Individual and historical development. The law of germinal similarity. biogenetic law. Recapitulation. The ratio of onto-phylogenesis. The law of germinal similarity of K. Baer. The main biogenetic law of F. Müller and E. Haeckel. Ontogeny as the basis of philology

Ontogeny is an individual development, a complex of development processes separate especially from the formation of a zygote to death. Development occurs due to the implementation of genetic information received from parents. Environmental conditions have a significant impact on its implementation. Phylogeny is the historical development of a species, the evolutionary development of organisms. Both processes are closely related. Knowing the directions and transformations of organs and their systems in the process of historical development, it is possible to understand and explain developmental anomalies arising in the process of embryogenesis.

The connection between otnogenesis and phylogenesis was reflected in a number of biological laws and patterns. In 1828, Karl Baer formulated three laws:

1. The law of germinal similarity - the embryo of any higher animal is not similar to another animal, but similar to its embryo

2. the law of the successive appearance of signs - more general signs characteristic of a given large group of animals are detected in their embryos earlier than more special signs

3. the law of mabrional divergence - each embryo of a given form of animals does not pass through other forms, but gradually separates from them.

These laws can be explained in such a way that in the early stages of embryogenesis, the embryos of animals of different classes of vertebrates (for example, fish, birds, mammals) are similar to each other. Over time, differences appear between them within classes, and then within orders (example: embryos of a pig and a person)

The law of germline similarity K. Baer

In 1828, Carl von Baer formulated a pattern called Baer's Law: "The earlier stages of individual development are compared, the more similarities can be found." Comparing the stages of development of embryos of different species and classes of chordates, K. Baer made the following conclusions.

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

In their development they successively move from more general characteristics of a 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.

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

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 isolation from each other - the actual isolation of the corresponding classes, orders, families, genera and species in the process of evolution.

The germline similarity is now explained by the actual relationship of organisms, and their gradual divergence (embryonic divergence) is an obvious reflection of the historical divergence of these forms (phylogenetic divergence). Therefore, the history of a given species can be traced by individual development.

Cenogenesis - changes in ontogenesis leading to a deviation from the path of ancestral forms, adaptations that arise in embryos, larvae, adapting them to their environment. In adult organisms, cenogenesis is not preserved, i.e. manifesting only in the early stages of ontogenesis, do not change the type of organization of the adult organism, but provide a higher degree of survival of the offspring. For example, for hobbits, as amniotic organisms, cenogenesis includes embryonic membranes, the yolk sac and allantois, and for hobbits, as placental animals, the placenta with the umbilical cord is also included.

Phylembryogenesis is an embryonic neoplasm that has phylogenetic significance. The time of their appearance and the methods are different (example: from shark scales develop: 1- reptile horn shields by deviation 2 bird feather - anabolism 3 - mammal hair - archallaxis. Evolution is more often by anabolism, therefore, recapitulation is observed. - the development of the organ changes completely. There is no recapitulation. 2- middle stages (deviation-deviation in development) 3- final stages (anabolia- superposition in the development of the organ)

Man and the biosphere. The noosphere is the highest stage in the evolution of the biosphere. The reaction of the body to a change in the environmental situation. Examples. Liebig-Thiemann rule. Barrel Liebig. Le Chatelier-Brown principle.

Biosphere and man. Modern man was formed about 30-40 thousand years ago. Since that time, a new anthropogenic factor began to operate in the evolution of the biosphere. The first Paleolithic (Stone Age) culture created by man lasted approximately 20-30 thousand years; it coincided with a long period of glaciation. The economic basis of the life of human society was the hunting of large animals: red and reindeer, woolly rhinoceros, donkey, horse, mammoth, tour. Numerous bones of wild animals are found at the sites of the Stone Age man, evidence of successful hunting. Intensive extermination of large herbivores has led to a relatively rapid reduction in their numbers and the extinction of many species. If small herbivores could make up for losses from persecution by hunters due to high birth rates, then large animals, due to evolutionary history, were deprived of this opportunity. Additional difficulties for herbivores arose due to changes in natural conditions at the end of the Paleolithic. 10-13 thousand years ago there was a sharp warming, the glacier retreated, forests spread in Europe, large animals died out. This created new living conditions, destroyed the existing economic base of human society. The period of its development, which was characterized only by the use of food, has ended. purely consumer attitude to the environment. In the next Neolithic era, along with hunting (horse, wild sheep, red deer, wild boar, bison, etc.), fishing and gathering (shellfish, nuts, berries, fruits), the food production process becomes increasingly important. The first attempts were made to domesticate animals and breed plants, and the production of ceramics was born. Already 9-10 thousand years ago there were settlements, among the remains of which wheat, barley, lentils, bones of domestic animals of goats, sheep, pigs are found. In different places of Western and Central Asia, the Caucasus, and Southern Europe, the beginnings of agricultural and cattle breeding are developing. Fire is widely used both for the destruction of vegetation in conditions of slash-and-burn agriculture, and as a means of hunting. The development of mineral resources begins, metallurgy is born. Population growth, a qualitative leap in the development of science and technology over the past two centuries, especially today, have led to the fact that human activity has become a factor on a planetary scale, the guiding force for the further evolution of the biosphere. IN AND. Vernadsky believed that the influence of scientific thought and human labor led to the transition of the biosphere to a new state, the noosphere (the sphere of reason).

NOOSPHERE - THE HIGHEST STAGE OF DEVELOPMENT OF THE BIOSPHERE

The sphere of interaction between society and nature, within which reasonable

activity appears to be the main, determining factor in the development of the biosphere and

humanity is called the noosphere.

For the first time the term "noosphere" in 1926 - 1927. used by French scientists E.

Lecroix (1870 - 1954) and P. Teilhard de Chardin (1881 - 1955) in the meaning of "new

cover", "thinking layer", which, originating at the end of the Tertiary period,

unfolds outside the biosphere over the world of plants and animals. In their

representation of the noosphere - the ideal, spiritual ("thinking") shell of the Earth,

emerged with the advent and development of human consciousness. Merit of filling

of this concept, the materialistic content belongs to Academician V.I.

Vernadsky (1965, 1978).

In the view of V. I. Vernadsky, a person is a part of living matter,

subordinated to the general law of organization of the biosphere, outside of which it

cannot exist. Man is part of the biosphere, argued an outstanding

scientist. The goal of social development should be to keep organized

biosphere. However, the preservation of its primary organization - "untouched

nature" - does not carry a creative principle into a powerful geological force. "And

before him, before his thought and work is the question of the restructuring of the biosphere

in the interests of a free-thinking humanity as a whole. This is new

the state of the biosphere, to which we are approaching without noticing it, is

"noosphere". The noosphere is a qualitatively new stage in evolution

biosphere, in which new forms of its organization are created as a new

unity resulting from the interaction of nature and society. In her

the laws of nature are closely intertwined with socio-economic laws

development of society, forming the highest material integrity of the "humanized

nature."

V. I. Vernadsky, who predicted the advent of the era of scientific and technical

revolution in the 20th century, the main prerequisite for the transition of the biosphere into the noosphere

considered scientific thought. Its material expression in a human-transformed

the biosphere is labor. The unity of thought and labor not only creates a new

the social essence of man, but also predetermines the transition of the biosphere into

noosphere. "Science is the maximum force for the creation of the noosphere" - this is the main thing

the position of V. I. Vernadsky in the doctrine of the biosphere, calling to transform,

not to destroy the ecumene.

The reaction of the body to a change in the environmental situation.

The same factor can have an optimal effect on different organisms at different values. In addition, living organisms are divided into those capable of existing in a wide or narrow range of changes in any environmental factor. Organisms adapt to each environmental factor in a relatively independent way. An organism may be adapted to a narrow range of one factor and a wide range of another. For the organism, not only the amplitude is important, but also the rate of fluctuations of one or another factor.

If the influence of environmental conditions does not reach the limit values, living organisms react to it with certain actions or changes in their state, which ultimately leads to the survival of the species. Overcoming the adverse effects of animals is possible in two ways:

1) by avoiding them,

2) by acquiring endurance. Plant responses are based on the development of adaptive changes in their structure and life processes. Variability is one of the main properties of living things at various levels of its organization. Genetic variability is the basis of hereditary variability of traits.

Liebig's minimum rule

According to Liebig's minimum rule, the yield (production), its magnitude and stability over time, is controlled by a variable of resources, such as space, time, matter, energy and diversity, which is at a minimum. This rule has now been extended to the operation of various objects and generally states that the state of a function is determined by the factor that has the minimum value. In the interpretation of Y. Odum (1986), at the organismic level in a stationary state, the limiting substance will be that vital substance, the available amounts of which are closest to the required minimum. E. A. Micherlich formulated the rule of the cumulative action of factors, which refines Liebig's minimum rule. For animals, the limiting (limiting) factors, as a rule, are: the availability of a sufficient amount of food, suitable shelters (shelters), climatic conditions.

lesson type - combined

Methods: partially exploratory, problematic presentation, explanatory and illustrative.

Target:

Formation in students of a holistic system of knowledge about wildlife, its systemic organization and evolution;

Ability to give a reasoned assessment of new information on biological issues;

Education of civic responsibility, independence, initiative

Tasks:

Educational: about biological systems (cell, organism, species, ecosystem); the history of the development of modern ideas about wildlife; outstanding discoveries in biological science; the role of biological science in shaping the modern natural-science picture of the world; methods of scientific knowledge;

Development creative abilities in the process of studying the outstanding achievements of biology, included in the universal culture; complex and contradictory ways of developing modern scientific views, ideas, theories, concepts, various hypotheses (about the essence and origin of life, man) in the course of working with various sources of information;

Upbringing conviction in the possibility of knowing wildlife, the need for careful attitude to the natural environment, one's own health; respect for the opinion of the opponent when discussing biological problems

REQUIREMENTS FOR LEARNING OUTCOMES-UUD

Personal Outcomes of Learning Biology:

1. education of Russian civil identity: patriotism, love and respect for the Fatherland, a sense of pride in their homeland; awareness of one's ethnicity; assimilation of humanistic and traditional values of the multinational Russian society; fostering a sense of responsibility and duty to the Motherland;

2. formation of a responsible attitude to learning, readiness and ability of students for self-development and self-education based on motivation for learning and cognition, conscious choice and building a further individual trajectory of education based on orientation in the world of professions and professional preferences, taking into account sustainable cognitive interests;

Meta-subject learning outcomes in biology:

1. the ability to independently determine the goals of one's learning, set and formulate new tasks for oneself in study and cognitive activity, develop the motives and interests of one's cognitive activity;

2. mastering the components of research and project activities, including the ability to see the problem, raise questions, put forward hypotheses;

3. the ability to work with different sources of biological information: find biological information in various sources (textbook text, popular scientific literature, biological dictionaries and reference books), analyze and

evaluate information;

cognitive: selection of essential features of biological objects and processes; bringing evidence (argumentation) of human kinship with mammals; the relationship between man and the environment; dependence of human health on the state of the environment; the need to protect the environment; mastering the methods of biological science: observation and description of biological objects and processes; setting up biological experiments and explaining their results.

Regulatory: the ability to independently plan ways to achieve goals, including alternative ones, to consciously choose the most effective ways to solve educational and cognitive problems; the ability to organize educational cooperation and joint activities with the teacher and peers; work individually and in a group: find a common solution and resolve conflicts based on the coordination of positions and taking into account interests; formation and development of competence in the field of the use of information and communication technologies (hereinafter referred to as ICT competencies).

Communicative: the formation of communicative competence in communication and cooperation with peers, understanding the characteristics of gender socialization in adolescence, socially useful, educational, research, creative and other activities.

Technologies: Health saving, problematic, developmental education, group activities

Receptions: analysis, synthesis, conclusion, transfer of information from one type to another, generalization.

During the classes

Tasks

To acquaint students with the essence and manifestation of the biogenetic law; the history of the discovery of this law; the value of the law for clarifying family ties between organisms.

Key points

The embryos show a certain general similarity within the phylum.

At different stages of embryonic development, new traits may appear.

Changes in embryos may be in the nature of restructuring, superstructing, or replacing an ancestral trait.

Ontogeny - it is an individual development, a complex of developmental processes separate especially from the formation of a zygote to death. Development occurs due to the implementation of genetic information received from parents. Environmental conditions have a significant impact on its implementation. Phylogeny is the historical development of a species, the evolutionary development of organisms. Both processes are closely related. Knowing the directions and transformations of organs and their systems in the process of historical development, it is possible to understand and explain developmental anomalies arising in the process of embryogenesis.

The connection between otnogenesis and phylogenesis was reflected in a number of biological laws and patterns. In 1828, Karl Baer formulated three laws:

1. Law of germinal similarity- the embryo of any higher animal is not similar to another animal, but is similar to its embryo

2. law of successive occurrence of signs- more general features characteristic of a given large group of animals are detected in their embryos earlier than more specific features

3. law of mabrional divergence- each embryo of a given animal form does not pass through other forms, but gradually separates from them.

The law of germline similarity K. Baer

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

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

The germline similarity is explained now the actual relationship of organisms, and their gradual divergence (embryonic divergence) is an obvious reflection of the historical divergence of these forms (phylogenetic divergence). Therefore, the history of a given species can be traced by individual development.

The biological essence of E. Haeckel's biogenetic law

Haeckel's biogenetic law and Severtsov's theory of phylembryogenesis play an important role in the development of morphology and evolutionary theory itself. The study of the individual development of animals has provided ample evidence of their historical development. The biogenetic law is an important component of the triple parallelism method developed by E. Haeckel, with the help of which phylogenesis is reconstructed. This method is based on a comparison of morphological, embryological, and paleontological data. Morphologists in the reconstruction of phylogeny still use Haeckel's principle, according to which the ontogenesis of descendants briefly repeats, recapitulates the stages of the phylogeny of ancestors. 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. To cenogenesis in placental mammals and humans - the placenta with the umbilical cord.

cenogenesis, manifesting only in the early stages of ontogenesis, do not change the type of organization of the adult organism, but provide 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.

Another type of phylogenetically significant transformations phylogenesis- 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: violation of cell proliferation, their movement, adhesion, death or differentiation. However, just like cenogenesis, they are distinguished from vices by their 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, arise 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 may be the development of the heart in the ontogeny of mammals, in which it recapitulates the tube stage, a 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 for mammals. In the development of the lungs in mammals, recapitulation of the early stages of the ancestors is also found, later morphogenesis proceeds in a new way.

3. Archallaxis- changes that are found at the level of rudiments and are expressed in 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 very early stages of development and differs from the anlage of other vertebrate skin appendages from the very beginning. According to the type of archallaxis, a notochord arises in primitive non-cranial animals, a cartilaginous spine in cartilaginous fish, and nephrons of the secondary kidney develop in reptiles.

It is clear that during evolution due to anabolism, the main biogenetic law is fully implemented 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.

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, then they often turn out to be incompatible with life.

In addition to cenogenesis and phylembryogenesis, in the evolution of ontogeny, deviations in the time of laying organs - heterochrony - and the place of their development - heterotopia can also be detected. 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.

Heterotopia 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 the new respiratory organs - the lungs, performing here, first of all, the function of delivering blood to the respiratory system for gas exchange.

Heterochrony and heterotopy Depending on the stages of embryogenesis and organ morphogenesis, they appear, they can be regarded as phylembryogenesis of different types. Testicular heterotopia in humans from the abdominal cavity through the inguinal canal to the scrotum, observed at the end of embryogenesis after its final formation, is a typical anabolism.

Cenogenesis, phylembryogenesis, as well as heterotopies and heterochronies, having proved useful, are fixed in the offspring and reproduced in subsequent generations until new adaptive changes in ontogeny 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.

All multicellular organisms develop from a fertilized egg. The processes of development of embryos in animals belonging to the same type are largely similar. In all chordates, in the embryonic period, an axial skeleton is laid - a chord, a neural tube appears, and gill slits form in the anterior part of the pharynx. The plan of the structure of chordates is also the same. In the early stages of development, vertebrate embryos are extremely similar. These facts confirm the validity of the law of germinal similarity formulated by K. Baer: "Embryos already from the earliest stages show a certain general similarity within the type." The similarity of the embryos serves as evidence of their common origin. Later, in the structure of the embryos, signs of a class, genus, species, and, finally, signs characteristic of a given individual appear. The divergence of signs of embryos in the process of development is called embryonic divergence and is explained by the history of this species, reflecting evolution one or another systematic group of animals.

The great similarity of embryos in the early stages of development and the appearance of differences in later stages have their own explanation. The study of embryonic variability shows that all stages of development are changeable. mutation process affects and genes conditioning features of the structure and metabolism of substances in the youngest embryos. But the structures that arise in early embryos (ancient features characteristic of distant ancestors) play a very important role in the processes of further development. As indicated, the notochord primordium induces the formation of the neural tube, and its loss leads to the cessation of development. Examples of the interaction of parts of the embryo in development and the functional importance of the structures formed in the early stages are numerous. Therefore, changes in the early stages usually lead to underdevelopment and death. On the contrary, changes in the later stages may be favorable for the organism and are therefore picked up by natural selection.

The appearance in the embryonic period of development of modern animal features characteristic of distant ancestors reflects evolutionary transformations in the structure of organs.

In its development, the organism passes through a unicellular stage (the zygote stage), which can be considered as a repetition of the phylogenetic stage of the primitive amoeba. In all vertebrates, including their higher representatives, a chord is laid, which is then replaced by the spine, and in their ancestors, judging by the lancelet, the chord remained all their lives. During the embryonic development of birds and mammals, including humans, gill slits appear in the pharynx and their corresponding septa. The fact of the laying of parts of the gill apparatus in the embryos of terrestrial vertebrates is explained by their origin from fish-like ancestors that breathed through gills. The structure of the heart of the human embryo during this period resembles the structure of this organ in fish: it has one atrium and one ventricle. Toothless whales develop teeth during the embryonic period. These teeth do not erupt, they are destroyed and resorbed. The examples given here and many others point to a deep connection between the individual development of organisms and their historical development.

This connection found its expression in the biogenetic law formulated by F Müller and E. Haeckel in the 19th century: ontogenesis(individual development) of each individual is a brief and quick repetition of the phylogenesis (historical development) of the species to which this individual belongs.

Questions and tasks for repetition

Give examples of the similarity of structural features in the embryos of different classes of vertebrates.

Give an explanation for the appearance in embryos of the appearance of animal structural features characteristic of their distant ancestors

Identification and description of signs of similarity between human embryos and other vertebrates.

BiogeneticLaw

Biogenetic law and embryonic variability

Resources

V. B. ZAKHAROV, S. G. MAMONTOV, N. I. SONIN, E. T. ZAKHAROVA TEXTBOOK "BIOLOGY" FOR GENERAL EDUCATIONAL INSTITUTIONS (grades 10-11).

AP Plekhov Biology with fundamentals of ecology. Series “Textbooks for universities. Special Literature» .

A book for teachers Sivoglazov V.I., Sukhova T.S. Kozlova T. A. Biology: general patterns.

Biology 100 most important topics V.Yu. Jameev 2016

Biology in schemes, terms, tables "M.V. Zheleznyak, G.N. Deripasko, Publishing house "Phoenix"

Visual guide. Biology. 10-11 grades. Krasilnikova

Educational portal http://cleverpenguin.ru/metabolizm-kletki

Presentation Hosting

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, and differentiation. The term "Oh." introduced by E. Haeckel (1866) when he formulated the 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 phylogeny was posed by C. Darwin and developed by F. Muller, E. Haeckel and others. All traits associated with changes in heredity, evolutionarily new traits, 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 of natural selection and transmitted to subsequent generations, i.e., 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.

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 (ontogeny) 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 characters - notochord, gill slit and gill arch anlages in all chordates, but also features of biochemical organization and physiology. Thus, in the evolution of vertebrates, there is a gradual loss of enzymes necessary for the breakdown of uric acid, a product of purine metabolism. In most invertebrates, the 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.

Ticket 96.

Ontogeny as the basis of phylogenesis. 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: violation of cell proliferation, their movement, adhesion, death or differentiation. However, just like cenogenesis, they are distinguished from vices by their 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 may be the development of the heart in the ontogeny of mammals, in which it recapitulates the tube stage, a 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 for mammals. In the development of the lungs in mammals, recapitulation of the early stages of the ancestors is also found, later morphogenesis proceeds in a new way.

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 very early stages of development and from the very beginning differs from the anlage of other vertebrate skin appendages.

According to the type of archallaxis, a notochord arises in primitive non-cranial animals, a cartilaginous spine in cartilaginous fish, and nephrons of the secondary kidney develop in reptiles.

If we compare the diagram of phylembryogenesis with K. Baer's table 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 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 physician to predict the possibility of atavistic congenital malformations in fetuses and newborns. Indeed, if atavistic malformations are possible due to recapitulation of ancestral states in an organ system that evolves through anabolism and deviations, then this is completely excluded in the case of archallaxis.

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 located 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 case it is anabolism.

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 , 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 in the phylogenesis of their ancestors during the ontogenesis of modern forms, i.e., they violate the 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.

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FILEMBRIOGENESIS (from the Greek phylon - genus, tribe, embryon - embryo and genesis - origin), an evolutionary change in the ontogeny of organs, tissues and cells, associated with both progressive development and reduction. The doctrine of phylembryogenesis was developed by the 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 of ancestral phylogenesis (i.e., they are recapitulations) and can serve for its reconstruction (see 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.

The reduction of organs that 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 a rudiment, or undergoes 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.

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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.
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Principles of phylogenetic transformations

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 can participate in the implementation of any complex function. A group of organs similar in origin that combine to perform a complex function is called system(circulatory, excretory, etc.). If a group of organs of different origin performs the same function, 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, organ transformations may have progressive or regressive character. 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.

The basic principle of the evolution of organic structures is the principle differentiation. Differentiation is the division of a homogeneous structure into separate parts, which, due to their different position, connections with other organs and various functions, acquire a specific structure. Thus, the complication of the structure is always associated with the complication of functions and the specialization of individual parts. A differentiated structure performs several functions, and its structure is complex.

An example of phylogenetic differentiation is the evolution of the circulatory system in the chordate type. So, in representatives of the non-cranial subtype, it is built very simply: one circle of blood circulation, the absence of a heart and capillaries in the system of branchial arteries.

The superclass of fish has a two-chambered heart and gill capillaries. In amphibians, for the first time, the division of the circulatory system into two circles of blood circulation appears, and the heart becomes three-chambered. Maximum differentiation is characteristic of the circulatory system of mammals, whose heart is four-chambered, and in the vessels complete separation of venous and arterial blood flows is achieved.

Separate parts of a differentiating, previously homogeneous structure, specializing in the performance of one function, become functionally more and more dependent on other parts of this structure and on the organism as a whole. Such a functional subordination of the individual components of the system in the whole organism is called integration.

The four-chambered mammalian heart is an example of a highly integrated structure: each department performs only its own special function, which makes no sense in isolation from the functions of other departments. Therefore, the heart is equipped with an autonomous system of functional regulation in the form of a parasympathetic atrioventricular nerve node and, at the same time, is strictly subordinated to the neurohumoral system of regulation of the body as a whole.

Thus, simultaneously with differentiation, the subordination of parts to the integral system of the organism is observed, i.e. integration process.

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 phylogenesis of the central nervous system of chordates, one can also see the differentiation and change in the functions of structures: the brain is formed from the anterior end of the neural tube. In the same way, new biological species are formed in the form of isolated populations of the original species (see § 11.6), and new biogeocenoses are formed due to the differentiation of pre-existing ones (see § 16.2).

Due to the fact that the phylogenies of specific organ systems will be considered below, we will dwell in more detail on the patterns of the emergence and disappearance of organs. 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 carried out 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. In the process of natural selection, those mammals were preserved and successfully reproduced in the first place, in the organisms of females of which the offspring developed the longest. As a result, a new organ appeared - the uterus, which provides the embryo with optimal conditions for intrauterine development (see Section 14.5.3) 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. At the heart of the formation of the organ of vision, as well as all sense organs, are the cells of the skin epithelium, among which receptor cells, in particular light-sensitive cells, are also differentiated. Combining them into groups leads to the emergence of primitive separate organs of vision, allowing animals only to evaluate illumination. The immersion of such a photosensitive organ under the skin ensures the safety of delicate cells, but at the same time, the visual function can be carried out only due to the appearance of transparency of the integuments. The sensitivity to light of the primitive organ of vision increases with the thickening of the transparent integuments and their acquisition of the ability to refract light and focus its rays on the sensitive cells of the eye. A complex organ requires an auxiliary apparatus - protective structures, muscles that set it in motion, etc. The increased level of complexity of the organization of the eye is necessarily accompanied by a complication of the regulation of its functions, which is expressed in the strengthening of its integration as an integral system.

disappearance, or reduction, an organ 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 way to the disappearance of organs is through the gradual weakening of their functions. Such situations usually arise when the conditions of existence change. An organ that performs almost no functions gets out of control of natural selection and usually exhibits increased variability. The resulting changes cause a violation of correlative relationships with other parts of the body. 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 be 2 to 20 cm long and be located in different ways (behind the peritoneum, on the long mesentery, behind the caecum, etc.). In addition, inflammation of the appendix (appendicitis) is much more common than inflammatory processes in other parts of the intestine.

The process of organ reduction is opposite to its normal morphogenesis. First of all, the bookmarks of such parts of the organ fall out, which are normally formed last. With underdevelopment of the limbs in a person, the phalanges of the I and V fingers, which are laid last, are usually the first to underdevelop. In cetaceans, which are completely devoid of hind limbs due to the weakening of their functions in phylogenesis, the anlage of elements of the pelvic girdle still remains, which are formed in the process of morphogenesis the earliest.

Studies of the genetic basis of organ reduction have shown that the structural genes that regulate morphogenesis do not disappear, while the genes that regulate the time of laying of rudimentary organs, or the genes responsible for the phenomenon of induction interactions in the developing embryo, undergo significant changes. Indeed, transplantation of the mesodermal material from the bottom of the oral cavity of a lizard embryo into the oral cavity of a developing chick can lead to the formation of a typical structure in the latter teeth, and transplantation of the skin mesoderm of the lizard under the epidermis of the chick’s back leads to the formation of typical horny scales in it instead of feathers.

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.

Law of germinal similarity

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

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

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

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.

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: 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.

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).

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.

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.

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.

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.

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.

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 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.

In 1828, Karl von Baer formulated a pattern: " The earlier stages of individual development are compared, the more similarities can be found.". Comparing the stages of development of embryos of different species and classes of chordates, K. Baer made the following conclusions.

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

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

Baer formulated the laws of germline similarity:

The most common characters of any large group of animals appear in the embryo earlier than the less common characters;

After the formation of the most general signs, less common ones appear, and so on until the appearance of special signs characteristic of this group;

The embryo of any animal species, as it develops, becomes less and less like the embryos of other species, and does not pass through the later stages of their development;

The embryo of a highly organized species may resemble the embryo of a more primitive species, but never resembles the adult form of that species.

Karl Baer himself did not accept the evolutionary teachings of Charles Darwin, but his laws are considered by biologists as "embryological proof of evolution."

“For example, a human embryo in nine months spent in the uterus goes through many stages - from invertebrate to fish, then to amphibian, to reptile, to mammal, to primate, to the likeness of hominids and to man as such.

Von Baer's law implies that evolutionary change occurs more often in the later stages of development, while the early stages are more evolutionarily conservative. This is because any mutation that affects early development is more likely to have a pronounced phenotypic effect than one that affects late development. Since development is continuous and cumulative, changes at an early stage will have more and more pronounced consequences compared to changes at later stages of development. The most likely outcome of any mutation occurring at an early stage is unfavorable and often fatal. Comparatively later (relative to the developmental age) mutations are more likely to have no negative effects, and in some cases they can even increase adaptation by subtle changes in the phenotype. ( This phenomenon can be illustrated by drawing an analogy with the construction of a skyscraper. If changes are made to the ground floor wall construction plan, there is a good chance that every floor above will be affected, and possibly in a negative way. Any changes to the last floor of a skyscraper will not affect the lower floors..)

Von Baer's law is more valid for organisms that develop inside the mother (for example, mammals) than for species that have a larval stage in which they must take care of themselves.

During intrauterine development, the pressure of natural selection from the external environment leading to change is minimal or absent. However, the larval organism, which ensures its own survival, is constantly subjected to the pressure of natural selection. This explains why the early stages of mammalian development are so similar across species, while in organisms such as insects the larval stage is very different from the adult."

At what stages of embryogenesis are the blastocoel, gastrocoel and coelom formed?

crushing stage. Blastocoel- the cavity of the blastula, which is formed on the 4-5th day of crushing between blastomeres in animal embryos. Filled with a liquid that differs in chemical composition from the environment. The cavity increases the surface area of the embryo, improving its ability to absorb nutrients and oxygen. It reaches its largest size by the end of crushing, at the blastula stage. In the process of gastrulation, it is gradually forced out during invagination (invagination) of the embryonic wall or filled (during immigration) with moving cells.

stage of gastrulation. Gastrocel- the primary intestine, the cavity of the gastrula, which is formed in the embryos of multicellular organisms in the event that gastrulation is carried out by intussusception. The gastrocoel is filled with liquid and communicates with the external environment through a special opening - the blastopore. The walls of the gastrocoel consist of invaginating primary endoderm. In the future, the gastrocoel becomes the cavity of the definitive intestine.

Stage of mesoderm differentiation. In general- secondary body cavity of multicellular animals. In trochophores, it is formed from specialized mesodermal cells - teloblasts as a result of their division and the subsequent formation of cavities within the resulting groups of cells. This method of coelom formation in ontogeny is called teloblastic. In deuterostomes, the coelom is formed by protrusion of the walls of the primary intestine and separation of the resulting protrusions. This method of coelom formation is called enterocoel. In both cases, the whole is considered a mesodermal formation. It differs from the primary body cavity by the presence of its own epithelial lining (wall). The epithelium that forms the lining of the coelom is called the coelothelium or mesothelium.

Splitting up. Within 3-4 days, crushing occurs in the oviduct. Light small blastomeres break up faster and surround dark large ones that stay inside. An embryo without a cavity, consisting of a dense accumulation of blastomeres, is called morula( formed on the 3-4th day of crushing). On the 4-5th day, the embryo enters the uterine cavity, from where it absorbs fluid and accumulates it in its cavity - blastocoel . Its wall is formed by small, light blastomeres - trophoblast . Dark cells are pushed to one of the poles and form embryoblast . The resulting blastula called blastocyst , or blastodermic vesicle. Up to 7 days, the blastocyst is in the uterine cavity in a free state, feeding on the secret of the uterine glands. This ends the initial (1st week) period of embryogenesis

Intussusception. It is observed in animals with isolecithal type of eggs (holothuria, lancelet). The vegetative pole of the blastula protrudes inwards. As a result, the opposite poles of the blastoderm practically close, so that the blastocoel either disappears or a small gap remains from it. As a result, a two-layer embryo appears, the outer wall of which is the primary ectoderm, and the inner wall is the primary endoderm. The invagination forms the primary intestine-archenteron, or gastrocoel. The hole through which it communicates with the external environment. called the primary mouth, or blastopore.

mesoderm differentiation. The ventral parts of the mesoderm are not segmented and form a splanchnotome. It is divided into two sheets - parietal and visceral, surrounding the secondary body cavity - the whole.