. Fertilization and development of the human embryo. Scientific criticism of the biogenetic law and further development of the doctrine of the relationship between ontogenesis and phylogenesis.

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The biogenetic law of F. Muller (1864) and E. Haeckel (1866), the law of irreversibility of evolution by L. Dollo (1893), the law of oligomerization by V. A. Dogel 91936). Illustrate them with examples

The Code of Merchant Shipping of Ukraine regulates the relations that arise in the course of merchant shipping.

Merchant shipping in this Code is understood as activities related to the use of ships for the transport of goods, passengers, baggage and mail, fishing and other marine trades, exploration and mining, towing, icebreaking and rescue operations, cable laying, as well as for other economic , scientific and cultural purposes

The first laws of evolutionary development - J. B. Lamarck (1809), J. Cuvier (1812), M Millen_Edwards (1851). Illustrate them with examples

biogenetic law: in the process of individual development (ontogeny), each organism briefly repeats the trait of periods T and phylogeny.
example:nauplius-crustacean-larva
melinegrid crayfish-sack with globular cells

evolution, like any development, is an irreversible phenomenon, if an organ disappears, it will never reappear, even if necessary, another organ will appear, of a different origin, as it will perform the required function.
example: crustacean heat-limb modifications
heat is calculated in the air - in the aquatic environment

The biogenetic law of F. Muller (1864) and E. Haeckel (1866), the law of irreversibility of evolution by L. Dollo (1893), the law of oligomerization by V. A. Dogel 91936). Illustrate them with examples.

2. Haeckel-Muller biogenetic law (also known as "Haeckel's law", "Muller-Haeckel's law", "Darwin-Muller-Haeckel's law", "basic biogenetic law"): each living being in its individual development (ontogeny) repeats to a certain extent the forms passed by its ancestors or its species (phylogenesis).

He played an important role in the history of the development of science, but at present, in its original form, it is not recognized 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 signs not of adult individuals of the ancestors, but of their embryos.
examples:
In the tadpole, as in lower fish and fish fry, the basis of the skeleton is the notochord, which only later becomes overgrown with cartilaginous vertebrae in the trunk part. The skull of the tadpole 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 the 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 any further, we should have no hesitation in classifying such an animal as a superclass of fish.
And while in the chicken embryo, until the end of the first week, both the hind and forelimbs look like the same 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.
Oligomerization
Discovered by V. A. Dogel
As differentiation occurs, oligomerization of organs occurs: they acquire a certain localization, and their number decreases more and more (with progressive morphophysiological differentiation of the remaining ones) and becomes constant for this group of animals.
[edit] Examples
New organs in phylogenesis can arise, for example, due to:
lifestyle changes
transition from a sedentary to an active lifestyle
from water to land
For the annelids type, body segmentation has a multiple, unsteady character, all segments are homogeneous.
In arthropods (derived from annelids), the number of segments:
reduced in most classes
becomes permanent
individual segments of the body, usually combined into groups (head, chest, abdomen, etc.), are specialized in performing certain functions.

The law of irreversibility of evolution by L. Dollo is the law according to which an organism (population, species) cannot return to its previous state, already implemented in the series of its ancestors, even after returning to their habitat.

Dollo's law of irreversibility of evolution.
A. R. Wallace also, independently of Darwin, came to the conclusion that evolution is irreversible. L. Dollo in 1893 formulated the law of the irreversibility of evolution in the following way: "The organism cannot either wholly or even partially return to the state already realized in the series of its ancestors."

The Belgian paleontologist L. Dollo formulated the general position that evolution is an irreversible process. This position was then repeatedly confirmed and received the name of Dollo's law. The author himself gave a very brief formulation of the law of irreversibility of evolution. He was not always correctly understood and sometimes caused not quite well-founded objections. According to Dollo, "an organism cannot return, even partially, to the previous state already realized in the series of its ancestors."

O. Abel gives the following, more extensive formulation of Dollo's law:

“The organ, reduced in the course of historical development, never again reaches its former level; an organ that has completely disappeared is never restored.
“If adaptation to a new way of life (for example, during the transition from walking to climbing) is accompanied by the loss of organs that were of great functional importance in the old way of life, then with a new return to the old way of life, these organs never reappear; instead of them, a replacement is created by other bodies.

The law of irreversibility of evolution should not be extended beyond its applicability. Terrestrial vertebrates are descended from fish, and the five-fingered limb is the result of the transformation of the paired fin of fish. The terrestrial vertebrate can again return to life in the water, and the five-fingered limb at the same time takes on the general form of a fin. The internal structure of the fin-shaped limb - the flipper retains, however, the main features of the five-fingered limb, and does not return to the original structure of the fish fin. Amphibians breathe with lungs, They have lost the gill breathing of their ancestors. Some amphibians returned to a permanent life in the water and again acquired gill breathing. Their gills are, however, larval external gills. The internal gills of the fish type have disappeared forever. In tree-climbing primates, the first toe is reduced to a certain extent. In humans, descended from climbing primates, the first finger of the lower (hind) limbs again underwent significant progressive development (in connection with the transition to walking on two legs), but did not return to some initial state, but acquired a completely unique shape, position and development.

Consequently, not to mention the fact that progressive development is often replaced by regression, and regression is sometimes replaced by new progress. However, development never goes back along the path already traveled, and it never leads to a complete restoration of the previous states.

Indeed, organisms, moving into their former habitat, do not completely return to their ancestral state. Ichthyosaurs (reptiles) have adapted to living in water. At the same time, their organization remained typically reptilian. The same goes for crocodiles. Mammals living in the water (whales, dolphins, walruses, seals) have retained all the features characteristic of this class of animals.

Haeckel-Muller biogenetic law, its interpretation by Severtsov. Palingeneses and cenogenesis

F. Muller in his work "For Darwin" (1864) formulated the idea that changes in ontogenetic development underlying the process of evolution can be expressed in changes in the early or late stages of organ development. In the first case, only the general similarity of young embryos is preserved. In the second case, an extension and complication of ontogeny is observed, associated with the addition of stages and repetition (recapitulation) in the individual development of traits of more distant adult ancestors. Müller's works served as the basis for the formulation by E. Haeckel (1866) basic biogenetic law, according to which ontogeny is a short and quick repetition of phylogeny. That is, an organic individual repeats during the rapid and short course of its individual development the most important of those changes in form that its ancestors went through during the slow and long course of their paleontological development according to the laws of heredity and variability. The signs of adult ancestors that are repeated in the embryogenesis of descendants, he called palingenesis. Adaptations to the embryonic or larval stages are called coenogenesis.

However, Haeckel's ideas were very different from Muller's views on the question of the relationship between ontogenesis and phylogenesis in the process of evolution. Müller believed that evolutionarily new forms arise by changing the course of individual development characteristic of their ancestors, i.e. changes in ontogeny are primary in relation to phylogenetic changes. According to Haeckel, on the contrary, phylogenetic changes precede changes in individual development. Evolutionary new signs arise not during ontogeny, but in an adult organism. An adult organism evolves, and in the process of this evolution, the signs are shifted to earlier stages of ontogeny.

Thus, the problem of the relationship between ontogenesis and phylogenesis arose, which has not been resolved to this day.

The interpretation of the biogenetic law in the understanding of Muller was later developed by A.N. Severtsov (1910-1939) in the theory of phylembryogenesis. Severtsov shared Müller's views on the primacy of ontogenetic changes in relation to changes in adult organisms and considered ontogeny not only as the result of phylogenesis, but also as its basis. Ontogeny is not only lengthened by the addition of stages: it is entirely restructured in the process of evolution; it has its own history, naturally connected with the history of the adult organism and partly determining it.