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Competition in biology (from lat. concurrere - Faced) - interaction in which two populations (or two individuals) in the struggle for the necessary conditions affect each other negatively, i.e. Mutually oppress each other. The most satisfactory is the formulation proposed by Bigon, Harper and Townsend ( BEGON, HARPER, TOWNSEND, 1986): "Competition - interaction that reduces that one organism consumes a resource that would be available for another organism and could be consumed." It should be noted that competition can manifest itself and then when there is enough resource, but its availability is reduced due to the active opposition of individuals, which leads to a decrease in the survival of competing individuals.
Competitors Call organisms that use the same resources for their livelihoods. Plants and animals compete with each other not only for food, but also for light, moisture, food, living space, asylum, nesting - for everything, from which the well-being of the species may depend on.
Two types of competition are distinguished: intraspecific competition and interspecific. Internal competition is competition between representatives of one or several populations of some kind of resource when it is missing. Competition is extremely widespread in nature. Competition between individuals of one species living on one territory is the most acute and tough in nature, as they have the same need for environmental factors.
Internal competition In one or another stage of the existence of a specific species, it is almost always found, therefore, in the process of evolution, the organisms have developed adaptations that reduce its intensity. The most important of them is the ability to resettle the descendants and the protection of the boundaries of the individual section (territoriality), when the animal protects the place of its nesting or a certain area, a sexual partner, a place for reproduction, the ability to extract food. Thus, intraspecific competition is the struggle between individuals of one species. Intraspecific strugglethe existence is enhanced with an increase in the number of population, a reduction in the range (territory) and the strengthening of the specialization of the species.
Examples of intraspecific territorial competition in animals
Rivalry individuals of one type of food resource, when it is not enough, you can observe the population of field mice of one species. Waning out and consuming food, mouses consume energy and expose themselves to be eaten predators. Under favorable conditions, when food is sufficient, the population density increases and the need for organisms arise to spend more energy to search for food. As a result, the chances of survival are reduced.
Internal competition It can be expressed in direct aggression (active competition), which is physical, psychological or chemical. For example, males, competing for the right to have a female, can fight among themselves. To demonstrate your appearance to eclip the opponent, or with the help of the smell, keep rivals at a distance. The struggle for females, space and light often leads to active competition.
Territoriality - Territoriality. Active dispersal of individuals of one or different species in space due to competition for itself and resources available in it. ( Source: "Anglo-Russian Dictionary of Genetic Terms").
Some fish, many types of birds and other animals are characterized by the so-called territoriality - intraspecific competition for space. In birds, this competition is manifested in the particular behavior of males. For example, at the beginning of the breeding season, the male chooses a habitat (territory) and protects it from the invasion of males of the same species (birds singing in the spring - a signal on the right of ownership of the busy area). So the males of many species of birds determine the competitiveness of opponents in voting, and seriously perceive only equal to themselves by age or senior birds, American ornithologists have proved. In the protected area of \u200b\u200bcare about the nest and juveniles will not be violated by the presence of other parent couples. During the reproduction of birds, the male guards a certain territory, to which, except for his female, does not allow any individual of its species. And the louder of the male shouts the more he scares the invader, the bird strengthens its singing, and soon goes into the offensive. The couple who secured the territory has more chances to find a sufficient amount of food and it helps to do everything you need to remove the offspring.
Under the territorial behavior they understand the set of signaling means ensuring dispersing and regulating the relationship of the owners of neighboring or partially overlapping areas of habitat. In different animal species, these signals can be contact and distant (bird singing, wolves, rogging of grasshoppers, etc.). A set of visual and tactile threatening signals (up to open aggression and fights) is used in the collision of neighbors on the overall boundary and territory. With the help of sounds, many vertebrates determine their territory. The males of the monkey are guarding their huge territory, publishing an extremely loud roar, which is heard 5 km. For each type of revunov, its special sound is characteristic. For marking boundaries, some animals use a variety of odorous substances.
Animals protect their territory with the help of special signs and they are trying to cast out strangers from it. Animals will sweat their territory using sounds, light signals, smells, and frighten the non-crushed guests with claws, culbs or plumage. Such animals as sea lions and marine elephants protect their territory only during the marriage season, and the rest of the time they do not show signs of aggression to other representatives of their species. Frogs and fish are also fighting for the territory only in the marital season. Everyone heard the evening triads of frogs in a pond near the house. The barley male during the breeding period protects the territory around the nest from the invasion of other males.
Interesting chemical signals with which animals will make their territory, can be observed at roe and antelope. In the autumn period, the Siberian Rosila rides the horns of the bark of small trees and shrubs, and then rub on their head or neck. So it leaves chemical labels on the bared parts of the trees, which are allocated by special glands located on the head and neck. Trees are marked in this way indicate other features of the population of this species roeble, which the territory is busy or here passed another animal. It is possible that the intensity of chemical discharge on the label other animals determine the time of passage (applying the label) of the animal - the host. Sometimes the same roebles knock out the hooves of the plates of the Earth, leaving the remaining smell of them between their finger glands.
The antelope on the bushes and high herbs bite the top of the escape and touching the cut before the eye gland left the label. Large gerbil, as a rule, makes the signal hilly, edrebing the earth to itself, and ironing them from above the belly, where it is located that is located the pryomons (special chemicals) of the middle abdominal iron. Barsuk marks the entrance to Noura secret under the tail, rabbit - chin. Many types of lemurs leave odorless secrets on branches that move.
Some rodents use interesting marks as limiting their territory. Large gerbil, as a rule, makes the signal hilly, edrebing the earth to itself, and ironing them from above the belly, where it is located that is located the pryomons (special chemicals) of the middle abdominal iron. In the forests of Panama and Costa Rica live two types of singing mice, Scotinomys Teguina. and S. Xerampelinus.who like the birds vote label their put on. Both types of mice make special vocal sounds that a person, however, can barely disassemble. This is not just a squeak: rodents get up on the hind paws, thrust our heads and produce a series of recurring sounds like a trill.
The movement of house mice occurs according to the same routes, thanks to the steady smells of pheromones standing out with the urine. On the legs of each individual there are also special glands with which they "mark" the territory. The smell of these glands is transmitted to any subject they touch. Urine also serves as a kind of signaling device.
Scientists have established the presence of rats in the urine not only the means of metabolism, but also a number of other components - pheromones, which in rats serve as signals that determine the position and state of the individual.
Ondatra - settled and territorial animal actively protects its territory from the invasion of neighbors. The boundaries are marked with bouches of excrement on elevated places in the water. Also, animals will make the boundaries of their "possession" of glands, the strong smell of which serves as a signal of the employment of this site.
Pins and feline dilated in certain places, stating thus on some territory. Dogs will make the territory, both urine and feces, spreading, thus, information about themselves, which other representatives of their species can receive. Cats will also be scolded by urine. Cats additionally mark their territory secrets (liquid), which is distinguished between the fingers and from the glands, located in the area from the corner of the lips to the foundation of the ear. Tags left by a dog in the form of excrement, the smell of which can be enhanced by the secreted secretion from the special glands, located in the rear pass of the animal not long. This secret attaches individual smell of dog excrement. However, this substance carries short-term information, as it has the ability to quickly disappear. In addition, dogs themselves actively lick the rear pass, thus getting rid of this smell. With the help of claws and urine, the tiger marks its territory on the bark of trees. Prints of claws on the crust carry information about the size and social status of their predator who left them.
Bears will make their territory that they rub back about the trees, "hanging out" on the trunks of the shred wool. First, they make special margins: when they are suitable for the border tree, radically change the gait and leave deeper, noticeable traces. Then they jump slices of the bark from the tree, scratch it and make snacks. At the same time, they can bite the tree at different heights: standing on four and on two paws. In addition, the bear marks its territory with the smell marks, leaving the allocation of glands on trees in the jar from claws. To split the bears space, a loud signal cry is often used. Sometimes the individual is simply attacked by each other.
Territorality Development Steps:
The first stage of the development of territority is an individual space surrounding each individual. It is clearly noticeable, for example, in the rods sitting on a tree, or from the starring in a flying flock. The individual protects it from the invasion and opens for another individual only after the courtship ceremony before mating.
The second stage is a defendant place for life, rest or sleep in the middle of the non-defendant area of \u200b\u200bactivity (many predators of the hunting site). Animals standing on the second stage are practically evenly distributed. These are bears, tigers, hyenas, as well as rodents.
The third step is the rational use of space, where these territories are formed - plots from which other individuals are expelled. The owner of the plot dominates on it, he is psychologically often stronger than a stranger, who tried to penetrate its territory, and often for exile in most cases, only demonstrations, threats, persecution, the largest - pretended attacks, which stop at the boundaries of the site, labeled visually, acoustically or odor (olfactory). It is noticed that even smaller individuals were expelled from their plot larger congor. So repeatedly observed, which is much smaller in size and younger than the ondatra ran out of its plot larger and older in age. At the examples of other animals, scientists have established that almost always the owner of the site drove the foreign representative of the same species, which entered into its territory.
Output:
Territorial competition in animals is manifested in the absence of a lack of resources and contributes to the optimization of the existence of each individual of this species. Each individual holds its area of \u200b\u200bterritory and is aggressively tuned towards neighbors. This leads to a clear separation of the territory inside the population.
Territorial behavior occurs at a wide range of animals, like fish, reptiles, birds, mammals and public insects. This phenomenon is based on the congenital desire of individuals on freedom of movement on some minimal area.
* Symbiosis and Mutualism
* Predatorism
Interspecific competition
Competition between species is extremely widespread in nature and concerns almost all, since it is rarely not at least a small pressure on the part of individual species. However, ecology considers interspecific competition in a concrete, more narrow sense? Only as mutually negative relations of species occupying a similar ecological niche.
Forms of manifestation of interspecific competition can be very diverse: from the tough struggle to almost peaceful coexistence. But, as a rule, of two species with the same environmental needs, one necessarily displaces another.
We give several examples of competition between environmentally friendly species.
In Europe, in the settlements of a man, gray rat completely displaced another type of the same kind? Black rat, which now lives in steppe and desert areas. Gray rat is larger, more aggressive, it is better floating, so managed to win. In Russia, a relatively small redhead cockroach-Prussac was completely outstretched by a larger black cockroach only because it was better to adapt to the specific conditions of human dwelling.
Sea shoots are well developing under the protection of pines, birch, oxes, but then, when growing spruce crowns, shoots of light-loving rocks are dying. Weeds depress cultural plants as a result of the interception of soil moisture and mineral nutrients, as well as as a result of shading and separation of toxic compounds. In Australia, an ordinary bee, brought from Europe, displaced a small native bee that does not have a sting.
Intervidal competition can be demonstrated on simple laboratory experiments. So, in the studies of the Russian scientist G.F. The Gause of the culture of two types of infusorium-shoes with a similar power of food was placed individually and together in the vessels with a hay infusion. Each type placed separately, successfully multiplied by achieving optimal numbers. However, when living together, the number of one of the species gradually decreased, and its individuals disappeared from infusion, while the second species infusories were preserved. It was concluded that a long joint existence of species with close environmental requirements is impossible. This conclusion was called? Competitive exception rule.
In another experiment, researchers figured out the effect of temperature and humidity on the outcome of interspecific competition between the two types of flour beetles. In the vessels with flour (with a certain combination of heat and moisture) were placed several individuals of one and other species. Here, the beetles began to multiply, but after some time only the individuals of one species remained. It is noteworthy that at high heat and moisture and moisture winning one species, and at low? other.
Consequently, the outcome of competition depends not only on the properties of interacting species, but also on the conditions in which there is a competitive struggle. Depending on the conditions folding in concrete habitat, the winner of the competition can be provided either one or another appearance.
In some cases, this leads to the coexistence of competing species. After all, heat and humidity, as well as other environmental factors, are not even uniform distributed in nature. Even within a small area (forests, fields or other habitats), you can detect zones that differ in the microclimate. In this variety of conditions, each species is mastering the place where he was being survived.
The main resource representing the subject of competition in plant organisms is light. Of the two similar species of plants coexisting in the same habitat, the advantages reaches the type that is capable of going into the upper, better illuminated tier. This can be promoted, on the one hand, rapid growth and early achievement of desirable, on the other? The presence of long stuffs and highly planted leaves. Rapid growth and early achievement of despostability give advantages in the initial period of vegetation, long cutters and highly planted leaves? At the stage of an adult organism.
Observations of populations of two joint-dwelling types of clover (one of which has advantages in growth rate, and the other? In the length of the leaf cuffs) show that in mixed herbs every species suppresses the development of another. Nevertheless, both are able to complete the life cycle and give seeds, that is, the complete displacement of one type does not happen. Both types, despite the strong competition for light, can coexist. This is due to the fact that the stage of development, when the growth rate of these species reaches the maximum (and the need for light is especially high), do not coincide in time.
Thus, in the community only those competing species that have adapted to at least break into environmental requirements. Thus, in African savannas, hoofs use pasture feed in different ways: zebras tear the tops of herbs, the antiflages of the GNU eaten the plants of certain species, the gazelles are plucking only the lower herbs, and the antiflands of the fopies feed high stems.
In our country, insectivore birds, rustling in trees, avoid competition with each other due to the different nature of the search for mining at different parts of the tree.
Competition as an environmental factor
Competitive relations play an extremely important role in the formation of the species composition and regulation of the number of species in the community.
It is clear that strong competition can be discovered only between the species involving similar ecological niches. The concept of "ecological niche" reflects not so much the physical position in the ecosystem, as a functional characterizing specialization ("profession") of these organisms in nature. Therefore, harsh competition can occur only between related species.
Ecologists know that organisms leading a similar lifestyle with a similar structure do not live in the same places. And if you live nearby, you use different resources and are active at different times. Their environmental niches are as if diverge in time or in space.
The discrepancy between ecological niches with the joint habitat of related species is well illustrated by an example with two types of marine fishing birds? Large and long-axis cormorants, which usually feed in the same waters and nest next door. It was possible to find out what the composition of the food of these birds differs significantly: the long-axis cormorant catches the fish floating in the upper layers of water, while the big cormorant produces it mainly at the bottom, where Cambals are dominated, bottom invertebrates, such as shrimp.
Competition has a huge impact on the distribution of nearby species, although it is often about this only indirect data. Views with very similar needs are usually inherent in different geographic areas or different habitats in the same area. Or they avoid competition in some other way, for example, due to differences in food or differences in daily, and even in seasonal activity.
The ecological action of natural selection, apparently, is aimed at excluding or preventing the continuous confrontation of species with a similar way of life. Environmental disagreement of closely related species is fixed during evolution. In Central Europe, for example, there are five close types of cells, the isolation of which is due to each other due to differences in habitats, sometimes in the field of feeding and production sizes. Environmental differences are reflected in a number of small parts of the external structure, in particular in changes in the length and thickness of the beak. Changes in the structure of organisms, accompanying the processes of discrepancies of their environmental niches, suggest that interspecific competition is one of the most important factors for evolutionary transformations.
Intervidal competition can play an important role in the formation of the appearance of the natural community. Having generated and fixing the variety of organisms, it contributes to increasing community sustainability, more efficient use of available resources ...
In the past two decades, fierce disputes are conducted in environmental literature about the role of competition in limiting the spread and dynamics of natural populations of different types, and, consequently, in determining the structure of the community. According to some researchers, populations included in natural communities are sufficiently strictly controlled by the system of competitive relations, sometimes, the truth is modified by the impact of predators. Others believe that competition between representatives of different species is observed in nature only episodically, and the population, for the most part, being limited by other factors, as a rule, do not reach those densities in which competitive relations become defining. There is also a compromise point of view, which involves the presence of some continuum of real natural communities, at one end of which - communities, stable in time, rich, or, more precisely, saturated with species that are rigidly controlled by biotic interactions, and in the other community unstable ( In most cases, due to the fact that abiotic conditions in their habitats are not stable), not saturated with species (T, E. allowing the introduction of new species) and controlled, as a rule, poorly predictable changes in external conditions.
To obtain direct evidence of the importance of the role of competition in determining the dynamics and distribution of populations in nature is very difficult. Usually we can judge about it only on the basis of indirect evidence, but we note that the indirect nature of certain certificates should not serve as a basis for ignoring them. In cases where a number of independently obtained indirect certificates are built into a logically substantiated and non-contrary to common sense, one should not reject this scheme on the basis that there are no direct evidence. It is also necessary to emphasize that the competition itself is not so often to observe in nature. The main mass of existing certificates of competition concerns such a distribution of species relative to each other in space or time, which can be interpreted as a result of competition. Below we present a few examples of this distribution.
Exploring changes in the species composition of birds in Peruvian Andes as raised to the mountains, Ya. Terborgh (Terborgh, 1971) found that the species of one kind are very clearly replacing each other, and the borders of the distribution are often not associated with the vertical belt of vegetation, but are probably determined Only competition between close species. In the Scheme (Fig. 57), borrowed from the work of Ya. Terborgha It is clear that the more species of the same kind on all the surveyed height range, the smaller the height interval accounts for an average of one species. So, from a height of 1000 to a height of 3,400 m there are two representatives of the same kind, then the interval of 1200 m occurs on each, and if three types of one kind in the same range are inhabited, then each species falls on average 800 m. Similar The distribution explicitly indicates competition, and it is unlikely to be explained without taking into account interspecific interactions (MacArthur, 1972). Important additional evidence of competition in the case described by Ya. Terborh, were obtained when studying the vertical distribution of birds held with the participation of the same author (Terborgh, Weske, 1975) in Andes, but not on the main ridge, but on a small insulated mountain range, Located from it 100 km. The number of types of species here was significantly less than on the ridge, but the same species met in a larger height range, indicating that it is competitive relationships, and not abiotic factors limit their distribution on the main ridge.
Many examples of interspecific competition gives the Island Fauna (Mayre, 1968), whose representatives often demonstrate a mutually exclusive distribution, although the mainland live side by side. So, M. Radovanovich (Radovanovic, 1959; quoted: Mayr, 1968), having studied the spread of lizards of the kind Lacerta. on the 46 islands of the Mediterranean Sea near the coast of Yugoslavia, found out that there were only 28 islands Lacerta Melisellensis, And on the rest - only Lacerta sicula. There is not a single island on which both types would have dwell together.
In more rare cases, researchers could directly observe the expansion of the distribution area of \u200b\u200bone species, accompanied by the disappearance or reduction of the number in this area of \u200b\u200banother species, which is its potential competitor. So, from the end of the XIX, up to the middle of the XX century. In Europe, there was a sharp reduction in the range of widespread cancer (Astacus Astacus) and the corresponding extension to the north-west of the area of \u200b\u200ba relative species - long-shaped cancer (Astacus Lepiodactylus), Capturing the entire Volga pool, and then penetrated the Neva and Seversk Donets (Birstein, Vinogradov, 1934) into the pool. Currently, both species are found in the Baltic States and Belarus, however, cases of their location in one reservoir are very rare (Zucerzis, 1970). The displacement mechanism of one species is not clear to others, with the exception of those few cases when the long-shaped cancer was specifically launched into those reservoirs, where widespread died in the epizootia of the "rach of the plague" - a fungal disease capable of completely destroying the population of river cancers. It is likely that the successful extension of the range A. Lepiodactylus. contributed to the fact that compared to A. Astacus. It grows faster, it is more fruitfulness and the ability to eat around the clock, and not only at night, like widespread cancer.
On the territory of the British Islands there was a sharp reduction in the range of ordinary proteins (Sciurus vulgaris) After being conjugable from North America close to it, the type of Caroline proteins (Sciurus Carolinensis), Although the nature of competitive displacement remained unknown. Types living on the islands are especially suffering from universal universities, which, as a rule, are more competitive. As E. Mair notes (1968), most of the bird species disappeared over the past 200 years were island.
It is obvious that the increase in the distribution area of \u200b\u200bone species, which coincides with the simultaneous reduction in the distribution area of \u200b\u200banother environmentally friendly species, does not necessarily be due to the consequence of competition. Other biotic factors can also affect a similar shift of habitats of habitats, such as predators, availability of feed objects or a change in abiotic conditions. So, as an example of competitive displacement was considered before the change in the distribution on Newfoundland of two types of hares: a polar hare Lepus Arcticus) n American hare-beyak Lepus Americanus). More than a hundred years ago, only the polar hare died on the island, which inhabited the most various biotopes, both in the mountains and in the forest valleys. Drawn on the island at the end of the last century, Zayac Besak spread through forest valleys, and the polar hare began to meet only in mountain flameshedral areas. There was a simple hypothesis of competitive displacement of one species to others, but then it turned out (Bergerud, 1967), then in the disappearance of the polar habit of forest areas is the predator - Lynx (Lynx Lynx), the number of which has sharply increased after the instill on the island of Zaitz-Belyak. An indirect argument in favor of the fact that the press of predators played in this case a decisive role, serves the disappearance of the polar hare from the areas where the bias-whisk penetrated, but which by the nature of vegetation are convenient for the persecution of Zaitsev's trot. Thus, the hypothesis of competitive exception in this case, although it was not fully rejected, should have yielded a hypothesis that takes into account the relationship between three species: two potential competitors and one predator.
Coexistence of competing species. Models of dynamics determined by the concentration of resources
If there is significantly proven cases of competitive outstanding one species to others in natural conditions, and on the value of competition as a factor determining the dynamics of populations and communities, endless discussions are underway, the numerous facts of coexistence are environmentally friendly and therefore most likely competing doubts do not cause . So, we have already mentioned the "plankton paradox", but with no less reason you can talk about the "meadow paradox", since a number of types of grassy plants, limited by light, moisture and the same set of mineral nutrition elements, grow side by side In one place, although they are in competitive relationships.
In principle, the coexistence of competing species (T, E. Failure to comply with the Law of the GAUZ) can be explained by the following circumstances: 1) the population of different types is limited to different resources; 2) the predator mainly eats a stronger competitor; 3) the competitive advantage of species varies depending on the impermanence of external conditions (i.e., competitive displacement does not reach the end, replacing a period favorable for the form previously displaced); 4) The populations of different species are in fact divided in space - time, and what is represented by an observer by one habitat, from the point of view of the studied organisms contains a whole set of different habitats.
To explain the coexistence of species competing for a limited number of resources, it is necessary to at least briefly consider the model dynamics of populations limited in its development of the amount of available resource. The basis of this model lies already mentioned above the idea of \u200b\u200bthe so-called threshold concentration of the resource R * i.e., the minimum concentration at which the birth rate is precisely balanced mortality (see Fig. 44), and the population retains a stationary number. Obviously, in different types depending on one resource, the values \u200b\u200bof threshold concentrations may not coincide, but if there is a lot of resource in the environment, then both types are growing with maximum speeds, and faster increasing its number that has more fertility in this concentration. and mortality (i.e. value b - D). Obviously, however, that in the natural situation as the number of organisms that consume this resource increases, its concentration is reduced in the medium, and when it reaches the threshold for this type of organisms of the magnitude, the population is beginning to fall. As a result of competition of two types, one resource wins the one for which the threshold concentration of the resource.
Now consider a model with two resources, the values \u200b\u200bof the concentrations of which in the environment R 1 and R 2. We postpone on two orthogonal axes (Fig. 58). In the coordinate space of these resources, we carry out a line corresponding to the values \u200b\u200bof the concentrations of the first and second resources, in which the population retains its number of constant ( dN / NDT \u003d 0). This line, called the isoclinic zero increase, actually corresponds to the threshold for this type by combinations of concentrations of the first and second resources. If the points corresponding to the resource-observed resource concentrations lie from this line closer to the beginning of the coordinates, then the population of these concentration values \u200b\u200bwill fall. If they lie for isoklin, then the population will grow.
Note that straight isocline on the considered graph is carried out only for simplicity. This case corresponds to the interchangeability of resources, so on. The possibilities of the species successfully exist, consuming only one of the resources or content with some combination thereof. In fact, the isocline may be concave (resource complementarity) in cases where, feeding with a mixture of different components, the body consumes them in an amount less than when powered by each of these components separately, and convex, for example, in synergies of the effects of toxic substances consumed with different food components. Note that to maintain a constant number in one type (Fig. 58, but) It takes a much larger second resource than the first, but another type (Fig. 58, b.) It may be a more effective consumer of the second resource that requires it, respectively, less than the first one.
Let us now try on the same schedule to spend the zero increase for the second type. Obviously, if the isocline of the type in will be closer to the beginning of the coordinates than isocline of the type A (Fig. 58, b), then the winner in competition will be the view of both the concentration of both resources to such a low level in which the stationary population will be Views can not exist. If the isocline of the type in will be further from the start of coordinates than isocline of the species A, then the winner in competition is precisely A (Fig. 58, d). If the isoclines of two species intersect, then with a certain ratio of resources in the medium, species can coexist, and with a friend - one type of one species can be observed. So, for example, in the situation shown in Fig. 58, d, With a high concentration of the second resource and low concentration of the first, the competitive advantage affects the form A, and at high concentration of the first resource and low concentration of the second advantage turns out to be at V. V.
The example above corresponded to the resources, completely interchangeable. However, for most organisms there is a number of resources of irreplaceable. So, for example, no matter how well a plant with nitrogen is well provided, it will not be able to grow and develop if there is no phosphorus in its nutrient medium. In the coordinate axes of the two resources of the zero increase in the population, limited to such "two resources, will be depicted with a line bent at a right angle, i.e. so that it is consisting of two branches parallel to the string axes (Fig. 59, but). The position of each branch corresponds to the threshold concentration of the first or second resource. If two species compete in two indispensable resources, then in the same way as in the case of interchangeable resources, various options for each other are the zero growth of these species relative to each other. Obviously, in the situation shown in Fig. 59, b, The winner will be the view A, and in the figure shown in Fig. 59, b - species V. When crossing isoclin (Fig. 59, g.) Both species can be achieved, since various resources are limiting for each of them.
The latter occasion is experimental confirmation. So, David Tilman (Tilman, 1982), which made a great contribution to the development of modern ideas about competition for resources,. spent a series of experiments with two types of diatom planktonal algae Asterionella Formosa. and Cyclotella meneghinia And on the basis of the data obtained, it was built for them with zero increase, depending on the concentration of two essential resources - phosphorus and silicon (Fig. 60).
As part of this model, it is relatively easy to explain the coexistence of different types if they are limited to different resources. However, the concept of "different resources" needs to be clarified. So, probably, everyone will agree that various types of plants for fitofophages can be considered as different resources. With slightly smaller grounds, but, apparently, we can say that different parts of one plants can be interpreted as different resources. However, the number of elements of mineral nutrition required by plants along with light and moisture is very limited. In any case, it is significantly less than the number of types of plankton algae, living within a small volume of water (remember the "plankton paradox"), or the number of types of grassy plants growing on one meadow. An attempt to explain the coexistence of many species competing for a small number of shared resources was undertaken by D. Tilman (Tilman, 1982). To clarify the essence of its reasoning, it is necessary to make some complications in the model described above.
Let's start with the fact that all previous arguments were based on the assumption of stable concentrations of resources. It is clear, however, that in fact, resources, as well as their populations, are in the constant dynamics of PLI, in any case, in a state of dynamic equilibrium, in which the resource consumption is balanced by the influx of it on Wednesday. If we imagine that consumers can withdraw from the environment, it is obvious that there are some higher concentrations of limiting resources. The point corresponding to the concentrations of resources in the absence of consumption, D. Tilman suggested calling the supply point (eng. Supply Point). In fact, in an implicit form, we have already used this concept when we discussed the models depicted in Fig. 58-59, and spoke about one or another observable concentration of resources. In fig. 61 In the space of two indispensable resources, the supply point is applied (its coordinates S 1, S 2) And the isocline of zero increase for one species. At each point on this isoblin, the fertility, by definition, is equal to mortality, but this does not mean that the ratio in the consumption of two resources is necessarily exactly equal to their relation when entering Wednesday. From each point we can conduct vector consumption FROMshowing the direction in which the population seeks to move the threshold concentration and the supply vector U, Directional to the supply point and showing the ratio of resources that would be established in the medium with some weakening of its consumption by this population. Vector consumption and supply vector can be directed in strictly opposite sides (at an angle of 180 °): In this case, the corresponding point on the isoclin will be called the equilibrium point (point E. In fig. 61). At other points of isoblin, vector consumption and supply vector may be at an angle less than 180 °: such a ratio of resources will be nonequilibrium.
Fig. 61. Izoklin zero population growth in coordinates of indispensable resources (by Tilman, 1982)
Fig. 62. Isoclines of two species limited to two indispensable resources: C A and C B - consumption vectors (by Tilman, 1982)
Fig. 63. Isoclines of four types (A, B, C, D), limited to two resources. Each of the circles shows a certain variability in a quantitative ratio of resource data in the medium (by Tilman, 1982)
In the case of intersection of the isocline of two species competing for two independent resources, the equilibrium point of resources is just an intersection point of isoclin. In fig. 62 shows the consumption vectors (and continuing their supply vectors) emanating from the equilibrium point. The coexistence of species in this case is steadily, since each of the competing species consumes the resource that limits the growth of its own population. In particular, in fig. 62 View and more consumes the second resource, and the view is first. If the situation was reverse, then the coexistence of species would be unstable. If you refer to the diagram shown in Fig. 62, where the numbers are indicated by separate areas, limited by isoclins and vectors, then in the region 1 none of the way but can not exist in the region 2 And may exist, and can not; And the area 6 The opposite position is observed - in may exist, and not; in area 4 both species successfully coexist; in area 3 A. competitively displaces in, and in the area 5 In Competence, A.
Instead of two species in the space of two resources, we can depict the isoclines of a number of species and from the intersection points of these isoclins to carry out the supply vectors that limit areas in which the coexistence of each pair of species is possible (Fig. 63). At different points of this space, one species, two views or any one can dwell. In other words, with a precisely defined quantitative ratio of two resources in each particular case, the principle of competitive exception is carried out: the number of coexisting species does not exceed the number of limiting resources. But if we turn to nature from an idealized model, we will find that even closely located points in any real space of any habitat (both ground and water) differ quite strongly on the quantitative ratio of limiting resources. In addition, a ratio defined for any point may vary in time. For example, by D. Tiliman, a very detailed study of the distribution of nitrogen content in the soil of a section of 12 × 12 m was shown by a variation of 42%, and the variation in the magnesium content on the same site reached 100%. Spatio-temporal variability in the receipt of resources on Wednesday in Fig. 63 can be depicted with a circle of a certain diameter. As can be seen from the scheme, if this circle is placed in the area of \u200b\u200bhigh concentrations, then no more than two types can coexist with such variations, but if the same circle is placed in the field of low values, it can cover the coexistence region at once a number of species. In other words, at very low concentrations of limiting resources, even very small variability of them from one point of space to another or from one point in time to another, it is enough to ensure the real possibility of coexistence at once a large number of species (in any case, much more than the number of limiting resources ). From this follows another curious conclusion: when enriching the environment of resources, we have the right to expect a decrease in species diversity. Such a reduction in the number of species and strengthening the numerical predominance of a few species are indeed observed both in the aquatic environment (eutrophing phenomenon) and in the ground (depletion of the species composition of the meadows with long-term fertilizer).
Conclusion
In nature, any population of the form of organisms enters into a network of relationships with other types of populations: relationship type predator - the victim (or resource - consumer) and competitive relationships are one of the most important in the lives of any organisms and at the same time some of the most studied. Under the increase in the number of victims, it is observed as a functional reaction of a predator (i.e., an increase in the number of victims consumed per unit of time by one person of the predator) and numerical (i.e., an increase in the number of predator population). Due to the ability of predators to the functional and numerical reaction, the press on the victims population acts as a factor depending on the density and therefore possessing regulatory effects.
According to the theory developed by mathematicians, the system of interrelated populations of the predator and the victim, most likely should demonstrate the oscillatory regime, but even in the laboratory conditions to obtain sustainable fluctuations in the predator - the victim is almost very difficult. In the same cases, when it succeeds, researchers, as a rule, limit the amount of food for the victim or create complex heterogeneous habitats, in which the victim and predator can migrate, and the speed of the victim's resettlement is somewhat larger than the predator resettlement rate. In natural conditions, we are usually visible only to follow the number of predator for vibrations of the victim, determined by other factors not directly related to the impact of this predator.
The evolution of the predator and the evolution of the victim is always intertwined closely. One of the possible victims of predators from the press of predators in the evolution is an increase in fertility (compensating for the corresponding increase in mortality from the predator). Other possible ways: this is an avoidance strategy with a predator or a strategy for developing morphological, physiological and biochemical means of protection against it. Both of these strategies aimed at direct decline in the predator mortality are conjugate to the victim with certain spending, which are eventually expressed in reducing the birth rate. The evolution of a predator is aimed at increasing its own fertility and (or) a decrease in mortality, which is almost always associated with an increase in the efficiency of the use of victims.
Competitive relations between populations of different species occur when they are in dire need of one resource existing in insufficient quantities. Competition can flow by type of operation, i.e., a simple use of a scarce resource, or by the type of interference, in which individuals one species creates interference to the individuals of the other in the use of shared resources.
In ecology there is a long tradition of a theoretical research of competition. According to the mathematical model of Volterry trays, later developed and confirmed experimentally, the city of F. Gause, two species competing for one resource, as a rule, cannot sustainably coexist in a homogeneous medium, and the outcome of competition is determined by the ratio of the intensity of self-restraint each of the populations and their constructions. . This rule, also known as the GAUZ law, or the principle of competitive exception, as a result of a comprehensive study of theorists and experimenters has undergone a certain development. In modern formulation, it states that the number of species that are unlimitedly coexistent in constant homogeneous habitat conditions cannot exceed the number of density-dependent factors limiting the development of their populations.
The Gause law continues to maintain heuristic importance for naturalists studying competition in nature. Direct evidence of the importance of the role of interspecific competition in nature is immeasurably harder than in the laboratory. Therefore, as a rule, the value of competition as a factor determining the dynamics and distribution of natural populations is judged by the aggregate of indirect evidence.
In some cases, the number of coexistent species competing for general, the resources limiting their development is clearly more than the number of such resources (an example is the plankton algae community or community of meadow plants), which contradicts the law of Gause. This contradiction is removed, however, the theory that takes into account the spatial and temporary variability in the provision of competing species with limiting resources.
In Russian, the word "ecology" was first mentioned, apparently, in a brief sentence of "general morphology", E. Geckel - a small book, published in 1868, edited by I. I. Mechnikov.
Now we are, however, we begin to realize that, perhaps, and for nothing to strive to develop ecology and biology in general by sample physics. It is possible that the biology of the future will be closer to the humanitarian sciences. In any case, the "fitness" is one of the central concepts in Darvinism (and this is the only fairly common eco-evolutionary theory) - refers to the field of semantic information (Zarengkov, 1984).
The richest group of organisms on earth - insects. Insect species are much larger than all other types of animals and plants combined. The total number of them remains unknown, since most inhabitants in the tropics are not yet described. Until recently, it was believed that insects 3-5 million species, but in recent years they have appeared (May, 1988), indicating that this figure should be increased, perhaps an order of magnitude, that is, the number of insect species on Earth At least 30 million grounds for this revaluation were, in particular, the results of the survey of the crowns of tropical trees. So, by applying the method of fumigation to exile insects from the crown, it was possible to show that at 19 copies. one type of tropical evergreen trees Geuhea Seemanni. In Panama, 1100 species lived in Panama.
The reduced definition, as indicated by the author, is a somewhat modified definition of the ecology proposed by the Australian researcher in Andrevartha (AndrewArtha. 1961), which in turn proceeded from ideas developed in the 20th centuries. C. Elton (1934; ELTON, 1927).
This situation was observed, however, in physics. As Waiskopf (1977) noted, the progress made by this science in a new time is associated with the refusal of attempts to establish all the truth and explain entirely the entire universe. Instead of setting general questions and receive private answers, scientists began to ask more private questions, but, no matter how surprisingly, they received more general answers.
Note that the expressions are "sufficiently perfect" or "sufficiently adapted" does not at all mean that this type is adapted in the best possible way, and continue to improve him. From the said it should not also be that each species lives in nature in the most optimal conditions. It often happens that the most optimal (in abiotic conditions) sections of its potential range is displaced by competitors or predators. It is enough to refer to at least the above example with an atrociety under a strong press of the listogryza Chrysolina.
In the English-language literature dedicated to the evolutionary aspects of ecology, the English saying "Jack of All Trades Is A Master of None" is very often quoted, which can be roughly translated into Russian: "The one who takes to do any job does not make one of them "
Systematics specialists are noticed (Skvortsov, 1988) that certain names of taxonomic categories are rather names of their own, not nine. For example, saying "Class of Monocoons" or "Class of Required", we first imagine one-bedroom and reptiles, and not a certain "class in general" is a conditional unit of systematics that agreed that classes are divided into units, but are combined into types.
Among the domestic scientists, such a point was defended by S. S. Schwartz (1969). Currently adheres to A. V. Yablov (1987), which in his book "Population Biology" determines the population as "... a minimal self-reproducing group of individuals of one species, throughout an evolutionary long time inhabiting a certain space forms an independent genetic system and forming its own ecological space "(p. 150). Explaining its definition, A. V. Appleov emphasizes that "... population is always a fairly numerous group of individuals, for a large number of generations to a high degree isolated from other similar groups of individuals" (p. 151).
Clons are usually called groups of individuals that occurred from one ancestral form through vegetative or parthenogenetic reproduction of h because being very close relatives. Environmentalists are very often used in their experiments clones of algae, simplest, travmatics and other organisms.
A similar point of view, phytocenologists are often particularly strictly adhered. Instead of the term "population", they prefer to use the term "priceopopulation", thus emphasizing that it is not just a set of plants of a certain species, but a totality, which is included in specific centencies (\u003d community).
N. P. Naumov in the 1960s. Consistently defended the "soft" definition of the population, rightly stressing that the disputes themselves about the possibility or inability to consider one or another grouping by the population are objective, since they reflect the natural hierarchical structure of the population. In our opinion, it is completely fair to N. P. Naumov (1965, p. 626) believed that the dynamics of the number is "a phenomenon that deployed not only in time, but also in space."
Assessment of the total population is especially important for disappearing, listed in the Red Book of species of animals and plants. The question of how the minimum permissible size of these populations may be acquired already purely practical.
Experts that study the methods of spatial distribution opens are recommended to use the indicator σ 2 / t. Only in cases where with an increase in the average (which is achieved by the use of larger platforms) dispersion increases according to a linear law. In other cases, other indicators of spatial aggregation (Romanovsky, 1979) are used.
We emphasize that in this example there is a dry mass of food (raw mass can be 10 times more). All figures are borrowed from the generalizing work B. D. Abaturova and V.N. Lopatina (1987).
The antibiosis is such a form of relationships in which both interacting species or one of them experience a harmful, overwhelming activity, influence from the other.
Neutralism is such a form of relationships, in which there are no direct interactions between the species and they do not have a noticeable influence on each other.
In nature, such relationships between organisms are defined rather difficult, since the complexity of biocenotic connections leads to the fact that most species indirectly affect each other.
For example, many forest animals (earthmock, small rodents, proteins, woodwoods) are not associated with a biocenosis direct relationships, but all depend on the stock of seeds of coniferous rocks and on this basis they indirectly affect each other.
The relationship of neutralism is characteristic of the rich species of communities.
Competition (- -).
Competition(from lat. Concurro - Face, knock) - this is a form of relationship, which is observed between organisms when we share the resources of the medium, the number of which is not enough for all consumers.
Competitive relationships will play an extremely important role in the formation of the species composition, the distribution of species in space and the regulation of the number of species in the community.
Distinguish intraspecific and interspecific competition.
Intraspecific competition - this is the struggle for the same medium resources that occur between individuals of the same species.
Intravidaya competition is the most important form of the struggle for the existence, which thoroughly increases the intensity of natural selection.
At the same time, interspecific competition manifests itself to the more severe, the more similar to the environmental needs of competitors.
Distinguish two forms of interspecific competitive relations: direct and indirect competition.
Direct (active) competition -suppression of one type of other.
With direct competition between species, directed antagonistic relations are developed, which are expressed in different forms of mutual oppression (fighting, overlapping access to the resource, chemical suppression of a competitor, etc.).
At the same time, many birds and animals aggression it is the main form of relationship, which determines the competitive displacement of one species to others in the process of struggle for shared resources.
for example:
- In forest biocenoses, competition between forest mice and red rowers leads to regular changes in habitats in these species. During the years with an increased number of forest mice, a variety of biotopes are populated, displacing red pools in less favorable places. And, on the contrary, the voles in numerical superiority are widely spread in places, of which were previously ousted by mice. It has been shown that the mechanism of competitive separation of habitats is based on aggressive interactions;
- Sea hedgehogs settled in coastal algae, physically eliminate other consumers from their pastures. Experiments with removal of marine hens have shown that the algae thickets are immediately populated by other animal species;
- In European settlements of a man, gray rat, like a larger and aggressive, completely displaced another species - a black rat, which now lives in steppe and desert areas.
Indirect (passive) competition -consumption of resources of the environment necessary by both types.
Indirect competition is expressed in the fact that one species worsens the conditions for the existence of another species with similar environmental requirements without providing direct forms of impact on a competitor.
With indirect competition, success in competitive struggle is determined by biological features of species: the intensity of reproduction, growth rate, population density, resource intensity, etc.
for example:
- In one reservoir, there can be jointly widespread and narrowly cancer. Usually the winner is narrowly cancer, as the most prolific and adapted to modern living conditions;
- In the settlements of a person, a small red-haired cockroach-Prussac pushed out a larger black cockroach only because it is more prolific and better adapted to the specific conditions of human dwelling.
Classic example of indirect interspear competitionare laboratory experiments conducted by Russian scientists G.F. Gause, according to the joint content of two types of infusories with a similar power character.
It turned out that with the joint growing of two types of infusories after a while in the nutrient medium there was only one of them. At the same time, the infusoria of one species did not attack individual species and did not allocate harmful substances to suppress a competitor. This was explained by the fact that these species differed in an unequal rate of growth and in competition for food fascinated the growing and multiplying appearance.
Model experiments conducted by G.F. Gause, led him to the wording widely known the principle of competitive exception (Theorem Gause):
Two ecological species of the species cannot jointly exist on the same territory, i.e. Cannot take a completely equal ecological niche. Such kinds must be separated in space or in time.
From this principle follows, what a joint habitat on one territory of nearby species is possible in cases where they differ in their environmental requirements, i.e. occupy various ecological niches.
for example:
- Insectivore birds avoid competition with each other at the expense of different food search sites: on tree trunks, in shrubs, on stumps, on large or small branches, etc.;
- Hawks and owls that feed about the same animals, avoid competition due to the fact that at different times of the day :: Hawks are hunting during the day, and Owls - at night.
Thus, interspecific competition arising between close species can have two consequences:
- displacement of one species to others;
- Different environmental specialization of species, allowing them to exist together.
The interactions of species in the composition of biocenosis are characterized not only by bonds on the line of direct trophic relations, but also by numerous indirect bonds that unite species of both one and different trophic levels.
Competition - this is The form of relationship arising in cases where two types use the same resources (space, food, shelter, etc.).
Distinguish 2 forms of competition:
- direct competition, in which directional antagonistic relations, expressed in different forms of oppression: fights, chemical suppression of a competitor, and so para;
- indirect competition, which expresses in the fact that one species worsens the conditions for habitat for the existence of another species.
Competition can be both inside the species and between several species of one kind (or several childbirth):
Internal competition is manifested between individuals of the same species. This type of competition is radically different from interspecific and is expressed mainly in the territorial behavior of animals that protect the places of their nesting and the famous area in the district. These are many birds and fish. The relations of individuals in populations (inside the form) are diverse and contradictory. And if species devices are useful for the entire population, then for individual individuals, they can be harmful and cause their death. With an excessive increase in the number of individuals, the intraspecific struggle is exacerbated. That is, the intraspess struggle is accompanied by a decrease in the fecundity and the death of part of the species of the species. There are a number of devices that help individuals of one population avoid direct clashes among themselves - you can meet mutual assistance and cooperation (joint feeding, education and protection of offspring);
Interwide competition is any interaction between populations that harmful affects their growth and survival. The interspest struggle is observed between populations of various types. It proceeds very quickly if kinds need similar conditions and belong to one family. The interspecific struggle for existence includes one-sided use of one species to others, i.e. the relationship "Predator - Victim". The form of the struggle for the existence in a broad sense is and favored by one species to another without prejudice to itself (for example, birds and mammals spread fruits and seeds); Mutual favored one species to another without prejudice to itself (for example, flowers and their pollinators). The fight against unfavorable environmental conditions is observed in any part of the range, when the external environmental conditions deteriorate: for daily and seasonal fluctuations in temperature and humidity. Biotic interactions of populations of two species are classified on:
neutralism - when one population does not affect the other;
competition is the suppression of both species;
amenzalism - one population suppresses another, but at the same time does not have a negative impact;
predation - individuals of the predator larger than the individuals of the victim;
commminasalism - the population benefits from the association with another population, and the latter is indifferent;
protocooperation - interaction favorably for both species, but not necessarily;
mutualism - interaction must necessarily be favorable for both species.
An example of a model of interpopulation interactions can serve "the spread of individuals of the" marine acorns "- Balyanus, which set on the rocks above the tidal zone, since not to withstand drying. Smaller chthameclus, on the contrary, are only above this zone. Although their larvae is settled in the settlement zone, direct competition from Balyanus, who are able to disrupt competitors from the substrate, impede their appearance in this territory. In turn, Balyanas may be ousted by mussels. But nevertheless later, when mussels occupy all the space, Balyanus begin to settle on their sinks, again increasing their number. In competition for nesting shelters, the big tit dominates the smallest Lazorovka, capturing the doupels with the years of larger size. Outside the competition of Lazorovka prefer the pilot in 32 mm, and in the presence of a big tity, they will settle in the doupels with a 26 mm flyer, unsuitable for a competitor. In forest biocenoses, competition between forest mice and red pools leads to regular changes in the biotopic distribution of species. During the years with an increased number of forest mice, a variety of biotopes are populated, displacing red pools in less favorable places.
The main types of interpopulation relationships ("Predator - Victim", Mutualism, Symbiosis)
Competitive relations can be the most different - from direct physical struggle to a peaceful joint existence. And at the same time, if two types with the same environmental needs turn out to be in one community, then it is necessarily one competitor displaces another. This environmental rule was called "law competitive exception", Formulated P. Gause. According to the results of his experiments, it can be said that among the species with a similar characteristic of nutrition after a while, the individuals of only one species survived in the struggle for food, since his population grew faster and multiplied. The winner in the competitive struggle is the one. The view that in this ecological situation has at least small advantages over others, and consequently a large fitness to the environmental conditions.
Competition performs one of the reasons that two types, weakly differing nutrition, behavior, lifestyle, etc., rarely cohabit in one community. In this case, competition is character Direct hostility. The most cruel competition with unforeseen consequences occurs if a person introduces the types of animals in the community without taking into account the already established relationships. But often competition is manifested indirectly, it is insignificant, since various types of otherwise perceive the same environmental factors. The more diverse the possibilities of organisms, the less tense there will be competition.
Mutualism (Symbiosis) - one of the stages of development of the dependence of two populations from each other, When the union occurs between very different organisms and the most important moustunistic systems occur between autotrophs and heterotrophs.Classic examples of Mutualistic relations - Actinia and inhabitants of their fishes fishes in the wreath; Hermitage Cancers and Actius. Other examples of this type of relationship are also known. So, ASPIDOSIPHON worm at a young age hides his body into a small empty shell of bunthogged clams.
Mutualistic forms of relations are also known in the plant world: in the root system of higher plants there are connections with mikrizing mushrooms, nitrogen-forming bacteria. Symbiosis with mineral mushrooms provides plants with minerals, and mushrooms - sugars. Similarly, nitrogen-fixing bacteria, supplying a plant with nitrogen, is obtained from it carbohydrates (in the form of sugars). On the basis of such relations, a complex of adaptations is formed, ensuring the stability and functional efficacy of mutualistic interactions.
Closer and biologically significant forms of connections occur with the so-called endosimbiosis - Cohabitation, in which one of the species is settled inside the body of another. These are the relationship of higher animals with bacteria and the simplest intestinal tract.
Many animals contain photosynthetic organisms in their fabrics (mostly lower algae). It is known a settlement of green algae in the wool of slides, while the algae use wool as a substrate, and for sloths create a patronage color.
Unlikely symbiosis of many deep-sea fish with luminous bacteria. This form of mutualism provides a light painting so important in the dark by creating glowing organs - photophors. Fabrics of luminous organs are abundantly supplied with nutrient substances necessary for the life of bacteria.
Predation. Laws of the system "Predator - Victim"
Predator - This is free-lived organism, eating by other animal organisms or vegetable foods, i.e., the organisms of the same population serve as a different population for organisms. A predator, as a rule, first catches the victim, kills her, and then eats. It has special devices for this.
W. victims Also historically developed Protective properties In the form of anatomy-morphological, physiological, biochemical features, for example: body grows, spikes, spines, shells, protective painting, poisonous glands, the ability to break into the ground, quickly hide, build inaccessible asylum predators, resort to danger alarm.
As a result of such interdependent devices, certain Grouping organisms In the form of specialized predators and specialized victims. Extensive literature is devoted to the analysis and mathematical interpretation of these relationships, starting from the classical Volterra-Lotch model (A Lotka, 1925; V. Volterra, 1926, 1931) to numerous modifications.
Laws of the "predator - victim" system (V. Volterra):
- law periodic cycle - the process of destroying the victim by a predator often leads to periodic fluctuations in the population of both species depending only on the growth rate of the predator population and victims, and on the initial ratio of their number;
- law middle Savings - the average number of populations for each species is constant, regardless of the entry level, provided that the specific speed of increasing the population number, as well as the effectiveness of predatoryness is constant;
- law middle Violations - with a similar violation of the population of a predator and the victim (for example, fish in the course of the fishery is proportional to their number), the average population of the victim is growing, and the population of the predator - falls.
Volterry trays model. The predator-victim model is considered as a spatial structure. Structures can be formed both in time and in space. Such structures are called "Spatio-temporal".
An example of temporary structures can serve as the evolution of the number of blessing bias and a fish, which is characterized by oscillations in time. Ryys feed on the hares, and the hares eate the vegetable feed, which is available in unlimited quantities, therefore the number of Zaitsev (the growth of reserves of available food for a fish) is increasing. As a result, the number of predators is increasing to the time when they become a significant% amount, and then the destruction of the hare occurs very quickly. As a result, the number of victims decreases, food reserves are dried and, accordingly, their number decreases. Then again the number of hares increases, respectively, the lynys begin to strengthen themselves, and everything is repeated first.
This example is considered in the literature as a model of trays - Volterra, which describes not only the vibration of the population in ecology, it is also a model of non-unforgettable concentric oscillations in chemical systems.
Limit factors
The idea of \u200b\u200bthe limiting factors is based on two laws of ecology: the law of the minimum and the law of tolerance.
Minimum law. In the middle of a last century, German chemist Y. Libik (1840), studying the effect of nutrients on the growth of plants, found that the crop depends not on those elements of power, which are required in large quantities and are present in abundance (for example, C0 2 and H 2 0), and from those that, though And we need a plant in smaller quantities, but practically absent in the soil or unavailable (for example, phosphorus, zinc, boron). This pattern of libes formulated this: "The growth of the plant depends on the element of the power, which is present in the minimum number." Later, this conclusion was known as the law of a minimum of libege and was distributed to many other environmental factors.
Limit, or limit, the development of organisms can heat, light, water, oxygen, and other factors, if their value corresponds to an environmental minimum.
For example, Tropical Fish "Marine Angel" dies if the water temperature drops below 16 ° C. And the development of algae in deep-sea ecosystems is limited to the penetration of sunlight: in the bottom layers there is no algae.
The libiha minimum law in general can be formulated as follows: The growth and development of organisms depend primarily from those factors of the natural environment, the values \u200b\u200bof which are approaching an environmental minimum.
Studies have shown that the minimum law has 2 restrictions that should be taken into account in practice:
- the first limitation is that the Libiha law is strictly applicable only in conditions stationary system status.
For example, in some reservoir, the growth of algae is limited in vivo the lack of phosphates. In this case, nitrogen compounds are contained in water in excess. If there is a high content with high content in such an oil: mineral phosphorus, then the reservoir can "bloody". This process will be progress until one of the elements is spent to a restrictive minimum. Now it can be nitrogen if phosphorus continues to flow. In the transitional moment (when nitrogen is not enough, and the phosphorus is already enough) the effect of a minimum is not observed, i.e. neither, one of these elements does not affect the growth of algae;
- second limitassociated with interaction of several factors. Sometimes the body is able Replace the deficient element other, chemically close .
So, in places where there is a lot of strontium, in mollusc sinks, it can replace calcium with the latter shortage. Or, for example, the need for zinc in some plants is reduced if they grow in the shade. Consequently, the low concentration "zinc will less limit the growth of plants in the shade than i in bright light. In these cases, the limiting effect of even an insufficient number of one or another element may not appear.
The law of tolerance (from lat. Tolerantia. - patience) was opened by an English biologist V. Shefod (1913), which drew attention to the fact that limiting the development of living organisms can not only those environmental factors that are minimal, but also those that are characterized by Environmental maximum. Excess heat, light, water and even nutrients can have an equally destructive effect, as well as their disadvantage. The range of the ecological factor between the minimum and maximum V. Sheford called the "Tolerance limit".
Tolerance limit Describes the amplitude of the vibrations of the factors that ensures the most complete existence of the population.
Later, the tolerance limits relative to various environmental factors for many plants and animals were established. Laws of Yu. Libiha and V. Sheford helped to understand many phenomena and the distribution of organisms in nature. Organisms cannot be distributed everywhere because populations have a certain limit of tolerance with respect to fluctuations in environmental environmental factors.
The law of tolerance V. Sheford Formulated: The growth and development of organisms depend, first of all, from those environmental factors, the meanings of which are approaching an environmental minimum or an environmental maximum. The following was established:
Organisms with a wide range of tolerance to all factors are widespread in nature and are often cosmopolitans (for example, many pathogenic bacteria);
Organisms can have a wide range of tolerance in relation to one factor and a narrow range relative to the other (for example, people are more enduring to the absence of food than to the absence of water, i.e. the tolerance limit relative to the water is narrower, than relative to food);
If the conditions according to one of the environmental factors become non-optimal, then the limit of tolerance for other factors can be changed (for example, with a lack of nitrogen in the soil of cereals, much more water is required);
Observed real limits of tolerance less potential capacity capabilities to adapt to this factor. This is due to the fact that in nature, the limits of tolerance in relation to the physical environment can be dried by biological relations: competition, lack of pollinators, predators, etc. Anyone is better implementing its potential
opportunities in favorable conditions (for example, athlete fees for special training before responsible competitions). The potential ecological plasticity of the organism, defined in laboratory conditions, more realized opportunities in natural conditions. Accordingly, distinguish Potential and implemented Environmental niches;
- the limits of tolerance in breeding individuals andthe offspring is less than adult individuals, that is, females during the reproduction period and their offspring are less hardy than adult organisms.
Thus, the geographical distribution of fishing birds is more often determined by the influence of climate on eggs and chicks, and not on adult birds. Caring for offspring and careful attitude towards motherhood are dictated by the laws of nature. Unfortunately, sometimes social "achievements" contradict these laws;
Extreme (stressful) values \u200b\u200bof one of the factors lead to a decrease in tolerance limit to other factors.
If the raged water is reset into the river, the fish and other organisms spend almost all their energy to overcome stress. They lack energy to produce food, protection against predators, reproduction, which leads to gradual extinction. Psychological stress can also cause many somatic (from Greek. Soma. -To) the disease is not only in humans, but also in some animals (for example, in dogs). With stressful values \u200b\u200bof the factor, adaptation to it becomes more and more difficult.
Many organisms can change tolerance to individual factors if the conditions change gradually. You can, for example, to get used to the high temperature of the water in the bath, if climb hot water, and then gradually add hot. Such an adaptation to a slow change in factor is a useful protective property. But it may be dangerous. Unexpected, without warning signals, even a small change may be critical. Becoming threshold effect. For example, a thin twig can lead to a fracture already overloaded camel back.
If the value of at least one of the environmental factors approaches a minimum or maximum, the existence and development of the body, the population or community becomes dependent on this, limiting the vital activity, factor.
Limit factor called Any environmental factor approaching extreme values \u200b\u200bof the limits of tolerance or exceeding them.Such strongly deviating factors are primarily acquired in the lives of organisms and biological systems. They are they control the conditions of existence.
The importance of the concept of limiting factors is that it allows you to understand complex relationships in ecosystems. Note that not all possible environmental factors regulate the relationship between the environment, organisms and man. Various limiting factors are prioritized in one or another segment. They need to focus their attention when studying ecosystems and managing them. For example, the oxygen content in terrestrial habitats is large, and it is so available that it almost never serves as a limiting factor (with the exception of large heights, anthropogenic systems). Oxygen is little interested in ecologists engaged in ground ecosystems. And in the water he is often a factor limiting the development of living organisms ("Zamok" of fish, for example). therefore Hydrobiologist Measures the oxygen content in water, in contrast to a veterinarian or an ornithologist, although for ground organisms oxygen is no less important than for water.
Limit factors determine and geographic Area species.So, the promotion of organisms to the north is limited, as a rule, disadvantage Heat.
The distribution of certain organisms often limit and biotic Factors.
For example, the figs brought from the Mediterranean in California did not be fruiting there until they guessed to get there and a certain appearance of the osse - the only pollinator of this plant.
The identification of limiting factors is very important for many activities, especially agriculture. With a focused impact on limiting conditions, it is possible to quickly and efficiently increase the yield of plants and animal productivity.
Thus, when breeding wheat on acidic soils, no agronomic measures give effect if not to use lime, which reduces the limiting effect of acids. Or if they grow corn on soils with a very low phosphorus content, then even with sufficient water, nitrogen, potassium and other nutrients, it stops growing. Phosphorus in this case is a limiting factor. And only phosphoric fertilizers can save the crop. Plants may die from too much water or excess: fertilizers, which in this case are limiting factors.
Knowledge of limiting factors gives the key to the management of ecosystems. However, in different periods of the life of the body and in different situations, various factors protrude as limiting. Therefore, only the skillful regulation of the existence conditions can give effective management results.
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