Rudimentary organs and atavisms in humans. Traces of evolution on the human body Caudal appendage in humans

Atavism and rudiment. Why be afraid?

Speaking about the danger to human life, of course, it is more appropriate to use the term atavism. Unlike a rudiment, these are anomalies of human development, some of which (but not all) under certain conditions can become a nosological form, that is, a disease.

These include continuous body hair, additional pairs of mammary glands, non-closure of the atrial septum of the heart, gill sacs, slits (against the background of an inferiorly developed auditory apparatus).

The tail vertebrae (coccyx), ear muscles, blinking ventricles of the larynx, wisdom teeth, pyramidal muscle, vermiform appendix of the caecum (appendix), epicanthus (third eyelid) can also be called a vestige.

evolutionary mistakes. What is the reason?

Despite the rather obvious differences between these two groups of traits, they have a common genetic essence, a common evolutionary base: organs (traits) that have become useless for the body are not lost overnight, but can persist for millions of years. They are slowly destroyed under the load of accumulating mutations.

Even if the external manifestation of a trait is completely lost, fragments of the genetic “programs” that ensured the development of this trait in ancestors can remain in the genome for a long time. One of the main and, perhaps, the most delicate principle of gene regulation is the so-called post-transcriptional control.

Speaking in common language, everything that the gene responsible for the development of atavism has “acquired” in the developing cell of the embryo is “cleaned up”. An unnecessary feature is not generated. Under special circumstances (mutations, extreme effects on the developing embryo), these gene programs can “work”. Then we get certain anomalies in the child that can develop into a deadly disease (as in the case of an unclosed atrial opening, an oval window).

The rudiments, in their genetic essence, are practically “invincible”. This allows them to be found in most of the adult population (for example, molars, coccygeal vertebrae, appendix of the caecum, etc.). Moreover, it is important to note that these traits generally do not cause significant harm to the individual (or, perhaps, they are a potential basis for the development of a useful trait in the future). It can be assumed that they will not be removed from the genetic code any time soon by evolution. Or they won't be removed at all.

Who are they, the rudiments?

One of the most famous vestiges, perhaps, is the appendix and the concept of appendicitis, which is inextricably linked with it, that is, inflammation of this very appendix. It is interesting to note that in general surgical practice, operations for appendicitis are among the most frequent. Often, the disease is fraught with formidable complications in the form of peritonitis (inflammation of the tissue covering the entire abdominal cavity), abscess (formation of an abscess in the abdominal cavity).

You involuntarily think about eugenics, which is somewhat forgotten today. By 2003, the international project "Human Genome" was successfully completed: 99% of the genome was sequenced with an accuracy of 99.99%. The basic principles of the formation of the genetic code are known. Is it not worth setting a goal - to form a more perfect person, devoid of this rudiment?

Despite all the available knowledge, the answer is likely to be negative. The appendix still carries some functions - maintaining the microbiological balance of the intestine, adequate digestion, local immunity due to the huge amount of lymphoid tissue in it. Someday, perhaps in the near "evolutionary" future, the human body will be able to do without an appendix, but not today.

epicanthus

Epicanthus is an equally interesting rudimentary human phenomenon. This is the so-called "Mongolian fold" - a special fold at the inner corner of the eye, to a greater or lesser extent covering the lacrimal tubercle.

It is of particular interest in connection with geographical and racial attachment. So, more than 60% of Asians have epicanthus, while representatives of the Negroid race, Europeans do not have it at all (almost 100 percent).

There are many hypotheses about this. The main one today is the so-called "combined-adaptive hypothesis". The main function of the fold is protection from the wind and solar radiation reflected from the snow. Very often, its presence is accompanied by a flattened bridge of the nose, increased deposition of adipose tissue on the face and in the area of ​​the upper eyelid.

Thus, being a useful feature in some groups of people, the epicanthus is fully vestigial in others. In clinical practice, it has been observed that this rudiment is detected in more than 80% of patients suffering from Down syndrome.

Disease or anomalous feature?

Separately, it should be noted that many signs that can be mistakenly recognized as rudiments or atavisms are anomalies in human development in general. These are “genetic errors” that have nothing to do with the work of the genes responsible for the normal development of organs or traits (including our “evolutionary ancestors”).

This group includes - "hare lip" (non-closure of the upper lip), "cleft palate" (non-closure of the middle part of the palate), "Gothic palate" (high arch of the palate) and a huge number of other anomalies, many of which form nosological forms, that is illness.
To date, the scientific world has achieved serious success in genetics. We are able to create "in vitro" though primitive, but living organisms. Create completely. From scratch.

So, in 2010, the Craig Venter Institute for the first time created an artificial life form, Mycoplasma mycoides JCVI-syn1.0. Does this mean that we are ready to improve our own “breed” today? It is impossible to give a precise and reasonable answer. In any case, one should be extremely careful and always keep in mind the already existing experience of eugenics of the 20th century.

Rudiments called organs that have no function or have a function that deviates from their structure. It is believed that in such bodies it is possible to establish a discrepancy between structure and function, that is, in these bodies, the structural costs seem excessively large for the function they perform. Loss of function or limitation of functional ability interpreted within the evolutionary theory loss of function in the course of evolution.

At first glance, it is clear that the rudiments cannot serve proof development from lower to higher forms. Anyway, the rudiments show dying process these organs. Rudiments are excluded as proof of progressive evolution.

But, in the end, there is another argument: vestigial organs testify and against act of creation for in a deliberate and planned creation such organs could not have taken place. Therefore, we consider the problem of rudiments in more detail and offer our own interpretation of the phenomenon of rudimentation within the framework of the creation model (for a more detailed discussion of this topic, see Junker, 1989).

Most of the rudiments have not lost their functions

For a long time it was considered a classic organ that had lost its functions. caecal appendix person. At present, however, it is known that the appendix has a protective function in general diseases and is involved in the control of the bacterial flora in the caecum.

Birds, reptiles and some mammals have a third eyelid, a transparent nictitating membrane. Protecting the eye, it stretches from its inner corner through the entire eyeball. . When birds fly, the nictitating membrane functions like a windshield wiper. . "Rudimentary" nictitating membrane in humans (Fig. . 6.15 ) performs the task of collecting foreign bodies that fall on the eyeball, it binds them in the corner of the eye into a sticky mass. From there they can be easily removed.

Coccyx a person is necessary to strengthen the muscles of the pelvis, which holds the internal organs of the small pelvis and thereby makes possible an upright gait. The mobility to which the coccyx owes its origin in ontogenesis from the spinal column is of decisive importance for the process of childbirth.

Attachment of the esophagus to the trachea also not pointless: mucus in the respiratory tract can be removed through the esophagus . In addition, such a structure saves space and makes it possible to breathe through the mouth, which is an extremely convenient way in case of a severe cold. Therefore, it cannot be considered as a superfluous structure due to phylogenetic development. All these structures, however, are quite explicable from the point of view of constructive development ( see 6.5.2).

Examples from the animal world

Embryonic rudiments of teeth in mustachioed whales, which never become true teeth, play an important role in the formation of jaw bones. The same goes for the primordia of the upper incisors of ruminants, which never erupt through the upper jaw.

Remains of kiwi wings(rice. 6.16) serve to adjust the balance. However, in this case, the rudiments are only an evolutionary-theoretical concept, it is based on the belief (which should have been proven first) that the ancestors of the kiwi were once able to fly.

Rudimentary bones of the pelvis and femur of a whale(rice. 6.17) serve as an attachment point for the muscles of the genital organs and the muscles of the anus, and if they are destroyed, the contents of the stomach of animals will be flattened under the influence of high hydrostatic pressure at great water depths. So in this case, there can be no question of loss of functionality, because without these bones, whales would not be able to dive to depth so well.

Remains hind limbs in the form of horny shields in boa and python("superrudimentary") are very helpful in moving snakes through branches, branches and serve as auxiliary organs during mating.

And finally, one should name one more, the so-called "rudiment behavior ": when a red deer threatens its fellow species, it raises its upper lip, as many animals with dagger-shaped fangs do. However, such teeth in a red deer are too small. But since threatening gestures are understandable even without clearly visible fangs, then in In this case, there is no urgent need to talk about the phenomenon of rudimentary.

It can be argued that the phenomenon of loss of function cannot be proven with absolute certainty. The arguments given are based, as a rule, on momentary ignorance.

Some rudiments arise through degeneration within one species and within a short period of time(degenerative microevolution). A typical example of this would be a person's "wisdom teeth". It is possible (both in the creation model and in the evolutionary model) to proceed from the fact that in the past all 32 human teeth were regularly used and were fully functionally loaded. The fact that modern man does not necessarily need wisdom teeth may be due to his changed eating habits. Therefore, the increased degenerative development did no harm. And since no structural change worthy of mention occurred with degenerative development, there can be no question of evolution in the sense of the evolutionary doctrine. Such degenerative development is possible only for a short period of time, it does not require either millions or hundreds of thousands of years. This is tantamount to considering "evolution" a greater predisposition to diseases or deteriorating vision.

Wisdom teeth atrophy varies from race to race. The Mongoloid race is especially advanced in this process. Discovered human fossils have functionally usable wisdom teeth.

The so-called well-known "diseases of civilization" may also be listed under this heading, such as the frequently mentioned examples of weakened intervertebral cartilage, inguinal hernia, hemorrhoids, varicose veins and flat feet. . This has nothing to do with "catastrophic planning", as the zoologist R. Riedl (1984, p. 192) recently put it, but only with "improper use". If the technical device is used improperly, then the resulting breakdowns cannot be explained by design flaws. A person is something more than a device, but his physical well-being also depends on his lifestyle.

A simple microevolutionary degeneration could explain the development of vestigial wings in ground beetles or in insects that live on islands subject to strong gusts of wind (see Fig. section 3.3.3). Rudimentary stamens, found, for example, in Norichnikova, could also be included here. (Scrophulariaceae).

Many rudiments in behavior can be explained by microevolution. For example, the fact that dogs spin before falling asleep is seen as a vestige of a former meaningful behavior in order to personally ascertain whether there is a threat.

Similarity Argument as a True Argument

The previous section could not include, for example, rudimentary pelvic and femoral bones of whales ( rice. 6.17]. They are. compared with the finally developed homologous parts of the skeleton of land animals, they perform only some functions. Partial loss of functions (according to locomotion) is compensated by a special adaptation to an atypical mode of locomotion for mammals, which cannot be acquired in the course of microevolution.

This example provides a good opportunity to compare approaches to argumentation when trying to explain vestigial organs within the framework of the evolutionary model and the creation model. .

Argument within evolutionary model: vestigial pelvic and femur bones of whales have a function, but this function is not required resemblance of these structures with the corresponding (homologous) bones of land mammals . The function described above can also be performed by non-homologous structures. Thus, this similarity indicates generic relationships. Thus, the true argument in favor of generic relationships in this case is the presence of similarity .

Within the framework of the model creation arguments can be made from Section 6. 1 (a variant of one general plan of creation for many different organisms). A programmer who is tasked with making many similar programs will not start from the beginning each time, but will each time use the "non-specialized" program that was made at the beginning, making modifications that are not necessary.

Multifunctionality of vestigial organs

Statement of the loss of functionality or discrepancy between structure and function is a rash step and possible only when the relationships are not known and taken into account during the entire ontogenesis. Particularly instructive are the results of studying individual human development ( section 6.5.2). That this is not an exceptional case is shown by the following example.

Many cave fish have atrophied eyes. About the cave dweller Astyanax mexicanus it is also known that his visual apparatus initially forms normal. Then, in the course of further individual development, there is a reverse development (atrophy) of already existing individual structures. . This remarkable fact, however, is understandable, since the ocular apparatus is of physiological importance in the formation of the head. The eye, therefore, in these cave animals is clearly very limited in its function of the apparatus of perception, but on the other hand it also performs a form-forming function in the early stages of development. Therefore, reduction is possible only from the moment the formative function is not violated.

This example, to which many more similar ones could be added, shows that the ratio of parts during ontogenesis should be taken into account when trying to interpret the phenomenon of rudiments, since in the process of ontogenesis some structures of the body have certain functions (for example, during the formation of an embryo) that are impossible observe in the finally formed organ.

The same structure can thus perform different tasks at the same time. This can be regarded as evidence of a general organizing principle (probably the "principle of creation"): organs usually perform many functions simultaneously or sequentially in the course of individual development. Only in the case just described was the principle discovered that a certain organ (the eye) could, under certain environmental conditions, become a vestige in relation to one of its functions.

AT evolutionary model such phenomena are interpreted as "development in a roundabout way" or "recapitulation development". If, as has been repeatedly demonstrated, there is an urgent physiological need in such "detours", then this interpretation is at least unconvincing. On the basis of such data, some biologists have come to the conclusion that the phenomenon of "roundabout development" should be regarded as evidence that it is on this path that the physiological selection pressure in the development of organisms is concentrated. Some researchers therefore consider it quite possible that for certain physiological problems of development there is only one way of formal solution, namely that the seemingly side ways of development are in fact "shortcuts to success"

atavisms

Structures that, by coincidence circumstances formed at separate individuals of the same species and which are intended to recall the supposed earlier phylogenetic stages of development, are called atavisms(lat. atavus- great-ancestor). In these cases, one speaks of a crisis in the previously passed historical and ancestral stages. As examples of atavisms in humans, fistulas in the throat, too pronounced hairline, ponytails and multi-nipples are given. .

Like "rudiments", atavisms are not evidence for progressive evolution. Moreover, it is clear that the reducible argumentation the appearance of atavisms is different inconsistency. Deformations (malformations) are only considered as evidence of a putative phylogeny (that is, interpreted as atavisms) if they show a resemblance to the putative ancestors of the affected organisms . To be consistent, it would be necessary to historically interpret all the phenomena of deformation, for example, branched ribs, and a cleft lip, and the phenomenon of six-fingeredness, and the formation of two heads: and the appearance of a fifth leg .

This means that even such deformations should be regarded as evidence of previous stages of phylogenetic development, which cannot be certain. However, the opposite is also unacceptable: to interpret this or that defect in development only when it fits within the framework of a pre-built concept. Therefore, atavisms cannot be regarded as evidence of the phylogeny of organisms. The fact that some (but only some) deformations resemble other organisms (presumably the ancestors of the organisms in question), due to the numerous manifestations of external similarity, is not something unexpected and does not deserve special attention. (Atavisms are often "borderline cases of the manifestation of the norm", cf. section 6.5.2.)

An example of atavism in animals is the extra toes in horses ( rice. 6.18). In this case, probably as a result of an erroneous control signal, the only leg structure under normal conditions was formed twice (without any visible benefit). By the way, in horses, only three- and four-fingered forms are known, among them there are no two-fingered ones (as in our case).

How erroneous an atavistic interpretation can be, if applied consistently, is shown by the following example: four-winged fruit flies are taken as evidence that dipterous insects (Deptera) descended from the four-winged. The emergence of four wings is regarded as an atavism. But there are also mutant fruit flies with four swaying halteres and no wings at all - an absurd "construct" that is absolutely unsuitable as a phylogenetic ancestor.

When trying to explain the phenomenon of deformation as an atavism, the same thing applies that was said about the rudiments: all attempts at interpretation are hasty until the underlying genetic and physiological situation of development and the functional significance in the growth process are revealed. Therefore, we have abandoned speculative interpretations of anomalous structural formations.

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Rice. 6.15. The nictitating membrane is a "rudiment" of a person.

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Rice. 6.16. Kiwi, a bird unable to fly, living in the Australian region. The lifestyle of a kiwi corresponds to that of a small mammal. Incapable of flight, bird species are common especially on the islands, since there are very few natural enemies living there. (Rosenstein Castle Museum, Stuttgart.)

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Rice. 6.17. Photo above: rudimentary pelvic bones of sperm whales, sei whales, fin whales (from top to bottom). Fin whales also have femoral rudiments. The lower picture shows the location of the pelvic rudiment in the abdomen of sei whales. Whale researcher Arvey believes that the pelvic rudiments of whales cannot be called homologous to the corresponding pelvic bones of land mammals. He calls these bones stomach bones. (Rosenstein Castle Museum, Stuttgart.)

Genotype and phenotype, their variability

Genotype is the totality of all the genes of an organism, which are its hereditary basis.

Phenotype - the totality of all signs and properties of the organism, which are revealed in the process of individual development under given conditions and are the result of the interaction of the genotype with a complex of factors of the internal and external environment.

Each species has its own unique phenotype. It is formed in accordance with the hereditary information embedded in the genes. However, depending on changes in the external environment, the state of signs varies from organism to organism, resulting in individual differences - variability.

Based on the variability of organisms, a genetic diversity of forms appears. There are modification variability, or phenotypic, and genetic, or mutational.

Modification variability does not cause changes in the genotype, it is associated with the reaction of a given, one and the same genotype to a change in the external environment: under optimal conditions, the maximum of the possibilities inherent in a given genotype is revealed. Modification variability is manifested in quantitative and qualitative deviations from the original norm, which are not inherited, but are only adaptive in nature, for example, increased pigmentation of human skin under the influence of ultraviolet rays or development of the muscular system under the influence of physical exercises, etc.

The degree of variation of a trait in an organism, that is, the limits of modification variability, is called the reaction norm. Thus, the phenotype is formed as a result of the interaction of the genotype and environmental factors. Phenotypic traits are not transmitted from parents to offspring, only the norm of reaction is inherited, that is, the nature of the response to changes in environmental conditions.

Genetic variability is combinative and mutational.

Combination variability arises as a result of the exchange of homologous regions of homologous chromosomes during meiosis, which leads to the formation of new gene associations in the genotype. Arises as a result of three processes: 1) independent divergence of chromosomes in the process of meiosis; 2) their accidental connection during fertilization; 3) exchange of sections of homologous chromosomes or conjugation. .

Mutational variability (mutations). Mutations are called spasmodic and stable changes in the units of heredity - genes, entailing changes in hereditary traits. They necessarily cause changes in the genotype that are inherited by offspring and are not associated with crossing and recombination of genes.

There are chromosomal and gene mutations. Chromosomal mutations are associated with changes in the structure of chromosomes. This may be a change in the number of chromosomes that is a multiple or not a multiple of the haploid set (in plants - polyploidy, in humans - heteroploidy). An example of heteroploidy in humans can be Down's syndrome (one extra chromosome and 47 chromosomes in the karyotype), Shereshevsky-Turner syndrome (one X chromosome is missing, 45). Such deviations in the human karyotype are accompanied by a health disorder, a violation of the psyche and physique, a decrease in vitality, etc.

Gene mutations - affect the structure of the gene itself and entail a change in the properties of the body (hemophilia, color blindness, albinism, etc.). Gene mutations occur in both somatic and germ cells.

Mutations that occur in germ cells are inherited. They are called generative mutations. Changes in somatic cells cause somatic mutations that spread to that part of the body that develops from the changed cell. For species that reproduce sexually, they are not essential, for vegetative reproduction of plants they are important.

Genetic heterogeneity of the population. S.S. Chetverikov (1926), based on the Hardy formula (see sections 3.3 and 8.4), considered the real situation in nature. Mutations usually arise and remain in a recessive state and do not disturb the general appearance of the population; the population is saturated with mutations, "like a sponge with water."

The genetic heterogeneity of natural populations, as shown by numerous experiments, is their main feature. It is maintained through mutations, the process of recombination (only in forms with asexual reproduction, all hereditary variability depends on mutations). The combinatorics of hereditary traits that occurs during sexual reproduction provides unlimited opportunities for creating genetic diversity in a population. Calculations show that in the offspring from crossing two individuals that differ only in 10 loci, each of which is represented by 4 possible alleles, there will be about 10 billion individuals with different genotypes. When crossing individuals that differ in total by 1000 loci, each of which is represented by 10 alleles, the number of possible hereditary variants (genotypes) in the offspring will be 10 1000, i.e. many times greater than the number of electrons in the universe known to us.

These potentialities are never realized, even to the smallest extent, if only because of the limited size of any population.

Genetic heterogeneity, maintained by the mutation process and crossing, allows the population (and the species as a whole) to use for adaptation not only newly emerging hereditary changes, but also those that arose a very long time ago and exist in the population in a latent form. In this sense, the heterogeneity of populations ensures the existence of a mobilization reserve of hereditary variability (S.M. Gershenzon, I.I. Shmalgauzen).

The genetic unity of a population. One of the most important conclusions of population genetics is the position of the genetic unity of a population: despite the heterogeneity of its constituent individuals (and perhaps precisely because of this heterogeneity), any population is a complex genetic system in dynamic equilibrium. A population is the smallest genetic system that can continue to exist for an unlimited number of generations. When crossing individuals within a population, many mutations occur in the offspring, including those that usually reduce viability due to homozygotization of individuals. Only in a real natural population, with a sufficient number of genetically diverse mating partners, is it possible to maintain the genetic diversity of the entire system at the required level. Neither an individual, nor a separate family or a group of families (dem) possess this property.

So, the main genetic characteristics of a population are constant hereditary heterogeneity, internal genetic unity and dynamic balance of individual genotypes (alleles). These features determine the organization of the population as an elementary evolutionary unit.

Ecological unity of the population. A feature of the population is the formation of its own ecological niche. Usually the concept of an ecological niche as a multidimensional space formed by each species in the biological and physical space-time continuum (J. Hutchinson) was used only for the species. However, since within a species there cannot be two populations identical in all their characteristics, the recognition of the fact that each population must have its own ecological characteristic characteristic only of it, i.e., occupy a specific place in the ecological hyperspace, is inevitable.

Mechanisms of interspecies isolation

The concept of a biological species implies the existence of interspecific reproductive isolation - that is, such isolation that prevents the interbreeding of individuals belonging to different species. Reproductive isolation ensures not only the coexistence of many closely related species, but also their evolutionary independence.

Distinguish between primary and secondary insulation. Primary isolation occurs without the participation of natural selection; this form of isolation is random and unpredictable. Secondary isolation arises under the influence of a complex of elementary evolutionary factors; this form of isolation occurs naturally and is predictable.

The simplest form of interspecies isolation is spatial , or geographical insulation. Species cannot interbreed because populations of different species are spatially isolated from each other. According to the degree of spatial isolation, allopatric, adjacent-sympatric and biotic-sympatric populations are distinguished.

Geographical areas allopatric populations do not overlap at all (examples: bison and bison, jackal and coyote). Geographical areas adjacent sympatric populations touch; such a degree of spatial isolation is characteristic of vicarious (replacement) species (examples: white hare and European hare). Geographical areas biotic-sympatric populations overlap to a greater or lesser extent (examples for the Bryansk region: the coexistence of four species of frogs, five species of larks, three species of swallows, nine species of tits, six species of buntings, six species of warblers, five species of thrushes, four species of warblers, five species of mice, six vole species).

Biotic-sympatric populations can interbreed with each other to form interspecific hybrids. But then, due to the constant formation of hybrids and their backcrosses with parental forms, pure species must sooner or later disappear altogether. However, in reality this does not happen, which indicates the existence of various mechanisms that effectively prevent interspecific hybridization in natural conditions, which were formed with the participation of specific forms of natural selection, known as the Wallace processes. (That is why ecological-geographic crossings between species that do not contact in natural conditions are most successful.)

Three groups of isolating mechanisms are usually distinguished: precopulatory, prezygotic, and postzygotic. At the same time, prezygotic and postzygotic isolation mechanisms are often combined under the general name "post-copulatory mechanisms".

Let us consider the main mechanisms of interspecific reproductive isolation that ensure the evolutionary independence of different species: AND and AT.

I. Precopulatory mechanisms - prevent copulation (mating in animals or pollination in plants). In this case, neither paternal nor maternal gametes (and corresponding genes) are eliminated.

Precopulatory isolation can be primary(random) or secondary(formed under the influence of natural selection in favor of the highest fertility and survival). Precopulatory mechanisms include the following forms of interspecies isolation:

1. Spatial geographic isolation. Kinds AND and AT are completely allopatric, meaning their geographic ranges do not overlap. (This form of isolation for the territory of the Bryansk region is irrelevant due to the lack of insurmountable spatial barriers (mountain ranges, deserts, etc.).)

2. Spatial-biotopic isolation. Kinds AND and AT are adjacent-sympatric, that is, they live in the same territory, but are part of different biocenoses. In this case, the distance between biocenoses exceeds the radius of reproductive activity (for example, the radius of pollen and seed transfer in plants). This form of isolation is possible, for example, between obligate alluvial floodplain and obligate forest swamp species. However, this barrier is not insurmountable due to the transgression of floodplain-alluvial species into forest swamp cenoses.

3. seasonal isolation. Kinds AND and AT are biotic-sympatric, that is, they are found in the same cenosis, but multiply (bloom) at different times. However, seasonal isolation is possible only for species with either very early or very late reproduction (flowering). For most species, seasonal isolation is irrelevant; some biotic-sympatric species reproduce simultaneously, but in nature they do not form hybrids, but successfully interbreed under laboratory conditions.

4. Ethological isolation. Plays an important role in animals; often due to differences in mating rituals between species AND and AT. In biotically pollinated plants, there is isolation due to differences in the behavior of pollinating animals that prefer one or another type of flowers; this form of isolation is relevant for the specialization of pollinators.

5. Mechanical isolation. Due to differences in the structure of the reproductive organs of species AND and AT, for example, copulatory organs in animals or pollination units in plants (flowers, inflorescences). This insulating barrier is not insurmountable: for example, flowers of different plant species are often visited by the same pollinators (for example, bees), which ensures (at least at first glance) the equiprobability of both intraspecific and interspecific xenogamy.

II. Prezygotic mechanisms - prevent fertilization. At the same time, it happens elimination of paternal gametes(genes), but maternal gametes (genes) are retained. Prezygotic isolation can be either primary, and secondary.

In animals, prezygotic isolation mechanisms are usually associated with the death of paternal gametes. For example, in insects, the death of male gametes in the genital ducts of inseminated females is observed due to immunological reactions.

Prezygotic mechanisms in plants include:

1. Death of male gametophytes of a foreign species: non-germination of pollen grains on the stigma of the pistil, death of pollen tubes in the style or in the ovule, death of spermatozoa in the pollen tubes or in the embryo sac.

2. Non-competitiveness of the pollen of a foreign species in relation to the pollen of its own species when they jointly fall on the stigma of the pistil.

III. Postzygotic mechanisms - prevent the transfer of genes of parental species to subsequent generations through hybrids. This form of interspecific isolation can occur among first-generation hybrids, second-generation hybrids, and among backcrosses (backcrosses). Postcopulation isolation leads to gamete death; formed randomly. The most common postzygotic mechanisms include the following forms:

1. Inability or reduced fitness of hybrids compared to parental species (or simply inability).

1.1. Full toconstitutional, or morphophysiological disability. Means the absolute impossibility of the development of hybrids even under controlled conditions. Associated with the impossibility of normal morphogenesis due to the incompatibility of parental genomes. Includes the death of zygotes, embryos, seedlings, juvenile and virginal individuals.

1.2. Reduced constitutional fitness. It is expressed in the appearance of morphoses and terat (deformities), a decrease in survival. Reduced constitutional fitness largely determines all other forms of disability.

1.3. Inability to adapt to abiotic (physico-chemical) habitat factors. It differs from constitutional unsuitability in that it is possible to create conditions in which hybrids that are unadapted in the natural environment will develop normally. For example, in plants, natural limiting factors for hybrids include: insufficient moisture, lack of light, lack of certain elements of mineral nutrition, environmental movement (wind, precipitation), temperature and humidity changes, and insufficient length of the growing season. In practice, the elimination of the adverse effects of physical and chemical factors means the germination of hybrid seeds on filter paper in a humid chamber, the cultivation of seedlings in peat-humus pots in closed ground, the early production of hybrids under controlled conditions (while they have time to prepare for wintering), the first wintering in closed ground.

1.4. Inability to adapt to the biotic factors of the habitat particularly resistance to pests and diseases.

1.5. Non-competitiveness(first of all, non-competitiveness in relation to parental or close species). In disturbed habitats, in anthropogenic landscapes, and on the periphery of ecological niches (for plants, on the periphery of edapho-phytocenotic areas), this form of unsuitability plays a lesser role.

2. Complete or partial decrease in the fertility of hybrids (infertility).

2.1. Complete (constitutional) infertility- consists in the impossibility of sexual reproduction in any conditions. In plants, it occurs with the complete absence of flowers or the formation of ugly flowers (for example, with interspecific hybridization in Willows).

2.2. Decreased fertility- for example, a decrease in the number of flowers in plants.

2.3. Segregation sterility- violation of the normal segregation of chromosomes during meiosis. As a result, normal gametogenesis (sporogenesis) is impossible. Among animals, such sterility is observed in mules (horse and donkey hybrids), nars (one-humped and two-humped camel hybrids), kidus (sable and marten hybrids), cuffs (brown hare and white hare hybrids).

2.4. Ethological-reproductive disability hybrids in animals. It consists in a violation of reproductive behavior, for example, deviant behavior during courtship, when building nests, when raising offspring.

For example, in different species of lovebird parrots (genus Agapornis) different behavior is observed during nest building: individuals of the same species ( A. personata) carry pieces of building material in their beaks, while representatives of another species ( A. roseicollis) put them under the feathers. Interspecific hybrids ( F 1 ) showed a mixed type of behavior: at first, the birds tried to put the building material into the feathers, then they took it out, took it in their beak, and then everything started all over again.

Similar intermediate forms of behavior were found in the demonstrative behavior of finches and in the nature of the sound signals of crickets.

So, in relation to sympatric species, the existence of a wide variety of isolating barriers that prevent their complete mixing (secondary intergradation) is possible. At the same time, none of these barriers (of course, with the exception of the complete constitutional inability of hybrids) is insurmountable. Therefore, the similarity between different species can be a consequence not only of convergence in similar habitats, but also the result of horizontal , or lateral gene transfer (gene flow).

Biodiversity

Biodiversity is the totality of different living organisms, the variability among them and the ecological complexes of which they are part, which includes diversity within species, between species and ecosystems.

Biological diversity is one of the most important biological resources.

A biological resource is genetic material, organisms or parts thereof, or ecosystems used or potentially useful to mankind, including the natural balance within and between ecosystems.

There are the following levels of biological diversity:

alpha diversity is the number of species in a community;

beta diversity - the number of communities in a certain area;

gamma diversity - the total number of species and communities in a certain area;

omega-diversity - global diversity (number of species and communities in vast areas).

However, all forms of diversity are based on genetic intraspecific (intrapopulation and interpopulation) diversity.

Building resilient ecosystems

The stability of a system in the simplest case is determined by the additive stability of its structural components. The main indicators of the resistance of individual plants include: winter hardiness, resistance to transpiration losses in the winter-spring period, resistance of buds, flowers and ovaries to frost, resistance to lack or excess of heat, solar radiation and a shortened growing season; heat resistance and drought resistance; correspondence between the rhythms of the passage of phenophases and seasonal changes in environmental conditions; resistance to certain pH values, salt concentrations; resistance to pests and diseases; balance of photosynthesis and reproductive processes. At the same time, the environment surrounding organisms is gradually changing - the problem of climate change is already becoming a global, political problem. For example, over the past 50 years (compared to 1940–1960) in central Russia, the average annual air temperature has increased by 1.2 °C, while relative humidity has decreased by 3%. These changes are even more pronounced in the winter-spring period: the air temperature in January, February and March increased by 4.4 °C, and the humidity in March and April decreased by 10%. Such changes in temperature and humidity significantly increase the transpiration losses of woody plants in the winter-spring period.

Unfortunately, the current level of development of science does not allow us to fully foresee the changes in the environment that will occur even in the near future, moreover, to foresee not only climate change, but also the emergence of new pests, pathogens, competitors, etc. Therefore, the only a reliable way to increase the stability and productivity of natural ecosystems is to increase the level of heterogeneity, genetic heterogeneity of ecosystem components. Such heterogeneous ecosystems provide the possibility of continuous and inexhaustible nature management, since in genetically heterogeneous systems there are compensatory interactions of individuals with different characteristics of growth and development, sensitivity to the dynamics of environmental factors. In relation to pests and diseases, such a heterogeneous ecosystem is characterized by collective group immunity, which is determined by the interaction of many structural and functional features of individual biotypes (ecotypes, isoreagents).

To create heterogeneous artificial plantations (plantations), vegetatively propagated plants are used clone mixtures , or polyclonal compositions - in a certain way selected combinations of seedlings belonging to different clone varieties. In addition, each clone must have characteristics that other clones do not have. The most important such characteristic is shoot development rhythm . In turn, the rhythms of shoot development are determined by the species and individual specificity of genetically determined programs of ontogeny.

Thus, in order to create polyclonal compositions, it is necessary to identify among wild plants (or in collection plantations) intraspecific groups that stably differ in a set of characters. At the same time, the main thing is not the strength of differences, but their constancy, i.e. the ability to persist through generations (at least in vegetative propagation) under certain growing conditions.

As such an intraspecific grouping, it usually appears the form(morph). Unfortunately, very often this term is treated quite freely, calling forms and ecotypes, and varieties (variations), and isoreagents (forms in the narrow sense of the word), and biotypes; in microsystematics, the form is considered as an intraspecific taxonomic category (forma).

When isolating forms, first of all, attention is paid to morphological features. At the same time, in different plant species, due to parallel variability, forms of the same name are distinguished, differing in leaf configuration (typical vulgaris, broad-leaved latifolia, angustifolia angustifolia, small-leaved parvifolia, lanceolate lancifolia, elliptical elliptica, rounded ovoid crassifolia, rounded rotundata; some types of leaf blades receive special names, for example, orbiculata- widely oval, heart-shaped at the base and pointed at the top), according to the color of the leaves (monochrome concolor, multicolored discolor, green viridis, dove glaucophylla, shiny splendens, silvery argentea), by crown configuration (spherical sphaerica, weeping pendula, pyramidal pyramidalis); various cultivars (cultivars) are usually assigned the rank f. cult with a detailed description of the morphology.

In a more detailed description of the forms, various morphometric indicators are used, which in woody plants include: growth force (in particular, the annual increase in trunk diameter), type of branching, branching angle, length of internodes, branching intensity and shoot length, leaf size. These indicators are revealed by direct observation, are easily digitized and can be mathematically processed using the methods of variation statistics, which allow assessing the genetic conditionality of traits.

Polyploidy is known to be widespread among plants. Therefore, the identification of intraspecific (intrapopulation) groups that differ by chromosome number, could make it possible to unambiguously describe the level of diversity. Various cytogenetic methods are used to determine chromosome numbers, in particular, direct chromosome count in dividing cells. However, this is not always possible, so chromosome numbers are often determined by indirect methods, for example, palinometric method(according to the size of pollen grains).

However, all of these indicators are static, they do not reflect the process of realization of genetic information. At the same time, it is known that any trait is formed in the course of morphogenesis. Based on the analysis of morphogenesis, a selection is made ontobiomorph, and according to seasonal changes in the habitus of plants, phenobiomorphs. When using dynamic indicators of diversity, the set of genes of an organism can be considered as a program of its ontogenesis (individual development), and in particular cases, as a program of morphogenesis (shaping).

The promise of this approach was shown in the works of C. Waddington, N.P. Krenke and other classics of natural science.

Hereditary polymorphism of natural populations. genetic load. The process of speciation with the participation of such a factor as natural selection creates a variety of living forms adapted to living conditions. Among the different genotypes that arise in each generation due to the reserve of hereditary variability and recombination of alleles, only a limited number determines the maximum adaptability to a particular environment. It can be assumed that the differential reproduction of these genotypes will eventually lead to the fact that the gene pools of populations will be represented only by "successful" alleles and their combinations. As a result, there will be a fading of hereditary variability and an increase in the level of homozygosity of genotypes. However, this does not happen, as the mutation process continues, and natural selection supports heterozygotes, because. they dampen the harmful effect of recessive alleles. Most organisms are highly heterozygous. Moreover, individuals are heterozygous for different loci, which increases the total heterozygosity of the population.

The presence in a population of several equilibrium coexisting genotypes in a concentration exceeding 1% in the rarest form (the level of hereditary diversity for which a mutation process is sufficient) is called polymorphism. Hereditary polymorphism is created by mutations and combinative variability. It is supported by natural selection and is adaptive (transitional) and stable (balanced).

Adaptive polymorphism arises if, in different, but regularly changing conditions of life, selection favors different genotypes.

Balanced polymorphism occurs when selection favors heterozygotes over recessive and dominant homozygotes. In some cases, balanced polymorphism is a round robin (see Figure 1.4, p. 14).

The phenomenon of selective advantage of heterozygotes is called overdominance. The mechanism of positive selection of heterozygotes is different.

Due to the diversity of environmental factors, natural selection acts simultaneously in many directions. In this case, the final result depends on the ratio of the intensity of different selection vectors. Thus, in some regions of the globe, the high frequency of the semi-lethal allele of sickle cell anemia is supported by the preferential survival of heterozygous organisms in conditions of a high incidence of tropical malaria. The end result of natural selection in a population depends on the overlap of many selection and counter selection vectors. Thanks to this, both the stabilization of the gene pool and the maintenance of hereditary diversity are achieved at the same time.

Balanced polymorphism imparts a number of valuable properties to a population, which determines its biological significance. A genetically heterogeneous population develops a wider range of living conditions, using the habitat more fully. A larger amount of reserve hereditary variability accumulates in its gene pool. As a result, it acquires evolutionary flexibility and can, changing in one direction or another, compensate for environmental fluctuations in the course of historical development.

In a genetically polymorphic population, organisms of genotypes are born from generation to generation, the fitness of which is not the same. At each point in time, the viability of such a population is below the level that would be achieved if it contained only the most “successful” genotypes. The amount by which the fitness of a real population differs from the fitness of an ideal population of the "best" genotypes possible with a given gene pool is called genetic cargo. It is a kind of payment for ecological and evolutionary flexibility. Genetic load is an inevitable consequence of genetic polymorphism.

Balanced genetic polymorphism, intraspecific diversity, ecological races and, probably, subspecies are among the reasons for the evolutionary immutability of species (Severtsov A.S., 2003). The existence of two or more morphs of balanced polymorphism, each of which is adapted in its own subniche of the species ecological niche, indicates that qualitatively different adaptive strategies of morphs ensure their equal fitness. When the ecological situation changes, one of these morphs gains an advantage at the expense of other (other) morphs. Their number is maintained or increased not only due to the preservation of fitness, but also due to the resources released during the reduction in the number or extinction of those morphs for which this change in the environment is detrimental.

An example is the history of polymorphism of the Moscow population of innanthropic rock pigeons. Columbia livia(Obukhova, 1987). The polymorphism of the populations of this species is represented by a continuous series of morphs that differ in plumage color: from gray (slate-gray), which is considered the original, to black (melanistic). There are two types of feather melanization. In one case, melanin is concentrated at the ends of the covert feathers, forming black speckles. As these specks increase, they merge into a solid black color. This more common form of melanization is due to the strong Black gene and 5-6 genes with little phenotypic effect. In another case, melanin is diffusely distributed over the feather fan. Therefore, intermediate morphs look more or less sooty or dirty, with more severe melanization they become black. This type of melanization is determined by the strong Dack gene and also 5-6 weak genes (Obukhova, Kreslavsky, 1984).

Before the Great Patriotic War, the gray morph prevailed in Moscow. Melanists were few in number. During the war, the Moscow population of pigeons almost completely died out or was destroyed. After the war, the number of pigeons recovered slowly until 1957, when, in connection with the World Festival of Youth and Students, the “bird of the world” began to patronize and feed. As the population increased, so did the proportion of melanistic morphs. By the end of the 60s of the twentieth century. the proportion of melanists and intermediate morphs was about 80%.

Changes in the ratio of morphs were due to differences in their behavior. The gray morph is more active, flies farther in search of food and actively guards its nesting territories. Melanists are passive. Their nests in attics can be located close to each other. Intermediate morphs are also intermediate in activity. Under the conditions of unlimited food resources provided by garbage dumps and top dressing and limited nesting sites in panel houses, the gray morph could not compete with the mass of melanists and intermediate morphs and was forced out into attics, inconvenient for nesting, where low density made it possible to protect nesting sites. Thus, changes in the ecological situation lead to changes in the frequencies of morphs. Either one of them (gray with a low population size), then the other (melanistic with a high abundance) gains an advantage, but in general the species retains its stability and does not change. It will exist even if any of the morphs die out.

An analysis of the color polymorphism of males of the pied flycatcher leads to similar results. Ficedula hypoleuca(Grinkov, 2000), White Sea gastropods (Sergievsky, 1987).

Ecological races are as important to maintaining evolutionary stasis as morphs of balanced polymorphism. An example is the ecological races of the willow leaf beetle, Lochmea caprea(Coleoptera, Chrysomelidae), on Zvenigorodskaya biological stations Moscow State University, studied by Mikheev (1985). One of the two races feeds leaves broad-leaved willows, mainly goat and eared willows, aspen is an additional fodder plant. Another race feeds mainly leaves downy birch, additional fodder plant - warty birch. The exchange within each of the races between beetles feeding on the main and additional plants is about 40%. The exchange between willow and birch races is 0.3-5%, although these trees in a number of disturbed phytocenoses are in contact with branches. The fact is that the larvae and adults of the willow race, with forced feeding birch leaves die in 100% of cases. On the contrary, beetles and their larvae of the birch race feed on willow leaves without harm to themselves. Thus, races are isolated both ecologically and genetically. A rigid relationship with forage plants means that birch beetles in this area are confined to a certain stage of succession - a small-leaved forest. The willow beetles are confined to humid habitats where the normal course of succession is disrupted - forest edges, neighborhoods of settlements, etc. When the stage of succession changes, the populations of the birch race will either move or die out. The dispersion of beetles from wintering is about 4 km. The same will happen to the populations of the willow race with a decrease in moisture or with an increase in anthropogenic pressure. However, the extinction of any of the races will not mean the extinction of the species, but mosaic biotopes ensures the sustainable existence of each of the races. Probably, similar reasoning can be applied to geographic races - subspecies (A.S. Severtsov, 2003).

Thus, population polymorphism ensures the stability of the population as a whole when the ecological situation changes, and is also one of the mechanisms for the stability of a species in evolutionary time.

. Biodiversity . Genetic polymorphism of populations as the basis of biological diversity. The problem of biodiversity conservation

Biodiversity refers to all "the many different living organisms, the variability among them and the ecological complexes of which they are part, which includes diversity within species, between species and ecosystems"; at the same time, one should distinguish between global and local diversity. Biological diversity is one of the most important biological resources (a biological resource is considered to be “the genetic material, organisms or parts thereof, or ecosystems used or potentially useful to mankind, including the natural balance within and between ecosystems”).

There are the following types of biological diversity: alpha, beta, gamma and genetic diversity. α-diversity is understood as species diversity, β-diversity is the diversity of communities in a certain territory; γ-diversity is an integral indicator that includes α- and β-diversity. However, these types of biodiversity are based on genetic (intraspecific, intrapopulation) diversity.

The presence of two or more alleles (and, accordingly, genotypes) in a population is called genetic polymorphism. It is conditionally accepted that the frequency of the rarest allele in polymorphism should be at least 1% (0.01). The existence of genetic polymorphism is a prerequisite for the conservation of biodiversity.

Ideas about the need to preserve genetic polymorphism in natural populations were formulated as early as the 1920s. our distinguished compatriots. Nikolai Ivanovich Vavilov created the doctrine of the source material, substantiated the need to create repositories of the world gene pool of cultivated plants. Alexander Sergeevich Serebrovsky created the very doctrine of the gene pool. The concept of "genofund" included the genetic diversity of a species that developed in the course of its evolution or selection and provided its adaptive and productive capabilities. Sergei Sergeevich Chetverikov laid the foundations for the study and methods for assessing the genetic heterogeneity of populations of wild plant and animal species.

Global environmental problems escalated after World War II. To solve them in 1948 was formed International Union for Conservation of Nature and Natural Resources(IUCN). The primary task of the IUCN was to compile Red Books– lists of rare and endangered species. In 1963-1966 the first International Red Book. In 1980, its fourth edition was published. In 1978-1984. the Red Book of the USSR is published, and in 1985 - the Red Book of the Russian Federation.

However, humanity realized the seriousness of this problem only in the last quarter of the 20th century. A little over thirty years ago (1972), the first UN conference on the human environment took place in Stockholm. At this forum, the general principles of international cooperation in the field of nature protection were outlined. Based on the decisions of the Stockholm Conference, modern principles for the preservation of the living environment were formulated.

The first principle is the principle of universal connection in wildlife: the loss of one link in a complex chain of trophic and other connections in nature can lead to unforeseen results. This principle is based on classical ideas about the existence of cause-and-effect relationships between the elements of superorganismal biological systems, and many of these relationships lead to the formation of various chains, networks and pyramids.

Hence follows the principle of the potential utility of each component of living nature : it is impossible to foresee what significance this or that species will have for humanity in the future . In the public mind, the distinction between “useful” and “harmful” species loses its meaning, and the notion that “a harmful or weedy species is just an organism out of place” is affirmed.

Based on the principles of universal connection and the potential utility of each component of living nature the concept of non-interference in the processes occurring in natural ecosystems is formed: “We do not know why this is will, so it's best to leave it as it is." The perfect way to save status quo considered the creation of protected areas with an absolute reserve regime. However, the practice of conservation has shown that modern ecosystems have already lost the ability to naturally restore themselves, and active human intervention is required to preserve them.

As a result, the transition from the concept of non-intervention and conservation of the status quo to concept of sustainable development society and the biosphere. The concept of sustainable development implies an increase in the ecological and resource potential of natural ecosystems, the creation of sustainable controlled ecosystems, the satisfaction of society's needs for natural resources based on scientifically based rational, sustainable and multi-purpose nature management, protection, protection and reproduction of all components of ecosystems.

Further development of the concept of sustainable development inevitably led to the principle of the need to conserve biological diversity : only diverse and diverse living nature is sustainable and highly productive . The principle of the need to preserve biological diversity is fully consistent with the basic principles of bioethics: "every form of life is unique and unrepeatable", "every form of life has the right to exist", "what is not created by us, should not be destroyed by us". At the same time, the value of a genotype is determined not by its usefulness for a person, but by its uniqueness. Thus, it was recognized that "the preservation of the gene pool is a responsibility to further evolution" (Frankel, XIII International Genetic Progress at Berkeley, 1974). Swaminathan (India) identified three levels of responsibility for the preservation of the gene pool: professional, political and public.

In 1980, the World Conservation Strategy was developed by the International Union for the Conservation of Nature and Natural Resources. The materials of the World Strategy note that one of the global environmental problems is the problem of nutrition: 500 million people are systematically malnourished. It is more difficult to take into account the number of people who do not receive adequate nutrition, balanced in proteins, vitamins and microelements.

The World Strategy has formulated the priority tasks of nature protection:

– maintenance of the main ecological processes in ecosystems.

– Conservation of genetic diversity.

– Long-term sustainable use of species and ecosystems.

In 1992, in Rio de Janeiro, at the United Nations Conference on Environment and Development (UNCED), a number of documents were adopted, signed by representatives of 179 states:

– Program of Action: Agenda 21.

– Statement of principles on forests.

– United Nations Convention on Climate Change.

– Convention on Biological Diversity.

The materials of the Convention on Biological Diversity note that "...diversity is important for the evolution and conservation of the life support systems of the biosphere." To preserve the life support systems of the biosphere, it is necessary to preserve all forms of biological diversity: “Countries that accede to the Convention must determine the components of biological diversity, ... control activities that may have a harmful effect on biological diversity.”

At the UNCED conference, it was recognized that the decline in biological diversity is one of the main causes of the progressive degradation of natural ecosystems. There is no doubt that only if the optimal level of diversity is maintained, it is possible to create ecosystems that are resistant to extreme effects of physical and chemical factors, pests and diseases.

In 1995, in Sofia, at a conference of European ministers of the environment, the Pan-European Strategy for the Conservation of Biological and Landscape Diversity was adopted. We list the principles of the Pan-European Strategy for the Conservation of Biological and Landscape Diversity of Nature:

– Protection of the most vulnerable ecosystems.

– Protection and restoration of disturbed ecosystems.

– Protection of territories with the highest species diversity.

– Preservation of reference natural complexes.

The halt in the productivity of artificial ecosystems is also associated with low levels of biodiversity, with only 150 species of cultivated plants currently cultivated and 20 species of domestic animals bred. At the same time, the low level of global diversity is combined with a low level of local diversity, with the dominance of monoculture or cultural rotations with a short rotation period. The pursuit of uniformity in plant varieties and animal breeds has led to a sharp narrowing of genetic diversity. A consequence of the decline in diversity is a decrease in resistance to extreme physical and chemical environmental factors and, to an even greater extent, to pests and diseases.

Numerous studies have shown that the only reliable way to increase the stability and productivity of natural ecosystems is to increase the level of their heterogeneity, since in genetically heterogeneous systems there are compensatory interactions of individuals with different characteristics of growth and development, sensitivity to the dynamics of environmental factors, diseases, and pests. It is heterogeneous plantations that provide the possibility of continuous and inexhaustible nature management.

Consequently, there is a need for a wider use of the species and intraspecific (genetic) potential of the largest possible number of species suitable for cultivation under controlled conditions. The whole variety of material to be preserved includes the following categories of organisms: varieties and breeds currently cultivated and bred; varieties and breeds that have gone out of production, but are of great genetic and breeding value in terms of individual parameters; local varieties and native breeds; wild relatives of cultivated plants and domestic animals; wild species of animal plants that are promising for introduction into culture and domestication; experimentally created genetic lines.

Naturally, in order to solve a complex of tasks related to the problems of biological diversity, it is first necessary to develop criteria for assessing biodiversity, to identify and assess the level of diversity in specific ecosystems (natural-territorial complexes), to develop recommendations for the conservation and enhancement of the identified diversity, to test and implement these recommendations for agro-industrial production.

Ears to hear. Eyes to see. Nose to breathe and smell. And so on. However, the purpose of some parts of the human body is not easy to explain. Why, for example, do you need a coccyx, hair on your legs?

Before Charles Darwin, scientists seriously believed that rudiments were "made for symmetry" or "to complete the scheme of nature." Darwin, on the other hand, gave a more logical explanation: organs that do not help, but do not particularly interfere with the process of natural selection, gradually degenerate. By the way, the rudiments served as one of the proofs of the theory of evolution.

If all people, without exception, have rudiments, then atavisms are the lot of the elite. We are talking about features that have been completely lost in the process of evolution (for example, a tail or a thick hairline all over the body, like animal fur). Scientists explain the appearance of atavisms by the fact that their genes do not disappear completely in the course of evolution, but only lose their activity, and can manifest themselves under certain conditions. In the old days, people with atavisms shied away or showed them for money at fairs: “Hurry to see an amazing man-beast and a tailed child!” Today everyone understands that atavism does not make a person inferior. At the same time, such people often resort to the services of plastic surgeons.

Rudiments and atavisms are interesting and useful to biologists. By examining them, one can trace the path of evolution. Theoretically, rudiments and atavisms can benefit humanity as a species: the presence of "extra" records in the genotype makes the species more flexible in adapting to changing conditions. However, why do we need low-functional, or even completely useless organs for an ordinary person? Are they of any use or just trouble?

Rudiments

The term "rudiment" in this sense is widely used in Russian scientific literature, despite the fact that it is the opposite of its original meaning in Latin. In English literature, along with it, the more adequate term vestige is used, derived from lat. vestigium - a trace (in the literal and figurative sense of the word). It is also advisable to use the term vestigial in Russian to denote an organ that has secondarily decreased and/or simplified in the course of evolution, so as not to confuse it with a germ - an organ that has not yet reached its final size and structure.

Charles Darwin's analysis of rudimentary (that is, vestigial) organs and parts of the body largely contributed to the formation of an evidence base for the origin of man from other representatives of the animal world.

In the 19th century, scientists counted about 180 rudiments. These included organs that are currently recognized as vital: knee menisci, thyroid, thymus and pineal glands. Today, the list of rudiments has been significantly reduced. Opponents of the theory of evolution argue that a person does not have a single unnecessary organ. However, most scientists agree that some organs have largely lost function, which allows them to be attributed to rudiments.

Man, unlike monkeys, does not need a tail. He is not. However, the part of the spine that supports the tail remains - this is the coccyx. The coccyx is made up of four to five small vertebrae below the sacrum. In an adult, these vertebrae fuse into a single, inactive structure.

Most people don't think about their coccyx. This rudiment does not help, but does not interfere with life. In women during childbirth, the coccyx folds back, skipping the fetus. However, sometimes the coccyx, being richly innervated, becomes a source of very unpleasant pain. They occur when it is excessively bent forward due to individual structural features or injury. What is characteristic: the pain occurs after prolonged sitting, especially on a soft chair. Usually, to eliminate pain, it is enough to advise patients to sit on a hard surface (in this case, the support goes to the ischial tuberosities, and not to the coccyx) and undergo a course of physiotherapy. In rare cases, when conservative treatment does not help, it is necessary to surgically remove the coccyx.

What to do with the appendix so that it does not cause worries? Currently, prophylactic removal of the appendix is ​​considered unjustified: it leads to a decrease in immunity, in addition, like any operation on the abdominal cavity, it can cause the formation of adhesions. It remains to live with an appendix and hope that it does not become inflamed. By the way, Italian scientists have shown that breastfeeding reduces the risk of appendicitis: with a feeding period of 4 to 7 months, the risk is reduced by 10%, and with a feeding period of more than 7 months - almost 2 times!

Mammary glands in men

With hormonal disorders (for example, as a side effect of taking certain medications or due to alcoholism), men's breasts can enlarge and even produce milk. Treatment consists in eliminating the cause that caused the violation.

Breast cancer is also possible for men, although it occurs 100 times less often than in women and has much less social significance. Men, as a rule, notice changes in breast size earlier than women, so treatment is timely. Yes, and the cosmetic effect of breast removal for men is of less psychological importance.

body hair

Wisdom teeth

ear muscles

The only plus of this rudiment is that the ear muscles can be used for a natural facelift with acupressure.

This anatomical structure owes its name to the fact that Charles Darwin mentioned it in his work "The Origin of Man and Sexual Selection" as an example of a rudiment. At the same time, Darwin himself called it the Woolner tip in honor of the English sculptor Thomas Woolner, who drew attention to the presence of this formation while working on the sculpture of Pak.

The gene for Darwin's tubercle is autosomal dominant, but has incomplete penetrance (that is, not everyone with the gene will have the tubercle).

atavisms

We are talking about atavisms and rudiments - these concepts often coexist with each other, sometimes cause confusion and have a different nature. The simplest and probably the most famous example, in which both concepts coexist, refers to, so to speak, the lower part of the human body. The coccyx, the end of the spine, in which several vertebrae have grown together, is recognized as rudimentary. This is the rudiment of the tail. As you know, many vertebrates have a tail, but for us, Homo sapiens, it seems to be useless. However, for some reason, nature has preserved the remains of this once functional organ for man. Babies with a real tail are extremely rare, but still born. Sometimes it's just a protrusion filled with adipose tissue, sometimes the tail contains transformed vertebrae, and its owner is even able to move his unexpected acquisition. In this case, we can talk about atavism, about the manifestation in the phenotype of an organ that was in distant ancestors, but was absent in the closest ones.

So, the rudiment is the norm, the atavism is the deviation. Living beings with atavistic deviations sometimes look frightening, and because of this, and also because of the rarity of the phenomenon, they are of great interest to the general public. But evolutionary scientists are even more interested in atavisms, precisely because these “ugliness” provide interesting clues about the history of life on Earth.

The eyes of moles living underground, as well as those of proteus - amphibians that live in water in dark caves, are rudiments. There are few benefits from them, which cannot be said about the wings of an ostrich. They play the role of aerodynamic rudders when running and are used for defense. The females protect the chicks from the scorching rays of the sun with their wings.

The secret hidden in the egg

None of modern birds have teeth. More precisely, like this: there are birds, for example, some species of geese, which have a number of small sharp outgrowths in their beaks. But, as biologists say, these “teeth” are not homologous to real teeth, but are precisely outgrowths that help to hold, for example, a slippery fish in the beak. At the same time, the ancestors of birds must have had teeth, because they are descendants of theropods, predatory dinosaurs. The remains of fossil birds are also known, in which teeth were present. It is not clear exactly why (perhaps due to a change in the type of food or in order to make the body lighter for flight) natural selection deprived birds of teeth, and one could assume that in the genome of modern feathered genes responsible for the formation of teeth, they no longer left. But this turned out not to be true. Moreover, long before humanity knew anything about genes, at the beginning of the 19th century, the French zoologist Etienne Geoffroy Saint-Hilaire expressed the conjecture that modern birds can grow like teeth. He observed some outgrowths on the beak of parrot embryos. This discovery caused doubts and rumors and was eventually forgotten.

And almost ten years ago, in 2006, American biologist Matthew Harris from the University of Wisconsin noticed outgrowths resembling teeth at the end of the beak of a chicken embryo. The embryo was affected by the lethal talpid 2 genetic mutation and had no chance of surviving to hatch from the egg. However, during this short life, two types of tissues have developed in the beak of the failed chicken, from which teeth are formed. The building material for such tissues is not encoded by the genes of modern birds - this ability was lost by the ancestors of birds tens of millions of years ago. The embryonic teeth in a chicken embryo were not like the blunt-pointed molars of mammals - they had a pointed conical shape, just like in crocodiles, which, like dinosaurs and birds, are included in the group of archosaurs. By the way, they tried to grow molars in chickens and successfully, when genes responsible for the development of teeth in mice were introduced into the chicken genome by genetic engineering. But the teeth of the embryo, which Harris examined, appeared without any outside intervention. "Tooth" tissues arose thanks to purely chicken genes. This means that these genes, which did not appear in the phenotype, were dormant somewhere in the depths of the genome, and only a fatal mutation awakened them. To confirm his assumption, Harris conducted an experiment with already hatched chickens. He infected them with a genetically engineered virus that imitated the molecular signals that occur when talpid 2 is mutated. The experiment brought results: teeth appeared on the beak of the chickens for a short time, which then disappeared into the tissue of the beak without a trace. Harris's work can be considered proof of the fact that atavistic traits are the result of disturbances in the development of the embryo that awaken long-silent genes, and most importantly, genes for long-lost traits can continue to be in the genome almost 100 million years after evolution has destroyed these traits. Why this happens is not exactly known. According to one hypothesis, "silent" genes may not be completely silent. Genes have the property of pleiotropicity - this is the ability to simultaneously influence not one, but several phenotypic traits. In this case, one of the functions can be blocked by another gene, while the others remain completely “working”.

Boas and pythons have so-called anal spurs - single claws, which are a vestige of the hind legs. There are known cases of the appearance of atavistic limbs in snakes.

Strange vitality

It was almost by accident that we learned about toothy chickens and made the discovery - all due to the fact that, as already mentioned, the mutation killed the embryo even before it was born. But it is clear that mutations or other changes that bring to life ancient genes may not be so fatal. Otherwise, how to explain the much more famous cases of atavisms found in quite viable creatures? Quite compatible with life are such atavisms observed in humans as multi-fingering (polydactyly) on the hands and feet, and multi-nippleness, which also occurs in higher primates. Polydactyly is characteristic of horses that, during normal development, walk on one finger, the nail of which has turned into a hoof. But for the ancient ancestors of the horse, multi-fingering was the norm.

There are isolated cases where atavism has led to a major evolutionary turn in the lives of organisms. Ticks of the family Crotonidae atavistically returned to sexual reproduction, while their ancestors reproduced by parthenogenesis. Something similar happened in the hairy hawkweed (Hieracium pilosella), a herbaceous plant of the Asteraceae family. Not all who are called quadrupeds (tetrapoda) in zoology are actually quadrupeds. For example, snakes and cetaceans are descended from terrestrial ancestors and are also included in the superclass tetrapoda. Snakes have lost their limbs completely, in cetaceans the forelimbs have become fins, and the hind limbs have practically disappeared. But the appearance of atavistic limbs is noted both in snakes and in cetaceans. There are cases when a pair of hind fins was found in dolphins, and the quadruped, as it were, was restored.

The vestigial pelvic bones of some cetaceans have long since lost their original function, but their uselessness has been questioned. This rudiment not only reminds that whales evolved from tetrapods, but also plays an important role in the process of reproduction.

More bone - more offspring

However, something else reminds us of tetrapodity in whales, and here we move on to the area of ​​rudiments. The fact is that in some species of cetaceans, rudiments of the pelvic bones have been preserved. These bones are no longer connected with the spine, and therefore with the skeleton as a whole. But what made nature save information about them in the gene code and pass it on to heredity? This is the main mystery of the whole phenomenon called rudimentation. According to modern scientific ideas, it is not always possible to speak of rudiments as superfluous or useless organs and structures. Most likely, one of the reasons for their preservation is precisely that evolution has found a new, previously uncharacteristic use for the rudiments. In 2014, American researchers from the University of South Carolina published an interesting paper in the journal Evolution. Scientists studied the size of the pelvic bones of whales and came to the conclusion that these dimensions are correlated with the size of the penises, and the muscles of the penis are attached just to the rudimentary pelvic bones. Thus, the size of the whale's penis depended on the size of the bone, and a large penis predetermined success in reproduction.

The same with the human coccyx, which was mentioned at the beginning of the article. Despite its rudimentary origin, this part of the spine has many functions. In particular, the muscles involved in the management of the genitourinary system, as well as part of the bundles of the gluteus maximus, are attached to it.

The appendix, a appendix of the cecum, sometimes causes a lot of trouble for a person, becoming inflamed and causing the need for surgical intervention. In herbivores, it is of considerable size and was "designed" to serve as a kind of bioreactor for the fermentation of cellulose, which is the building block of plant cells but is poorly digested. In the human body, the appendix does not have such a function, but there is another one. The intestinal process is a kind of nursery for E. coli, where the original flora of the cecum is preserved intact and multiplies. Removal of the appendix entails a deterioration in the state of the microflora, for the restoration of which it is necessary to use drugs. It also plays a role in the body's immune system.

It is much more difficult to see the benefit of such rudiments as, for example, ear muscles or wisdom teeth. Or the eyes of moles - these organs of vision are rudimentary and do not see anything, but can become the “gates” of infection. Nevertheless, it is clearly not worth rushing to declare something in nature superfluous.

According to the theory of evolution, humans evolved from monkeys. For millions of years, due to this process, the appearance, character, mental capabilities of Homo Sapiens have changed, moving it away from its ancestors. The era of technological progress brought the human species to the highest stage of evolutionary development. The presence of common ancestors with the animal world is now presented in the form of rudiments, examples of which will be discussed in this material.

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Characteristic

Vestigial organs- certain parts of the body that have lost their original meaning in the course of evolutionary development. Previously, they performed the leading functions of the body, now they carry secondary ones. They are laid at the initial stage of embryonic formation, not fully developing. Rudiments are preserved throughout the life of an individual. The function that they carried during standard development is significantly weakened in their ancestors, lost. The modern world cannot fully explain the essence of the presence of such underdeveloped organs in the physiological structure.

Vestigial organs are the main example of evidence for evolution by Charles Darwin, who spent many years observing the animal world before coming to a revolutionary conclusion.

Such body parts are directly confirm family ties between extinct and modern representatives of the planet, helping to establish the path of historical development of organisms. Natural selection, which serves as the basis, removes unnecessary features, improving others.

Examples of Rudiments among the animal world:

• bird fibula;
• the presence of eyes in underground mammals;
• residual hipbones, partial hairline of cetaceans.

Rudiments of man

To rudiments of man include the following:

• coccyx;
• wisdom teeth;
• pyramidal muscle of the abdomen;
• appendix;
• ear muscles;
• epicanthus;
• blinking stomach.

Important! Examples of rudiments in different people are common. A few tribes and races have similar organs, characteristic only of their species. Each example of rudiments in humans can be identified and described in detail to bring clarity to the topic under consideration.

Types of basic rudiments

Coccyx represents the lower spine, including several fused vertebrae. The function of the anterior part of the organ serves to attach ligaments and muscles.

Thanks to him, there is a correct, uniform load on the pelvis. The coccyx is an example of a rudimentary tail in modern man, which served as a center of balance.

Wisdom teeth - these are the most belated and obstinate bone formations of the oral cavity. The original function was an auxiliary process of chewing hard, tough food.

The modern meal of people includes more thermally processed products, therefore, in the course of evolution, the organ atrophied. Located last in a row, wisdom teeth often come out in people at a conscious age. A common phenomenon is the absence of "eights", partial eruption.

Morgan's ventricle- paired saccular depressions located in the right and left parts of the larynx. Organs help create a resonant voice. Apparently, they helped their ancestors to reproduce certain sounds, to protect the larynx.

Appendix- vermiform appendage of the caecum. Helped distant ancestors to digest coarse food. At present, its functions have diminished, but an important role has been preserved, which consists in concentrating the focus of the formation of beneficial microorganisms. The presence of this organ in humans has a significant negative quality - the possibility of inflammation. In this case, it must be removed surgically. The microflora after the operation is hardly restored, infectious diseases become more frequent.

ear muscles also belong to the rudimentary features surrounding the human ear. Ancient ancestors had the ability to move their ears, enhancing the hearing needed to avoid encounters with predators.

Attention! Intentionally getting rid of some of the listed organs is strongly discouraged, because they still perform secondary functions.

Vestigial organs of certain races

Epicanthus - rudimentary vertical extension upper fold of the eye. The exact causes and functional features of this organ are not thoroughly known. There are suggestions that the skin fold protected the eyes from the weather. Characteristic of the Bushmen.

The pyramidal muscle of the abdomen continues the list of vestigial organs, representing the triangular shape of muscle tissue. The main function is to stretch the white line of the abdomen.

Steatopygia - accumulation of fat in the upper parts of the buttocks. It has a reserve role, like a camel's hump. It is characteristic of some African tribes, although this is a rudiment or pathology that has not been fully elucidated.

Human atavisms and differences from rudiments

There are peculiar external signs of the relationship of the human species with the animal world. Atavism is a sign that was present among the ancestors, but not present in its current form.

Those who encode it persist, continuing to pass on its properties to the next generation. They can be called "sleeping", they wake up only at the birth of an individual with an atavistic trait. This happens with the loss of genetic control, or with external stimulation.

The main difference between atavism is the manifestation of signs in single individuals. The human individual during embryonic development partially passes the path of distant ancestors. Embryos in certain weeks have gills and processes in the form of a tail. If these signs persist during childbirth in a child, then they represent an atavism.

Atavisms and rudiments alike serve as evidence theory of evolution, but if the first signs of the function are absent, then the second carry a certain useful value. Some types of this phenomenon can bring a threat to health, or disrupt some life processes. Some are still thinking about the topic: is the appendix the norm in the form of a rudimentary organ or an atavism.

Attention! Many atavistic signs are easily removed surgically, making life easier for the wearer.

Examples of atavisms

Many people still confuse atavisms and rudiments, referring one to the other. The former have two types of signs:

• physiological;
• reflex.

The examples of human atavism should be thoroughly studied in order to make the difference clearer.

If people do not have external signs of one or another, this does not mean that the genes for the signs are absent, having the ability to manifest themselves in the future.

Atavisms are extremely rare in the population and appear only in those cases when the ancient genes of the ancestors unexpectedly appear in humans.

Here are the most common and obvious types of human atavism, which make up the following list:

• excessive hairiness;
• protruding tail;
• cleft lip;
• polynipillarity in humans;
• second row of teeth;
• hiccups
• grasp reflex in newborns.

These features clarify the dispute of many about whether wisdom teeth, hidden or erupted, are a vestige or atavism. They are characteristic of many species, but not all come out. If wisdom teeth, or other rudimentary parts of the body were found only in single specimens, then it would be possible refer them to atavism.

We study what rudiments are, examples

12 rudiments in humans

Conclusion

Homo Sapiens is a complex organism with a diverse system of vital activity, changing million years of evolution. Everyone has examples of their types. The main difference between atavism and rudimentary parts of the body is that only a few possess them, and a person can easily live without them.