The importance of self-regulation of biocenosis is. What is Biogeocenosis? - Definition, characteristics, types and examples. The population is threatened with death if its numbers

The author of the doctrine of biogeocenoses was the Soviet scientist V.N.Sukachev. By this term, he meant a set of living organisms and factors that are located in a certain territory. Any biogeocenosis is associated with a specific land area, that is, it depends on the plant community.

Difference between biogeocenosis from agrocenosis, biocenosis and ecosystem

Agrocenosis means artificial, which was created by people. She, unlike biogeocenosis, does not have stable connections. Each natural community has been formed over the centuries. Its development was influenced by natural selection. Man-made fields and plantations are subject to artificial selection. With the help of people, agrocenoses receive additional energy, while biogeocenoses exist due to solar energy.

A biocenosis is a collection of living organisms that inhabit a specific space. It can be not only a piece of land, but also a body of water. The concept of biogeocenosis is much broader, it includes biocenosis and environmental factors.

The term "ecosystem" was coined by the English botanist A. Tensley. It is much broader than biogeocenosis and agrocenosis. Both concepts are identical when it comes to, or fields. , in which it is impossible to distinguish a phytocenosis, fall under the definition of an ecosystem. Each biogeocenosis is an ecosystem, but not every ecosystem corresponds to a biogeocenosis.

Biogeocenosis properties

The main properties of biogeocenosis are:

Integrity... Solar energy and nutrients provide all living organisms. Unused food is transferred to the external environment, returning to the cycle of substances, which occurs continuously;
Sustainability... The established biogeocenosis is able to withstand the tests of the external environment;
Self-regulation... Maintaining a certain number of living things in different food chains and webs;
Self-replication... The ability of organisms to reproduce and recreate populations;
The change... The phenomena associated with affect the size of organisms.

Indicators of biogeocenosis

There are three indicators of biogeocenosis. Species diversity is understood as the totality of all groups of organisms. If any link in the power supply chain is broken, the entire system will suffer. The population density is directly related to the supply of food. The productivity of biogeocenosis is influenced by biomass, living matter in all plant and animal groups.

Biogeocenosis structure

The species composition of systems is always different. It is influenced by the supply and distribution of light, soil composition and climatic conditions. Scientists are considering several structures:

Species... It assumes a variety of living organisms, their composition and quantity. The reduction of one species threatens the existence of biogeocenosis.
Spatial... Populations are distributed in longlines, depending on their needs. Most often, the longline is determined by the plants. Animals contribute to the spread of seeds and pollen.
Environmental... The ratio of living things depends on the inorganic environment.
Trophic... Animals in the same biogeocenosis serve as food for each other. Complex food connections form food webs.

Since biogeocenoses have been developing for many hundreds of years in a row, scientists periodically introduce new components into their structure.

Types and examples of biogeocenosis

The system is a collection of plants, animals, microorganisms and fungi. The main components are carbon, oxygen, sunlight and living organisms. The sun provides the necessary supply of energy, resulting in a circulation of energy. It is transmitted from protozoa to heterotrophs.

Examples of biogeocenosis are forest, pond, meadow, steppe or desert.

Change of biogeocenoses

The number of species in one system is constantly changing. Due to various factors, some biogeocenoses are replaced by others. The speed of these changes can vary. will change the ecosystem within a single generation of people. It will take millennia for forests to be formed instead of dunes.

Plants play the main role in the development of biogeocenosis. The process of self-development of communities is called succession. The simplest example of a change in biogeocenosis is the overgrowth of a reservoir. First, it becomes covered with mud, and then swamp. The species composition of organisms will differ significantly from the inhabitants of the reservoir.

Stability of biogeocenosis

Resilience refers to the ability to continuously maintain a structure. Most of all, it is influenced by the richness of the species composition. It is on him that the circulation of substances and energy depends. Poor communities are fragile. Complex biogeocenoses, characterized by multi-tiered and varied nutritional relationships, are ready for adverse effects.

Forms of relationships between organisms in biogeocenoses
All elements of the system are closely related to each other. The relationship can be positive, negative and neutral. Relationships that benefit one or both organisms are named. They arise among animals, birds, plants, fungi. Bees and flowers are a prime example of symbiosis.

Implies that only one of the species will benefit. When two species living in the same biogeocenosis do not depend on each other in any way. As a rule, animals do not contact. Competition implies that two species will vie with each other for the same resources.

Properties of biocenoses: self-regulation and self-reproduction. Le Chatelier's principle

The main properties of biocenoses, which distinguish them from non-living components, are ability to produce living matter, to possess self-regulation and self-replication... In biocenosis, individual species, populations and groups of species can be replaced, respectively, by others without much damage to the community, and the system itself exists due to balancing the forces of antagonism (competition) between species. It takes time for a biosystem to acquire these properties.

A very important property of biocenoses, like any biological material systems, is an self-regulation- the ability to withstand high negative loads, the ability to return to a state close to the initial state after significant violations of components, structure, relationships. Self-regulation reflects the Le Chatelier principle.

According to Le Chatelier's principle, the biogeocenosis is able to maintain its state in case of sharp, unfavorable for it, external factors or disturbances. At the same time, it changes in such a way that reduces the effect of perturbation and, thus, retains its status quo.

Example. Restoration of the previous type of community after fire, forest felling, windblow, trampling, etc. There is a high growth activity and a high rate of metabolic processes in plants growing in extreme conditions.

Since the components of the cenosis are in constant interaction with each other - they are connected with each other by flows of matter and energy, then, speaking about the equilibrium of the biogeocenosis, one should keep in mind not the static, but dynamic balance, first of all, the balance of flows of matter and energy. If the ecosystem is taken out of the state of dynamic equilibrium, then it seeks to return to it, using part of its internal energy and orderliness (orderliness is structural negentropy). If there is enough reserve of internal energy and negentropy, then the system returns to a state close to the original one. If the resources of matter and energy are insufficient, then the system (biogeocenosis) is either irrevocably destroyed, or passes into a new state of dynamic equilibrium, but at a much lower energy level. At the same time, they say that the ecosystem has degraded.

EXAMPLE degradation is the plowing and destruction of natural vegetation in large areas in the dry steppe zone. This impact sharply reduces the moisture reserves in the soil, contributes to wind erosion of soil and the ecosystem passes into a new state with very low biological productivity. Steppe ecosystems are replaced by desert ecosystems. Some environmental scientists believe that this is how the Sahara desert was formed on the site of the savanna in North Africa about 10 thousand years ago.

One of the most characteristic examples of irreparable destruction of biogeocenoses is mountain ranges, where mining is carried out in an open way. Forest floodplain biogeocenoses, the most productive and diverse in terms of species composition, turn into lunar landscapes. The destruction of the heat-insulating layer - the vegetation cover - on soils with permafrost also leads to a violation of the dynamic balance and the phenomenon of thermokarst.

For any biogeocenosis, there are limits of tolerance (resistance). Some are more tolerant, or resistant, to the effects of external disturbing factors, others are less. But so far little is known about the tolerance limits of natural ecosystems, and there is disagreement among scientists. For example, some say that tundra ecosystems are very unstable and easily vulnerable. Others, on the contrary, believe that the most unstable ecosystems are tropical rainforest ecosystems, and tundra ecosystems are no less stable than taiga and steppe ecosystems. The tolerance of different ecological systems should be studied as soon as possible, otherwise the most vulnerable ecosystems will be under powerful anthropogenic impact.

This problem is very complicated because different ecosystems are resistant to destructive factors to varying degrees.

FOR EXAMPLE, a track from a tractor on a slope in the taiga zone will overgrow and disappear in 50 years, but the same track in the tundra zone in 50 years will turn into a ravine up to 20-30 m deep and up to 10-20 m wide.

Students, graduate students, young scientists who use the knowledge base in their studies and work will be very grateful to you.

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SELF-REGULATION IN ECOSYSTEMS

A general idea of the structure of the ecological system was presented when characterizing the levels of organization of life (topic 1). Let us recall that a full-fledged ecosystem is a biogeocenosis - an indissoluble unity of a biocenosis and a biotope. A biocenosis is a complex community of populations of organisms of different species - animals, plants, fungi, microorganisms that inhabit a certain area. In this case, a population is a set of individuals of the same species living in a given area. A biotope is the totality of factors of the inanimate environment, the area in which a given biocenosis lives.

So: biocenosis + biotope = biogeocenosis (ecosystem).

Before considering the mechanisms of self-regulation in ecosystems, it is necessary to characterize environmental factors, without which it is impossible to understand the essence of intra-system environmental relations.

All environmental conditions, including living and nonliving objects, on which the life of an individual organism or population depends, are designated by the concept of environmental factors. For specific populations, different factors may be necessary, harmful, indifferent (neutral). Environmental factors are divided into abiotic and biotic. In addition, anthropogenic factors generated by human production activities are distinguished into a special group.

Abiotic factors - factors of inanimate nature, mainly climatic. This includes light, heat ("temperature"), humidity, the content of chemical elements in the soil, the salinity of sea water, the level of radiation, etc.

1. Competition - for habitat, food, light, sexual partners and other conditions. Competition can be intraspecific - between individuals of the same species and interspecific - between individuals of different species of animals or plants living in the same area and requiring the same living conditions. Competition is an obligatory form of relations for a number of living organisms and constitutes one of the forms of the struggle for existence.

2. Predation is a way of obtaining food and nutrition for animals (rarely plants), in which they catch and eat other animals. Predatory prey is one of the most common bonds within a community. Intraspecific predation, known as cannibalism, is common among predatory insects, spiders, and fish. Among the plants are known aquatic pemphigus, marsh sundew, zhiryanka and others that feed on insects. The victim is captured by the rapid closure of leaves or petals, digested by enzymes and acids secreted outside, and then simple organic substances are absorbed by the cells of the plant's epidermis. This is how the nitrogen deficiency in plant tissues is replenished.

4. Symbiosis (from the Greek symbiosis - living together) - mutually beneficial cohabitation. Examples of symbiosis are nodule bacteria and leguminous plants (bacteria get food from the plant, the plant from bacteria - assimilated nitrogen), fungi and plant roots, termites and flagellate protozoa living in their intestines that digest fiber. A person has a similar relationship with the intestinal microflora - a variety of bacteria that digest certain components of food. Violation of this symbiosis - dysbiosis - leads to intestinal disorders, digestive disorders.

Each species has its own limits for each ecological factor. By many factors, the brown bear has wide limits of endurance: it tolerates large fluctuations in temperature, humidity, is unpretentious in choosing food - it is omnivorous. Arctic fish, on the other hand, have very narrow temperature limits - from -2 to +2 degrees Celsius. Among the plants there are light-loving, light-tolerant and shade-loving.

Having clarified the nature of environmental factors and the nature of their impact on organisms, one can proceed to consider the essence of the issue - about environmental self-regulation.

Being under the influence of a wide variety of environmental factors, a well-balanced biocenosis nevertheless self-regulates and maintains internal constancy - homeostasis. The state of homeostasis is expressed in the following:

organisms reproduce normally, therefore:

the number of different populations in the community is maintained at certain levels, albeit in an oscillatory mode;

the biocenosis remains stable and reproduces itself even under fluctuating climatic conditions.

Let's take a closer look at these patterns.

Elementary self-regulation is carried out at the level of individual populations of specific species of animals, plants, fungi, bacteria. The size of the population depends on the opposition of two principles: the reproductive potential of the population and the resistance of the environment, between which a direct and reverse relationship is established (Fig. 24). Let us clarify this with a specific example. When the Europeans brought rabbits to Australia, the latter, without encountering predators, quickly settled in areas rich in vegetation and their numbers grew rapidly. This was facilitated by the high reproductive potential (fertility) of rabbits. But soon there was not enough food, hunger arose, diseases spread - the number of rabbits began to decline. The factor of resistance of the environment worked, which acted as a negative feedback. While the rabbit population was in a depressed state, the environment (vegetation) recovered and the process went on a new wave. After several cycles, the amplitude of fluctuations in the number of rabbits decreased, and a certain average population density was established. This indicator is designated in ecology as the supporting capacity of the environment.

In fact, in a biocenosis, everything is more complicated, since it consists of several interacting communities (zoocenoses, phytocenoses, microbocenoses), and communities include different populations of specific species. All this interacts on the basis of numerous forward and backward connections. First of all, trophic (food) connections are important, which can also be defined as energy ones, since energy is transferred between organisms with food. According to the position in food relations, all organisms are divided into three large groups: producers, consumers and decomposers.

Producers - primary producers of organic substances (primarily glucose and amino acids) from inorganic substances of inanimate nature: H2O, CO2, NH3. These are autotrophic organisms - plants and some (chemosynthetic) bacteria that use the energy of sunlight and chemoenergy for the primary synthesis of glucose (see segment 13). Thus, external energy is fixed for the producers' own needs and for further use by animals. A significant part of the energy is taken out of circulation, as it is stored in fossil residues of plant origin: coal (mineralized wood), amber (hardened plant resins).

Consumables are consumers of primary products. These are animal organisms - heterotrophs, in turn, lined up in a food row: herbivores (many groups of mollusks, insects, fish, birds, ungulate mammals, rodents), omnivores (found in most groups) and carnivores - predators (also found in different groups of invertebrates and vertebrates). The consumables gradually change the primary organic matter and extract energy from it. Part of this energy is spent on their own vital activity, part in the form of heat goes into the external environment, and a third part is stored in dead remains. The energy contained in mineralized remains (bottom chalk deposits of foraminifera shells, molluscs and other animals) actually disappears for further use, and the energy of soft tissues is transferred to the next level.

Reducers - destroyers of organic matter. This includes many bacteria, fungi, and from animals - some worms (earthworms, etc.), insects (termites, dung beetles, fly larvae) and others. All of them are heterotrophs, since they feed on organic, albeit dead, matter - dead plants, animals and their excreta products. Reducers bring the decay of biomass to inorganic substances: H 2 O, CO 2, NH 3 and release them into the external environment - soil, water, air. The intercepted energy is used by decomposers for their vital activity and, as a result, is dispersed in different shells of the biosphere - lithosphere, hydrosphere, atmosphere, and the released inorganic substances again come to producers.

Thus, all organisms are connected by the transfer of matter and energy, through them and through the external environment, a global circulation of matter on Earth takes place. The main donor of energy for maintaining this cycle is the Sun - its light energy provides photosynthesis of glucose in plants. The pathways for the transfer of matter and energy through the food relations of organisms are designated as food chains, or food chains. These chains have a one-way direction: from the autotrophic biomass of producers - mainly green plants - to heterotrophic consumers and further to decomposers. A significant part of the substance returns to the cycle, but the energy received from the sun is irretrievably lost for living organisms, it either accumulates in new soil minerals and bottom sediments (coal, chalk and other fossils), or accumulates in the form of heat in the shells of the Earth (heating atmosphere), or dissipates into Space. Examples of food chains are shown in Fig. 25 and 26.

Power chains are of different complexity, the number of links in each of the three levels can be different. Let's say a variant of a short chain: plants - hare - wolf - worms, bacteria. Long chain: plants - herbivorous insects (locust, forest bug, etc.) - predatory insects (ground beetle, dragonfly larva, water bug, etc.) - insectivorous birds (swallows, flycatchers, etc.) - birds of prey (eagle, kite, etc.) etc.) - worms, bacteria. Marine chain: phytoplankton - small crustaceans, worms - fish that feed on crustaceans and worms - predatory fish - birds of prey ... In any chain, numerous branches and alternate routes are possible. If any member falls out, the flow of matter goes through other channels. Let's say that the loss of dragonfly larvae is compensated for by water bugs, both of which are aquatic predators. If the main type of food vegetation disappears, herbivores switch to secondary food. If butterflies disappear, the swallows catch flies. From herbivorous insects, the chain can go in a completely different way: frog-heron-fox, etc. Omnivores and, of course, humans are especially confusing in food chains, since they are "embedded" in chains in various links. So, in fact, there are not chains, but food webs - each trophic level is formed by many species. This situation stabilizes the flows of matter and energy through living communities, increases the stability of biocenoses. Nevertheless, the general direction of the trophic flow is unchanged - producers - consumers of several orders - reducers.

It is important to take into account that each trophic level transfers to another level the energy contained in the macromolecules of organisms. Moreover, this energy is only a part of the energy received from the previous level, since its main share is spent on the vital activity of organisms of this level (biosynthesis, movement, transport of ions, etc.), and is also lost in the form of heat or built minerals. The same proportions can be expressed through the concept of biomass. The so-called ecological pyramid is being built - during the transition from lower trophic levels to higher amounts of internal (free, contained in organisms) energy and the total biomass of organisms decrease. It is estimated that about 10% of the energy is transferred from level to level, and only 0.01% of the energy received by plants from the sun comes from plant matter to predators and from them to decomposers. An illustrative example of a food pyramid built by the number of inhabitants per hectare of land is given below:

350 thousand predatory insects

700 thousand herbivorous insects

9 million plants.

The food pyramid of an ecosystem, as a reflection of its structure, maintains self-regulation and sustainable development. The characteristic proportion of different inhabitants of the biocenosis is established by itself, as a result of self-regulation processes, and reflects in general the supporting capacity of the environment. The given figures are average, but in fact, in all populations there is a fluctuation in the number of individuals, and fluctuations at the lowest level invariably lead to the same fluctuations at the next level, and the system as a whole maintains an equilibrium state.

In fig. 27 shows an example of a self-regulating biocenosis of 4 trophic levels. Let us trace how direct and feedback relationships are manifested in the dynamics of the number of organisms of different trophic levels. Depending on fluctuations in weather and climatic conditions (solar activity, precipitation, etc.), the yield of forage plants - producers varies from year to year. Following the growth of green biomass, the number of herbivores - consumers of the first order (direct positive relationship) increases, but already next year this will negatively affect the yield of plants, since most of them will not have time to produce seeds, since they will be eaten (negative feedback). In turn, an increase in the number of herbivores will create conditions for good nutrition and reproduction of predators - consumers of the second order, their numbers will begin to increase (direct positive relationship). But then the number of herbivores will decline (negative feedback). By this time, grass litter from the first wave of harvest and excrement of herbivorous animals and, to a lesser extent, predators will have time to decompose in the soil to mineral substances, which will create favorable conditions for plant growth. The second harvest wave will begin and the cycle will repeat itself. From year to year, the number of individuals of different trophic levels will vary, but on average, the biocenosis will maintain a stable state for many years. This is homeostasis.

As noted at the beginning, the biocenosis should not only self-regulate (judging by the above diagram, it is not so difficult), but it should be resistant to changes in external (abiotic, weather and climatic) factors, so to speak - a margin of safety in case of adverse conditions Wednesday. A number of conditions will contribute to maintaining the high stability of the biocenosis:

high, but balanced reproductive potential of individual populations - in case of mass death of individuals;

adaptation (adaptation) of certain species to the experience of unfavorable conditions;

diversity of communities and branched food webs - the disappeared object must be replaced by another, normally secondary.

Thus, the stability of the ecosystem, its self-regulation, or homeostasis, manifests itself in its self-reproduction, self-regulation of the number and resistance to extreme environmental factors.

But the sustainability of the ecosystem is relative, not unlimited. It is violated mainly in two cases:

with strong changes in the external environment - fires, floods, prolonged droughts, glaciers and other natural disasters;

with drastic changes in the composition of communities - usually by humans, for example, as a result of mass shooting of predators, colonization of new species, as was the case with rabbits in Australia, deforestation, plowing of steppes, etc.

At the same time, ecosystems change, their transition to a new quality, which means a new cycle of development in the direction of increasing sustainability. The biocenosis is being restored, but already with new communities of organisms, with new direct and feedback links. This process of changing the ecosystem and its development to a new state of stability occurs in stages and very slowly and is denoted by the concept of succession (from the Latin successio - continuity, inheritance). We emphasize that succession no longer represents self-regulation, but its opposite - self-organization, development, since during the restructuring of the system, positive feedbacks prevail, instead of negative ones, and its quantitative and qualitative characteristics change.

Distinguish between primary and secondary succession.

Primary succession - self-organization of an ecosystem on a free primary substrate: rock formed during geological faults in the earth's crust; the bottom of a dried-up reservoir, for example, the Aral or Caspian seas; the desert formed after the retreat of the glacier; empty quarry after mining, etc. Below is a typical dynamics of the primary succession.

Primary substrate (rock, sand, silt, rubble, etc.);

weathering, erosion of rocks (destruction under the influence of wind, water, temperature changes);

colonization by bacteria, algae, microscopic fungi, which leads to nitrogen fixation and soil formation;

settlement of mosses and lichens, an increase in the soil layer;

settlement of grasses, formation of meadows and steppes; simultaneous settlement of small animals - worms, insects, rodents; displacement of mosses and lichens as a result of competition;

settlement of shrubs, an increase in the diversity of animals (the appearance of birds, large mammals);

settlement of trees, the formation of a multi-tiered forest community with an extensive food web.

This is the end of development - a new stable self-regulating ecosystem has been formed, with a new ecological homeostasis. Such a complete, balanced community of animals, plants, fungi, microorganisms is called a climax community. However, the final composition of the ecosystem depends on the latitude and climate. The tundra, savannah, even the desert can also become stable - each with its own set of organisms adapted to these conditions. The primary succession usually takes several thousand years to form.

Secondary succession is the process of ecosystem restoration after damage caused by external influences: after a storm, fire, deforestation, cattle grazing, etc. Secondary successions are usually incomplete, simplified, depleted in the species composition of communities. The role of secondary successions increases with the increase in the human population of the Earth, especially with the development of cities, industrial production and intensive farming. Human influence on the state of ecosystems has become decisive today. Secondary successions develop over several years or decades.

Thus, despite self-regulation in ecological systems, nature changes naturally and irreversibly. This is a natural biogeochemical process that occurs independently of the will and human activity. When it proceeds without sharp deviations, they talk about the sustainable development of ecosystems and the Earth's biosphere as a whole. This definition reflects the unity of opposites: stability, homeostasis, on the one hand, and development, irreversible change, on the other. Disruption of sustainable development means the onset of an ecological crisis, fraught with such a change in the biosphere that will become incompatible with the life of mankind. The main reason for irreversible changes in the biosphere in the XX century was human economic activity. The task of ecology science is to understand the driving forces of sustainable development, to predict the ecological crisis, and the task of society is to perceive new ecological thinking and take timely measures to prevent crisis conditions.

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