Lecture number 5

(for the direction of the bachelor's degree "Standardization and Metrology)

Topic: “Ecological communities and ecosystems. Biocenosis. Biogeocenosis ".

1. The concept of biocenosis

2. Species structure of biocenosis

3. Spatial structure of biocenosis

4. Relationships of organisms in biocenoses

5. Ecological niches

6. Ecological structure of biocenosis

7. Borderline effect

The concept of biocenosis

Populations of different species in natural conditions are combined into systems of a higher rank - communities and biocenosis. From lat. bios - life, coenosis - general.

The term "biocenosis" was proposed by the German zoologist K. Moebius.

Biocenosis Is a set of populations of all types of living organisms inhabiting a certain geographic territory, which differs from other neighboring territories in the chemical composition of soils, waters, as well as in a number of physical indicators (height above sea level, the amount of solar irradiation, etc.)

The biocenosis includes: plant and animal components, a component of microorganisms.

Specific communities are formed in strictly defined environmental conditions. Interacting with components of the biocenosis such as plants and microorganisms, soil and groundwater form edaphotop and the atmosphere is climatop.

Components related to inanimate nature form ecotope. A relatively homogeneous space in terms of abiotic environmental factors occupied by a biocenosis is called biotope.

The part of ecology that studies the composition of communities and the living together of organisms in them is called synecology.

Biocenosis and biotope have a mutual influence on each other, expressed mainly in a continuous exchange of energy.

Small communities are part of larger ones, and these, in turn, are parts of communities of even larger scales.

Species structure of biocenosis.

The species structure of the biocenosis is understood as the diversity of species in it and the ratio of their number or mass.

Each specific biocenosis is characterized by a strictly defined species composition.

Young, just emerging biocenoses have a smaller set of species than long-established ones.

Biocenoses created by man (orchards, vegetable gardens, fields) are usually poorer in species, in comparison with natural systems similar to them (forest, meadow, steppe).

To assess the role of a particular species in the species structure of the biocenosis, indicators based on quantitative accounting are used. This is the abundance of the species, the frequency of occurrence of the species, the constancy of the species.

Abundance of species Is the number of individuals of a given species per unit area or volume of occupied space.

Frequency of occurrence... It characterizes the uniformity or unevenness of the distribution of the species in the biocenosis. This indicator is calculated as the percentage of the number of samples where this species occurs to the total number of samples.

Constancy... This indicator is the ratio of the number of samples R containing this species multiplied by the total number of samples R and divided by the total number of samples. C = p. P expressed in%.

Depending on the value of the value WITH the following categories of species constancy are distinguished:

- permanent species occurring in more than 50% of samples

- additional species found in 25-5% of samples

- random species occurring in less than 25% of samples

In a biocenosis, which consists of several species, one or two species occupy the main area or volume. These species are called dominant or dominant. Terrestrial biocenoses, as a rule, are named after the dominant species, for example, birch forest, feather grass steppe, and so on.

Dominance degree Is the ratio of the number of individuals of a given species to the number of individuals of all species of a given biocenosis.

So, if out of 200 birds registered in a given territory, 100 are finches, then the degree of dominance of this species is 50%.

Species that live off dominants are named predominants. For example, in a pine forest, insects, squirrels, and murine rodents are the predominant species that feed on pine trees.

In each biocenosis there are species that, by their vital activity, create an environment for the entire community and without which the existence of most other species is impossible. These species are called edifiers... Removal of an edificator species from a biocenosis leads to a change in the microclimate of the entire biotope of a given biocenosis.

Certain plant species are edificators of terrestrial biocenoses: in birch forests - birch, in pine forests - pine

In addition to a relatively small number of dominant species, the biocenosis also includes small numbers of species and even rare forms. There is a definite connection between the number of dominant species and the general species composition of the community. Within the biocenosis, close groupings are formed, depending on edificator plants or on other elements of the biocenosis, which are called consortia.

Consortium- is a set of populations of organisms, the vital activity of which within the same biocenosis is professionally or topically related to the central species - an av-otrophic plant.

In the role of the central species is the plant-edifier, which determines the characteristics of the biocenosis. The populations of the remaining species of the consortium form its core, due to which there are species that destroy the organic matter created by autotrophs.

The population of an autotrophic plant on the basis of which the consortium is formed is called determinitis, and the species united around it are called consorts.

Consorts are associated with the determinant trophically, that is, food connections, or topically, that is, they find a dwelling or shelter on it.

For example, insects that feed on the leaves of a tree are trophically related to it, and the birds that eat these insects and live on these trees are tied toptically.

In this regard, all consorts consist of consorts 1, 2 and so on.

The composition of the consortium is the result of a long process of selecting species that can exist in the habitat of the determinant. Each consortium is a special structural unit of the biocenosis.

The spatial structure of the biocenosis. - is determined primarily by the addition of its plant part - phytocenosis, the distribution of the ground and underground mass of plants.

In the course of a long evolutionary development, adapting to certain abiotic and biotic conditions, living organisms have found their place in the biocenosis. In most cases, this distribution is tiered.

Tiering is a vertical stratification of biocenoses into equally high structural parts. The layering is especially clearly traced in phytocenoses (plant communities).

A phytocenosis acquires a tiered character if it contains plants that differ in height. For example wood, vertical structure.

Plants of each tier create their own microclimate and a specific habitat for specific animals, which in each tier form their own community. For example, such species of birds as chickens or grouse nest only on the ground (in the ground layer), blackbirds, bullfinches - in the shrub layer, finches, goldfinches - in the crowns of trees, etc.

In biocenoses, the vertical distribution of organisms also determines a certain structure in the horizontal direction. The dissection of the biocenosis in the horizontal direction is called mosaics and is characteristic of almost all phytocenoses.

Mosaicity is due to such reasons as the heterogeneity of the microrelief, biological characteristics of plants, variegated soil fertility, human activities (deforestation, mining, etc.) by the influence of the animal world (trampling of meadows with hooves, etc.)

Interspecific relations in biocenosis according to the classification of V.N. Beklemishev are divided into four types: trophic, topical, phoric, factory. So:

1. Trophic connections- these are such connections when one species feeds on another: either living individuals, or their dead remains, or the products of their vital activity. With the competition of two species due to nutrition, an indirect trophic relationship arises between them, since the activity of one species affects the supply of food to the other.

2. Topical connections- these are such connections when a change in the living conditions of one species occurs as a result of the vital activity of another. This type of relationship is very diverse. Topical connections consist in the creation of an environment for another by one type, in the formation of a substrate on which another species settles, etc.

3. Phoric connections- these are such connections in which one species takes part in the distribution of another. An example of this type of relationship is the transfer of seeds, spores, and pollen by animals. (zoochory), and the transfer of some animals (smaller) by others (phoresia).

4. Factory connections- these are such connections in which a given species uses excretion products or dead remains of other species for its structures.

For example, birds use grass leaves, mammalian wool, down and feathers of other bird species to build their nests.

For the normal development of a particular species, the conditions for its vital activity must be optimal. There are two criteria to characterize the living conditions: physiological and synecological optima.

Physiological Optimum- this is a favorable combination of all abiotic factors for the species, at which the fastest growth and reproduction rates are possible.

Synecological optimum- this is a biotic environment in which the species experiences the least pressure from enemies and competitors, which allows it to reproduce successfully.

Physiological and synecological optima do not always coincide. An example of this discrepancy could be the mass reproduction of the Hessian fly after particularly harsh winters, which should have adversely affected the number of this pest. In normal years, the Hessian fly is largely exterminated by several species of its natural enemies. However, due to the weak frost resistance, the enemies of the Hessian fly are almost completely killed. This makes it possible for the Hessian fly to regain its numbers.

Ecological niches. An ecological niche is the position of a species that it occupies in the general system of biocenosis. This is a complex of its biocenotic relationships and requirements for abiotic environmental factors.

According to Elton (1934), an ecological niche is this is a place in a living environment, the relation of the species to food and enemies.

The ecological niche reflects the participation of this species in the biocenosis. This does not mean its territorial location, but the functional manifestation of the organism in the community.

The existence of a species in a community is determined by the combination and action of many factors. When determining the belonging of a particular species to a particular niche, it is necessary to take into account the nature of the nutrition of these organisms, their ability to obtain food.

Thus, plants, taking part in the formation of the biocenosis, provide the existence of a number of ecological niches. These can be niches covering organisms feeding on root tissues or leaf tissues, flowers, fruits, etc.

Each of these niches includes groups of organisms of different species composition. So, nematodes and the larvae of some beetles (May beetle, click beetles) enter the ecological niche of root-eaters. And bugs and aphids enter the niche of plant sucking juices.

Thus, the specialization of species in relation to food resources reduces competition and increases the stability of the community structure.

There are different types of resource sharing:

1. It is a specialization of morphology and behavior according to the type of food, for example, a bird's beak can be adapted for catching insects, gouging holes, cracking nuts, and so on.

2. Vertical separation, for example, between the inhabitants of the crown of the tree and the forest floor.

3. Horizontal division, between inhabitants of different microhabitats. For example, there is a division of birds into ecological groups based on the place of their feeding: air, foliage, trunk, soil.

The specialization of a species in nutrition, use of space, time of activity, and other conditions is characterized as a narrowing of its ecological niche. And the reverse processes are like its extension.

Competitors have a great influence on narrowing or expanding the ecological niche of a species in a community. According to the rule formulated by Gause, two species do not get along in one ecological niche.

A way out of competition can be achieved by diverging requirements for the environment, changing the way of life, that is, by delimiting ecological niches. Only in this case they acquire the ability to coexist in one biocenosis.

So, for example, in the European part of Russia, there are closely related species of titmice, the isolation of which from each other is due to differences in habitat, feeding places and the size of prey. The ecological differences between these tit species are reflected in a number of small details of the external structure - for example, the length and thickness of the beak.

Numerous groups of animals feeding on grass include steppe biocenoses. Such as ungulates (horses, sheep, saigas) and rodents (ground squirrels, marmots, mouse-like). All of them make up one functional group of biocenosis - herbivores. However, the role of these animals in the consumption of plant matter is not the same. So ungulates (horses, cattle) eat mainly tall, most nutritious grasses, biting them off at a considerable height (5-7 cm) from the surface. Marmots living here also choose food among the herbage thinned and crushed by hooves. Marmots settle and feed only where there is no high grass stand.

Smaller animals - gophers prefer to collect food where the grass stand is more disturbed, Here they collect what is left from feeding ungulates and marmots.

Between these three groups of herbivores that form a zoocoenosis, there is a division of functions in the use of the biomass of the herbaceous cover.

The relations that have developed between these groups of animals are not of a competitive nature, but on the contrary ensure their higher numbers.

Ecological niches of species are variable in space and time. Often, in the biocenosis, the same species can occupy different ecological niches at different periods of development. So the tadpole eats plant food, and the adult frog is a typical plate-eating animal. Therefore, they are characterized by different ecological niches and specific trophic levels.

In insectivorous birds, winter ecological niches differ from summer ones. Etc.

The ecological niche of the species is significantly influenced by interspecific and intraspecific competition.

With interspecific competition, the habitat of a species can be reduced to optimal boundaries, where it has an advantage over its competitors.

If interspecific competition narrows the ecological niche of a species, then intraspecific competition, on the contrary, promotes the expansion of ecological niches.

With the increased number of the species, the use of additional food begins, the development of new habitats, the emergence of new biocenetic relationships.

The ecological structure of the biocenosis. Biocenoses are composed of specific ecological groups of organisms that express the ecological structure of a community. Ecological groups of organisms, occupying similar ecological niches, in different biocenoses can have a different species composition. So, in humid areas, hygrophytes (plants of excessively humid habitats) dominate, and in arid conditions, xerophytes (plants in dry habitats) dominate.

The ecological structure of the biocenosis is significantly influenced by the ratio of groups of organisms that are united by a similar type of nutrition. For example, in forests, saprophages (animals that feed on the corpses of other animals, destroying rotting remains) predominate in the steppe and semi-desert zones - phytophages (animals that eat only plant foods).

In the depths of the ocean, the main type of food for animals is predation, and in the surface, illuminated zone, there are many species with a mixed type of food.

Differences in the ecological structure of the biocenosis are most clearly manifested when comparing the communities of organisms in similar biotopes of different regions. For example, marten in the European taiga and sable in the Asian. These species occupy similar ecological niches and perform the same functions. These species determine the ecological structure of the community and are called replacing or vicarious.

Thus, the ecological structure of a biocenosis is its composition of ecological groups of organisms that perform certain functions in a community in each ecological niche.

The ecological structure of the biocenosis in combination with the species and spatial structure, with the peculiarities of the ecological niche, serves as a macroscopic characteristic of the biocenosis.

A macroscopic characteristic makes it possible to determine the properties of a particular biocenosis, to find out its stability in space and time, and also to foresee the consequences of changes caused by the influence of anthropogenic factors.

Border effect... The most important feature of the structural characteristics of biocenoses is the presence of community boundaries. It should be noted, however, that these boundaries are rarely clear cut.

As a rule, neighboring biocenoses gradually pass one into the other, forming transitional or border zones on the border of two biocenoses, differing in special conditions.

Here, as it were, the typical conditions of neighboring biocenoses intertwine. In the transition zone, plants grow that are characteristic of both biocenoses. The abundance of plants in the border zone attracts a variety of animals here, so the border zone is often richer in life than each of the biocenoses separately. That is, with the spatial transition of one biocenosis to another, the number of ecological niches increases.

In these transitional zones, a concentration of species and individuals occurs, the so-called edge effect is observed.

Example of an edge effect .................. Pure fallow - seeding

Biogeocenosis... Living organisms and their inanimate environment are inseparably connected with each other, are in constant interaction. These components form a more complex ecological community, an ecosystem or biogeocenosis.

The term biogeocenosis was proposed in 1940 by the Russian ecologist Sukachev. By his definition biogeocenosis(from the Greek - bios-life, geo-earth, cenosis-general) is a stable self-regulating ecological system in which organic components are inextricably linked with inorganic ones.

The main functional unit in modern ecology is the ecosystem. The term ecosystem was first coined by the English ecologist Tansley in 1935.

By his definition ecosystem Is any set of organisms and inorganic components in which the circulation of substances can take place.

In other words, the combination of a specific physicochemical environment (biotope) with a society of living organisms (biocenosis) forms an ecosystem.

It is believed that the concept biogeocenosis to a greater extent reflects the structural characteristics of the studied macrosystem, while in the concept ecosystem first of all, its functional essence is invested.

In fact, there is no fundamental difference between these terms. And in the modern view, biogeocenosis and ecosystem are synonymous.

The vertical structure of a broadleaf forest can be represented by the following diagram:

1. Tree layer

2. Shrub layer

3. Herbaceous layer

4. Ground layer

5. Litter

6. Arable layer

7. Subsoil

8. Mother breed

The structure of the biocenosis and the scheme of interaction between its components.

Ecotop

Atmosphere Soil-soil

(climatop) (edaphotop)

Biotope

Vegetation Animals

(phytocenosis) (zoocenosis)

Microorganisms

The structure of any system is the patterns in the relationship and connections of its parts. Under species structure biocenosis understand the diversity of species in it and the ratio of their number or mass. Each specific biocenosis is characterized by a strictly defined species composition. Wherever the conditions of the abiotic environment approach optimal for life, species-rich communities arise, for example, tropical forests, coral reefs, river valleys in arid regions, etc. An increase in species diversity as one moves from north to south was formulated by A. Wallace in 1859 . and received the name Wallace's rule. It concerns both the species and the communities that make up them. The species composition of biocenoses depends on both the duration of their existence and the history of each biocenosis.

Young, emerging communities, as a rule, have a smaller set of species than long-established, mature ones. Biocenoses created by man (vegetable gardens, orchards, fields, etc.) are usually poorer in species in comparison with natural systems similar to them (forest, meadow, steppe). However, even the most impoverished biocenoses include several dozen species of organisms that belong to different systematic and ecological groups. At the same time, some types of biocenosis can be represented by numerous populations, while others are small in number. Hence it follows that in any biocenosis one or several species can be distinguished that determine its appearance. Thus, the appearance of a forest or steppe biocenosis is represented by one or several plant species. In the forest - pine, spruce; in the feather-grass-fescue steppe - feather-grass and fescue. To assess the quantitative ratio of species in biocenoses, ecological literature uses diversity index, calculated by Shannon's formula:

where is the sign of the sum,

pi is the share of each species in the community (by number or mass),

log 2 Pi is the binary logarithm of pi.

To assess the role of a particular species in the species structure of the biocenosis, different indicators based on quantitative accounting are used. The abundance of the species - it is the number of individuals of a given species per unit area or volume of occupied space. For example, the number of birds nesting per 1 km 2 of the steppe area, or the number of small crustaceans per 1 dm 3 of water in a reservoir, etc. To calculate the abundance of a species, instead of the number of individuals, the value of their total biomass is sometimes used. The abundance of a species as an indicator changes over time (seasonal, annual and random fluctuations in numbers) and in space (from one biocenosis to another). It is not always easy to pinpoint the abundance of species. In this regard, in practice, they are often limited to the use of a less accurate point estimate, highlighting five degrees of abundance: 0 - no; 1 - rarely and absent-mindedly; 2 - often; 3 - abundant; 4 - very abundant.

Frequency of occurrence characterizes the uniformity or uneven distribution of the species in the biocenosis. Calculated as the percentage of the number of samples and counting sites where the species occurs to the total number of such samples or sites. It is possible to calculate the frequency for one sample and for all samples of a given biocenosis and, on this basis, construct a histogram of frequencies.

Consistency. Represents the following ratio, expressed as a percentage:

where p is the number of samples containing the species under study,

P is the total number of samples taken.

Depending on the value of C, there are the following categories of species:

permanent species are found in more than 50% of samples;

additional species are found in 25-50% of samples;

random species are found in less than 25% of samples.

The abundance and occurrence of the species are not directly related. The species may be small in number, but the occurrence is quite high, or numerous, but with a low occurrence. In a forest that consists of dozens of plant species, usually one or two of them give up to 90% of the timber. These species are called dominant and dominant. They occupy a leading, dominant position in the biocenosis. Terrestrial biocenoses, as a rule, are named after the dominant species: birch forest, feather grass-fescue steppe, sphagnum bog.

Dominance degree - this is an indicator that reflects the ratio of the number of individuals of a given species to the number of individuals of all species of the group under consideration. So, if out of 200 birds registered in a given territory, 100 are finches, the degree of dominance of this species among birds will be 50%.

In all biocenoses, small forms prevail numerically - bacteria and other microorganisms. When comparing species of different sizes, the indicator of dominance in numbers cannot reflect the characteristics of the community. It is calculated not for the community as a whole, but for individual groupings, within which the difference in size can be neglected.

Species that live off dominants are called predominants. For example, in a pine forest, these are insects, squirrels, and murine rodents feeding on a pine tree.

However, not all dominant species have the same effect on the biocenosis. The biocenosis also contains the so-called edifiers - species that by their life activity to the greatest extent create an environment for the entire community and without which, in this regard, the existence of most other species is impossible. They are community builders. Removal of the edificator species from the biocenosis entails a change in the physical environment, primarily the microclimate of the biotope. The edificators of terrestrial biocenoses are certain types of plants: in birch forests - birch, in pine forests - pine, in the steppes - cereals (feather grass, fescue, etc.). Spruce in the taiga zone forms dense, heavily shaded forests. Only plants that are adapted to conditions of strong shading, high air humidity, and acidic podzolized soils can live under its canopy. In accordance with this, a specific animal population is formed in the spruce forests. In this case, the spruce acts as a powerful edifier, which determines a certain biocenosis.

In pine forests, the edificator is pine. However, in comparison with spruce, pine is a weaker edifier, since the pine forest is relatively light and sparsely. The species composition of plants and animals is much richer and more diverse here than in the spruce forest.

Edificator species are found in almost any biocenosis. In some cases, animals are also edificators. In the territories occupied by marmot colonies, it is their burrowing activity that determines for the most part the nature of the landscape, the microclimate and the conditions for the growth of plants.

In addition to a relatively small number of dominant species, the biocenosis includes; as a rule, a significant number of small and even rare forms. There is a definite connection between the number of dominant species and the general species composition of the community. With a decrease in the number of species, the abundance of individual forms usually increases sharply, biocenotic connections weaken, the most competitive species get the opportunity to reproduce without hindrance. The more specific the environmental conditions, the poorer the species composition of the community and the higher the number of individual species.

Thus, all the species that make up the biocenosis are to a certain extent associated with the dominant species and edificators. Within the biocenosis, to a greater or lesser degree, close groupings, complexes of populations are formed that depend on edificator plants or on other elements of the biocenosis; peculiar structural units of the biocenosis - consortia - are created. For the first time the term "consortium" was introduced by L.G. Ramensky (1952).

A consortium is a set of populations of organisms, the vital activity of which within one biocenosis is trophically or topically related to the central species - an autotrophic plant. The central species is usually the edificator - the main species that determines the characteristics of the biocenosis. The populations of the other species of the consortium form its core, due to which there are species that destroy the organic matter created by autotrophs. Populations of an autotrophic plant, for example birch, on the basis of which a consortium is formed, are called determinant, and the views united around him - consorts(fig. 2).

biocenosis ecological niche organism

Rice. 2.

Rice. 3.

Central view (consortium determinant); I, II, III - concentrates _ - consorts, among them: I - phytophages, epiphytes, symbionts; II, III - zoophages (after V.V. Mazin, 1966)

Each consortium, as we can see, covers a large number of species. Number their it is also great because the determinants are represented in biocenoses (ecosystems) by a different age composition. Often, each age stage of organisms is accompanied by its own consortium population. So, stem pests affect mostly adult spruce, and at the same time, rust fungi more affect young specimens. With the age of the spruce, the composition of its consorts, feeding on root secretions, changes.

The composition of the consortium is the result of a long process of selecting species that can exist in the habitat of the determinant. Each consortium is a special structural unit of the biocenosis, ecosystem.

Each organism lives surrounded by many others, enters into a wide variety of relationships with them both with negative and positive consequences for itself, and ultimately cannot exist without this living environment. Communication with other organisms is a necessary condition for nutrition and reproduction, the possibility of protection, mitigation of unfavorable environmental conditions, and on the other hand, it is a danger of damage and often even an immediate threat to the existence of an individual. The whole amount of influences that living beings have on each other are united by the name biotic factors of the environment.

The immediate living environment of the organism constitutes it biocenotic environment. Representatives of each species are able to exist only in a living environment where connections with other species provide them with normal living conditions. In other words, diverse living organisms are found on Earth not in any combination, but form certain cohabitations, or communities, which include species adapted to cohabitation.

Groupings of co-living and mutually related species are called biocenoses (from Lat. "bios" - life, "cenosis" - general). The adaptability of members of the biocenosis to living together is expressed in a certain similarity of requirements for the most important abiotic environmental conditions and natural relationships with each other.

The concept of "biocenosis" is one of the most important in ecology. This term was proposed in 1877 by the German hydrobiologist K. Möbius, who studied the habitats of oysters in the North Sea. He found that oysters can live only under certain conditions (depth, currents, the nature of the soil, water temperature, salinity, etc.) and that a certain set of other species constantly lives with them - molluscs, fish, crustaceans, echinoderms, worms , coelenterates, sponges, etc. (Fig. 75). They are all interconnected and subject to environmental influences. Mobius drew attention to the pattern of such cohabitation. “Science, however, does not have a word by which such a community of living beings could be designated,” he wrote. - There is no word to denote a community in which the sum of species and individuals, constantly limited and subject to selection under the influence of external living conditions due to reproduction, continuously owns a certain territory. I propose the term "biocenosis" for such a community. Any change in any of the factors of the biocenosis causes changes in other factors of the latter ”.

According to Möbius, the possibility of species to coexist for a long time with each other in the same biocenosis is the result of natural selection and has developed in the historical development of species. Further study of the patterns of composition and development of biocenoses led to the emergence of a special section of general ecology - biocenology.

The scales of biocenotic groups of organisms are very different, from communities of lichen cushions on tree trunks or decaying stumps to populations of entire landscapes: forests, steppes, deserts, etc.

Rice. 75. Biocenoses of the Black Sea (after S.A.Zernov, 1949):

A - biocenosis of rocks: 1 - Pachygrapsis crab; 2 - barnacles Balanus; 3 – the Patella clam; 4–5 - seaweed; 6 - mussels; 7 - sea anemones; 8 - sea ruff;

B - sand biocenosis: 9 - nemeretina; 10 - Saccocirrus worms; 11 - amphipods; 12 - molluscs Venus; 13 - sultan fish; 14 - flounder; 15 - hermit crabs;

B - biocenosis of Zostera thickets: 16 - zostera; 17 - marine needles; 18 - greenfinches; 19 - Sea Horses; 20 - shrimps;

D - oyster biocenosis: 21 - oysters; 22 - scallops;

D - biocenosis of mussel ooze: 23 - mussels; 24 - red algae; 25 – red sponge Suberites; 26 - ascidian Ciona;

E - biocenosis of phaseolin sludge: 27 - phaseolin mollusc; 28 - echinoderm amphiura; 29 - mollusc Trophonopsis;

F - hydrogen sulfide kingdom of bacteria;

З - biocenosis of open sea plankton: 31 - jellyfish, etc.

The term "biocenosis" in modern ecological literature is more often used in relation to the population of territorial areas, which on land are distinguished by relatively homogeneous vegetation (usually along the boundaries of plant associations), for example, a spruce-sorrel biocenosis, a dry meadow biocenosis, a white-moss pine forest, a feather grass steppe biocenosis, wheat field, etc. This refers to the entire totality of living things - plants, animals, microorganisms, adapted to cohabitation in a given territory. In the aquatic environment, biocenoses are distinguished that correspond to the ecological subdivisions of parts of water bodies, for example, biocenoses of coastal pebble, sandy or silty soils, abyssal depths, pelagic biocenoses of large water cycles, etc.

In relation to smaller communities (the population of trunks or foliage of trees, moss bumps in swamps, burrows, anthills, decaying stumps, etc.), various terms are used: "microcommunities", "biocenotic groupings", "biocenotic complexes", etc.

There is no fundamental difference between biocenotic groupings of different scales. Smaller communities are a constituent, albeit relatively autonomous, part of larger ones, and these, in turn, are parts of communities of even larger scales. So, the entire living population of moss and lichen cushions on a tree trunk is part of a larger community of organisms associated with this tree and including its subcrustal and trunk inhabitants, the population of the crown, rhizosphere, etc. In turn, this group is only one from the constituent parts of the forest biocenosis. The latter is included in more complex complexes that ultimately form the entire living cover of the Earth. Thus, the organization of life at the biocenotic level is hierarchical. With an increase in the scale of communities, their complexity and the proportion of indirect, indirect connections between species increase.

Natural associations of living beings have their own laws of addition, functioning and development, that is, they are natural systems.

Discussing the general principles of the organization of life on Earth, the well-known Russian biologist VN Beklemishev wrote: “All biocenotic stages of organization, from oceanic and epicontinental complexes to some microscopic lichens on the trunk of a pine tree, are very little individualized, little integrated, poorly organized, poorly closed. These are vague, not very definite, often hardly perceptible collective formations, intricately intertwined, imperceptibly passing into each other and nevertheless quite real, existing and acting, which we need to understand in all their complexity and vagueness, which is the task of biocenology with all its branches ”.

Thus, being, like organisms, structural units of living nature, biocenoses nevertheless take shape and maintain their stability on the basis of other principles. They are systems of the so-called frame type, without special control and coordinating centers (such as, for example, the nervous or humoral systems of organisms), but they are also built on numerous and complex internal connections, have a regular structure and certain boundaries of stability.

According to the classification of the German ecologist W. Tischler, the most important features of the systems related to the supraorganic level of life organization are the following:

1. Communities always arise, are made up of ready-made parts (representatives of various species or whole complexes of species) available in the environment. In this way, the way of their occurrence differs from the formation of a separate organism, an individual, which occurs through the gradual differentiation of primordia.

2. Parts of the community are replaceable. One species (or a complex of species) can take the place of another with similar ecological requirements without prejudice to the entire system. Parts (organs) of any organism are unique.

3. If the whole organism maintains constant coordination, consistency of the activity of its organs, cells and tissues, then the supraorganismic system exists mainly due to the balancing of oppositely directed forces. The interests of many species in biocenosis are directly opposite. For example, predators are antagonists of their prey, but nevertheless they exist together, within a single community.

4. Communities are based on the quantitative regulation of the number of some species by others.

5. The maximum size of an organism is limited by its internal hereditary program. The sizes of the superorganic systems are determined by external factors. Thus, the biocenosis of a white moss pine forest can occupy a small area among bogs, or it can extend over a considerable distance in an area with relatively uniform abiotic conditions.

These special principles of the formation of supraorganismic systems have caused a long discussion of ecologists, and primarily geobotanists, about the "continuity" and "discreteness" of the vegetation cover, which is the basis of terrestrial biocenoses ("continuum" - continuous, continuous, "discrete" - discontinuous). Proponents of the concept of the continuum focus on the gradual transitions from one phytocenosis to another, the absence of clear boundaries between them. From their point of view, phytocenosis is a rather conventional concept. In the organization of the plant community, the decisive role is played by environmental factors and the ecological individuality of species, which does not allow them to be grouped into clear spatial associations. Within the phytocenosis, each species behaves relatively independently. From the standpoint of continuity, species meet together not because they have adapted to each other, but because they have adapted to the common environment. Any variation in habitat conditions causes changes in the composition of the community.

The earlier concept of the discreteness of phytocenoses, which was put forward by S.G.Korzhinsky at the beginning of the formation of phytocenology, asserted the relationships of plants, that is, internal factors, as the main ones in the organization of the plant community. Its modern supporters, recognizing the presence of transitions between phytocenoses, believe that plant communities exist objectively, and are not a conditional separation from a continuous vegetation cover. They pay attention to the frequency of occurrence of the same combinations of species under similar conditions, the important environmental-forming role of the most significant members of the phytocenosis, which affect the presence and distribution of other plants.

From the standpoint of the modern systemic approach to the organization of living nature, it becomes obvious that both previously irreconcilable points of view, as was often the case in the history of science, contain rational elements. Continuity, as a fundamental property of superorganic systems, is complemented by the important role of internal connections in their organization, which, however, manifest themselves in a different form than in organisms.

7.2. Biocenosis structure

The structure of any system is the patterns in the relationship and connections of its parts. The structure of the biocenosis is multifaceted, and when studying it, various aspects are distinguished.

7.2.1. Species structure of biocenosis

Distinguish between the concepts of "species richness" and "species diversity" of biocenoses. Species richness Is a general set of community species, which is expressed by lists of representatives of different groups of organisms. Species diversity Is an indicator that reflects not only the qualitative composition of the biocenosis, but also the quantitative relationships of species.

Distinguish between poor and species-rich biocenoses. In polar arctic deserts and northern tundras with extreme heat deficiency, in waterless hot deserts, in reservoirs heavily polluted by wastewater - wherever one or several environmental factors deviate far from the average optimal level for life, communities are strongly depleted, since few species can adapt to such extreme conditions. The species spectrum is also small in those biocenoses that are often subjected to some kind of catastrophic impacts, for example, annual flooding due to river floods or regular destruction of vegetation during plowing, the use of herbicides and other anthropogenic interventions. Conversely, wherever the conditions of the abiotic environment approach the optimal average for life, communities are extremely rich in species. Examples of these are tropical forests, coral reefs with their diverse populations, river valleys in arid regions, etc.

The species composition of biocenoses, in addition, depends on the duration of their existence, the history of each biocenosis. Young, just emerging communities usually include a smaller set of species than long-established, mature ones. Biocenoses created by man (fields, orchards, vegetable gardens) are also poorer in species than natural systems similar to them (forest, steppe, meadow). Man maintains the uniformity and species poverty of agrocenoses with a special complex system of agrotechnical measures - just remember the fight against weeds and plant pests.

However, even the most impoverished biocenoses include at least hundreds of species of organisms belonging to different systematic and ecological groups. In addition to wheat, the agrocenosis of a wheat field includes, at least in minimal quantities, a variety of weeds, wheat pests and predators that feed on phytophages, murine rodents, invertebrates - inhabitants of the soil and the ground layer, microscopic organisms of the rhizosphere, pathogenic fungi and many others.

Almost all terrestrial and most aquatic biocenoses include microorganisms, plants and animals. However, in some conditions, biocenoses are formed in which there are no plants (for example, in caves or reservoirs below the photic zone), and in exceptional cases, consisting only of microorganisms (for example, in an anaerobic environment at the bottom of reservoirs, in rotting silts, hydrogen sulfide springs, etc. . NS.).

It is rather difficult to calculate the total number of species in the biocenosis due to the methodological difficulties of accounting for microscopic organisms and the undeveloped taxonomy of many groups. It is clear, however, that species-rich natural communities include thousands and even tens of thousands of species, united by a complex system of diverse interrelationships.

The complexity of the species composition of communities largely depends on the heterogeneity of the habitat. In such habitats, where species of different ecological requirements can find conditions for themselves, communities richer in flora and fauna are formed. The influence of a variety of conditions on the diversity of species is manifested, for example, in the so-called borderline, or marginal, effect. It is well known that the forest edges are usually lush and richer vegetation, more species of birds nest, and more species of insects, spiders, etc., than in the depths of the forest. The conditions of illumination, humidity, temperature are more varied here. The stronger the differences between two adjacent biotopes, the more heterogeneous the conditions at their borders and the stronger the border effect is. The species richness increases strongly in the places of contact between forest and herbaceous, aquatic and terrestrial communities, etc. The manifestation of the boundary effect is characteristic of the flora and fauna of intermediate zones between contrasting natural zones (forest-tundra, forest-steppe). VV Alekhin (1882–1946) figuratively called the exceptional species richness of the flora of the European forest-steppe “Kursk floristic anomaly”.

In addition to the number of species that make up the biocenosis, to characterize its species structure, it is important to determine their quantitative ratio. If we compare, for example, two hypothetical groups, including 100 individuals of five identical species, from a biocenotic point of view, they may turn out to be unequal. A grouping, in which 96 out of 100 individuals belong to one species and one individual to four others, looks much more monotonous than the one in which all 5 species are represented in the same way - 20 individuals each.

Number a particular group of organisms in biocenoses strongly depends on their size. The smaller the individuals of the species, the higher their number in biotopes. So, for example, in soils the abundance of protozoa is calculated in many tens of billions per square meter, nematodes - several million, ticks and collembolans - tens or hundreds of thousands, earthworms - tens or hundreds of individuals. The number of burrowing vertebrates - murine rodents, moles, shrews - is no longer counted on square meters, but on hectares of area.

Dimension species that make up natural biocenoses differ on a gigantic scale. For example, whales outnumber bacteria 5 million times in length and 3 × 10 20 in volume. Even within individual taxonomic groups, such differences are very large: if we compare, for example, giant trees and small grasses in the forest, tiny shrews and large mammals - elk, brown bear, etc. time. For example, the life cycles of unicellular organisms can occur within an hour, and the life cycles of large plants and animals are stretched over tens of years. The living space of an insect such as a gall midge can be limited by a closed gall on one leaf of a plant, while larger insects, bees, collect nectar within a radius of a kilometer or more. Reindeer regularly migrate within hundreds or even more than a thousand kilometers. Some migratory birds live in both hemispheres of the Earth, covering tens of thousands of kilometers annually. On the one hand, natural biocenoses represent the coexistence of different dimensional worlds, and on the other hand, the closest connections are realized in them precisely among organisms of different sizes.

Naturally, in all biocenoses, the smallest forms, bacteria and other microorganisms, prevail numerically. Therefore, when comparing species of different sizes, the indicator of dominance in abundance cannot reflect the characteristics of the community. It is calculated not for the community as a whole, but for individual groupings, within which the difference in the sizes of individual forms can be neglected. Such groups can be distinguished according to different characteristics: systematic (birds, insects, grasses, Compositae), ecological and morphological (trees, grasses) or directly by size (microfauna, mesofauna and macrofauna of soils, microorganisms in general, etc.). Comparing the general characteristics of diversity, the quantitative ratios of the most abundant species within different size groups, the abundance of rare forms, and other indicators, one can obtain a satisfactory idea of ​​the specificity of the species structure of the compared biocenoses.

Species of the same size class that are part of the same biocenosis differ greatly in abundance (Fig. 76). Some of them are rare, others so often that they determine the external appearance of the biocenosis, for example, feather grass in the feather grass steppe or oxalis in the oxalis spruce forest. In each community, it is possible to distinguish a group of main species, the most numerous in each size class, the connections between which, in fact, are decisive for the functioning of the biocenosis as a whole.

The dominant species are dominants community. For example, in our spruce forests, spruce dominates among trees, in the grass cover - oxalis and other species, in the bird population - kinglet, robin, chiffchaff, among murine rodents - red and red-gray voles, etc.

Dominants dominate the community and constitute the “species core” of any biocenosis (Fig. 77). Dominant, or mass, species determine its appearance, maintain the main connections, and to the greatest extent affect the habitat. Typically, typical terrestrial biocenoses are named according to the dominant plant species: blueberry pine forest, hairy sedge birch forest, etc. In each of them, certain species of animals, fungi and microorganisms also dominate.

Rice. 76. The relationship between the number of species in a community and the number of individuals per species (according to Yu. Odum, 1975): 1, 2 - different types of communities

Rice. 77. The species structure of the collembola community for 5 years (according to N. A. Kuznetsova, A. B. Babenko, 1985).

The total species richness is 72 species. Dominants: 1 - Isotoma notabilis; 2 - Folsomia fimetarioides; 3 - Sphaeridia pumilis; 4 - Isotomiella minor; 5 - Friesea mirabilis; 6 - Onychiurus absoloni; 7 - other types

However, not all dominant species have the same effect on the biocenosis. Among them, there are those that, by their vital activity, to the greatest extent create an environment for the entire community, and without which, therefore, the existence of most other species is impossible. Such species are called edifiers (literal translation from Latin - builders) (Fig. 78). Removal of the edificator species from the biocenosis usually causes a change in the physical environment, primarily the microclimate of the biotope.

Rice. 78. Madrepore corals are the main edificators of coral reefs, determining the living conditions for thousands of species of aquatic organisms

The main edificators of terrestrial biocenoses are certain types of plants: in spruce forests - spruce, in pine forests - pine, in the steppes - turf grasses (feather grass, fescue, etc.). However, in some cases, animals can also be edificators. For example, in territories occupied by marmot colonies, it is their burrowing activity that mainly determines the nature of the landscape, and the microclimate, and the conditions for the growth of plants. In the seas, the typical edificators among animals are reef-forming coral polyps.

In addition to a relatively small number of dominant species, the biocenosis usually includes many small and even rare forms. The most common distribution of species by their abundance is characterized by the Raunkier curve (Fig. 79). A sharp rise in the left side of the curve indicates the predominance of small and rare species in the community, and a slight rise in the right side indicates the presence of a certain group of dominants, a “species core” of the community.

Rice. 79. The ratio of the number of species with different occurrence in biocenoses and the Raunkier curve (after P. Greig-Smith, 1967)

Rare and scarce species are also very important for the life of the biocenosis. They create its species richness, increase the diversity of biocenotic relationships and serve as a reserve for the replenishment and replacement of dominants, i.e., they give stability to the biocenosis and ensure the reliability of its functioning in different conditions. The larger the reserve of such "minor" species in the community, the more likely it is that among them there will be those that will be able to play the role of dominants under any changes in the environment.

There is a definite relationship between the number of dominant species and the general species richness of the community. With a decrease in the number of species, the abundance of individual forms usually increases sharply. In such impoverished communities, biocenotic connections are weakened and some of the most competitive species are able to reproduce without hindrance.

The more specific the environmental conditions, the poorer the species composition of the community and the higher the number of individual species can be. This pattern was named rules of A. Tinemann, named after a German scientist who studied the peculiarities of the species structure of communities in the 30s of the last century. In species-poor biocenoses, the number of individual species can be extremely high. Suffice it to recall outbreaks of mass reproduction of lemmings in the tundra or insect pests in agrocenoses (Fig. 80). A similar pattern can be traced in communities of all sizes. In piles of fresh horse manure, for example, an almost anaerobic environment, a lot of ammonia and other toxic gases, a high temperature due to the activity of microorganisms, that is, sharply specific living conditions deviating from the usual norm are created for various animals. In such heaps, the species composition of invertebrates is initially extremely poor. Drosophila fly larvae develop, and few species of saprophagous nematodes (family Rhabditidae) and carnivorous gamasid mites (genus Parasitus) breed. But on the other hand, all these species are extremely numerous, there are almost no rare forms. In such cases, the curve describing the distribution of species by their abundance has a strongly smoothed left part (as in Fig. 76). Such communities are unstable and are characterized by sharp fluctuations in the abundance of individual species.

Rice. 80. The structure of dominance in the insect community of the stalk of cereals in the fields (after N.I.Kulikov, 1988). The abscissa shows species in descending order of abundance

Gradually, as the manure decomposes and environmental conditions soften, the species diversity of invertebrates increases, while the relative and absolute numbers of mass forms noticeably decrease.

In the richest biocenoses, almost all species are few in number. In tropical forests, it is rare to find several trees of the same species nearby. In such communities, outbreaks of mass reproduction of certain species do not occur; biocenoses are highly stable. A curve reflecting a species structure of this type would have in Fig. 76 is a particularly steep left side.

Thus, even the most general analysis of the species structure can give enough for an integral characterization of the community. The diversity of the biocenosis is closely related to its sustainability. Human activities greatly reduce diversity in natural communities. This raises the need to anticipate its consequences and take measures to maintain natural systems.

Quantitative characteristics of the species in the biocenosis. To assess the role of a particular species in the species structure of the biocenosis, different indicators based on quantitative accounting are used. Abundance of species Is the number of individuals of a given species per unit area or volume of occupied space, for example, the number of small crustaceans in 1 dm 3 of water in a reservoir or the number of birds nesting per 1 km 2 of a steppe area, etc. Sometimes, to calculate the abundance of a species, instead of the number of individuals use the value of their total mass. For plants, the projective abundance, or area coverage, is also taken into account. Frequency of occurrence characterizes the uniformity or uneven distribution of the species in the biocenosis. It is calculated as the percentage of the number of samples or counting sites where the species occurs to the total number of such samples or sites. The abundance and occurrence of the species are not directly related. The species can be numerous, but with a low occurrence, or scanty, but quite common. Dominance degree - an indicator reflecting the ratio of the number of individuals of a given species to the total number of all individuals of the considered group. So, for example, if out of 200 birds registered in a given territory, 80 are finches, the degree of dominance of this species among the bird population is 40%.

To assess the quantitative ratio of species in biocenoses, modern ecological literature often uses diversity index, calculated by Shannon's formula:

H = – ?P i log 2 P i,

where? - the sign of the sum, p i Is the share of each species in the community (by number or mass), a log 2 p i- binary logarithm p i.

7.2.2. Spatial structure of biocenosis

The area of ​​the abiotic environment occupied by the biocenosis is called biotope, i.e., otherwise, bitop is the habitat of the biocenosis (from lat. bios- life, topos- a place).

The spatial structure of the terrestrial biocenosis is primarily determined by the addition of its plant part - phytocenosis, and the distribution of the terrestrial and underground plant masses.

When plants of different heights live together, the phytocenosis often acquires a clear tiered folding: assimilating aboveground plant organs and their underground parts are arranged in several layers, using and changing the environment in different ways. Layering is especially noticeable in temperate forests. For example, in spruce forests, arboreal, grass-shrub and moss layers are clearly distinguished. Five or six tiers can be distinguished in a broad-leaved forest: the first, or upper, tier is formed by trees of the first size (pedunculate oak, heart-shaped linden, plane maple, smooth elm, etc.); the second - trees of the second size (mountain ash, wild apple and pear, bird cherry, goat willow, etc.); the third layer is the undergrowth formed by shrubs (common hazel, buckthorn brittle, forest honeysuckle, European spindle tree, etc.); the fourth one consists of tall grasses (wrestlers, spreading pine forest, forest chase, etc.); the fifth tier is composed of lower grasses (common runny, hairy sedge, perennial forested forest, etc.); in the sixth tier - the lowest grasses, such as the European clefthoof. The undergrowth of trees and shrubs can be of different ages and sizes and do not form special layers. The most multi-tiered rainforests are rainforests, the least - artificial forest plantations (Fig. 81, 82).

There is always and in the woods inter-tiered (out-of-tier) plants - these are algae and lichens on the trunks and branches of trees, higher spore and flowering epiphytes, vines, etc.

Rice. 81. The multi-tiered rainforest of the Central Amazon. Vegetation of the strip 20 m long and 5 m wide

Rice. 82. Single-storey planted spruce forest. Monocultures of different ages

Tiering allows plants to more fully use the light flux: under the canopy of tall plants, shade-tolerant ones, up to shade-loving ones, can exist, intercepting even weak sunlight.

Layering is also expressed in herbaceous communities (meadows, steppes, savannas), but not always clearly enough (Fig. 83). In addition, they usually have fewer tiers than forests. However, in forests, there are sometimes only two clearly defined tiers, for example, in a white-moss forest (arboreal, formed by pine, and ground - from lichens).

Rice. 83. Layering of vegetation of the meadow steppe (after V.V. Alekhin, A.A.Uranov, 1933)

The tiers are distinguished according to the bulk of the assimilating organs of plants, which have a great influence on the environment. The vegetation layers can be of different lengths: the arboreal layer, for example, is several meters thick, and the moss cover is only a few centimeters thick. Each tier participates in its own way in creating a phytoclimate and is adapted to a specific set of conditions. For example, in a spruce forest, plants of the herb-dwarf shrub layer (oxalis, double-leaved mine, bilberry, etc.) are in conditions of dim lighting, equal temperatures (lower during the day and higher at night), weak wind, high humidity and CO2 content. Thus, the arboreal and grass-shrub layers are in different ecological conditions, which affects the functioning of plants and the life of animals living within these layers.

The underground layering of phytocenoses is associated with different rooting depths of the plants that make up their composition, with the location of the active part of the root systems. In forests, several (up to six) underground levels can often be observed.

Animals are also predominantly confined to one or another layer of vegetation. Some of them do not leave the corresponding tier at all. For example, the following groups are distinguished among insects: soil inhabitants - geobium, ground, surface layer - herpetobium, moss layer - briobium, grass stand - phyllobium, higher tiers - aerobic. Among the birds there are species that nest only on the ground (chickens, grouse, skates, buntings, etc.), others - in the shrub layer (songbirds, bullfinches, warblers) or in tree crowns (finches, kinglets, goldfinches, large predators, etc. .).

Dissection in the horizontal direction - mosaic - is characteristic of almost all phytocenoses, therefore, structural units are distinguished within them, which have received different names: microgroups, microcenoses, microphytocenoses, parcels, etc. These microgroups differ in species composition, quantitative ratio of different species, closeness, productivity and other properties.

Mosaicity is due to a number of reasons: the heterogeneity of the microrelief, soils, the environment-forming influence of plants and their biological characteristics. It can arise as a result of the activity of animals (the formation of soil emissions and their subsequent overgrowth, the formation of anthills, trampling and grazing of grass by ungulates, etc.) or humans (selective felling, fireplaces, etc.), as a result of tree felling during hurricanes, etc. ...

AA Uranov substantiated the concept of "phytogenic field". This term denotes that part of the space, which is affected by an individual plant, shading it, removing mineral salts, changing the temperature and moisture distribution, supplying litter and metabolic products, etc. the structure of phytocenoses.

Changes in the environment under the influence of the vital activity of individual plant species create the so-called phytogenic mosaicity. It is well expressed, for example, in mixed coniferous-deciduous forests (Fig. 84). Spruce is stronger than deciduous trees, shades the soil surface, retains more rain moisture and snow with its crowns, spruce litter decomposes more slowly, contributes to podzolization of the soil. As a result, nemoral grasses grow well in spruce-deciduous forests under broadleaved species and aspen, and typical boreal species under spruce.

Due to the differences in the environment-forming activity of different plant species, individual areas in the spruce-broad-leaved forest differ in many physical conditions (illumination, the thickness of the snow cover, the amount of litter, etc.), therefore life in them goes on differently: the herbage, undergrowth, root systems of plants, small animals, etc.

Rice. 84. Phytogenic mosaic of the lipo-spruce forest (after N.V. Dylis, 1971). Plots: 1 - spruce-hairy-sedge; 2 - spruce-mossy; 3 - dense spruce undergrowth; 4 - spruce-linden; 5 - aspen undergrowth; 6 - aspen-runny; 7 - large fern in the window; 8 - spruce-shchitnikovy; 9 - horsetail in the window

Mosaicity, like tiering, is dynamic: some microgroups are replaced by others, they grow or shrink in size.

7.2.3. Ecological structure of biocenosis

Different types of biocenoses are characterized by a certain ratio of ecological groups of organisms, which expresses ecological structure community. Biocenoses with a similar ecological structure can have a different species composition.

Species that perform the same functions in similar biocenoses are called vicarious (i.e., replacing). The phenomenon of ecological vicariate is widespread in nature. For example, marten in the European and sable in the Asian taiga, bison in the prairies of North America, antelopes in the savannas of Africa, wild horses and kulans in the steppes of Asia play a similar role. The specific species for the biocenosis is to a certain extent a random phenomenon, since communities are formed from those species that are in the environment. But the ecological structure of biocenoses that develop in certain climatic and landscape conditions is strictly natural. So, for example, in biocenoses of different natural zones, the ratio of phytophages and saprophages naturally changes. In steppe, semi-desert and desert regions, phytophagous animals prevail over saprophages, in forest communities of the temperate zone, on the contrary, saprophagy is more developed. The main type of food for animals in the depths of the ocean is predation, while in the illuminated, surface zone of the pelagic zone, there are many filter feeders that consume phytoplankton, or species with a mixed diet. The trophic structure of such communities is different.

The ecological structure of communities is also reflected by the ratio of such groups of organisms as hygrophytes, mesophytes and xerophytes among plants or hygrophils, mesophiles and xerophiles among animals, as well as the spectra of life forms. It is quite natural that in dry arid conditions, the vegetation is characterized by a predominance of sclerophytes and succulents, and in highly humid biotopes, hygrophytes and even hydrophytes are richer. The diversity and abundance of representatives of a particular ecological group characterize a biotope no less than accurate measurements of the physical and chemical parameters of the environment.

This approach to the assessment of biocenoses, which uses the general characteristics of its ecological, species and spatial structure, ecologists call macroscopic. This is a generalized large-scale characteristic of communities, which makes it possible to navigate the properties of the biocenosis when planning economic activities, to predict the consequences of anthropogenic impacts, and to assess the stability of the system.

Microscopic approach- this is a deciphering of the connections of each individual species in the community, a detailed study of the finest details of its ecology. This task has not yet been completed for the overwhelming majority of species due to the extraordinary diversity of living forms in nature and the laboriousness of studying their ecological characteristics.

7.3. Relationships of organisms in biocenoses

The basis for the emergence and existence of biocenoses is represented by the relationships of organisms, their connections, in which they enter with each other, inhabiting the same biotope. These connections determine the basic living conditions of species in the community, the possibility of obtaining food and conquering new space.

Predators usually refers to animals that feed on other animals, which they capture and kill. Predators are characterized by special hunting behavior.

The extraction of a victim requires from them a significant expenditure of energy for searching, chasing, capturing, overcoming the resistance of the victims.

If the size of the prey is much smaller than the size of the animals that feed on them, the number of food items is high and they themselves are easily accessible - in this case, the activity of the carnivorous species turns into a search and simple collection of prey and is called gathering.

Gathering requires the expenditure of energy mainly to search, not to capture food. Such "gathering" is typical, for example, for a number of insectivorous birds - plovers, plovers, finches, skates, etc. However, between typical predation and typical gathering in carnivores, there are many intermediate ways of obtaining food. For example, a number of insectivorous birds are characterized by hunting behavior when catching insects (swifts, swallows). Shrikes, flycatchers lie in wait and then catch up with the prey as typical predators. On the other hand, the way of feeding carnivorous gatherers is very similar to the collection of motionless food by herbivorous animals, for example, seed-eating birds or rodents (turtledove, rock dove, lentils, wood mouse, hamsters, etc.), which are also characterized by specialized search forms of behavior.

Gathering can include filtration nutrition of aquatic animals, sedimentation, or sedimentation of water suspension, collection of food by silt-eaters or earthworms. The so-called plant predation is also adjacent to it. In many plants, with a lack of nitrogen in their nutrition, methods have been developed for capturing and fixing insects arriving at them and for digesting the proteins of their bodies with proteolytic enzymes (pemphigus, sundew, nepentes, Venus flytrap, etc.).

By the way of mastering food objects, gathering approaches the typical pasture phytophages. The specificity of grazing consists in eating stationary food, which is in relative abundance, and you do not have to spend a lot of effort looking for it. From an ecological point of view, this way of feeding is typical both for a herd of ungulates in a meadow, and for leaf-gnawing caterpillars in the crown of a tree or larvae of ladybirds in aphid colonies.

With a passive method of defense, protective coloration, hard shells, spines, needles, instincts for concealing, using shelters inaccessible to predators, etc. develop. Some of these methods of defense are characteristic not only for sedentary or sedentary species, but also for animals actively fleeing from enemies.

The defensive adaptations of potential victims are very diverse, sometimes very complex and unexpected. For example, cuttlefish, fleeing from a pursuing predator, empty their ink sac. According to the hydrodynamic laws, the liquid thrown out of the bag by a fast-swimming animal does not spread out for some time, acquiring the shape of a streamlined body close in size to the cuttlefish itself. Deceived by the dark outline that appeared in front of his eyes, the predator “grabs” the ink liquid, the narcotic effect of which temporarily deprives him of the opportunity to navigate in the environment. The method of protection in puffer fish is peculiar. Their shortened body is covered with adjoining spines. A large bag extending from the stomach allows these fish, in case of danger, to swell into a ball, swallowing water; at the same time, their needles are straightened and make the animal practically invulnerable to a predator. An attempt by a large fish to grab a blowfish can end in death for it from a thorny ball stuck in its throat.

In turn, the difficulty of detecting and capturing prey contributes to the selection of predators for the best development of the sense organs (vigilance, subtle hearing, flair, etc.), for a faster reaction to prey, endurance in pursuit, etc. Thus, ecological relationships between predators and prey guide the evolution of related species.

Predators usually have a wide range of food. The extraction of victims requires a lot of strength and energy. Specialization would make predators highly dependent on the number of a certain prey species. Therefore, most of the species leading a predatory lifestyle are able to switch from one prey to another, especially to the one that is more accessible and abundant in a given period. True, many predators have preferred prey species, which they prey more often than others. This selectivity can be due to various reasons. First, the predator actively chooses the most nutritious food in terms of food. For example, diving ducks and whitefish in northern reservoirs are chosen from among aquatic invertebrates mainly the larvae of chironomid mosquitoes (bloodworms), and their stomachs are sometimes filled with bloodworms, despite the presence of other food in the reservoir.

The nature of the food may also be due to passive selectivity: the predator primarily eats such food for the prey of which it is most adapted. For example, many passerines feed on all insects that live openly on the soil surface, on grass, leaves, etc., but do not eat soil invertebrates, for which special devices are needed. Finally, the third reason for the food selectivity of predators may be active switching to the most massive prey, the appearance of which stimulates hunting behavior. With a high number of lemmings, even peregrine falcons, whose main method of hunting is to catch birds in the air, begin to hunt lemmings, seizing them from the ground. The ability to switch from one type of prey to another is one of the necessary ecological adaptations in the life of predators.

7.3.2. Commensalism

Commensalism - this is a form of relationship between two species, when the activity of one of them delivers food or shelter to the other (to the commensal). In other words, commensalism is the unilateral use of one species by another without harming it. Commensalism, based on the consumption of food leftovers from the owners, is also called parasitism. Such, for example, is the relationship between lions and hyenas, picking up the remains of the prey that have not been eaten by lions. The commensals of large sharks are the accompanying fish, adhered, etc. The attitude of parasailing is established even between insects and some plants. In the liquid of pitchers of insectivorous nepentes, dragonfly larvae live, protected from the digestive action of plant enzymes. They feed on insects that end up in trapping jars. Excreta consumers are also commensals of other kinds.

The use of shelters is especially developed either in buildings or in bodies of other types. Such commensalism is called lodging. Fieraster fish hide in the aquatic lungs of sea cucumbers, juveniles of other fish - under the umbrellas of jellyfish protected by stinging threads. Commensalism is the settlement of epiphytic plants on the bark of trees. In the nests of birds, holes of rodents, a huge number of arthropod species live, using the microclimate of shelters and finding food there due to decaying organic remains or other species of cohabitants. Many species are specialized in this way of life and do not occur outside their burrows at all. Permanent burrowing or nesting cohabitants received the name nidicolov.

Relationships such as commensalism are very important in nature, as they contribute to closer cohabitation of species, more complete development of the environment and the use of food resources.

Often, however, commensalism is transformed into other types of relationships. For example, in the nests of ants, among a large number of their cohabitants, there are species of rove beetles from the genera Lomechusa and Atemeles. Their eggs, larvae and pupae are kept together with juvenile ants, which take care of them, lick and transfer them to special chambers. The ants also feed adult beetles. However, beetles and their larvae eat the eggs and larvae of the hosts, without meeting any resistance from their side. On the sides of the chest and the first segments of the abdomen, these beetles have special outgrowths - trichomes, at the base of which droplets of secretion are secreted, extremely attractive to ants. The secret contains ethers, which have an intoxicating, narcotic effect on ants, similar to the effect of alcohol. Ants constantly lick Lomehus and Atemeles. As a result, their instincts are upset, coordination of movements is disturbed, and even some morphological changes appear. Working ants in families with many Lomehus are inactive and lethargic. Families become small and die as a result.

7.3.3. Mutualism

A typical symbiosis is represented by the relationship between termites and their intestinal cohabitants - the flagellate order Hypermastigina. These protozoa produce the enzyme b-glucosidase, which converts fiber into sugars. Termites do not have their own intestinal enzymes for digesting cellulose and without symbionts they die of hunger. Young termites emerging from eggs lick the anus of adults, infecting themselves with flagellates. Flagellates find in the intestines of termites a favorable microclimate, protection, food and conditions for reproduction. In a free-living state, they do not actually occur in nature.

Intestinal symbionts involved in the processing of coarse plant feed have been found in many animals: ruminants, rodents, grinder beetles, May beetle larvae, etc. Species that feed on the blood of higher animals (ticks, leeches, etc.), as a rule, have symbionts, helping to digest it.

In multicellular animals and plants, symbiosis with microorganisms is very widespread. Many tree species are known to cohabit with mycorrhizal fungi, leguminous plants - with the nodule bacteria Rhizobium, which fix the molecular nitrogen of the air. Nitrogen-fixing symbionts were found on the roots of about 200 species of other groups of angiosperms and gymnosperms. Symbiosis with microorganisms sometimes goes so far that colonies of symbiotic bacteria can be considered as specialized organs of multicellular organisms. Such, for example, are the mycetomas of cuttlefish and some squid - sacs filled with luminous bacteria and which are part of the organs of luminescence - photophores.

The line between symbiosis and other types of relationships is sometimes rather arbitrary. It is interesting to use their intestinal microflora by lagomorphs and some rodents. In rabbits, hares, pikas, regular eating of their own feces was found. Rabbits produce two types of excrement: dry and soft, mucous membranes. They lick soft feces directly from the anus and swallow without chewing. Studies have shown that this coprophagia is quite natural. Rabbits, deprived of the opportunity to consume soft feces, lose weight or gain poorly in weight and are more likely to be susceptible to various diseases. Soft feces of rabbits are almost unchanged contents of the cecum, enriched with vitamins (mainly B 12) and protein substances. The cecum of lagomorphs is a fermentation vat for processing fiber and is saturated with symbiotic microorganisms. There are up to 10 billion bacteria in 1 g of soft feces. Getting into the stomach of a rabbit together with feces, microorganisms are completely killed under the influence of acid and are digested in the stomach and long small intestine. Thus, in exclusively herbivorous lagomorphs, coprophagia is a way of obtaining essential amino acids.

Less obligatory, but extremely essential, is the mutualistic relationship between the Siberian cedar pine and the birds nesting in the cedar forests — the nutcracker, nuthatch, and kuksa. These birds, feeding on pine seeds, have instincts for storing food. They hide small portions of "nuts" under a layer of moss and forest litter. A significant part of the stock is not found by birds, and the seeds germinate. The activity of these birds, thus, contributes to the self-renewal of cedar forests, since the seeds cannot germinate on a thick layer of forest litter, which blocks their access to the soil.

A mutually beneficial relationship is between plants that have succulent fruits and birds that feed on these fruits and spread seeds that are usually indigestible. Mutualistic relations with ants develop in many plants: about 3000 species are known that have adaptations for attracting ants. A typical example is cecropia, a tree native to the Amazon. Ants of the genera Azteca and Cramatogaster colonize the voids in the articulated trunk of the cecropia and feed on special rounded formations about 1 mm in diameter - "Müllerian bodies", which the plant produces on the bulges located on the outside of the leaf sheath. House ants vigilantly protect leaves from pests, especially from leaf-cutting ants of the genus Atta.

The more diverse and stronger the ties that support the cohabitation of species, the more stable their cohabitation. Communities with a long history of development are therefore more durable than those that arise after sudden disturbances in the natural environment or are created artificially (fields, orchards, vegetable gardens, greenhouses, greenhouses, aquariums, etc.).

7.3.4. Neutralism, amensalism

Neutralism - this is a form of biotic relations in which the cohabitation of two species on the same territory does not entail either positive or negative consequences for them. Under neutralism, the species are not directly related to each other, but depend on the state of the community as a whole. For example, squirrels and moose, living in the same forest, practically do not contact each other. However, the oppression of the forest by a prolonged drought or its exposure during mass reproduction of pests affects each of these species, although to a different extent. Relations of the type of neutralism are especially developed in species-rich communities, including members of different ecology.

At amensalism for one of the two interacting species, the consequences of cohabitation are negative, while the other receives neither harm nor benefit from them. This form of interaction is more common in plants. For example, light-loving herbaceous species growing under a spruce are oppressed as a result of strong shading by its crown, while their neighborhood may be indifferent to the tree itself.

Relationships of this type also lead to the regulation of the number of organisms, affect the distribution and mutual selection of species.

7.3.5. Competition

Competition - This is the relationship of species with similar ecological requirements existing at the expense of common resources that are in short supply. When such species live together, each of them is at a disadvantage, since the presence of the other reduces the opportunities for mastering food, shelter and other livelihoods that the habitat has. Competition is the only form of environmental relations that negatively affects both interacting partners.

Forms of competitive interaction can be very different: from direct physical struggle to peaceful coexistence. Nevertheless, if two species with the same ecological needs end up in the same community, sooner or later one competitor crowds out the other. This is one of the most general environmental rules, which is called competitive exclusion law and was formulated by GF Gause.

In a simplified form, it sounds like "two competing species do not get along together."

The incompatibility of competing species was emphasized even earlier by Charles Darwin, who considered competition to be one of the most important components of the struggle for existence, playing a large role in the evolution of species.

In the experiments of GF Gause with the cultures of the slippers of Paramecium aurelia and P. caudatum, each of the species, placed separately in test tubes with hay infusion, multiplied successfully, reaching a certain level of abundance. If both species with similar feeding patterns were placed together, then at first there was an increase in the number of each of them, but then the number of P. caudatum gradually decreased, and they disappeared from the infusion, while the number of P. aurelia remained constant (Fig. 86).

Rice. 86. Growth in the number of ciliates Paramaecium caudatum (1) and P. aurelia (2) (according to GF Gause from F. Dre, 1976): A - in a mixed culture; B - in separate cultures

The winner in the competition is, as a rule, the species that, in a given ecological situation, has at least small advantages over another, that is, it is more adapted to environmental conditions, since even closely related species never coincide across the entire ecological spectrum. So, in the experiments of T. Parkas with laboratory cultures of flour beetles, it was revealed that the result of competition can be determined by the temperature and humidity at which the experiment proceeds. In numerous cups of flour, in which were placed several specimens of two species of beetles (Tribolium confusum and T. castaneum) and in which they multiplied, after a while only one of the species remained. At high temperature and humidity of flour it was T. castaneum, at lower temperature and moderate humidity it was T. confusum. However, with average values ​​of factors, the “victory” of one type or another was clearly random, and it was difficult to predict the outcome of competition.

The reasons for the displacement of one species by another can be different. Since the ecological spectra of even closely related species never coincide completely, despite the general similarity of requirements for the environment, the species still differ in some way from each other. Even if such species coexist peacefully together, but the intensity of reproduction of one is slightly more than the other, then the gradual disappearance of the second species from the community is only a matter of time, since with each generation more and more resources are captured by a more competitive partner. Often, however, competitors actively influence each other.

In plants, the suppression of competitors occurs as a result of the interception of mineral nutrients and soil moisture by the root system and sunlight by the leaf apparatus, as well as as a result of the release of toxic compounds. For example, in mixed crops of two types of clover, Trifolium repens forms a leaf canopy earlier, but then it is shaded by T. fragiferum, which has longer petioles. When duckweed Lemna gibba and Spirodela polyrrhiza are grown together, the number of the second species first increases and then decreases, although in pure crops the growth rate of this species is higher than that of the first. The advantages of L. gibba in this case are that in conditions of thickening, it develops aerenchyma, which helps to stay on the surface of the water. S. polyrrhiza, which lacks aerenchyma, is pushed down and shaded by a competitor.

The chemical interactions of plants through their metabolic products are called allelopathy. Similar ways of influencing each other are characteristic of animals. In the above experiments of GF Gause and T. Park, suppression of competitors occurred mainly as a result of the accumulation of toxic metabolic products in the environment, to which one of the species is more sensitive than the other. Higher plants with a low demand for nitrogen, the first to appear on fallow soils, suppress the formation of nodules in legumes and the activity of free-living nitrogen-fixing bacteria by root excretions. By preventing the enrichment of the soil with nitrogen, they gain an advantage in competition with plants that need a large amount of nitrogen in the soil. Cattail in overgrown water bodies is allelopathically active in relation to other aquatic plants, which allows it, avoiding competitors, to grow in almost clean thickets.

In animals, there may be cases of direct attack by one species on another in a competitive struggle. For example, the larvae of the egg-eaters Diachasoma tryoni and Opius humilis, caught in the same host egg, fight each other and kill the rival before starting to feed.

The possibility of competitive displacement of one species by another is the result of ecological individuality of species. In unchanged conditions, they will have different competitiveness, since they necessarily differ from each other in tolerance to any factors. In nature, however, in most cases, the environment is changeable both in space and in time, and this makes it possible for many competitors to coexist. For example, if weather conditions more or less regularly change in favor of one or another species, the beginning processes of displacing each other by them do not reach the end and change their sign to the opposite. So, in wet years, mosses can grow in the lower tier of the forest, and in dry years they are pressed by the cover of hairy sedges or other grasses. These species also coexist in one phytocenosis, occupying forest areas with different moisture conditions. In addition, species competing not for one but for several resources often have different thresholds of limiting factors, which also prevents the completion of competitive exclusion processes. Thus, the American ecologist D. Tilman, cultivating two species of diatoms together, found that they do not displace each other, because they have different sensitivity to the lack of nitrogen and silicon. A species that is able to reproduce ahead of another at a low nitrogen content cannot achieve this due to a lack of silicon for it, while its competitor, on the contrary, has enough silicon, but little nitrogen.

Competing species can get along in the community even if the increase in the number of a stronger competitor is not allowed by the predator. In this case, the activity of the predator leads to an increase in the species diversity of the community. In one of the experiments from the bottom of the coastal area of ​​the sea, where 8 species of sessile invertebrates lived - mussels, sea acorns, sea ducks, chitons - a predator, a starfish, which ate mainly mussels, was removed. After a while, mussels occupied the entire area of ​​the bottom, displacing all other species.

Thus, biocenoses in each group of organisms contain a significant number of potential or partial competitors, which are in dynamic relations with each other. A species may not have strong rivals either, but it may be slightly influenced by each of the many others, partly using its resources. In this case, they talk about "Diffuse" competition, the outcome of which also depends on many circumstances and may end with the displacement of this species from the biocenosis.

Competition, therefore, has a double meaning in biocenoses. It is a factor that largely determines the species composition of communities, since intensely competing species do not get along together. On the other hand, partial or potential competition allows species to quickly capture additional resources that are released when the activities of neighbors are weakened and replace them in biocenotic connections, which preserves and stabilizes the biocenosis as a whole.

As with any form of biotic relationship, competition is often difficult to separate from other types of relationship. In this regard, the behavioral features of ecologically similar ant species are indicative.

Large meadow ants Formica pratensis build bulk nests and guard the area around them. In the smaller F. cunicularia, the nests are small, in the form of earthen mounds. They often settle on the periphery of the nesting territory of meadow ants and hunt in their foraging areas.

With the experimental isolation of meadow ant nests, the hunting efficiency of F. cunicularia increases 2–3 times. The ants produce larger insects, which are usually prey for F. pratensis. If F. cunicularia nests are isolated, the production of meadow ants does not increase, as one would expect, but halves. It turned out that the more mobile and active foragers of F. cunicularia serve as stimulators of the search activity of meadow ants, a kind of scouts for protein food. The intensity of movement of foragers of meadow ants along the roads in those sectors where there are nests of F. cunicularia is 2 times higher than where they are not. Thus, the overlap of the hunting territory and food spectra allows us to consider F. cunicularia as a competitor to meadow ants, but an increase in the efficiency of F. pratensis hunting indicates the benefits of F. cunicularia stay on their territory.

Rice. 87. A female deep-sea anglerfish with three males attached to it

Mutualistic and competitive relationships are the main essence of intraspecific relationships. The study of the role of these relationships within the species, diversity and specificity of their forms is the subject of a special section of synecology - ecology of populations.

As can be seen from the above examples, the formal classification of the types of biotic connections cannot fully reflect all their diversity and complexity in living nature, but still allows one to navigate in the main types of interaction between organisms. Other classifications draw attention to other aspects of biotic relationships using different approaches.

VN Beklemishev subdivided relations between species in a community into direct and indirect. Direct connections arise from direct contact of organisms. Indirect links represent the influence of species on each other through the habitat or by affecting third species.

According to the classification of V.N. Beklemishev, direct and indirect interspecific relations, according to the value they may have in the biocenosis, are divided into four types: trophic, topical, phoric, and factory.

7.3.6. Trophic connections

Trophic connections arise when one species feeds on another - either living individuals, or their dead remains, or waste products. And dragonflies, catching other insects on the fly, and dung beetles, feeding on the droppings of large ungulates, and bees collecting plant nectar, enter into a direct trophic relationship with the species that provide them with food. In the case of competition between two species due to food objects, an indirect trophic relationship arises between them, since the activity of one is reflected in the supply of food to the other. Any effect of one species on the consumption of another or the availability of food for it should be regarded as an indirect trophic relationship between them. For example, caterpillars of nun butterflies, eating pine needles, facilitate access to weakened trees for bark beetles.

Trophic connections are the main ones in communities. It is they who unite the species living together, since each of them can live only where there are food resources it needs. Any species is not only adapted to certain food sources, but also itself serves as a food resource for others. Food interactions create a food web in nature, which ultimately extends to all species in the biosphere. The image of this food web can be recreated by placing any species in the center and connecting it with arrows to all others that are in direct or indirect food relations with it (Fig. 88), and then continue this procedure for each species involved in the scheme. As a result, all wildlife will be covered, from whales to bacteria. As the studies of Academician A. M. Ugolev have shown, there is "an extraordinary uniformity of the properties of assimilation systems at the molecular and supramolecular levels in all organisms of the biosphere," which allows them to receive energy resources from each other. He argues that behind the endless variety of types of nutrition there are common fundamental processes that form a single system of trophic interactions on a planetary scale.

Rice. 88. Herring food links are part of the ocean food web

Any biocenosis is permeated with food connections and is a more or less localized in space section of a common food web that connects all life on Earth.

7.3.7. Topical connections

Individual consortia can be of varying degrees of complexity. The largest number of consortium connections are those plants that play the main role in creating the internal environment of the biocenosis. Since each member of a large consortium can, in turn, be the center of a smaller association, consortia of the first, second and even third order can be distinguished. Thus, a biocenosis is a system of interconnected consortia that arise on the basis of the closest topical and trophic relationships between species. Consort relationships, which are based on topical relationships, form a kind of block structure of the biocenosis.

Topical and trophic relationships are of the greatest importance in the biocenosis, they form the basis of its existence. It is these types of relationships that keep organisms of different species close to each other, uniting them into fairly stable communities of different scales.

7.3.8. Phoric connections

Phoric connections Is the participation of one species in the spread of another. Animals act as transporters. The transfer of seeds, spores, pollen by animals is called zoochory, transfer of other, smaller animals - phoresis (from lat. foras- out, out). The transfer is usually carried out with the help of special and various devices. Animals can capture plant seeds in two ways: passive and active. Passive seizure occurs when the body of an animal accidentally touches a plant, the seeds or seedlings of which have special hooks, hooks, outgrowths (string, burdock). They are usually distributed by mammals, which sometimes carry such fruits on wool over rather long distances. An active way of capturing is eating fruits and berries. Animals shed non-digestible seeds with their droppings. Insects play an important role in the transfer of fungal spores. Apparently, the fruiting bodies of fungi arose as formations attracting settling insects.

Rice. 89. Phoresia of mites on insects:

1 - the deutonymph of the uropod mite is attached to the beetle with a stalk of hardened secretory fluid;

2 - phoresis of ticks on ants

Phoresia of animals is widespread mainly among small arthropods, especially among various groups of ticks (Fig. 89). It represents one of the methods of passive dispersal and is characteristic of species for which transfer from one biotope to another is vital for conservation or prosperity. For example, many flying insects - visitors to accumulations of rapidly decaying plant debris (carcasses of animals, ungulate droppings, heaps of rotting plants, etc.) carry gamasid, uropodic or thyroglyphoid mites, which migrate in this way from one accumulation of food materials to another. Their own resettlement opportunities do not allow these species to cover significant distances for them. Dung beetles sometimes crawl with raised elytra, which are unable to fold due to mites densely dotted with body. Some types of nematodes spread to insects by means of phoresia (Fig. 90). The legs of dung flies often look like lamp brushes due to the abundance of nematodrabditids attached to them. Among large animals, phoresia is almost never found.

Rice. 90. Dissemination of nematode larvae on beetles:

1 - larvae waiting for the settler;

2 - larvae attached under the beetle's elytra

7.3.9. Factory connections

Factory connections - this is a type of biocenotic relationship that a species enters into, which uses excretion products for its structures (fabrications), or dead remains, or even living individuals of another species. For example, birds use tree branches, mammalian wool, grass, leaves, down and feathers of other bird species, etc. to build nests. Caddis larvae build houses from pieces of branches, bark or leaves of plants, from the shells of small types of coils, capturing even shells with live shellfish. The megahila bee places eggs and supplies in cups made from soft leaves of various shrubs (rose hips, lilacs, acacia, etc.).

Rice. 91. Scheme of the influence of pH on the growth of various plants when grown in single-species crops and under competitive conditions:

1 - curves of the physiological optimum;

2 - synecological optimum (according to V. Larher, 1978)

The position of the species that it occupies in the general system of biocenosis, the complex of its biocenotic relationships and requirements for abiotic environmental factors are called ecological niche species.

The concept of an ecological niche has proven to be very fruitful for understanding the laws of species living together. Many ecologists have worked on its development: J. Grinnell, C. Elton, G. Hutchinson, J. Odum, and others.

Ecological niche should be distinguished from habitat. In the latter case, it means that part of the space that is inhabited by the species and which has the necessary abiotic conditions for its existence. The ecological niche of a species depends not only on the abiotic conditions of the environment, but also, to no less extent, on its biocenotic environment. The nature of the occupied ecological niche is determined both by the ecological possibilities of the species and by the extent to which these possibilities can be realized in specific biocenoses. This is a characteristic of the way of life that a species can lead in a given community.

G. Hutchinson put forward the concept of a fundamental and realized ecological niche. Under fundamental the whole set of conditions under which a species can successfully exist and reproduce is understood. In natural biocenoses, however, species do not master all the resources suitable for them due, first of all, to competitive relations. Realized ecological niche - This is the position of the species in a specific community, where it is limited by complex biocenotic relationships. In other words, the fundamental ecological niche characterizes the potential of the species, and the realized one - that part of them that can be realized under the given conditions, given the availability of the resource. Thus, the realized niche is always less than the fundamental one.

In ecology, the question of how many ecological niches a biocenosis can accommodate and how many species of a particular group with similar environmental requirements can live together is widely discussed.

The specialization of a species in nutrition, use of space, time of activity, and other conditions is characterized as a narrowing of its ecological niche, the reverse processes - as its expansion. Competitors have a great influence on the expansion or narrowing of the ecological niche of the species in the community. Competitive exclusion rule, formulated by GF Gause for ecologically close species, it can be expressed in such a way that two species do not get along in one ecological niche.

Experiments and observations in nature show that in all cases when species cannot avoid competition for basic resources, weaker competitors are gradually pushed out of the community. However, in biocenoses, there are many opportunities for at least partial delimitation of ecological niches of ecologically close species.

The way out of competition is achieved due to the divergence of requirements for the environment, a change in lifestyle, which, in other words, is the delineation of ecological niches of species. In this case, they acquire the ability to coexist in the same biocenosis. Each of the species living together, in the absence of a competitor, is capable of a more complete use of resources. This phenomenon is easy to observe in nature. Thus, spruce herbaceous plants are able to be content with a small amount of soil nitrogen, which remains from the interception of it by tree roots. However, if the roots of these spruces are chopped off in a limited area, the conditions for nitrogen nutrition of the grasses are improved and they grow vigorously, taking on a dense green color. Improvement of living conditions and an increase in the number of a species as a result of the removal from the biocenosis of another, close in ecological requirements, is called competitive release.

The division by co-living species of ecological niches with their partial overlap is one of the mechanisms of stability of natural biocenoses. If any of the species sharply decreases its number or drops out of the community, others take on its role. The more species there are in the biocenosis, the lower the number of each of them, the more pronounced their ecological specialization. In this case, one speaks of “denser packing of ecological niches in the biocenosis”.

In closely related species living together, very fine delineations of ecological niches are usually observed. So, ungulates grazing in the African savannas use pasture food in different ways: zebras cut off mainly the tops of grasses, wildebeests feed on what the zebras leave them, while choosing certain types of plants, gazelles pluck out the lowest grasses, and swamp antelopes are content with high dry stems left over from other herbivores. The same "division of labor" in the southern European steppes was once carried out by wild horses, marmots and ground squirrels (Fig. 92).

Rice. 92. Different types of herbivores eat grass at different heights in the African savannas (upper rows) and in the steppes of Eurasia (lower rows) (after F.R.Fuente, 1972; B.D. Abaturov, G.V. Kuznetsov, 1973)

In our winter forests, tree-feeding insectivorous birds also avoid competition with each other due to their different search patterns. For example, nuthatches and pikas collect food on trunks. At the same time, nuthatches rapidly inspect the tree, quickly seizing insects or seeds that come across large cracks in the bark, while small pikas carefully rummage the slightest cracks on the surface of the trunk, into which their thin awl-shaped beak penetrates. In winter, in mixed flocks, great tits search extensively in trees, bushes, stumps, and often in the snow; titmouse-chicks mainly examine large branches; long-tailed tits seek food at the ends of branches; small beads carefully ransack the upper parts of the coniferous crowns.

Ants exist in natural conditions in multi-species associations, the members of which differ in their way of life. In the forests of the Moscow Region, the following association of species is most often found: the dominant species (Formica rufa, F. aquilonia, or Lasius fuliginosus) occupies several tiers, L. flavus is active in the soil, Myrmica rubra is active in the forest litter, L. niger and F. fusca, trees - Camponotus herculeanus. Specialization to life in different tiers is reflected in the life form of the species. In addition to separation in space, ants also differ in the nature of obtaining food, in the time of daily activity.

In deserts, the most developed complex of ants collecting food on the soil surface (herpetobionts). Among them, representatives of three trophic groups stand out: 1) daytime zooonecrophages are active in the hottest time, feed on the corpses of insects and small live insects that are active during the day; 2) nocturnal zoophages - they hunt sedentary insects with soft covers that appear on the surface only at night, and molting arthropods; 3) carpophages (day and night) - they eat plant seeds.

Several species from one trophic group can live together. The mechanisms for getting out of competition and delimiting ecological niches are as follows.

1. Dimensional differentiation (fig. 93). For example, the average weights of workers of the three most common daytime zooonecrophages in the sands of the Kyzyl Kum desert are 1: 8: 120. Approximately the same ratio of weights in a medium-sized cat, lynx and tiger.

Rice. 93. Comparative sizes of four species of ants from the group of daytime zooonecrophages in the sandy desert of the Central Karakum desert and the distribution of prey of three species by weight classes (according to G.M.Dlussky, 1981): 1 - medium and large workers Cataglyphis setipes; 2 - C. pallida; 3 - Acantholepis semenovi; 4 - Plagiolepis pallescens

2. Behavioral differences consist in different foraging strategies. The ants that create roads and use the mobilization of carriers to transport discovered food to the nest feed mainly on the seeds of the clumping plants. Ants, whose foragers work as solitary collectors, collect mainly seeds from dispersed plants.

3. Spatial differentiation. Within the same tier, food collection by different species can be confined to different areas, for example, in open places or under wormwood bushes, on sandy or clay areas, etc.

4. Differences in activity times They mainly relate to the time of day, but in some species mismatches in activity and seasons of the year (mainly spring or autumn activity) were noted.

Ecological niches of species are variable in space and time. They can be sharply differentiated in individual development, depending on the stage of ontogenesis, as, for example, in caterpillars and adults of lepidoptera, larvae and beetles of May beetle, tadpoles and adult frogs. In this case, both the habitat and the entire biocenotic environment change. In other species, the ecological niches occupied by young and adult forms are closer, but nevertheless, there are always differences between them. Thus, adult perches and their fry living in the same lake use different energy sources for their existence and enter different food chains. The fry live off small plankton, the adults are typical predators.

The weakening of interspecific competition leads to the expansion of the ecological niche of the species. On oceanic islands with poor fauna, a number of birds, in comparison with their relatives on the mainland, inhabit more diverse habitats and expand the range of food, since they do not collide with competing species. In island inhabitants, there is even an increased variability in the shape of the beak as an indicator of the expansion of the nature of food connections.

If interspecific competition narrows the ecological niche of a species, preventing all its potencies from manifesting itself, then intraspecific competition, on the contrary, promotes the expansion of ecological niches. With the increased number of the species, the use of additional food begins, the development of new habitats, the emergence of new biocenotic relationships.

In reservoirs, plants completely submerged in water (elodea, hornwort, urut) find themselves in different conditions of temperature, illumination, gas regime than those floating on the surface (telores, vodokras, duckweed) or rooting at the bottom and carrying leaves to the surface (water lily, egg-capsule, victoria). They also differ in their relationships with the environment. Epiphytes of tropical forests occupy similar, but still not identical niches, since they belong to different ecological groups in relation to light and water (heliophytes and sciophytes, hygrophytes, mesophytes and xerophytes). Various epiphytic orchids have highly specialized pollinators.

In a mature broad-leaved forest, trees of the first tier - common oak, smooth elm, plane maple, heart-leaved linden, common ash - have similar life forms. The tree canopy formed by their crowns turns out to be in the same horizon, in similar environmental conditions. But close analysis shows that they participate in the life of the community in different ways and, therefore, occupy different ecological niches. These trees differ in the degree of light love and shade tolerance, the timing of flowering and fruiting, the methods of pollination and distribution of fruits, the composition of consorts, etc. Oak, elm and ash are anemophilic plants, but the saturation of the environment with their pollen occurs at different times. Maple and linden are entomophiles, good honey plants, but bloom at different times. The oak has zoochoria, the rest of the broad-leaved trees have anemochory. The composition of the consorts is different for everyone.

If in a broad-leaved forest the crowns of trees are in the same horizon, then the active root ends are located at different depths. The roots of the oak penetrate the deepest, the roots of the maple and even more superficially - the ash are located higher. The litter of different types of trees is utilized at different rates. Linden, maple, elm, ash leaves almost completely decompose by spring, and oak leaves still form a loose forest floor in spring.

In accordance with the ideas of L.G. Ramenskiy about the ecological individuality of species and taking into account the fact that plant species in the community participate in different ways in the development and transformation of the environment and the transformation of energy, it can be assumed that in the existing phytocenoses, each plant species has its own ecological niche ...

In ontogeny, plants, like many animals, change their ecological niche. As they age, they use and transform the environment more intensively. The transition of a plant to the generative period significantly expands the range of consorts, changes the size and intensity of the phytogenic field. The environment-forming role of aging, senile plants is decreasing. They lose many consorts, but the role of their associated destructors increases. Production processes are weakened.

In plants, there is an overlap of ecological niches. It increases in certain periods when environmental resources are limited, but since species use resources individually, selectively and with different intensities, competition in stable phytocenoses is weakened.

Rice. 94. Correlation between the diversity of deciduous layers and species diversity of birds (Shannon MacArthur indices from E. Pianca, 1981)

In phytocenology, classifications of plants have been developed according to their ability to grow together and coenotic significance. The general provisions of these classifications can be applied to animals, since they characterize a kind of strategy of species that determine their place in biocenoses. Most commonly used system of L. G. Ramensky and D. Grime.

Groups of plants that occupy a similar position in phytocenoses are called phytocoenotypes. L. G. Ramenskiy proposed to distinguish three types among co-living plants - violets, patents and explents. He popularly characterized them as siloviki, hardy and performing (i.e., filling free space), likening them to lions, camels and jackals. Violent have a high competitive ability in these conditions: "while vigorously developing, they capture the territory and hold it for themselves, suppressing, drowning out rivals with the energy of vital activity and the full use of environmental resources." Patents "In the struggle for existence ... they take it not by the energy of vital activity and growth, but by their endurance to extremely harsh conditions, permanent or temporary." They are content with the resources that remain from the violets. Explorents "Have a very low competitive power, but they are able to very quickly capture the liberated territories, filling the gaps between strong plants, they are just as easily displaced by the latter."

More detailed classifications also distinguish other, intermediate types. In particular, one can also distinguish the group pioneer species that quickly occupy newly emerging territories that have not yet had any vegetation. Pioneer species partially possess the properties of explents - low competitiveness, but, like patents, they have high endurance to the physical conditions of the environment.

In the 70s of the last century, 40 years after L.G. Ramenskiy, the identification of the same three phytocoenotypes was repeated by the botanist D. Greim, unfamiliar with his classification, denoting them with other terms: competitors, tolerants and ruderals.

Practically in any group of organisms, species similar in their ability to coexist are distinguished, therefore, the classification of coenotic strategies of Ramensky-Greim can be attributed to general ecological.

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Introduction

1. Biocenosis - general information and concepts

2. The structure of the biocenosis

3. Modern problems of biocenoses and ways to solve them

Conclusion

Bibliography

Introduction

A biocenosis is a historically formed set of animals, plants, fungi and microorganisms that inhabit a relatively homogeneous living space (a certain area of ​​land or water area), and are connected with each other and their environment. The concept of "biocenosis" is one of the most important in ecology, since it implies that living things form complexly organized systems on Earth, outside of which they cannot stably exist.

Biocenosis is one of the main objects of ecology research. Problems of stability of biocenoses, a decrease in the number of populations, the disappearance of whole species of living organisms are acute problems facing mankind today. Therefore, the study of biocenoses, their structure and conditions of sustainability is an important ecological task, which has been and continues to be given great attention by ecologists of all countries of the world, including Russian scientists.

In this work, I will dwell on such issues as the properties and structure of the biocenosis, the conditions for their stability, as well as the main modern problems and ways to solve them. It should be noted that in the mind of a person who is not an expert in the field of ecology, there is confusion in the concepts of "biocenosis", "ecosystem", "biogeocenosis", "biosphere", therefore I will briefly dwell on the issue of similarities and differences between these concepts and their interrelationships. Biocenosis is one of the main objects of ecology research. Ecologists of all countries of the world, including Russian scientists, have paid and continue to pay great attention to the study of biocenoses. In the process of working on the abstract, I used textbooks written by well-known foreign ecologists: Y. Odum, V. Tishler; and by Russian authors: Korobkin V.I., Peredelsky L.V., as well as modern electronic resources indicated in the list of references.

1. Bioc enosis - general information and concepts

Biocenosis (from the Greek. VYapt - "life" and kpint - "common") is a historically formed set of animals, plants, fungi and microorganisms that inhabit a relatively homogeneous living space (a certain area of ​​land or water area), and are interconnected and their environment. Biocenoses have arisen on the basis of the biogenic cycle and provide it in specific natural conditions. Biocenosis is a dynamic system capable of self-regulation, the components of which (producers, consumers, reducers) are interconnected.

The most important quantitative indicators of biocenoses are biodiversity (the total number of species in it) and biomass (the total mass of all types of living organisms in a given biocenosis).

The concept of “biocenosis” is one of the most important in ecology, since it implies that living things form complexly organized systems on Earth, outside of which they cannot stably exist. The main function of a community is to ensure equilibrium in an ecosystem based on a closed cycle of substances.

Biocenoses can include thousands of species of various organisms. But not all of them are equally significant. Removal from the community of some of them does not have a noticeable effect on them, while the removal of others leads to significant changes.

Some types of biocenosis can be represented by numerous populations, while others are small in number. The scale of biocenotic groups of organisms is very different - from communities of lichen cushions on tree trunks or a decaying stump to the population of entire landscapes: forests, steppes, deserts, etc.

The organization of life at the biocenotic level is subordinated to the hierarchy. With an increase in the scale of communities, their complexity and the proportion of indirect, indirect connections between species increase.

Natural associations of living beings have their own laws of functioning and development, i.e. are natural systems.

Thus, being, like organisms, structural units of living nature, biocenoses, nevertheless, develop and maintain their stability on the basis of other principles. They are systems of the so-called frame type - without special control and coordinating centers, and are also built on numerous and complex internal connections.

The most important features of systems related to the supraorganic level of organization of life, for example, according to the classification of the German ecologist W. Tischler, are the following:

1) Communities always arise, are made up of ready-made parts (representatives of various species or whole complexes of species) available in the environment. This is the way of their occurrence differs from the formation of a separate organism, which occurs through the gradual differentiation of the simplest initial state.

2) Parts of the community are interchangeable. Parts (organs) of any organism are unique.

3) If the whole organism maintains constant coordination, the consistency of the activity of its organs, cells and tissues, then the superorganismic system exists mainly due to the balancing of oppositely directed forces.

4) Communities are based on the quantitative regulation of the number of some species by others.

5) The limiting dimensions of an organism are limited by its internal hereditary program. The sizes of the superorganic systems are determined by external factors.

A homogeneous natural living space (part of the abiotic environment) occupied by a biocenosis is called a biotope. It can be a piece of land or a body of water, a seashore or a mountainside. Biotope is an inorganic environment, which is a prerequisite for the existence of a biocenosis. Biocenosis and biotope closely interact with each other.

The scale of biocenoses can vary - from communities of lichens on tree trunks, moss bumps in a swamp or decaying stump to populations of entire landscapes. So, on land, one can distinguish a biocenosis of a dry (not flooded with water) meadow, a biocenosis of a white moss pine forest, a biocenosis of a feather-grass steppe, a biocenosis of a wheat field, etc.

Distinguish between the concepts of "species richness" and "species diversity" of biocenoses. Species richness is a general set of species of a community, which is expressed by a list of representatives of different groups of organisms. Species diversity is an indicator reflecting not only the qualitative composition of the biocenosis, but also the quantitative relationships of species.

Distinguish between poor and species-rich biocenoses. The species composition of biocenoses, in addition, depends on the duration of their existence, the history of each biocenosis. Young, just emerging communities usually include a smaller set of species than long-established, mature ones. Biocenoses created by man (fields, orchards, vegetable gardens) are also poorer in species than natural systems similar to them (forest, steppe, meadow). Man maintains the uniformity and species poverty of agrocenoses with a special complex system of agrotechnical measures.

Almost all terrestrial and most aquatic biocenoses include microorganisms, plants and animals. The stronger the differences between two adjacent biotopes, the more heterogeneous the conditions at their borders and the stronger the border effect is. The number of a particular group of organisms in biocenoses strongly depends on their size. The smaller the individuals of the species, the higher their number in biotopes.

Groups of organisms of different sizes live in a biocenosis at different scales of space and time. For example, the life cycles of unicellular organisms can occur within an hour, and the life cycles of large plants and animals are stretched over tens of years.

Naturally, in all biocenoses, the smallest forms, bacteria and other microorganisms, prevail numerically. In each community, it is possible to distinguish a group of basic species, the most numerous in each size class, the connections between which are decisive for the functioning of the biocenosis as a whole. The dominant species (productivity) are the dominant species of the community. Dominants dominate the community and constitute the “species core” of any biocenosis.

For example, when studying a pasture, it was found that the maximum area in it is occupied by a bluegrass plant, and among the animals grazing there, there are most of all cows. This means that bluegrass dominates among producers, while cows dominate among consumers.

In the richest biocenoses, almost all species are few in number. In tropical forests, it is rare to find several trees of the same species nearby. In such communities, outbreaks of mass reproduction of certain species do not occur; biocenoses are highly stable.

The totality of all types of a community makes up its biodiversity. Typically, a community includes several major species with a high abundance and many rare species with a small abundance.

Biodiversity is responsible for the equilibrium state of the ecosystem, and therefore for its sustainability. The closed cycle of nutrients (biogens) occurs only due to biological diversity.

Substances that are not assimilated by some organisms are assimilated by others, therefore the release of nutrients from the ecosystem is small, and their constant presence ensures the balance of the ecosystem.

Human activities greatly reduce the diversity in natural communities, which requires forecasts and forecasts of its consequences, as well as effective measures to maintain natural systems.

1.1 Biocenosis, ecosystem, biosphere

Ecosystem (from ancient Greek pkpt - dwelling, dwelling place and ueufzmb - system) is a biological system consisting of a community of living organisms (biocenosis), their habitat (biotope), a system of connections that exchange matter and energy between them. Thus, the biocenosis is the main component of the ecosystem, its biotic component.

The ecological view of the world is based on the idea that every living creature is surrounded by many different factors influencing it, which form its habitat in a complex - a biotope. Consequently, a biotope is an area of ​​a territory that is homogeneous in terms of living conditions for certain species of plants or animals (a slope of a ravine, an urban forest park, a small lake or part of a large one, but with uniform conditions - the coastal part, deep-water part).

Organisms characteristic of a particular biotope constitute a vital community, or biocenosis (animals, plants and microorganisms of a lake, meadow, coastal strip).

The biocenosis forms a single whole with its biotope, which is called an ecological system (ecosystem). An example of natural ecosystems is an anthill, lake, pond, meadow, forest, city, farm. A classic example of an artificial ecosystem is a spaceship. species spatial trophic biocenosis

Close to the concept of ecosystem is the concept of biogeocenosis. Supporters of the ecosystem approach in Zapkada, incl. Y. Odum, consider these concepts to be synonyms. However, a number of Russian scientists do not share this opinion, seeing a number of differences. Of particular importance for the identification of ecosystems are the trophic relationships of organisms, which regulate the entire energy of biotic communities and the ecosystem as a whole.

Attempts to create a classification of the ecosystems of the globe have been undertaken for a long time, but there is still no convenient, universal classification. The thing is that because of the huge variety of types of natural ecosystems, because of their lack of rank, it is very difficult to find that single criterion, based on which such a classification can be developed.

If a puddle, a hummock in a swamp, or a sand dune with fixed vegetation can be a separate ecosystem, then, naturally, all possible variants of hummocks, puddles, etc. can be calculated. does not seem possible. Therefore, ecologists decided to focus on large combinations of ecosystems - biomes. A biome is a large biosystem that is characterized by some dominant type of vegetation or other feature of the landscape. According to the American ecologist R. Whittaker, the main type of community of any continent, distinguished by physiognomic characteristics of vegetation, is the biome. Moving from the north of the planet to the equator, there are nine main types of land biomes: tundra, taiga, temperate deciduous forest biome, temperate steppe, Mediterranean ooze vegetation, desert, tropical savannah and grassland biome, tropical or thorny woodland, tropical forest biome ...

The main components of ecosystems are:

1) inanimate (abiotic) environment. These are water, minerals, gases, as well as organic substances and humus;

2) biotic components. These include: producers or producers (green plants), consumers or consumers (living creatures that feed on producers), and decomposers or decomposers (microorganisms).

The biomass created by organisms (the substance of the bodies of organisms) and the energy contained in them are transferred to other members of the ecosystem: animals eat plants, these animals are eaten by other animals. This process is called the food, or trophic, chain. In nature, food chains often intersect to form a food web. Examples of food webs: plant - herbivore - predator; cereal - field mouse - fox, etc. and the food web are shown in Fig. 1.

Rice. 1. Food web and direction of flow of matter

The biosphere is the shell of the Earth, inhabited by living organisms, under their influence and occupied by the products of their vital activity. The biosphere is the global ecosystem of the Earth. It penetrates into the entire hydrosphere, the upper part of the lithosphere and the lower part of the atmosphere, that is, it inhabits the ecosphere. The biosphere is a collection of all living organisms. It is home to over 3,000,000 species of plants, animals, fungi and bacteria. Man is also a part of the biosphere, his activity surpasses many natural processes.

The state of equilibrium in the biosphere is based on the interaction of biotic and abiotic environmental factors, which is maintained due to the continuous exchange of matter and energy between all components of ecosystems.

In the closed cycles of natural ecosystems, along with others, two factors must participate: the presence of decomposers and the constant supply of solar energy. In urban and artificial ecosystems, there are few or no decomposers; therefore, liquid, solid and gaseous wastes accumulate, polluting the environment.

1.3 History of the study of biocenosis

In the late 70s. XIX century. German hydrobiologist Karl Möbius studied the complexes of benthic animals - clusters of oysters (oyster banks). He observed that together with oysters there were also such animals as starfish, echinoderms, bryozoans, worms, ascidians, sponges, etc. The scientist concluded that these animals live together, in the same habitat, not by chance. They need the same conditions as oysters. Such groupings appear due to similar requirements for environmental factors. The complexes of living organisms constantly occurring together in different points of the same water basin under the same conditions of existence were called biocenoses by Mobius. The term "biocenosis" (from the Greek bios - life and koinos - general) was introduced by him into the scientific literature in 1877 in the book "Die Auster und die Austernwirthschaft" to describe all organisms that inhabit a certain territory (biotope), and their relationship.

The merit of Mobius is that he not only established the presence of organic communities and proposed a name for them, but also managed to reveal many patterns of their formation and development. Thus, the foundations were laid for an important direction in ecology - biocenology (ecology of communities).

It should be noted that the term “biocenosis” has become widespread in the scientific literature in German and Russian, and in English-speaking countries it corresponds to the term “community”. However, strictly speaking, the term “community” is not synonymous with the term “biocenosis”. If a biocenosis can be called a multi-species community, then a population (a component of a biocenosis) is a single-species community.

2. The structure of the biocenosis

The structure of the biocenosis is multifaceted, and when studying it, various aspects are distinguished. Based on this, the structures of the biocenosis are subdivided into the following types:

1) species;

2) spatial, in turn subdivided into vertical (tiered) and horizontal (mosaic) organization of the biocenosis;

3) trophic.

Each biocenosis consists of a certain set of living organisms belonging to different species. But it is known that individuals of the same species are combined into natural systems called populations. Therefore, the biocenosis can also be defined as the totality of populations of all types of living organisms inhabiting common habitats.

The composition of the biocenosis includes a set of plants in a certain area - phytocenosis; a set of animals living within a phytocenosis - a zoocenosis; microbocenosis - a set of microorganisms that inhabit the soil. Sometimes, as a separate constituent element in the biocenosis, they include mycocenosis - a collection of fungi. Examples of biocenoses are deciduous, spruce, pine or mixed forest, meadow, swamp, etc.

A specific biocenosis includes not only organisms that constantly inhabit a certain territory, but also those that have a significant impact on it. For example, many insects breed in water bodies, where they serve as an important source of food for fish and some other animals. At a young age, they are part of the aquatic biocenosis, and in adulthood they lead a terrestrial lifestyle, i.e. act as elements of land biocenoses. Hares can eat in the meadow and live in the forest. The same applies to many species of forest birds that seek food for themselves not only in the forest, but also in the adjacent meadows or swamps.

2.1 Species structure of biocenosis

The species structure of a biocenosis is a combination of its constituent species. In some biocenoses, animal species may prevail (for example, the biocenosis of a coral reef), in other biocenoses, plants play the main role: the biocenosis of a floodplain meadow, feather grass steppe, spruce, birch, and oak forests.

A simple indicator of biocenosis diversity is the total number of species, or species richness. If any kind of plant (or animal) quantitatively predominates in the community (has a large biomass, productivity, abundance or abundance), then such a species is called a dominant, or dominant species (from Latin dominans - dominant). There are dominant species in any biocenosis. For example, in the spruce forest, using the main share of solar energy, they increase the greatest biomass, shade the soil, weaken the movement of air and create a lot of inconveniences for the life of other inhabitants of the forest.

The number of species (species diversity) in different biocenoses is different and depends on their geographic location. The most famous pattern of changes in species diversity is its decrease from the tropics towards high latitudes. The closer to the equator, the richer and more diverse the flora and fauna. This applies to all forms of life, from algae and lichens to flowering plants, from insects to birds and mammals.

In the rain forests of the Amazon basin, on an area of ​​about 1 hectare, you can count up to 400 trees of more than 90 species. In addition, many trees support other plants. Up to 80 species of epiphytic plants grow on the branches and trunk of each tree.

In contrast to the tropics, the pine forest biocenosis in the temperate zone of Europe can include a maximum of 8-10 tree species per hectare, and in the north of the taiga region, 2-5 species are present on the same area.

The poorest biocenoses in terms of the set of species are alpine and arctic deserts, the richest are tropical forests. Panama's rainforests are home to three times as many species of mammals and birds as Alaska.

Biocenoses are not isolated from each other. Although one can visually distinguish one plant community from another, for example, a dry forest biocenosis from a wet meadow biocenosis, which is replaced by a swamp, it is rather difficult to draw a clear boundary between them. Almost everywhere there is a kind of transitional strip of various widths and lengths, because rigid, sharp boundaries in nature are a rare exception. They are typical mainly for communities subject to intense anthropogenic impact.

In the early 30s. XX century. American naturalist A. Leopold proclaimed the need to take into account the so-called "edge effect" in the activities of the hunting industry. In this case, the border was understood not only as the edge of the forest, but also any border between two biocenoses, even between two massifs of different crops. On both sides of this conventional feature, the relative species diversity of plants and animals increases, the forage and protective conditions for game improve, the disturbance factor is weakened, and most importantly, this zone has increased productivity. Such a transitional strip (or zone) between adjacent physiognomically distinguishable communities is called an ecotone.

More or less sharp boundaries between biocenoses can be observed only in cases of a sharp change in the factors of the abiotic environment. For example, such boundaries exist between aquatic and terrestrial biocenoses, in places where there is a sharp change in the mineral composition of the soil, etc. Often the number of species in the ecotone exceeds their number in each of the bordering biocenoses. This tendency to an increase in the diversity and density of living organisms at the boundaries of biocenoses is called the marginal (marginal, boundary) effect. The edge effect is most clearly manifested in the zones separating the forest from the meadow (the zone of shrubs), the forest from the swamp, etc.

2.2 Spatial structure of biocenosis

Species can be distributed differently in space in accordance with their needs and habitat conditions. Such a distribution of the species that make up the biocenosis in space is called the spatial structure of the biocenosis. Distinguish between its vertical and horizontal structures.

1) The vertical structure of the biocenosis is formed by its individual elements, special layers, which are called tiers. Tier - co-growing groups of plant species differing in height and position in the biocenosis of assimilating organs (leaves, stems, underground organs - tubers, rhizomes, bulbs, etc.). As a rule, different tiers are formed by different life forms (trees, shrubs, shrubs, grasses, mosses). The layering is most clearly expressed in forest biocenoses (Fig. 2).

The first, arboreal, layer usually consists of tall trees with high foliage, which is well lit by the sun. Unused light can be absorbed by trees that form the second, sub-log, tier.

Rice. 2. Tiers of the forest biocenosis

The undergrowth layer is made up of shrubs and shrub forms of tree species, for example, hazel, mountain ash, buckthorn, willow, forest apple, etc. In open places under normal environmental conditions, many shrub forms of such species as mountain ash, apple, pear, would have the appearance of trees of the first size. However, under the forest canopy, in conditions of shade and lack of nutrients, they are doomed to exist in the form of undersized, often not barking seeds and fruits of trees. As the forest biocenosis develops, such species will never enter the first tier. This is how they differ from the next layer of the forest biocenosis.

Young small (from 1 to 5 m) trees, which in the future will be able to enter the first tier, belong to the understorey layer. These are the so-called forest-forming species - spruce, pine, oak, hornbeam, birch, aspen, ash, black alder, etc. These species can reach the first tier and form biocenoses with their dominance (forests).

Under the canopy of trees and shrubs, there is a grass-shrub layer. This includes forest grasses and shrubs: lily of the valley, oxalis, strawberries, lingonberries, blueberries, ferns.

The ground layer of mosses and lichens forms a moss-lichen layer.

So, in the forest biocenosis stands out stand, undergrowth, undergrowth, grass cover and moss-lichen layer.

Similar to the distribution of vegetation over the tiers, in biocenoses, different species of animals also occupy certain levels. Soil worms, microorganisms, earth-moving animals live in the soil. In leaf litter, on the soil surface, various centipedes, ground beetles, ticks and other small animals live. Birds nest in the upper canopy of the forest, and some can feed and nest below the upper tier, others in the bushes, and still others near the ground. Large mammals live in the lower tiers.

Layering is inherent in oceans and seas biocenoses. Different types of plankton keep different depths depending on the light. Different types of fish live at different depths depending on where they find their food.

2) Individuals of living organisms are unevenly distributed in space. Usually they make up groupings of organisms, which is an adaptive factor in their life. Such groupings of organisms determine the horizontal structure of the biocenosis - the horizontal distribution of individuals that form various kinds of patterning, spotting of each species.

There are many examples of such a distribution: these are numerous herds of zebras, antelopes, elephants in the savannah, coral colonies on the seabed, schools of sea fish, schools of migratory birds; thickets of reeds and aquatic plants, accumulations of mosses and lichens on the soil in the forest biocenosis, spots of heather or lingonberry in the forest.

The elementary (structural) units of the horizontal structure of plant communities include microcenosis and microgrouping.

The microcenosis is the smallest structural unit of the horizontal division of the community, which includes all the layers. Almost every community includes a complex of microcommunities or microcenoses.

Microgrouping - concentration of individuals of one or several species within a layer, intra-layer mosaic spots. For example, in the moss layer, various moss spots can be distinguished with the dominance of one or several species. In the herb-dwarf shrub layer, bilberry, bilberry-oxalis, and blueberry-sphagnum microgroups are found.

Mosaicity is essential for the life of the community. Mosaicity allows for a more complete use of various micro-habitats oozes. Individuals forming groups are characterized by a high survival rate, they use food resources most efficiently. This leads to an increase and diversity of species in the biocenosis, contributes to its stability and vitality.

2.3 Trophic structure of biocenosis

The interaction of organisms that occupy a certain place in the biological cycle is called the trophic structure of the biocenosis.

In the biocenosis, three groups of organisms are distinguished.

1. Producers (from Latin producens - producing) - organisms that synthesize from inorganic substances (mainly water and carbon dioxide) all the organic substances necessary for life, using solar energy (green plants, cyanobacteria and some other bacteria) or energy oxidation of inorganic substances (sulfur bacteria, iron bacteria, etc.). Usually, producers are understood as green chlorophyll-bearing plants (autotrophs) that provide primary production. The total dry matter weight of phytomass (plant mass) is estimated at 2.42 x 1012 tons. This is 99% of all living matter on the earth's surface. And only 1% is accounted for by heterotrophic organisms. Therefore, only vegetation the planet Earth owes to the existence of life on it. It was green plants that created the necessary conditions for the emergence and existence of a variety of prehistoric animals, and then humans. When the plants died, they accumulated energy in coal deposits, peat and even oil.

Producer plants provide people with food, raw materials for industry, and medicines. They purify the air, retain dust, soften the temperature regime of the air, and muffle noise. Thanks to vegetation, there is a huge variety of animal organisms that inhabit the Earth. Producers are the first link in food value and are at the heart of ecological pyramids.

2. Consumables (from Lat. Consumo - I consume), or consumers, are heterotrophic organisms that feed on ready-made organic matter. Consumers themselves cannot build organic matter from inorganic and receive it ready-made, feeding on other organisms. In their organisms, they transform organic matter into specific forms of proteins and other substances, and into the environment they emit waste generated in the process of their vital activity.

Grasshopper, hare, antelope, deer, elephant, i.e. herbivores are first-order consumers. A toad that seizes a dragonfly, a ladybug that feeds on aphids, a wolf hunting for a hare - these are all second-order consumers. A stork eating a frog, a kite carrying a chicken into the sky, a snake swallowing a swallow are consumers of the third order.

3. Reducers (from Latin reducens, reducentis - restoring, restoring) - organisms that destroy dead organic matter and turn it into inorganic substances, and they, in turn, are assimilated by other organisms (producers).

The main reducers are bacteria, fungi, protozoa, i.e. heterotrophic microorganisms in the soil. If their activity decreases (for example, when a person uses pesticides), the conditions for the production process of plants and consumers deteriorate. Dead organic remains, be it a tree stump or the corpse of an animal, do not disappear into anywhere. They rot. But dead organics cannot rot by themselves. Reducers (destructors, destroyers) act as "gravediggers". They oxidize dead organic residues to C0 2, H 2 0 and simple salts, i. E. to inorganic components, which can again be involved in the circulation of substances, thereby closing it.

3. Modern problems and ways to solve them

The most acute problem of biocenoses is the reduction of populations of various living organisms up to the disappearance of whole species of animals, plants and microorganisms. This leads to disruption of the stability of biocenoses and poses a threat to the entire biosphere of the planet.

Each species participates in the circulation of substances, maintains a dynamic balance in natural ecosystems. Therefore, the loss of any biological species is highly undesirable for the biosphere.

The loss of species has occurred as a result of evolutionary processes. As a result of human activities, the planet's biological resources are being lost much faster. Tens of thousands of plant and animal species are endangered. The reasons for this situation are:

1) loss of habitat: destruction of forests, drainage of swamps and floodplain lakes, plowing of steppes, change and shallowing of river beds, reduction of the area of ​​sea estuaries suitable for nesting, molting and wintering of waterfowl, road construction, urbanization and other changes resulting from human economic activity;

2) pollution of the environment with toxic chemicals and xenobiotics, oil and oil products, salts of heavy metals, solid household waste;

3) the spread of introduced species of plants and animals, actively occupying vast territories and displacing the natural inhabitants of ecosystems. Unintentional, accidental dispersal of animals has increased with the development of transport;

4) merciless exploitation of natural resources - minerals, soil fertility, aquatic ecosystems, overhunting of animals, birds and aquatic organisms.

Active, sometimes urgent, measures must be taken to protect endangered species. One of the most effective methods of animal protection is the creation of reserves or sanctuaries. On the territory of the Russian Federation, there are more than 150 nature reserves in which a large number of animals have been preserved. Among them are the Amur tiger, saiga, goral, Bukhara deer, kulan and others. Zoos throughout the country are helping to breed endangered species.

In order to preserve and increase the number of rare species, states on all continents of the Earth are adopting laws regarding the protection and use of the animal world. In the Russian Federation, such a law was adopted on June 25, 1980. To account for rare species both in Russia and in other countries of the world, the so-called Red Data Books are being created. Endangered species of animals around the world need separate registration, for this the International Red Book has been created.

It is necessary to use natural resources rationally, including in agriculture. Limit deforestation, as well as hunting and fishing, and completely ban rare and endangered species.

Conclusion

Biocenosis is one of the main objects of ecology research. A biocenosis is a collection of populations of plants, animals and microorganisms. The main function of the biocenosis is to ensure equilibrium in the ecosystem based on a closed cycle of substances. The place occupied by the biocenosis is called a biotope. Types of biocenosis structures: species, spatial (vertical (tiered) and horizontal (mosaic) organization of the biocenosis) and trophic. The species structure of the biocenosis covers all species living in it. The spatial structure includes a vertical structure - tiers and horizontal - microcenoses and microassociations. The trophic structure of the biocenosis is represented by producers, consumers and decomposers. The transfer of energy from one species to another by eating them is called the food (trophic) chain. The place of an organism in the food chain associated with its food specialization is called the trophic level. The trophic structure of the biocenosis and ecosystem is usually displayed by graphic models in the form of ecological pyramids. Distinguish between ecological pyramids of numbers, biomass and energy. The rate of fixation of solar energy determines the productivity of biocenoses. The set of environmental factors within which a species lives is called an ecological niche.

Humanity is now facing an acute problem of the disappearance of species of various living organisms, leading to a violation of the stability of biocenoses and the biosphere as a whole. To prevent population decline and extinction of entire species, it is necessary to take urgent and active measures: entry of endangered species into the Red Data Books; creation of nature reserves and national parks; restriction of hunting, fishing and deforestation; rational use of all natural resources.

Bibliography

1. Korobkin V.I., Peredelsky L.V. Ecology. - R.-on-Don, 2001 - 576 p.

2. Odum Y. Ecology: in 2 volumes. T. 1 - M., 1986 - 328 p .; T. 2 - M., 1986 - 376 p.

3. Articles from the electronic resource "Wikipedia": Biocenosis, Biosphere, Ecosystem

4. Tishler V. Agricultural ecology. - M., 1971 - 455 p.

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Consideration of the principles of the Bari Commoner's theory, the laws of minimum, necessity, the energy pyramid, the concept of succession (successive change of communities by sex by the influence of time), biocenosis, tolerance, environmental resistance, stability of the natural community.

Ecological structure- the ratio of organisms of different ecological groups. Biocenoses with a similar ecological structure can have a different species composition. This is due to the fact that the same ecological niches can be occupied by ecologically similar, but far from related species. These types are called replacing or vicarious.

Any biocenosis, natural or artificial, has a certain set of populations of various sizes. However, in defining the nature and functions of a community, not all organisms have the same meaning. Of the large number of species included in any community, often only a small number of them have a decisive effect on it, due to their number, size, production and other parameters. In a community, the role of each species does not depend on taxonomic relations, since organisms that have a regulatory effect often belong to different taxonomic groups.

Species structure- the number of species forming a given biocenosis, and the ratio of their number or mass. That is, the species structure of the biocenosis is determined by the species diversity and the quantitative ratio of the number of species or their mass among themselves.

Species diversity is the number of species in a given community. There are poor and species-rich biocenoses. Species diversity depends on the age of the community (young communities are poorer than mature ones) and on the favorableness of the main environmental factors - temperature, humidity, food resources (biocenoses of high latitudes, deserts and high mountains are poor in species). Distinguish between α- and β-variety. α-diversity is the species diversity in a given habitat, β-diversity is the sum of all species of all habitats in a given area.

Ecotones are distinguished by a high species diversity - transition zones between communities, and an increase in species diversity here is called the edge effect.

In the community, the following species are distinguished: dominant, predominant in number, and "secondary", small in number and rare. Among the dominants, edificators (builders) are especially distinguished - these are species that determine the microenvironment (microclimate) of the entire community. As a rule, these are plants.

The importance of a particular species in the species structure of the biocenosis is judged by several indicators: the abundance of the species, the frequency of occurrence, and the degree of dominance. The abundance of a species is the number or mass of individuals of a given species per unit area or volume of space it occupies. Frequency of occurrence - the percentage of the number of samples or counting sites where the species is found to the total number of samples or counting sites. It characterizes the uniformity or unevenness of the distribution of the species in the biocenosis. Dominance degree - the ratio of the number of individuals of a given species to the total number of all individuals of the considered group .

The main communities are made up of producers, consumers and decomposers. Within the named groups, individual species can take a predominant role in the regulation of energy metabolism and have a more noticeable effect on the habitat of other species. These types are called ecological dominants. The degree of dominance in a community of one or more species is expressed dominance indicator , which reflects the importance of each species to the community.

A simplified classification of a biotic community can be shown by the following example: bluegrass, clover, oak, beef cattle, chickens, turkeys, sheep, horses can coexist on a pasture. A simple list of a community does not give a complete picture of it; a quantitative assessment of the species is required. For example, meadow bluegrass - 20 hectares, creeping clover - 0.8 hectares, oak - 2 trees, beef cattle - 2 individuals, dairy cattle - 48 individuals, goats - 6 individuals, sheep - 1 individual, turkeys - 1 individual, horses - 1 individual. Now it is obvious that bluegrass dominates among producers, and dairy cattle dominate among consumers. Naturally, information on seasonal variations in pasture use, annual productivity, etc., would give a more complete picture. Dominants can be called those species that are most productive at their trophic level, prevail over other species in the community in terms of mass or number.

Classification of community elements. Any biocenosis, both natural and artificial, can determine a set of populations of various sizes. Of the large number of species included in the community, only a small number of them have a decisive effect on it, due to their number, size and other parameters within the community, certain species occupy a dominant role in the regulation of energy metabolism, and have a more noticeable effect on the habitat of other species , such species are called ecological dominants. The degree of one or several species dominating in the biocenosis expresses the indicators of dominance, which reflects the importance of each species for the community. Let us consider a simplified classification of a biotic community using the example of a pasture. On the pasture, mint, clover, oak, beef cattle, chickens, turkeys, horses can coexist. A simple list of a community does not give a complete picture of it; a quantitative assessment of the species is required. Those. meadow broom 20 hectares, creeping clover 0.8 hectares, oak 2 trees, beef cattle 2 individuals, dairy cattle 48, goats 6 individuals, sheep 1 individual. Turkeys 1 individual, 1 horse, 3 hens. From this it can be seen that bluegrass dominates among producers, and dairy cattle dominate among consumers. Dominants can be called those species that are most productive at their level, prevail over other species in the community in terms of mass and number.

Dominance indicator (with), reflecting the degree of dominance of each species in the community, is defined as the sum of the squares of the ratios of the species significance indicators (n,) to the overall significance assessment (N):

The dominance of some species in a community does not mean that numerous species play no role. They determine the species diversity, which is no less important for the structure of the community.

The following criteria can be used to assess species diversity: species richness (d); evenness score (e), overall diversity score (H), or Shannon score:

Species richness (d):

d 1 = (S -1) / log N; d 2= S / 100 individuals,

where S is the number of species, N is the overall assessment of the significance of the species.

Equality index (e):

e = H / logS.

Overall diversity score (H), or Shannon score:

Н = ∑ (n; / N) log (n i / N), or Н = ∑P i logP i,

where n i, - the assessment of "significance" for each species;

P is the probability of "significance" for each species Pi< n/N.

It is rather difficult to create a classification of communities of a population according to any one indicator, since species diversity, the ratio between species and the structure of the biotic community, as a rule, are specific for certain conditions. It is convenient to name and classify biotic communities according to:

With the main structural indicators, such as dominant species, life forms or indicator species;

WITH living conditions communities;

WITH functional features, such as the type of metabolism of the community.

In the community, not many of its constituent species have a significant number, high biomass, productivity. If the main amount of energy is consumed by the dominant species, then the species diversity of this group is determined by the main rarer species.

The indicator of species diversity is the ratio between the number of species and some indicator of the significance of the number, biomass, productivity, the composition of communities most often includes several species with a high abundance and several species with a low abundance.

The number of ratios between which varies widely, despite the fact that the total energy flow entering the ecosystem affects species diversity. These values ​​are not linearly related. A highly productive community can have very high species diversity rates.

Ecosystem stability is closely related to species diversity or productivity. Species diversity is greatly influenced by the functions of the relationship between trophic levels and taxonomic units (the scale of grazing or predation significantly affects the diversity of grass stand on pastures; moderate predation reduces the density of dominants, allowing competing species to better use space and resources).

Species that live off dominants are called preomenants. For example, in a pine forest, these are insects feeding on a pine tree, murine rodents. In biocenoses, there are species that are called edifiers, creating by their life activity the environment for the entire community and without which, in this regard, the existence of most other species is impossible. Removal of the edificator species from the biocenosis entails a change in the physical environment and, first of all, the microclimate of the biotope, thus. all the species that make up the biocenosis are to a certain extent associated with the dominant species and edificators.

Consortia. Within the biocenosis, groupings of a complex of populations are formed, which depend on the erification plant or other elements of the biocenosis and create peculiar structural units of the biocenosis - consortia (Ramenskiy 1952). Consortium- a set of populations of organisms, the vital activity of which within the same biocenosis, trophically or topically associated with the central species - an autotrophic plant. The central view is played by edifier- the main species that determines the characteristics of the biocenosis. The populations of the remaining species of the consortium form its core due to which there are species that destroy the organic matter created by autotrophs. The popularity of the autotroph of a birch plant on the basis of which a consortium is formed is called a determinant, and the species united around it are called consorts.

Groups of consorts of one order or another, united around a determinant, are called concentrates. Each consortium covers a large number of species, among which there are species that are part of only one consortium and species that are members of 20 or more consortia, thereby contributing to the unification of organisms of the biocenosis into a single complex. The composition of the consortia is the result of a long process of selecting species that can exist in the habitat of the determinant. Each consortium is a special structural unit of biocenosis and ecosystem.

Rice. 2. Diagram of the structure of the consortium:

/, //, III- concentrates, / - central view - consortium determinant (autotroph), 2 - consorts of the first concentrate, 3 - “, consorts of the second and third concentrators.

Usually a consortium is depicted as a concentric figure (Fig.), Placing an autotrophic plant in its center - determinant of the consortium. Around it are groups of organisms that directly interact with the determinant - these are the so-called consorts. These include phytophagous animals, microorganisms, fungi, the combination of which forms first concentr.

Second concentrator are zoophagous animals that eat phytophagous animals, as well as species in the suite of consorts of the first concentrate. As the trophic level increases, the autonomy of the consortium decreases more and more, since the zoophagous predator can eat phytophages that feed on various plants. In addition, there are many omnivores.

At present, it is considered quite legitimate to isolate both autotrophic (the core of the consortium is a green plant) and heterotrophic (the core is an individual of a heterotrophic species) consortia. The existence of the latter is ensured by the energy of the central living individual, regardless of whether it assimilates this energy through photosynthesis or by eating living or dead organic matter. Thus, any organism of not only autotrophic, but also heterotrophic nutrition is a source of energy for other organisms associated with it by consortium ties. Therefore, the consortium is considered as a general biological phenomenon. In this regard, the opinion of botanists is disputed that only an autotrophic organism should be considered the core of the consortium.

Ecological Niche (Grinnell 1917 Elton 1933). Any population (species) occupies a certain habitat and a certain ecological niche.

Habitat is a territory or water area occupied by a population (species) with a complex of environmental factors inherent in it. The habitat of a species is a component of its ecological niche. In relation to terrestrial animals, the habitat of the species is called station, community habitat - biotope.

Ecological niche- a set of all environmental factors within which the existence of a species in nature is possible. That is, an ecological niche is a place of a species in nature, including not only its position in space and attitude to abiotic factors, but also its functional role in the community (primarily trophic status). Habitat is like an “address” of an organism, and an ecological niche is its “profession”.

To characterize an ecological niche, two important indicators are usually used: niche width and degree of overlap her with the neighbors. Ecological niches of different types can be of different widths and overlap to varying degrees.

The division of ecological niches between species occurs due to the confinement of different species to different habitats, different food and different times of use of the same habitat. Competitive exclusion principle (Gause principle) states: “Two species cannot coexist in the same locality if their ecological needs are identical. Such species must necessarily be separated in space or time. "

Groups of species in a community that have similar functions and niches of the same size, i.e. whose role in the community is the same or comparable are called guilds. For example, rainforest vines are represented by many plant species. There is especially intense competition among species within the guild.

Species that occupy the same niches in different geographic areas are called ecological equivalents. For example, the large kangaroos of Australia, the bison of North America, the zebras and antelopes of Africa, etc. are ecological equivalents. Nowadays, they are significantly replaced by cows and sheep.

There are 4 types of location of ecological niches of 2 species of one biotope:

Rice. 1 Variations of possible mutual answers, illustrated by an auxiliary observer of the scholarship (evil) and models of the theory of many (on the right):

a - nisha all the middle nisha. Nishi mind 2 (S) There can be two inheritances of competition: 1) if the view is 2 ma perevagu (redistribution of the line), then it will be successful in case of an incomplete victorious sleeping resirs with a view і; 2) if perevagi is type 1 (succinct lines), then the whole city of resirs will be victorious, and type 2 will be vicious;

6 - perekrivanya nish of the same width. Competition is the same in both directions;

v - perekrivannya nish is not the same width. Competition is not the same for two straight lines, there is a small part of the open space, how to enter to the area of ​​recrimination, in sight of 2 more, lower in sight of 1;

G- adhere to nish. Direct competition is not merciful, but it can be more unique;

d - rezdіl nіsh. Competition is not merciful and it is important to increase the transfer rate. Why isn't there a competition for fodder? And besides, the dermal one of the species in the process of the Evolution has attached itself to its ecological benefit.

Ecological nisha- the physical space with the powerful ecological minds, so that there is a sense of being in any body, at the same time in nature, but including not depriving one’s position in the open space, but the functional role in the middle of the biocenosis and setting the factor up to the abbreviation. Ecological nisha characterizes the steps of biological specialization of a given species.

There is a fundamental (potential) niche that the body could occupy in the absence of competitors, predators and other enemies, and in which the physical conditions are optimal; and realized - the actual range of conditions for the existence of an organism, which is either less than or equal to the fundamental niche.

The fundamental niche is sometimes called pre-competitive, and the realized one is called post-competitive.

Two species with exactly the same needs cannot exist together: one of them will surely be supplanted after some time. This provision received the status of a law known as the principle of competitive crowding out or the Gause principle. The exception is cormorants.