MINISTRY OF GENERAL AND PROFESSIONAL

EDUCATION OF THE RUSSIAN FEDERATION

TOMSK STATE UNIVERSITY OF SYSTEMS

OFFICE AND RADIO ELECTRONICS (TUSUR)

Test work number 1

on Ecology

option number 10

Completed:

Why does the productivity of ecosystems increase in the process of ecological succession?

Changing communities.

During the course of the succession, the face of the community is constantly changing. The functioning of the ecosystem is also changing. If we stop cultivating the arable field that was once reclaimed from the forest, then the forest that previously occupied this territory will return here again. However, before that a number of communities will arise in this place, which, replacing each other, will prepare the way for the forest. These successive communities can be likened to the developmental stages that many organisms go through before reaching maturity.

Communities change over time. Their species composition, the abundance of certain groups of organisms, trophic structure, productivity and all other indicators change. Such changes take a long time and for very different reasons than the seasonal changes in the abundance of organisms that occur when individuals complete their life cycles.

The off-season process, which is a certain sequence of the appearance and disappearance of populations of different species in a given habitat, is called ecological succession and is natural. The succession is governed by the community itself and does not depend on the location or species of its constituent organisms.

Equilibrium in the community.

In ecology, the total energy consumption is called the common breath of the community. Ideally, neither biomass accumulation nor losses can occur. Therefore, the biomass of organisms in such a system remains constant, while the system itself remains unchanged, or equilibrium: the production processes are balanced by the respiration processes.

Different types of community balance:

It is characteristic of a closed community: no additional products come here, and their own remains entirely within it.

It is typical for some ecosystems of flowing water. Here, organic matter arises not only as a result of the functioning of autotrophs, but also from an influx from outside.

It is typical for agricultural ecosystems, where there is a constant withdrawal of part of the product.

If general breathing less gross primary production, the ecosystem will accumulate organic matter, if more - its disappearance. Both will lead to community change. With an abundance of resources, there will always be species that can master it. With a lack of resources, some of the species will become extinct. Such changes are the essence of ecological succession. The main feature of this process is that community changes always take place in the direction of an equilibrium state.

Autotrophic and heterotrophic successions.

The development of a forest on an abandoned field is an example of a succession that occurs in a clearly expressed autotrophic state, because at the first moment autotrophic organisms appear. Such a succession is called autotrophic. The species composition of organisms changes from year to year, and organic matter is accumulating in the community. Autotrophic succession is a widespread phenomenon in nature that begins in an uninhabited environment and is characterized by an early and long-term predominance of autotrophic organisms.

An example of another type of succession is a river polluted with a large amount of organic waste. In this case, excess organic matter begins to be actively used by heterotrophs. At the same time, it is consumed faster than it is created, that is, there is a constant decrease in organic matter. It - heterotrophic succession.

Heterotrophic succession is characterized by the initial predominance of heterotrophic organisms and occurs when the environment is oversaturated with organic matter. Energy reserves are at first maximum here and decrease with succession, unless, of course, additional organic matter is introduced.

The flow of energy passing through the community decreases during the heterotrophic succession. In contrast, with an autotrophic type of succession, the energy flow may even increase.

1. What is called the trophic structure of a community?

Answer. The trophic structure of a community is an ecological indicator of food interactions in it. Any community can be represented as a food web, that is, a diagram of all food, or trophic (from the Greek tropho - food), relationships between the species of this community. The food web (its weaves are very complex) usually consists of several food chains, each of which is a separate channel through which both matter and energy are transmitted. A simple example of a food chain is given by the following sequence: vegetation - an insect feeding on vegetation - a population of a predatory insect - an insectivorous bird - a bird of prey. In this chain, there is a unidirectional flow of matter and energy from one group of organisms to another.

2. What environmental factors are you aware of?

Answer. Environmental factors are individual elements of the environment that interact with organisms.

Distinguish between abiotic, biotic factors and anthropogenic factors. Abiotic factors: light, temperature, humidity and other components of the climate, the composition of air, soil and others, that is. elements of inanimate nature.

Biotic factors: living bodies, or organisms, all kinds of interactions between them (phytogenic, zoogenic).

Anthropogenic factors: deforestation, drainage of swamps, construction of a dam, release of various chemicals into the atmosphere, etc. (i.e. human activities).

Questions after § 86

1. What is succession?

Answer. The communities are constantly changing. Their species composition, the number of certain groups of organisms, trophic structure, productivity and all other indicators change. Communities change over time.

The natural and consistent process of changing communities in a certain area, caused by the interaction of living organisms with each other and the abiotic environment surrounding them, is called succession (from Latin successio - heritage, generational change, sequence).

2. Is equilibrium possible in a community where the “general respiration” of organisms is not equal in terms of gross production?

Answer. In order to understand the nature of ecological succession, let us imagine an ideal community in which the gross, i.e., total, production of autotrophs in terms of energy exactly corresponds to the energy consumption spent on ensuring the vital activity of its constituent organisms. In ecology, the total energy consumption is called the general respiration of the community.

It is clear that in such an ideal case, the production processes are balanced by the respiration processes. Consequently, the biomass of organisms in such a system remains constant, and the system itself remains unchanged, or equilibrium.

If the “total respiration” is less than the gross primary production, the accumulation of organic matter will occur in the ecosystem, if it is greater, it will decrease. Both will lead to community change. With an excess of the resource, there will always be species that can master it, with a shortage of it, some of the species will become extinct. Such changes are the essence of ecological succession. The main feature of this process is that community changes always take place in the direction of an equilibrium state.

Each stage of succession is a community with a predominance of certain species and life forms. They replace each other until a state of stable equilibrium occurs.

3. What types of successions do you know?

Answer. Distinguish between primary and secondary successions.

Primary successions arise on substrates not affected by soil formation and are associated with the formation of not only phytocenosis, but also soil. An example of a primary succession is the settlement of crustose and leaf lichens on stones. Under the influence of lichen secretions, the stony substrate gradually turns into a kind of soil, where bushy lichens, green mosses are already settled, then grasses and other plants, etc.

Secondary successions develop in the place of formed biocenoses after their disturbance, for example, as a result of erosion, drought, fire, deforestation, etc.

4. What are the differences between young and mature communities?

Answer. The duration of the succession is largely determined by the structure of the community. In the primary succession, it takes many hundreds of years for a sustainable community to develop.

Secondary successions are much faster. This is due to the fact that the primary community leaves behind a sufficient amount of nutrients, developed soil, which creates conditions for the accelerated growth and development of new settlers.

A mature community with its great diversity and abundance of organisms, developed trophic structure and balanced energy flows is able to withstand changes in physical factors (for example, temperature, humidity) and even some types of chemical pollution to a much greater extent than a young community. However, the young community is capable of producing new biomass in much larger quantities than the old one.

Thus, a person can harvest a rich harvest in the form of pure products, artificially supporting the community in the early stages of succession. Indeed, in a mature community at the stage of stability and stability, the net finished product is spent mainly on the “common respiration” of plants and animals and may even be zero.

On the other hand, the stability of a mature community, its ability to withstand the effects of physical factors (and even manage them) is a very important and highly desirable property.

Have you ever observed successive changes in nature? Tell us about your observations.

Answer. When a community is destroyed by human activity or natural disasters, such as a flood or fire, a slow process of recovery begins, known as succession. Succession is a sequential series of changes that ultimately lead to the formation of a climax community (provided that no further disturbances occur).

An example of succession is the restoration of a climax deciduous forest on an abandoned field. When the field ceases to be cultivated, it soon becomes overgrown with annual herbaceous plants that form a variegated carpet: black mustard, ragweed, dandelions. These "pioneers", who came to a new habitat, grow rapidly and produce seeds adapted to spread over a relatively large area with the help of wind or animals. Taller plants such as the golden rod and perennial grasses soon appear here. As these aliens shade the ground and their extensive root systems take all moisture from the soil, the seedlings of the species that enter the field first become difficult to grow. But just as these tall weeds drown out the sun-loving first species, they are in turn shaded and deprived of water by the seedlings of pioneer trees, such as bird cherry and aspen, which settle more slowly, but, having reached sufficient size, take up the lion's share of all resources ... The succession does not end there, since pioneer trees do not belong to the species forming a mature climax forest; the slow-growing oak and hickory or beech and maple are the last species to emerge and crowd out the pioneers, shading their young trees.

Succession in an abandoned field is an example of a secondary succession that proceeds relatively quickly because it occurs on the soil left over from the original climax forest. If the soil is severely depleted as a result of its mismanagement or is completely absent (as on bare rocks exposed after the retreat of ice, or on solidified lava flows), then the succession proceeds much more slowly, since the growth of most plants becomes possible only after the formation of the soil.

A succession beginning on bare rocks is called a primary succession. Soil formation can occur as a result of erosion of the matrix surface by acid released by lichens, or the freezing and thawing of water accumulating in crevices, causing rock to collapse. In addition, dying lichens introduce organic matter into the newly formed soil, and mosses can gain a foothold even on a very thin layer of lichen residues and mineral dust. As the mosses destroy the rock more and more and add their own dead material to the accumulating soil, germination and growth of small rooting plants becomes possible, beginning a process much like the succession of an "abandoned field".

The succession can be observed even on a city street. Mosses, lichens and weeds infest cracks in sidewalks; in some corner, where fallen leaves and dirt accumulate, rather large plants can grow, and on roofs requiring repair, mosses can grow. If you stop cleaning and repairing streets, then even the center of a large city within a generation can turn into a wooded area strewn with stones.

The existence of diverse sites undergoing succession provides a constant source of "wandering" plants - fast-growing weeds that appear suddenly and just as suddenly disappear. The seeds of these species can be spread over fairly long distances with the help of wind or animals. In addition, the seeds of many "wandering" plants are capable of dormancy for long periods, germinating after any disturbance in the environment creates the appropriate conditions, for example, increased illumination.

Equilibrium- this is the state of the ecosystem in which the composition and productivity of its biotic part (biocenosis) at each moment of time most fully corresponds to abiotic conditions - soil and climate; and this balance ensures the long-term stable existence of this natural complex.

The state of equilibrium is characterized, first of all, by the following signs:

A) The constancy of the species composition of the biocenosis. Those. there is a well-balanced set of species of animals, plants, microorganisms. Trophic links are stable, ecological niches are densely filled. the environment created in such a biogeocenosis is so specific that it limits the introduction of new species into the community; and as such, indigenous communities can remain stable for a significant number of years.

B) Consistency of nutrient cycles. All carbon and nitrogen assimilated by the ecosystem from the atmosphere returns to it as a result of the activity of decomposers. All elements of mineral nutrition (P, K, Ca, etc.), after decomposition of dead organic matter, return to the soil solution for reuse by plant roots. If part of the organic matter turns into detritus, then the rate of its accumulation corresponds to the rate of its decomposition by reducers. Those. all substances assimilated by biota are returned to the environment.

Various balance types. The first one is characteristic for a closed community : no additional products come here, and the community's own products remain entirely within the community. Equilibrium here means that all gross production of autotrophs corresponds to the costs spent on ensuring the vital activity of organisms that make up a given biocenosis... Let's call it "Common breathing"... Such a community is like a factory in which the cost of production is exactly equal to the profit received. The production process is balanced by the "general breathing" processes. The second type of balance is characteristic for some ecosystems of "flowing water" , in which organic matter arises not only as a result of the functioning of autotrophs, but also as a result of an influx from outside. Equilibrium here means that "Total respiration" is equal to the gross production of the community itself, supplemented by the intake of organic matter from the outside... For some ecosystems, the removal of matter outside their boundaries is so great that their stability is maintained mainly due to the inflow of the same amount of matter from the outside; while the internal circulation is ineffective. These are flowing reservoirs, rivers, streams, areas on steep mountain slopes. In agricultural agroecosystems (the third type of equilibrium), on the contrary, there is a constant withdrawal of part of the production, as already mentioned. Therefore, in such ecosystems equilibrium is achieved only when "general breathing" is provided by the amount of production that will have to remain in the system after the removal of a part of it by Man (harvest). it principle about the impossibility of complete withdrawal of products from the system, if there are no additional compensating supplies of resources from the outside.

With all this, it must be said that in reality not one, even the largest ecosystem on the Earth, has a completely closed cycle of substances. Those ecosystems that have a more or less complete cycle of substances are still autonomous in fact only relatively (forests, meadows, lakes, etc.). The continents exchange matter with the ocean, the lithosphere (with the participation of the atmosphere in these processes); and our entire planet receives a part of matter and energy from space, and gives a part to space.

If the “total respiration” is less than the gross primary production, the organic matter will accumulate in the ecosystem. If more - its disappearance. Both will lead to a change in the community. With an abundance of resources, there will always be species that can master it. With a lack of resources, some species will become extinct. Those. the ecosystem will again return to an equilibrium state, but already another - new. Thus, the main feature of ecological balance is its mobility. Such changes constitute the essence of the so-called ecological succession - the successive replacement of one community by another... The main feature of this process is that community change always happen towards equilibrium .

C) Complete dissipation of the energy supplied to the ecosystem. All the energy assimilated by the ecosystem, after passing through the trophic chains, dissipates in the form of heat and is "burned" by organisms in the process of life and work. The ecosystem maintains balance due to the fact that it is constantly receiving new solar or chemical energy.

Ecological balance in ecosystems is maintained by complex mechanisms of relationships between living organisms and environmental conditions; between individuals of the same species and individuals of different species with each other, which we have already talked about. The relationship between organisms of the same trophic level is called horizontal.(competition) , and between organisms of different trophic levels - vertical(predation, symbiosis).

In addition to the equilibrium state, any ecosystem is also characterized by the degree of stability, stability and endurance. Sustainability ecosystems is the ability to withstand any external and internal disturbances, including anthropogenic ones, and each time return to its original equilibrium state. Those. the ability to recover every time. Stability ecosystems - the ability to remain unchanged, to maintain their structure and functional features, indefinitely, thanks to their internal regulatory mechanisms. If an unstable ecosystem can deviate in one direction or another in its development even without any special disturbances from the outside, then a stable one always remains unchanged. Endurance - the ability to endure long-term external and internal disturbances and adapt to them, while maintaining a dynamic (mobile) balance. Those. the ability to adapt to experience adverse conditions.

History knows many cases when a person's short-sightedness caused the most serious ecosystem disturbance... What are reasons this can be caused by:

a)extermination of the predator from the ecosystem(at the same time, the populations of victims and the resources that they feed on suffer - all the grass is eaten by ungulates);

b)inclusion in the ecosystem of a species for which there is no reducer- as a consequence, the accumulation of undecomposed detritus (in Australia, cows and dung beetles);

v)inclusion in the ecosystem of plant species that do not have phytophages here- as a result - excessive reproduction and suppression of native species (in Australia, the punch and the fire butterfly);

G)similar consequences have the opposite effect - the destruction of the phytophage in the ecosystem;

g)changes in climatic, soil, hydrological conditions includes a change in the flora and fauna of the ecosystem.

Equilibrium (stability) and diversity are linked by very complex interdependencies. Not always great diversity provides the biocenosis with the proper stability and stability. After all, systems that are too large and complex with many highly specialized and carefully matched elements are often easy to destroy.

DYNAMICS OF ECOSYSTEMS

There are no frozen, static processes in living nature. Naturally, ecosystems are constantly changing. They bring the ecosystem back into balance over and over again. As we have already said, the main feature of ecological balance is its mobility - dynamism. At their core, these ecosystem changes can be attributed to two main types: a) reversible cyclic (periodic) and b) irreversible translational.

A) Cyclic processes are connected with the periodicity of external conditions. Diurnal rhythms changes in temperature, humidity, and illumination cause a corresponding change in the activity of various organisms inhabiting the ecosystem. Seasonal changes in ecosystems occur during the year from spring to spring and already affect the quantitative indicators characterizing the state of the biocenosis. This is especially evident in climatic zones with contrasting conditions of winter and summer. The ratio of different species of organisms at different times of the year can vary significantly depending on the breeding cycles, seasonal roaming and migrations. In addition, a number of species can completely disappear from the life of the community, falling into torpor or hibernation. In plants, depending on the seasons of the year, some layers may be completely absent (annual grasses in winter). Long-term periodic variability depends primarily on changes in climatic indicators over the years.

B) In addition to the noted cyclical changes in ecosystems, directional progressive processes leading to irreparable changes, irreversible consequences. As a result, a biocenosis may appear that is qualitatively different from the previous one. Sometimes in nature, a change in biocenoses occurs suddenly, as a result of abrupt and even catastrophic events in the environment.(fire, spill of large amounts of oil, deforestation, flooding or lowering of the groundwater level, the passage of wheels of machinery in the tundra). This can happen either under the influence of natural forces, or as a result of human activity. At the same time, the factor causing the change is in no way connected with the previous course of development of the ecosystem and sets a different direction for its development, which can lead to disruption of biocenotic relationships, ecological balance, and even to the death of the biocenosis. But with the termination of the effect of the factor in this territory, a new line of development of the living cover may begin, which, over time, step by step, will lead to the emergence of a new community here, possibly similar to the indigenous, destroyed one. But more often in natural nature, the replacement of one biocenosis by another occurs gradually, as if stepwise, sequentially, in parallel with changes in environmental conditions.- with an increase (or decrease) in the moisture or richness of the soil, with a change in climate, etc. In this case, the composition of living organisms, the type of cycle of substances and the level of productivity of the ecosystem change. Gradually, the role of some species decreases, while others increase; different species drop out of the ecosystem or, conversely, replenish it. This phenomenon of the sequential gradual replacement of one biogeocenosis with another is called succession... Such changes in the community lead, as a rule, from a less stable state to a more stable one. Those. any biogeocenosis tends in its natural development to balance, as already mentioned.

Many ecosystems have existed for tens or even hundreds of years.

The stability of ecosystems is their ability to withstand fluctuations in external factors and maintain their structure and functional characteristics. To maintain such stability of ecosystems, it is necessary to balance the flows of matter and energy, exchange processes between organisms and their environment. A sustainable ecosystem must get the right amount of substances from the environment and get rid of waste. Ecosystems are divided into open and closed depending on the way of maintaining sustainability.

Open ecosystems are continuously supplied with energy and matter from the environment. In such ecosystems, the processes of accumulation and decomposition of matter are constantly going on. Natural ecosystems belong to this type, the balance in them is maintained spontaneously.

In closed ecosystems, there is no constant exchange of matter and energy with the environment. The system is unable to dispose of unnecessary products. Equilibrium in this case can be maintained artificially. Closed systems are unstable without outside interference and quickly become unstable.

Ecological equilibrium is the relative constancy of the species composition of living organisms, their number, productivity, distribution in space, as well as seasonal changes, biological circulation of substances and other biological processes in an ecosystem, leading to a long-term existence of this ecosystem. Of course, no ecosystem is absolutely stable, immobile: the number of some species periodically increases, while the number of others decreases. Such processes occur periodically and, as a whole, do not unbalance the system. Therefore, the main feature of ecological balance is its mobility. There are two types of balance mobility:

Reversible changes in an ecosystem are changes that occur from spring to spring in an ecosystem while maintaining the species composition;

Ecological succession (Latin succesio - succession, inheritance) is a sequential change of ecosystems arising in the same territory or water area (biotope) under the influence of natural or anthropogenic factors. Depending on the initial state of the substrate on which the succession develops, there are primary and secondary successions.

Primary succession is the process of development of ecosystems in previously unpopulated areas, starting with their colonization. For example, the settlement of islands that have arisen as a result of volcanic activity. Or the overgrowth of bare rock, first with lichens, then with mosses, grasses and other plants. In the process of primary succession, not only phytocenoses are formed (Greek phyton - plant, koinos - common), i.e. plant biocenoses, but also soil.

Secondary succession is the restoration of ecosystems that once existed in a given biotope. In such places, rich vital resources are usually conserved. Therefore, secondary successions lead to the formation of biocenoses much faster than primary ones.

Distinguish between autotrophic and heterotrophic successions.

Autotrophic succession occurs under the influence of solar energy, while autotrophic organisms predominate in the community. In the course of autotrophic succession, the community becomes more complex, and the stability of ecosystems increases.

An example of autotrophic succession is an ecosystem that begins to recover in a forest fire (Fig. 5). After 1-2 years, the site of the fire is overgrown with grass, after a few years the first shrubs appear, after 20-25 years the territory is covered with forest: first deciduous, and then shade-loving conifers grow.

Fig. 5. Autotrophic succession in a forest fire

Heterotrophic succession is typical for those cases when there is an excess of organic matter in the ecosystem (polluted water bodies, rotting plant remains, etc.) In this case, heterotrophic organisms predominate in the community, so the energy supply does not increase, but decreases. The result of heterotrophic succession is either the death of all organisms or a significant simplification of the community.

An example of heterotrophic succession is the “aging” of water bodies. There are two main stages of succession - developing and mature. These stages are characterized by different properties and varying degrees of stability.

Mature systems are more capable of storing substances in the exchange fund. The gyres in them are mostly closed. Increasing the stability of ecosystems during the succession leads to the fact that each subsequent stage lasts longer than the previous one.

Mature systems are the most stable over time. But they can also be destroyed in the course of natural and man-made disasters. If we consider long periods of time, it turns out that any succession is a cyclical process. The cycles may not completely repeat each other, take different periods of time, but the cyclicality remains.

Depending on the reasons that caused the change of ecosystems, successions are divided into autogenous and allogeneic.

Autogenic successions (self-generating) arise due to internal causes (changes in the environment under the influence of the community), allogeneic (generated from the outside) are caused by external causes (for example, climate change).

In the last stages of succession, stable communities are usually formed, which are called climax.

Climax community, climax (Greek klimax - ladder) is characterized by the highest productivity and the greatest diversity.

The ability of a population or ecosystem to maintain a mobile-stable balance when environmental conditions change is called ecosystem homeostasis.

The mechanism for maintaining homeostasis is based on two principles:

The principle of cyclicity is the repeated use of nutrients in the ecosystem. This makes the reserves of mineral substances in the ecosystem practically inexhaustible.

The principle of "feedback" is that the deviation of an ecosystem from a state of equilibrium sets in motion forces that return it to an equilibrium state.

BIOSPHERE

4.1. BIOSPHERE - THE LIVING SHELL OF THE EARTH

The biosphere, according to the definition of V. I. Vernadsky, "zone of life", covers the lower part of the atmosphere (troposphere), the entire hydrosphere and the upper part of the lithosphere (soil). In other words, the biosphere is a global biotope inhabited by all living organisms, including humans.

The biosphere is a set of parts of the geospheres (litho-, hydro- and atmosphere), which is inhabited by living organisms, is under their influence and is occupied by the products of their vital activity. It does not form a dense layer with clear boundaries, but, as it were, "permeates" other geospheres of the planet. The upper boundary of the biosphere extends from the Earth's surface to the ozone layer, the maximum density of which is at an altitude of 20-25 km. Above this limit, organisms cannot live: ultraviolet radiation from the Sun and a very low temperature (-56 ° C) affect them.

Almost the entire hydrosphere, including the deepest depression (Mariana) of the World Ocean (11022 m), is busy with life.

The lower boundary of the biosphere runs along the ocean floor in the hydrosphere and at a depth of 3.0-3.5 km in the earth's crust of the continental zone, where the subsoil temperature reaches 100 ° C and higher. This temperature is also destructive for all living things.

The most densely populated by organisms is land, the surface waters of the ocean and its bottom at a shallow depth (up to 250 m), where the sun's rays penetrate. The living conditions are especially favorable here.

The biosphere is on average a little over 20 km thick. Compared to the diameter of the globe (13,000 km), the biosphere is a thin film. Nevertheless, in mountain glaciers, at altitudes of up to 6 km, mite communities live; from birds, the condor can rise to an altitude of 7 km; in the depths of the ocean (up to 11 km), there are communities of animals and microorganisms, in the underground oil waters of the land at depths of up to 15 km, communities of bacteria (chemoautotrophs) can be found.

The mass of the biosphere is estimated to be about 1.5 · 10 21 kg.

The biosphere has a system of properties that ensure its functioning, self-regulation, stability and other parameters. The main properties are as follows.

1. The biosphere is a centralized system. Living organisms (living matter) are its central link.

2. The biosphere is an open system. To maintain life on Earth, it is necessary to receive energy from the outside, and part of this energy, being reflected, goes into outer space.

3. The biosphere is a self-regulating system , for which, as V.I. Vernadsky noted, organization is characteristic. This property is now called homeostasis.

4. The biosphere is a highly diverse system. The biosphere, as a global ecosystem, is characterized by the maximum diversity among other systems. For any natural system, diversity is one of its most important properties. Associated with it is the possibility of duplication, safety net, replacement of some links with others, the degree of complexity and strength of food and other connections. Therefore, diversity is considered as the main condition for the sustainability of any ecosystem and biosphere as a whole.

5. The presence in the biosphere of mechanisms that ensure the circulation of substances and the associated inexhaustibility of individual chemical elements and their compounds.

The biosphere is a complex natural system. It includes:

Living matter - a set of bodies of living organisms that live on planet Earth;

A biogenic substance is a substance created and processed by living organisms (coal, limestone, bitumen);

Inert substance is a substance in the formation of which life does not participate (rocks, gases);

Bioinert substance is a substance that is created simultaneously by living organisms and inert processes (natural water, soil, salt sea water, weathering crust, troposphere);

Radioactive elements have a complex isotopic composition coming from the depths, dispersed and dispersed, creating and changing the energetics of the biosphere;

Scattered atoms;

Substance of cosmic origin (meteorites, cosmic dust).

Living organisms have significantly changed the appearance of our planet, transformed the earth's crust, hydrosphere and lower layers of the atmosphere. And now they are involved in the destruction of rocks, in the formation of soil, minerals, such as peat, regulate the content of oxygen and carbon dioxide in the atmosphere.

Even at the early stages of evolution, living matter spread throughout the lifeless spaces of the planet, occupying all places potentially available for life, changing them and turning them into habitats. VI Vernadsky called this ability to spread living matter "the ubiquity of life."

VI Vernadsky considered living matter to be the most powerful geochemical and energetic factor, the leading force of planetary development. The pinnacle of the evolution of living matter on Earth was a man who acquired not only consciousness (a perfect form of reflection of the surrounding world), but also the ability to make and use tools in his life. By means of tools, mankind began to create an artificial environment, its habitat, and the evolution of the biosphere entered a new phase - the phase of the noosphere. Noosphere (Greek noos - mind, sphaira - ball) - the sphere of the mind, the highest stage of development of the biosphere, when intelligent human activity becomes the main determining factor of its global development. The term "noosphere" was first introduced in 1927 by the French philosopher E. Leroy to designate the shell of the Earth, which includes human society with its industry, language and other types of intelligent activity. VI Vernadsky wrote: “The noosphere is a new geological phenomenon on our planet. In it, for the first time, man becomes the largest geological force. He can and must rebuild with his work and thought the area of ​​his life, rebuild radically in comparison with what was before. "

Natural ecological systems (biogeocenoses) exist for a long time - tens and hundreds of years, retaining their structure and functional properties. those. have a certain stability. To maintain the stability of the ecosystem, it is necessary to balance the flows of matter and energy, metabolic processes between organisms and the environment.

The state of the ecosystem, in which the composition and productivity of the biotic component at each specific time point corresponds to abiotic conditions, is characterized as ecological balance.

Imagine a community in which the gross (that is, total) production of autotrophs in terms of energy exactly corresponds to the energy consumption spent on ensuring the vital activity of its constituent organisms. The total energy consumption is called the general respiration of the community.

It is clear that in this ideal case, neither biomass accumulation nor biomass loss can occur. Therefore, the biomass of organisms in such a system remains constant, and the system itself remains unchanged, or equilibrium (production processes are balanced by respiration processes).

You can imagine different types of balance.

First of them is characteristic of a closed community: no additional production comes here, and the community's own production remains entirely within it.

The second type of balance is characteristic of some ecosystems of flowing water, the organic matter of which arises not only as a result of the functioning of autotrophs, but also an influx from the outside. Equilibrium here means that "total respiration" is equal to the gross production of the community itself, supplemented by the input of organic matter from the outside.

The third type of balance(in agricultural ecosystems), on the contrary, implies the constant withdrawal of part of the product. Therefore, in such ecosystems, equilibrium is achieved only when the “total respiration” is equal to the amount of production that remains in the system after the removal of its part.

If the “total respiration” is less than the gross primary production, the accumulation of organic matter will occur in the ecosystem, if it is greater, it will disappear. Both will lead to community change. With an abundance of resources, there will always be species that can master it. With a lack of resources, some of the species will become extinct. The main feature of this process is that community changes always take place in the direction of the equilibrium state.

Stability an ecosystem for a long time assumes a relative immutability of the populations of its species. It can be long-lasting only if the changes in the environment caused by some organisms are precisely compensated by the activities of others, with opposite ecological requirements. This condition is violated when the circulation of substances is disturbed, and then some of the populations that cannot withstand competition are displaced by others for whom these conditions are favorable, and homeostasis is restored.

The position of a species population in an ecosystem is determined, on the one hand, by a set of requirements for abiotic conditions, and, on the other, by a set of connections with populations of other species and a form of participation in the general functions of the biocenosis. The place of an organism in nature and the whole way of its vital activity (the so-called vital status), including its relation to environmental factors, types of food, time and methods of feeding, breeding grounds and shelters, etc. defined as ecological niche... Long-term coexistence within a single multi-species community has led to the evolutionary formation of such a system of relationships in ecosystems, in which each species spatially and functionally occupies a certain position in the biocenosis, i.e. occupies its own ecological niche.

The set of species, the composition and complexity of food webs, the most stable forms of interaction of populations in an ecosystem reflect adaptability to the characteristics of the environment and are aimed at maintaining the cycle in these conditions.

An important characteristic of ecosystems is their steadiness, which is understood as the ability of an ecosystem to return to its original (or close to it) state after exposure to factors that bring it out of balance. The most stable, for the reasons discussed above, are distinguished by ecological systems with many relatively few species.

§4 Dynamics of ecosystems (succession)

The main feature of the ecological balance of an ecosystem is its mobility. Any ecosystem, adapting to changes in the external environment, is in a state of dynamics. Distinguish between cyclical and directional dynamics. An example of cyclical dynamics is a seasonal change in the activity of the vital activity of organisms, or a periodic change in the number of certain species in a long-term series. Directional dynamics represent the progressive development of ecosystems. This type of dynamics is characterized by either the introduction of new species into ecosystems, or the replacement of some species by others, which ultimately leads to a change in biocenoses and ecosystems as a whole. Changes in the species structure and biocenotic processes in an ecosystem are called ecosystem succession. Thus, succession is a process of successive change of ecosystems taking place in time with a gradual directional change in environmental conditions.

Large-scale changes in the geographic setting or the type of landscape under the influence of natural disasters or human activities lead to certain changes in the state of biogeocenoses of the area and to the gradual replacement of some communities by others. Such changes are called ecological succession(from lat ... successio- continuity, consistency).

Yu. Odum (1986) understands the whole process of ecosystem development by ecological succession. A more specific definition of this phenomenon is given by N.F. Reimers (1990): "Succession- a sequential change of biocenoses, successively arising in the same territory (biotope) under the influence of natural factors (including internal contradictions of the biocenoses themselves) or human impact ”.

Ecological succession occurs in a certain period of time, during which the species structure of the community and the abiotic environment of its existence change until the culmination of its development - the emergence of a stabilized system. In a narrower sense, it is a sequence of communities replacing each other in a given area.

If autotrophic organisms appear at the first moment, the succession is called autotrophic... For example, the development of a forest on an abandoned field. The species composition of organisms varies from year to year, and organic matter is accumulating in the community.

Heterotrophic succession characterized by the initial predominance of heterotrophic organisms and occurs in cases where the environment is oversaturated with organic matter. Energy reserves are at first maximum here and decrease with succession, unless, of course, additional organic matter is introduced.

The flow of energy passing through the community decreases during the heterotrophic succession. It ends after the excess of organic matter has been exhausted. In contrast, with an autotrophic type of succession, the energy flow may even increase.

For the occurrence of succession, free space is required, and depending on the initial state of the substrate, there are primary and secondary succession.

Primary succession– this is if the formation of communities begins on an initially free substrate, and the secondary su-cession– it is a sequential replacement of one community that existed on a given substrate with another, more perfect for the given abiotic conditions.

Primary succession allows you to trace the formation of communities from the very beginning. It can arise on a slope after a landslide or a landslide, on a sandbank formed during the retreat of the sea and a change in the river channel, on the exposed aeolian sands of the desert, not to mention anthropogenic disturbances: fresh cutting, an alluvial strip of the sea coast, artificial reservoirs.

A typical example is the settlement of rock outcrops. First, lichens appear on the rocks and algae form a complex of species of microscopic algae, protozoa, nematodes, some insects and mites, which contributes to the formation of primary soil. Later, other forms of lichens, specialized species of mosses appear, then vascular plants settle and the fauna is enriched.

Figure 4 shows a diagram of the development of a typical terrestrial primary succession.

Fig. 4.

Development diagram of a typical terrestrial primary succession.

Yelnik is the last climax stage in the development of the ecosystem in the climatic conditions of the North, that is, already the root biocenosis. Initially, birch, alder, aspen forests develop here, under the canopy of which spruces grow. Gradually, they outgrow the birch and displace it, capturing space (Fig. 5). The seeds of both tree species are easily carried by the wind, but even if they germinate at the same time, birch grows much faster - by 6-10 years, spruce barely reaches 50-60 cm, and birch - 8-10 m.

Rice. 5.

Change of a birch forest with a spruce forest (after I. N. Ponomareva, 1978)

Under the already closed crowns of birches, its own microclimate already arises, the abundance of leaf litter contributes to the formation of special soils, many animals settle, a diverse herbaceous cover appears, birch consortia with the environment are created. And the spruce continues to grow in such a favorable environment, and, finally, the birch does not withstand competition with it for space and light and is replaced by spruce.

Aging of lake ecosystems is a classic example of natural succession. eutrophication. It is expressed in the overgrowth of lakes with plants from the shores to the center. There are a number of overgrowth stages– from the initial – far from the coast - to reached by the coast. These stages are shown and described in Fig. 6.

Rice. 6.

Overgrowth of a eutrophic reservoir with stagnant or low-flowing water(Soloviev, 1983)

(the dotted line shows the lower water level)

Zones: 0 - free-floating plants, 1 – low (bottom) submerged plants, 2 – tall submerged plants, 3 - plants with floating leaves, 4 - tall emerging plants, 5 - low and medium-tall emerging plants, 6 - black alder bog.

Deposits: 1 - sapropelite, 2- 3 - sapropelite peat, 4 - reed and reed peat, 5 – sedge peat, 6 - forest peat

Ultimately, the lake turns into a peat bog, representing a stable climax-type ecosystem. But it is not eternal either - in its place, a forest ecosystem can gradually emerge thanks to a terrestrial succession in accordance with the climatic conditions of the area,

The eutrophication of the reservoir is largely determined by the introduction of nutrients from the outside. Under natural conditions, biogens are removed from the catchment area. Such eutrophication has the features of a primary progressive succession.

Secondary succession is, as a rule, a consequence of human activity. In particular, the above-described change of vegetation during the formation of a spruce forest often occurs as a result of a secondary succession that occurs in clearings of a previously existing forest (spruce forest). The secondary succession ends with a stable stage of the community in 150-250 years, and the primary one lasts 1000 years.

Secondary, anthropogenic succession also manifests itself in eutrophication. The rapid "blooming" of reservoirs, especially artificial reservoirs, is the result of their enrichment with nutrients, due to human activities. The "triggering mechanism" of the process is usually an abundant supply of phosphorus, less often nitrogen, sometimes carbon and silicon. Phosphorus usually plays a key role.

The biocenosis is almost completely reborn. There are massive fish killings. In especially severe cases, the water acquires the color and consistency of a pea soup, an unpleasant putrid smell: the life of aerobic organisms is excluded.

A sequential series of communities gradually and regularly replacing each other in the succession is called succession series. It is observed in nature not only in forests, swamps and lakes, but also on the trunks of dying trees and in stumps, where there is a regular change of saprophytes and saprophages, in puddles and ponds, etc. In other words, successions are of different scales and hierarchical, as well as well as the ecosystems themselves.

Each stage of succession represents a certain community with a predominance of certain species and life forms. The individual stages of the development of the succession are called serial stages, and the state of final equilibrium is menopause.

Successions caused by external factors are called exogenetic.Such successions can be caused, for example, by climate change in one direction (cooling or warming) and other changes in abiotic conditions. Such changes can occur over centuries and millennia and are called secular successions. If, as a result of changes in environmental conditions, some species die out, while others change under the influence of natural selection, this process is considered as an evolutionary succession.

If the succession occurs due to internal interactions, it is called endogenetic... Endogenetic successions are observed in nature when, in the course of its development, a community changes the environment so that it becomes more favorable for another community. The emerging new community, in turn, makes the environment even more unfavorable for the former community. A process of ecosystem change takes place, passing through several stages, until the final population equilibrium is reached. The succession ends with the formation of a community adapted to climatic conditions, capable of sustaining itself indefinitely, the internal components of which are balanced with each other and with the environment. The community that completes the succession - stable, self-renewing and in equilibrium with the environment - is called climax community.

How quickly ecosystems change depends on the degree of their balance shift. Successions are a natural process of ecosystem development. With successions, changes occur slowly and gradually. At all stages of the process of replacing some species with others, the system is sufficiently balanced. In the process of succession, more and more complex biocenoses and ecosystems are formed, and their productivity increases.

In the case of sudden abrupt changes that cause a "population explosion" of some species due to the death of most other species, one speaks of an ecological violation.

Violations can occur with the invasion of introduced species or with thoughtless human impact on nature. In modern conditions, the constant growth of anthropogenic load on natural ecosystems (drainage of swamps, excessive loads on forests, for example, as a result of recreation of the population, fires, increased grazing, chemical pollution of the environment) often leads to a relatively rapid change in their structure. Anthropogenic impacts often lead to the simplification of ecosystems. Such phenomena are usually called digressions (for example, grazing, recreational and other digressions). When the disturbances are so great that practically no component of the ecosystem is preserved, they speak of its death. After the destruction of the ecosystem, a new succession may begin on the vacated area.