CONVERGENCE IN BIOLOGY. in bio In logic, the term "convergence" is most often used in comparative anatomy, embryology, and paleontology. The concept of K. was introduced by the zoologist Oskar Schmidt. It coincides with Ray Lankester's concept of homoplasy and the parallelism of most phylogeneticists. Some scientists (Abel, Severpev) artificially draw a line between K. and parallelism. In zoology and botany, K. means convergence or parallelism in individual adaptive characters or the sum of characters (for taxonomic categories of any volume) observed in animals and plants, phylogenetically in relation to these compared characters are not related to each other. Incorrectly common confusion of K. with analogy. The polarity of thinking in terms requires the opposition of K.-divergence, analogy of same-homology. Besides To. takes place both concerning similar, and homologous bodies (the same and with divergence). An example \ . homologous organs is the specific shape, structure and function of the anterior pair of limbs of vertebrates living in the same environment (for example, fish, plesiosaurs, ichthyosaurs, sea turtles, penguins and whales), or a reduced pelvis in whales and sirens. A remarkable example of K. at once of a number of organs, external habitus "and behavior based on the complete homology of the compared elements is a striking coincidence in the structure of the skeleton (skull, ribs, limbs, vertebrae, etc.), muscles (absence of certain muscles of the limbs), sense organs (rudiments of eyes hidden under the skin) and habitus "a (lack of auricles, silky hair, etc.) two in a system of burrowing underground mammals far apart from each other: namely, the South African insect-eating golden mole (Chrysochloris) and the Australian marsupial mole (Notoryctes). In general, the order of marsupials is saturated with convergent forms (marsupial mole, marsupial flyer, marsupial wolf, marsupial marten, marsupial rat, etc.). Another example of saturation with convergent forms: on the island of Madeira in the Atlantic Ocean, on a small group of volcanic islands in the Antarctic and other islands, there is a huge number of species of usually winged insects, either completely losing wings or having only rudiments of such (wingless flies, wingless butterflies, etc.). P.); winglessness in these various groups of insects is a typical convergence. This also includes the similar yellow color of desert animals, the white color of many mammals and birds of the Arctic; absence of clavicula in running ungulates, some running rodents and carnivores, absence of eyes in cave or underground vertebrates. An example of convergence based on similar organs can be the wings of insects and the wings of birds, the gills of mollusks and fish, the eyes of cephalopods and vertebrates, etc. - Let us mention from the field of botany: the structure of the stems of succulent or succulent desert plants in various families, expressed in the fact that there are no leaves, the stems are swollen and covered abundantly with thorns or spines; another example: the formation by unrelated plants in the arctic belt and on high mountains (in the form of an adaptation to low temperatures) loose or dense cushions from numerous shoots closely adjacent to each other, due to which the daytime warmth is retained by the plant longer. With regard to plants, it is often very difficult to establish whether we are dealing with real K. (coincidence in genotypic characters), or only with modification (see), or finally further with the phenotypic response of each individual individually to these local conditions. In the last two cases, convergence should be sought not just in the identified trait, but in the norm of the reaction (example: water and air leaves in the same species, depending on whether ontogenesis proceeds in water or on land; often both types of leaves are found even in the same individual). All convergent phenomena should be considered secondary formations that arose in the process of pedigree development as new formations independently and independently in a given phylogenetic series in order to adapt to new specific living conditions, different from those in which the ancestors of these forms lived. - Phenomenon K. It is especially typical for numerous sedentary marine invertebrates, as well as for endoparasites (reduction of locomotor organs, the muscular system, sensory organs, the nervous system, and even the intestinal tract). Of course, the convergence of positive signs is never complete, because That is, in such a way that the coinciding signs or a group of signs in different organisms would be identical. Coincidence is always partial and relative. The impossibility of identity in the coincidence of positive signs is the result of the fact that the history of specific species, their phylogeny, is an irreversible process, since both the organism itself and the environment itself surrounding it, and the possible interactions between the organism and the environment in all their diversity cannot repeat the existing ones. combinations. The dialectics of the development of nature is the progressive movement of concrete matter in the direction of a constant qualitative new formation, which excludes the identity of processes even in the phenomena of the circulation of substances, metabolism and ontogeny. Every circular, reversible process in reality is therefore a process that takes place in a spiral. That is why in cases of K., even within the same systematic group, convergent characters are never absolutely similar, an exact repetition of the characters of other organisms. On the contrary, the convergence of negative features in the limit of their complete disappearance is repeated exactly, while all degrees of reduction give only relative convergence. The relativity and limitation of the cosmos is especially clear where convergent formations appear as an analogous organ in the same phylogenetic series of a relatively small systematic category after the disappearance of a particular organ. An excellent example of such a case and at the same time proof of the irreversibility of the phylogenetic process (i.e., n. "Dollo's law") gives the history of leatherback turtles (Dermochelyidae). The leatherback turtle has a shell of tessellated bony plates, unlike other turtles, which have a full bony shell typical of turtles; the early ancestors of the leatherback turtles were littoral (lived by the sea) and had a full bony shell; from these ancestors descended pelagic forms (living in the open sea), which almost completely lost their bone armor; these pelagic forms again switched to a coastal way of life, and then a new hard shell formed again, but not full bone, but mosaic. With this shell, the modern leatherback turtle (Der-mochelys) moved back to life on the high seas. The convergent organs here are the armor (mosaic and full bone). This example also proves the incorrectness of the usual definition of K. by comparative anatomists and paleontologists, who introduce the lack of close relationship of the compared groups into the definition of convergence and do not take into account the possibility of the emergence of similar organs (complete bone and mosaic armor are similar, not homologous formations) in the group morphologically and phylogenetically very close to each other and even one phylogenetic series of forming organisms. The phenomenon of transformation follows from the limitation of possible transformations common to all real bodies that have their own history. The organism develops on the basis of certain limits of variability, determined by the stages it has already passed and creating some limitation of genotypic variation. Each new expansion and narrowing of the scope of variation is the result of the interaction of the mutational process and natural selection. Metaphysical interpretation of coping as a result of the immanent orientation or reversibility of evolution leads to idealistic theories of the "autonomy" of the evolutionary process, to the theories of autogenesis, orthogenesis and nomogenesis, metaphysically isolating endogenous factors from exogenous and self-propulsion of the part from the self-propulsion of the whole. This idealistic understanding of convergence also leads to metaphysical views on polyphyletics. origin of the whole variety of animal and plant forms. These include the well-known idealistic theories of Lamarck, Naegeli, Cope, Friedman, Steinman, Fleishman, in the USSR, Berg, Sobolev, and others. Lamarckists and orthogenetics usually talk about the “law” of K., although there is no “law” of K. . K. is not a law and not a factor of evolution, but the result of evolution, the interaction of specific organisms with a specific environment. The statement about the immanence of K. is scientifically untenable. Identical conditions, acting on unequal organisms, cause various transformations both in the direction of k., and divergence. It is impossible to predict the need for a certain direction in the development of organs, functions, or behavior of organisms in the direction of K., even with maximum knowledge of external conditions and maximum knowledge of the laws of self-motion of the idioplasm, since the interaction of internal and external factors in the phylogenetic aspect is not unambiguous, but ambiguous. Consequently, K. in itself not only does not explain anything, but, on the contrary, itself needs an explanation. K., like divergence, are problems that can be solved exclusively by the selection theory of Charles Darwin. Lit.: Berg L., Nomogenesis, P., 1922; Gaake V., Origin of the Animal World, St. Petersburg, without a year; Depere Sh., Transformations of the animal world, P., 1921; Kashkarov D. and S t and h and a certain V., Course of biology of vertebrates, M.--L., 1929; Lyubov precisely V., Biology of plants, part 1, L., 1924; Severdev A., Modern problems of evolutionary theory, M., 1914; Abel O., Palaobiologie u. Stammesge-schichte, Jena, 1929; Cuenot L., L "adaptation, P., 1925; Detto C, Die Theorie der direkten An-passung, Jena, 1904; Pried man n H., Die Kon-vergenz der Organismen, V., 1904; Novikoff M., Das Prinzip der Analogie u. die vergleichende Ana-tomie, Jena, 1930; Osborn H., The origin a. evolution of Pge, L., 1918; Rabaud E., Les phenome-nes de convergence en biologie, P., 1925 M. Levin.

Convergence (in biology) Convergence(from lat. Converge - I approach, converge) in biology, the convergence of signs in the process of evolution of non-closely related groups of organisms, their acquisition of a similar structure as a result of existence in similar conditions and equally directed natural selection. As a result of K., organs that perform the same function in different organisms acquire a similar structure. For example, in the swimming fossil reptiles of ichthyosaurs and in mammalian dolphins, the shape of the body and forelimbs in the process of evolution acquired a convergent resemblance to the shape of the body and fins of fish ( rice. see article Analogy in biology). Convergent similarity is never deep. Wed Divergence. A. A. Makhotin.

Great Soviet Encyclopedia. - M.: Soviet Encyclopedia. 1969-1978 .

See what "Convergence (in biology)" is in other dictionaries:

    CONVERGENCE IN BIOLOGY- CONVERGENCE IN BIOLOGY. In biology, the term "convergence" is most often used in comparative anatomy, embryology and paleontology. The concept of K. was introduced by the zoologist Oskar Schmidt. It matches the concept... Big Medical Encyclopedia

    CONVERGENCE (from Latin convergo I approach, converge), in biology, the emergence of similarities in structure and functions in groups of organisms relatively distant in origin in the process of evolution. The result of living in similar conditions and the same ... ... encyclopedic Dictionary

    Similarities between thylacine and wolfs. Initially, the aardvark, due to a number of striking structural features, was assigned to the same family as the South American anteaters, but the superficial resemblance to them turned out to be the result of a convergent ... Wikipedia

    - (from the Latin convergens, the genitive convergentis is declining, approaching), convergence, convergence, for example, the convergence of languages, the emergence of common properties in different languages ​​due to prolonged and intense contacts, leading to ... ... Modern Encyclopedia

    - (from lat. convergo I approach, I converge), in biology, the emergence of similarities in structure and functions in groups of organisms relatively distant in origin in the process of evolution. The result of living in similar conditions and in the same direction ... ... Big Encyclopedic Dictionary

    English convergence; German Konvergenz. 1. In sociology, the process of gradual convergence of opposing societies and systems. 2. In biology, the emergence in the course of evolution of a similar structure and functions of unrelated organisms due to their adaptation to ... ... Encyclopedia of Sociology

    AND; well. [from lat. convergens (convergentis) convergent] 1. Spec. What kind of coincidence signs in phenomena independent of each other. The theory of convergence. 2. Biol. The appearance in unrelated organisms of similar characteristics resulting from ... ... encyclopedic Dictionary

    Convergence of state and law- a theory that has become widespread since the 50s. 20th century (P. Sorokin, J. Galbraith and others). The term is borrowed from biology, where it denotes the acquisition by various organisms of similar features due to living in the same environment. According to the theory in... Theory of state and law in schemes and definitions

    I Convergence (from lat. Converge I approach, I converge) in biology, the convergence of signs in the process of evolution of non-closely related groups of organisms, their acquisition of a similar structure as a result of existing in similar conditions and equally ... ... Great Soviet Encyclopedia

    - (lat. converge to converge, converge from con + verge to be directed) in biology, the similarity of the shape of the body, the structure of the organs of movement, sensory organs and other signs in groups of organisms relatively distant in origin, arising in the process ... ... Big Medical Dictionary

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  • Living organization. The company is like a living organism. The Coming Convergence of Computer Science, Nanotechnology, Biology and Business, Christopher Meyer, Stan Davis. "A handbook for every leader who wants to understand what forces will shape the economy of the near future. In their book, Meyer and Davis give you the tools to develop" - Mike ...

According to the theory of evolution, all living beings on Earth evolved from the simplest forms to more complex ones. But if everything moved in one straight line, where did such a variety of species and populations come from? Divergence and convergence can explain this phenomenon. In biology, these concepts denote the features and patterns of development of species.

Features of evolutionary theory

The main theory about the development of life on our planet, which is supported by science, is the theory of evolution. Its first provisions and laws were formulated in the 17th century. It implies a long natural process of changes in living organisms to a qualitatively new level.

The theory assumes the development of organisms from the simplest to the most complex forms, which was accompanied by genetic mutations, adaptations, extinction and the formation of species. The modern theory is based on Charles Darwin's assumptions about natural selection and population genetics data on mutations, genetic drifts, changes in the frequency of alleles.

Evolution implies that living organisms have a common root, from which their development began. In this case, the assumption of one or a pair of progenitors is not necessary. Scientists argue that there could have been more ancestral organisms, but they all belonged to related groups.

The main patterns of evolution are convergence and divergence. In biology, examples and features of these processes were described by Charles Darwin. Read more about what they are below.

Divergence in biology

From Latin, the term is translated as "divergence" and can be used not only in relation to wildlife. Divergence in biology refers to the occurrence of differences in traits between organisms. At its core, this is multidirectional variability, which arises as a result of the adaptation of living beings to different conditions.

It manifests itself in changing parts of the body or some organs and acquiring partially new functions and capabilities. Divergence in biology is a common occurrence. It appears as a result of natural selection, that is, the struggle for existence. The acquisition of traits reduces competition - each new population can occupy its ecological niche without affecting other individuals. It also occurs as a result of isolation.

Divergence can occur at the level of species, genus, family, and order. With its help, for example, the class of mammals was divided into rodents, carnivores, proboscis, cetaceans, primates and other orders. They, in turn, broke up into smaller groups that differ in external and internal structure.

Divergences in biology: examples

Divergence leads to the fact that organisms of different structure appear that belong to the same systematic group. However, they still have a common basis, the modified parts of the body perform the same functions. For example, ears remain ears, only in some they have become more elongated, in others rounded, the wings of some birds are short, others are long.

A good example is the type of limbs in mammals. In different species, they differ depending on the way of life and habitat. So, felines have soft pads on their paws, while primates have long and movable fingers to grab branches, the sea lion has developed flippers, and cows have hooves. To understand what divergence in biology is, you can use the example of whites. Butterflies of this family eat different foods at the caterpillar stage: some eat cabbage, others eat turnips, others eat beets, etc.

In plants, the divergence of characters manifests itself in the form of leaves. In cacti, they have become thorns; in barberry, needles have developed. Also, divergence can be traced at the level of the root system. Some plants have sucker roots, in potatoes they are tubers, in beets and carrots they have added thickness and turned into root crops.

Convergence

If divergence is characteristic of related organisms, then convergence, on the contrary, is observed in distant groups. It manifests itself in the similarity of signs in systematically different organisms. Like divergence, it appeared as a result of natural selection, but in this case it is directed in the same way in different species, orders, etc.

Animals or plants that belong to completely different classes acquire the same organs in structure and function. This is due to the common habitat or the similarity of lifestyle. But their similarity does not extend to the whole body, convergence affects only those organs that are necessary for adaptability to certain conditions.

So, animals that move through the air have wings. But some may refer to insects, while others to vertebrates. Water-dwelling organisms have a streamlined body shape, although they are not necessarily related to each other.

Examples of Convergence

The body shape of dolphins, whales and fish is a typical convergence. Because of their resemblance to sharks, whales and dolphins were originally considered fish. Later it was proved that they are mammals, as they breathe with lungs, are born by live birth and have a number of other signs.

An example of convergence is the wings of bats, birds, and insects. The presence of these organs is associated with the way of life of animals that move by flight. At the same time, the type and structure of their wings differ significantly.

Another example is the presence of gills in fish and molluscs. Sometimes convergence is manifested in the absence of any organs. So, on some volcanic islands, wingless butterflies, flies and other insects live.

Date: 2011-05-11

Convergence - what is it?

M. Makhlin St. Petersburg

Convergence in biology is called the development in unrelated organisms of the same characteristics that appeared as a result of adaptation to similar living conditions. These signs can refer to both the appearance and behavioral reactions of living beings.

Usually when studying biology at school, the most obvious examples are given convergence. For example, a whale, as you know, has nothing to do with fish. This is a typical mammal, like its ancestors that lived on land. But adaptation to the aquatic environment has caused the whales to develop a "fishy" appearance with its inherent attributes: a streamlined body and fins. An equally striking example is bats, flying foxes are also mammals that acquired bird-like wings during the development of the air environment.

Photo convergence

Examples convergence can be observed in the aquarium. As such, live birth of fry can be cited. They hatch in the body of the female, the eggs receive oxygen and nutrients through her blood (that is, this is a kind of pregnancy, and not a false live birth, when the eggs simply linger in the body of the female until the offspring hatch from them), the fry are born without a yolk sac, and immediately ready for active swimming and feeding. Live birth is characteristic of both American platies and South Asian half-snouts. But guppies, platies. swordtails belong to the order cyprinodontids, and hemiramphus. dermogenis - to the detachment Sarganiformes.

An example of convergence is the bearing of offspring in a special throat pouch of one of the parent fish. It is typical for African cichlids and labyrinths (a number of species of fighting fish, chocolate gourami). The ability to knock insects off the leaves above the water is shown by laliuses and spatter fish.
Similar habitat conditions also form the convergent appearance of fish. So, flatheads, which are part of the cypriniform order, are indistinguishable in appearance from some catfish from the catfish order.
A convergent appearance was formed under similar conditions of existence in many aquatic plants. In the aquatic environment, plants need to increase the assimilating (absorbing during respiration and nutrition) surface of the leaf blade. However, if evolutionary adaptation followed the path of a simple increase in size, huge leaves would begin to obscure each other, preventing water from flowing around them.
Therefore, adaptation occurred not due to an increase in the leaf, but due to its various geometric modifications, in which the assimilating surface of the leaves increases without detriment to the light and water permeable structure of the plant as a whole.

Vallisieria, sagittaria and a number of krynums have formed long ribbon-like leaves, freely creeping with the flow. In cabombs, hottons. limnophila, myriophyllum, some ludwigia and a number of other aquatic grasses, the leaves are segmented into narrow needle-shaped segments that freely transmit light and are washed on all sides by water.

Photo convergence

Floating plants and representatives of aquatic flora with floating leaves have another problem: they need to have drying upper surfaces of the leaf (to capture light and evaporate moisture) and provide the leaf with buoyancy by including air chambers in its tissue - air-filled cavities.
Phyllanthus floating freely on the surface of the water looks like a floating salvinia fern. Nymphoides have the same floating leaves as water lilies, and those, in turn, look like hydrocleis.

Especially plants that live in nutrient-poor waters have to excel. And there are many of them in the tropics. In order not to starve, plants need to increase the leaf blade, to develop its assimilating surface to the maximum.
Nature resolved the contradiction between the desire for compactness of the leaf blade and the need to increase the absorbing surface in an original way, by “inventing” the bulloid (ie, covered with bumps and pits) leaf surface. This decision made it possible, while maintaining the dimensions of the sheet plate, to increase its total assimilation surface by 3-4 times. Bullond leaves are characteristic of the Madagascar anonogethons A.boivinianus and A.bernierianus. some forms of other species of the same genus from the island of Madagascar and A. bullosus living in Australia.

Similar "crumpled" leaves appeared in the African "floating" (in fact, it is completely submerged) Crinum natans and in a number of crintocorins (C.bullosa. C.huidoroi. C.usteriana, C.aponogetifolia), the latter even in the scientific name (apoiogetonolifolia) contains the actual recognition of its convergence with aponogetons.
As you can see, convergence is a fairly common phenomenon, not alien to the inhabitants of the aquarium, as full-fledged participants in the biokinetic, assimilation and evolutionary processes of Nature.

Magazine Aquarium 2000 №1