Large geological cycle of substances. Small biological (geographic) cycle of substances

Solar energy on Earth causes two cycles of substances: large (geological), most clearly manifested in the water cycle and atmospheric circulation, and small, biological(biotic), developing on the basis of a large and consisting of a continuous, cyclical, but uneven in time and space, and accompanied by more or less significant losses in the natural redistribution of matter, energy and information within ecological systems of various levels of organization. Both cycles are mutually connected and represent, as it were, a single process.

Lasts for millions of years. Rocks are destroyed, weathered and carried by streams of water into the World Ocean, where they form powerful marine strata. Some chemical compounds dissolve in water or are consumed by the biocenosis. Large slow geotonic changes, processes associated with the subsidence of continents and the rise of the seabed, the movement of seas and oceans over a long period of time lead to the fact that these strata return to land and the process begins again.

Biological cycle, being part of a larger one, occurs at the level of biogeocenosis and consists in the fact that nutrients from soil, water, air accumulate in plants, are spent on creating their mass and life processes in them. The decay products of organic matter under the influence of bacteria are again decomposed into mineral components accessible to plants, and are drawn into the flow of matter by them.

Interaction abiotic factors and living organisms of the ecosystem is accompanied by a continuous circulation of matter between the biotope and the biocenosis in the form of alternating organic and mineral compounds. Exchange chemical elements between living organisms and the inorganic environment, the various stages of which occur within an ecosystem is called biogeochemical cycle, or biogeochemical cycle.

The existence of such cycles creates the opportunity for self-regulation (homeostasis) of the system, which gives the ecosystem stability: an amazing constancy of the percentage of various elements.

Basic biochemical cycles .

The water cycle

About a third of the solar energy reaching the Earth is spent on setting the water cycle in motion. The sea loses more water due to evaporation than it receives through precipitation. On land the situation is the opposite. That is, a significant part of the precipitation that supports land ecosystems comes to us from the sea.

However, the vegetation of a given area also makes a significant contribution to the water cycle, especially in areas located in the interior of the continent, or “screened” from the sea by a ridge of mountains. The fact is that the water entering plants from the soil almost completely (97-99%) evaporates through the leaves. This is called transpiration. Evaporation cools the leaves and promotes the movement of nutrients in plants.

Carbon cycle

Carbon is one of the most essential components for life. It is included in organic matter during photosynthesis. Then the bulk of it enters the food chains of animals and accumulates in their bodies in the form of various types of carbohydrates.

The main role in the carbon cycle is played by the atmospheric and hydrosphere funds of carbon dioxide CO2. This fund is replenished by the respiration of plants and animals, as well as by the decomposition of dead organic matter. Some carbon escapes from the cycle into landfills. However, the person in Lately It is quite successful in developing these burial sites, returning carbon and other elements important for life, accumulated over millions of years, to the cycle of life. The photosynthetic green belt and the sea's carbonate system maintain a constant level of CO2 in the atmosphere.

Nitrogen cycle

Nitrogen is part of amino acids, which are the main building materials for proteins. The main source of nitrogen is the atmosphere, from where nitrogen enters the soil and then into plants only in the form of nitrates, which are the result of the activity of nitrogen-fixing organisms (certain types of bacteria, blue-green algae and fungi.

The second source of nitrogen for plants is the result of the decomposition of organic matter, in particular proteins. In this case, ammonia is initially formed, which is converted by nitrifying bacteria into nitrates and nitrites.

The return of nitrogen to the atmosphere occurs as a result of the activity of denitrifying bacteria, which decompose nitrates into free nitrogen and oxygen.

Phosphorus cycle

Phosphorus is a necessary component of nucleic acids (RNA and DNA), which perform functions in biological systems related to recording, storing and reading information about the structure of the body. Phosphorus is a fairly rare element. Phosphorus is found in only a few chemical compounds. It circulates, turning organic matter into phosphates, which can then be used by plants. The peculiarity of the phosphorus cycle is that there is no gaseous phase in it. That is, the main reservoir of phosphorus is not the atmosphere, but rocks and other deposits formed in past eras. These rocks are subject to erosion, releasing phosphates into ecosystems. After repeated consumption by land and sea organisms, phosphorus is eventually excreted into bottom sediments. This threatens phosphorus deficiency. In the past, seabirds appear to have returned phosphorus to the cycle. Nowadays, the main supplier of phosphorus is humans, who catch large quantities of sea fish and also process bottom sediments into phosphates.

Sulfur cycle

Sulfur is an element necessary for the synthesis of many proteins. Biosystems require very little sulfur.

The sulfur cycle occurs through air, water and soil. SO4 sulfate, like nitrate and phosphate, is the main available form of sulfur, which is reduced by plants and incorporated into proteins. It then passes through the food chains of ecosystems and returns to the cycle with animal excrement. The main sources of sulfur compounds entering the biosphere are human production activities (combustion of coal and sulfur-containing hydrocarbons), volcanoes, decomposition of organic matter and decomposition of sulfur-containing ores and minerals.

Ways to return elements to the cycle :

• through microbial decomposition;
• through animal excrement;
• direct transmission from plant to plant in symbiosis;
• physical processes (lightning, ionization, etc.);
• due to fuel energy (for example, during industrial nitrogen fixation);
• autolysis (self-dissolution) - the release of nutrients from plant debris and excrement without the participation of microorganisms.

If you do not destroy the natural recycling mechanisms and do not poison them, then they mostly spontaneously return water and nutrients to the cycle. Unfortunately, man accelerates the movement of many substances so much that the cycles become imperfect or the process loses its cyclicality: in some places there is a deficiency, and in others there is an excess of some substances.

Large (geological) and small (biogeochemical) cycle of substances

All substances on our planet are in the process of circulation. Solar energy causes two cycles of substances on Earth:

Large (geological or abiotic);

Small (biotic, biogenic or biological).

Cycles of matter and flows of cosmic energy create the stability of the biosphere. The cycle of solid matter and water that occurs as a result of the action of abiotic factors (inanimate nature) is called the great geological cycle. During a large geological cycle (lasting millions of years), rocks are destroyed, weathered, substances dissolve and enter the World Ocean; geotectonic changes, continental subsidence, and seabed uplift occur. The water cycle time in glaciers is 8,000 years, in rivers - 11 days. It is the great cycle that supplies living organisms with nutrients and largely determines the conditions of their existence.

The large geological cycle in the biosphere is characterized by two important points: oxygen, carbon, geological

• a) is carried out throughout the entire geological development of the Earth;
• b) is a modern planetary process that takes a leading part in the further development of the biosphere.

At the present stage of human development, as a result of the large cycle, pollutants such as sulfur and nitrogen oxides, dust, and radioactive impurities are also transported over long distances. The areas of temperate latitudes of the Northern Hemisphere were the most contaminated.

Small, biogenic or biological cycle of substances occurs in solid, liquid and gaseous phases with the participation of living organisms. The biological cycle, as opposed to the geological cycle, requires less energy. The small cycle is part of a large one, occurs at the level of biogeocenoses (within ecosystems) and consists in the fact that soil nutrients, water, and carbon accumulate in plant matter and are spent on building the body. Decay products of organic matter decompose into mineral components. The small cycle is not closed, which is associated with the flow of substances and energy into the ecosystem from the outside and with the release of some of them into the biosphere cycle.

Many chemical elements and their compounds are involved in the large and small cycles, but the most important of them are those that determine the current stage of development of the biosphere, associated with human economic activity. These include the cycles of carbon, sulfur and nitrogen (their oxides are the main pollutants of the atmosphere), as well as phosphorus (phosphates are the main pollutant of continental waters). Almost all pollutants act as harmful substances and are classified as xenobiotics. Currently, the cycles of xenobiotics - toxic elements - mercury (a food contaminant) and lead (a component of gasoline) are of great importance. In addition, many substances of anthropogenic origin (DDT, pesticides, radionuclides, etc.) that cause harm to biota and human health come from the large cycle to the small one.

The essence of the biological cycle lies in the occurrence of two opposite but interconnected processes - the creation of organic matter and its destruction by living matter.

Unlike the large gyre, the small gyre has a different duration: seasonal, annual, perennial and secular small gyres are distinguished. The cycling of chemicals from the inorganic environment through vegetation and animals back into the inorganic environment using solar energy from chemical reactions is called the biogeochemical cycle.

The present and future of our planet depends on the participation of living organisms in the functioning of the biosphere. In the cycle of substances, living matter, or biomass, performs biogeochemical functions: gas, concentration, redox and biochemical.

The biological cycle occurs with the participation of living organisms and consists in the reproduction of organic matter from inorganic and the decomposition of this organic to inorganic through the food trophic chain. The intensity of production and destruction processes in the biological cycle depends on the amount of heat and moisture. For example, the low rate of decomposition of organic matter in polar regions depends on heat deficiency.

An important indicator of the intensity of the biological cycle is the rate of circulation of chemical elements. The intensity is characterized by an index equal to the ratio of the mass of forest litter to litter. The higher the index, the lower the intensity of the circulation.

Index in coniferous forests - 10 - 17; broad-leaved 3 - 4; savanna no more than 0.2; in tropical rainforests no more than 0.1, i.e. Here the biological cycle is most intense.

The flow of elements (nitrogen, phosphorus, sulfur) through microorganisms is an order of magnitude higher than through plants and animals. The biological cycle is not completely reversible; it is closely related to the biogeochemical cycle. Chemical elements circulate in the biosphere along various pathways of the biological cycle:

• - are absorbed by living matter and charged with energy;
• - leave living matter, releasing energy into the external environment.

These cycles are of two types: the cycle of gaseous substances; sedimentary cycle (reserve in the earth's crust).

The gyres themselves consist of two parts:

• - reserve fund (this is the part of the substance not associated with living organisms);
• - mobile (exchange) fund (a smaller part of the substance associated with direct exchange between organisms and their immediate environment).

Gyres are divided into:

• - gyres gas type with a reserve fund in the earth's crust (carbon, oxygen, nitrogen cycles) - capable of rapid self-regulation;
• - sedimentary cycles with a reserve fund in the earth's crust (cycles of phosphorus, calcium, iron, etc.) are more inert, the bulk of the substance is in a form “inaccessible” to living organisms.

Gyres can also be divided into:

• - closed (the cycle of gaseous substances, for example, oxygen, carbon and nitrogen - a reserve in the atmosphere and hydrosphere of the ocean, so the shortage is quickly compensated);
• - open-ended (creating a reserve fund in the earth's crust, for example, phosphorus - therefore losses are poorly compensated, i.e. a deficit is created).

The energy basis for the existence of biological cycles on Earth and their initial link is the process of photosynthesis. Each new cycle is not an exact repetition of the previous one. For example, during the evolution of the biosphere, some of the processes were irreversible, resulting in the formation and accumulation of biogenic sediments, an increase in the amount of oxygen in the atmosphere, changes in the quantitative ratios of isotopes of a number of elements, etc.

The circulation of substances is usually called biogeochemical cycles. The main biogeochemical (biosphere) cycles of substances: water cycle, oxygen cycle, nitrogen cycle (participation of nitrogen-fixing bacteria), carbon cycle (participation of aerobic bacteria; annually about 130 tons of carbon are discharged into the geological cycle), phosphorus cycle (participation of soil bacteria; annually in 14 million tons of phosphorus are washed out of the oceans), the sulfur cycle, the cycle of metal cations.

The water cycle

The water cycle is a closed cycle that can occur, as mentioned above, even in the absence of life, but living organisms modify it.

The cycle is based on the principle: evapotranspiration is compensated by precipitation. For the planet as a whole, evaporation and precipitation balance each other. At the same time, more water evaporates from the ocean than returns with precipitation. On land, on the contrary, more precipitation falls, but the excess flows into lakes and rivers, and from there again into the ocean. The moisture balance between continents and oceans is maintained by river flow.

Thus, the global hydrological cycle has four main flows: precipitation, evaporation, moisture transfer, and transpiration.

Water, the most abundant substance in the biosphere, not only serves as a habitat for many organisms, but is also an integral part of the body of all living beings. Despite the enormous importance of water in all life processes occurring in the biosphere, living matter does not play a decisive role in the large water cycle on the globe. The driving force of this cycle is the energy of the sun, which is spent on the evaporation of water from the surface of water basins or land. Evaporated moisture condenses in the atmosphere in the form of clouds carried by the wind; When clouds cool, precipitation occurs.

The total amount of free unbound water (the proportion of oceans and seas that contain liquid salt water) accounts for 86 to 98%. The remaining amount of water ( fresh water) is stored in the polar caps and glaciers and forms water basins and its groundwater. Precipitation falling on the surface of land covered with vegetation is partially retained by the leaf surface and subsequently evaporates into the atmosphere. Moisture that reaches the soil may join surface runoff or be absorbed by the soil. Having been completely absorbed by the soil (this depends on the type of soil, the characteristics of the rocks and vegetation cover), excess sediment can seep deeper into the groundwater. If the amount of precipitation exceeds the moisture capacity upper layers soil, surface runoff begins, the speed of which depends on the condition of the soil, the steepness of the slope, the duration of precipitation and the nature of vegetation (vegetation can protect the soil from water erosion). Water retained in the soil can evaporate from its surface or, after being absorbed by plant roots, transpirate (evaporate) into the atmosphere through the leaves.

The transpiration flow of water (soil - plant roots - leaves - atmosphere) is the main path of water through living matter in its large cycle on our planet.

Carbon cycle

The entire diversity of organic substances, biochemical processes and life forms on Earth depends on the properties and characteristics of carbon. The carbon content in most living organisms is about 45% of their dry biomass. All living matter on the planet participates in the cycle of organic matter and all carbon on the Earth, which continuously arises, changes, dies, decomposes, and in this sequence carbon is transferred from one organic matter to the construction of another along the food chain. In addition, all living things breathe, releasing carbon dioxide.

Carbon cycle on land. The carbon cycle is maintained by photosynthesis by land plants and ocean phytoplankton. By absorbing carbon dioxide (fixing inorganic carbon), plants, using the energy of sunlight, convert it into organic compounds - creating their biomass. At night, plants, like all living things, breathe, releasing carbon dioxide.

Dead plants, corpses and animal excrement serve as food for numerous heterotrophic organisms (animals, saprophytic plants, fungi, microorganisms). All these organisms live mainly in the soil and in the process of life they create their own biomass, which includes organic carbon. They also release carbon dioxide, creating “soil respiration.” Often, dead organic matter does not completely decompose and humus (humus) accumulates in soils, which plays an important role in soil fertility. The degree of mineralization and humification of organic substances depends on many factors: humidity, temperature, physical properties of the soil, composition of organic residues, etc. Under the influence of bacteria and fungi, humus can decompose into carbon dioxide and mineral compounds.

Carbon cycle in the World Ocean. The carbon cycle in the ocean is different from the cycle on land. The ocean is the weak link of organisms at higher trophic levels, and therefore all links of the carbon cycle. The time it takes for carbon to pass through the trophic link of the ocean is short, and the amount of carbon dioxide released is insignificant.

The ocean acts as the main regulator of carbon dioxide in the atmosphere. There is an intense exchange of carbon dioxide between the ocean and the atmosphere. Ocean waters have a high dissolving capacity and buffer capacity. A system consisting of carbonic acid and its salts (carbonates) is a kind of carbon dioxide depot, connected to the atmosphere through CO diffusion? from water to atmosphere and back.

In the ocean during the day, phytoplankton photosynthesis occurs intensively, while free carbon dioxide is intensively consumed, carbonates serve as an additional source of its formation. At night, when the content of free acid increases due to the respiration of animals and plants, a significant part of it again enters into the composition of carbonates. The processes taking place go in the following directions: living matter? SO?? N?SO?? Sa(NSO?)?? CaCO?.

In nature, a certain amount of organic matter does not undergo mineralization as a result of a lack of oxygen, high acidity of the environment, specific burial conditions, etc. Some carbon leaves the biological cycle in the form of inorganic (limestone, chalk, corals) and organic (shale, oil, coal) deposits.

Human activities are making significant changes to the carbon cycle on our planet. Landscapes, types of vegetation, biocenoses and their food chains change, huge areas of land surface are drained or irrigated, soil fertility improves (or worsens), fertilizers and pesticides are introduced, etc. The most dangerous is the release of carbon dioxide into the atmosphere as a result of fuel combustion. At the same time, the rate of carbon circulation increases and its cycle shortens.

Oxygen cycle

Oxygen is a prerequisite for the existence of life on Earth. It is included in almost all biological compounds, participates in biochemical reactions of oxidation of organic substances, providing energy for all life processes of organisms in the biosphere. Oxygen ensures the respiration of animals, plants and microorganisms in the atmosphere, soil, water, and participates in chemical oxidation reactions occurring in rocks, soils, silts, and aquifers.

The main branches of the oxygen cycle:

• - the formation of free oxygen during photosynthesis and its absorption during the respiration of living organisms (plants, animals, microorganisms in the atmosphere, soil, water);
• - formation of an ozone screen;
• - creation of redox zoning;
• - oxidation of carbon monoxide during volcanic eruptions, accumulation of sulfate sedimentary rocks, oxygen consumption in human activity, etc.; Molecular oxygen of photosynthesis is involved everywhere.

Nitrogen cycle

Nitrogen is part of the biologically important organic substances of all living organisms: proteins, nucleic acids, lipoproteins, enzymes, chlorophyll, etc. Despite the nitrogen content (79%) in the air, it is deficient for living organisms.

Nitrogen in the biosphere is in a gaseous form (N2) inaccessible to organisms - it is chemically little active, so it cannot be directly used by higher plants (and most lower plants) and the animal world. Plants absorb nitrogen from the soil in the form of ammonium ions or nitrate ions, i.e. so-called fixed nitrogen.

There are atmospheric, industrial and biological nitrogen fixation.

Atmospheric fixation occurs when the atmosphere is ionized cosmic rays and during strong electrical discharges during thunderstorms, in this case, nitrogen and ammonia oxides are formed from molecular nitrogen in the air, which, thanks to precipitation, are converted into ammonium, nitrite, and nitrate nitrogen and enter the soil and water basins.

Industrial fixation occurs as a result of human economic activity. The atmosphere is polluted with nitrogen compounds by factories producing nitrogen compounds. Hot emissions from thermal power plants, factories, spacecraft, and supersonic aircraft oxidize air nitrogen. Nitrogen oxides, interacting with water vapor from air and precipitation, return to the ground and enter the soil in ionic form.

Biological fixation plays a major role in the nitrogen cycle. It is carried out by soil bacteria:

• - nitrogen-fixing bacteria (and blue-green algae);
• - microorganisms living in symbiosis with higher plants (nodule bacteria);
• - ammonifying;
• - nitrifying;
• - denitrifying.

Free-living nitrogen-fixing aerobic (existing in the presence of oxygen) bacteria (Azotobacter) in the soil are capable of fixing atmospheric molecular nitrogen using the energy obtained from the oxidation of soil organic matter during respiration, ultimately binding it with hydrogen and introducing it in the form of an amino group (- NH2) into the amino acid composition of its body. Molecular nitrogen is also capable of fixing some anaerobic (living in the absence of oxygen) bacteria that exist in the soil (Clostridium). As they die, both microorganisms enrich the soil with organic nitrogen.

Blue-green algae, which are especially important for the soils of rice fields, are also capable of biological fixation of molecular nitrogen.

The most effective biological fixation of atmospheric nitrogen occurs in bacteria living in symbiosis in nodules leguminous plants(nodule bacteria).

These bacteria (Rizobium) use the energy of the host plant to fix nitrogen, while at the same time supplying the host's terrestrial organs with nitrogen compounds available to it.

By assimilating nitrogen compounds from the soil in nitrate and ammonium forms, plants build the necessary nitrogen-containing compounds of their body (nitrate nitrogen is pre-reduced in plant cells). Producing plants supply nitrogenous substances to the entire animal world and humanity. Dead plants are used, according to the trophic chain, as bioreducers.

Ammonifying microorganisms decompose organic substances containing nitrogen (amino acids, urea) to form ammonia. Some of the organic nitrogen in the soil is not mineralized, but is converted into humus substances, bitumen and components of sedimentary rocks.

Ammonia (in the form of ammonium ion) can enter root system plants, or used in nitrification processes.

Nitrifying microorganisms are chemosynthetics; they use the energy of the oxidation of ammonia to nitrates and nitrites to nitrates to ensure all life processes. Using this energy, nitrifiers reduce carbon dioxide and build organic matter in their bodies. Ammonia oxidation during nitrification proceeds through the following reactions:

NH? + 3O? ? 2HNO? + 2H?O + 600 kJ (148 kcal).

HNO? +O? ? 2HNO? + 198 kJ (48 kcal).

Nitrates formed during nitrification processes again enter the biological cycle, are absorbed from the soil by plant roots or after entering with water runoff into water basins - phytoplankton and phytobenthos.

Along with organisms that fix atmospheric nitrogen and nitrify it, there are microorganisms in the biosphere that are capable of reducing nitrates or nitrites to molecular nitrogen. Such microorganisms, called denitrifiers, when there is a lack of free oxygen in waters or soil, use nitrate oxygen to oxidize organic substances:

C?H??O?(glucose) + 24KNO? ? 24KHCO? + 6CO? +12N? + 18H?O + energy

The energy released in this case serves as the basis for all the life activity of denitrifying microorganisms.

Thus, living substances play an exceptional role in all parts of the cycle.

Currently, industrial fixation of atmospheric nitrogen by humans plays an increasingly important role in the nitrogen balance of soils and, consequently, in the entire nitrogen cycle in the biosphere.

Phosphorus cycle

The phosphorus cycle is simpler. While the reservoir of nitrogen is the air, the reservoir of phosphorus is the rocks from which it is released by erosion.

Carbon, oxygen, hydrogen and nitrogen migrate more easily and quickly in the atmosphere, since they are in gaseous form, forming gaseous compounds in biological cycles. For all other elements, except for sulfur necessary for the existence of living matter, the formation of gaseous compounds in biological cycles is uncharacteristic. These elements migrate mainly in the form of ions and molecules dissolved in water.

Phosphorus, assimilated by plants in the form of orthophosphoric acid ions, takes a large part in the life of all living organisms. It is part of ADP, ATP, DNA, RNA and other compounds.

The phosphorus cycle in the biosphere is not closed. In terrestrial biogeocenoses, phosphorus, after being absorbed by plants from the soil through the food chain, again enters the soil in the form of phosphates. The main amount of phosphorus is reabsorbed by the root system of plants. Phosphorus can be partially washed out with rainwater runoff from the soil into water basins.

In natural biogeocenoses there is often a lack of phosphorus, and in an alkaline and oxidized environment it is usually found in the form of insoluble compounds.

Lithosphere rocks contain large amounts of phosphates. Some of them gradually pass into the soil, some are developed by humans for the production of phosphate fertilizers, and most of them are leached and washed into the hydrosphere. There they are used by phytoplankton and associated organisms located at different trophic levels of complex food chains.

In the World Ocean, the loss of phosphates from the biological cycle occurs due to the deposition of plant and animal remains at great depths. Since phosphorus moves mainly from the lithosphere to the hydrosphere with water, it migrates to the lithosphere biologically (eating fish by seabirds, using benthic algae and fishmeal as fertilizer, etc.).

Of all the elements of plant mineral nutrition, phosphorus can be considered deficient.

Sulfur cycle

For living organisms, sulfur is of great importance, because it is part of sulfur-containing amino acids (cystine, cysteine, methionine, etc.). Being part of proteins, sulfur-containing amino acids maintain the necessary three-dimensional structure of protein molecules.

Sulfur is absorbed by plants from the soil only in oxidized form, in the form of an ion. In plants, sulfur is reduced and is included in amino acids in the form of sulfhydryl (-SH) and disulfide (-S-S-) groups.

Animals assimilate only reduced sulfur found in organic matter. After the death of plant and animal organisms, sulfur returns to the soil, where, as a result of the activity of numerous forms of microorganisms, it undergoes transformations.

Under aerobic conditions, some microorganisms oxidize organic sulfur to sulfates. Sulfate ions, being absorbed by plant roots, are again included in the biological cycle. Some sulfates may be included in water migration and removed from the soil. In soils rich in humic substances, a significant amount of sulfur is found in organic compounds, which prevents its leaching.

Under anaerobic conditions, the decomposition of organic sulfur compounds produces hydrogen sulfide. If sulfates and organic substances are in an oxygen-free environment, the activity of sulfate-reducing bacteria is activated. They use the oxygen of sulfates to oxidize organic substances and thus obtain the energy necessary for their existence.

Sulfate-reducing bacteria are common in groundwater, mud, and stagnant seawater. Hydrogen sulfide is a poison for most living organisms, so its accumulation in water-filled soil, lakes, estuaries, etc. significantly reduces or even completely stops life processes. This phenomenon is observed in the Black Sea at a depth below 200 m from its surface.

Thus, to create a favorable environment, it is necessary to oxidize hydrogen sulfide to sulfate ions, which will destroy the harmful effects of hydrogen sulfide, sulfur will transform into a form accessible to plants - in the form of sulfate salts. This role is performed in nature by a special group of sulfur bacteria (colorless, green, purple) and thionic bacteria.

Colorless sulfur bacteria are chemosynthetics: they use the energy obtained from the oxidation of hydrogen sulfide by oxygen to elemental sulfur and its further oxidation to sulfates.

Colored sulfur bacteria are photosynthetic organisms that use hydrogen sulfide as a hydrogen donor to reduce carbon dioxide.

The resulting elemental sulfur in green sulfur bacteria is released from the cells, and in purple bacteria it accumulates inside the cells.

The overall reaction of this process is photoreduction:

CO?+ 2H?S light? (CH?O)+ H?O +2S.

Thionic bacteria oxidize elemental sulfur and its various reduced compounds to sulfates using free oxygen, returning it back to the main stream of the biological cycle.

In the processes of the biological cycle, where the transformation of sulfur occurs, living organisms, especially microorganisms, play a huge role.

The main reservoir of sulfur on our planet is the World Ocean, since sulfate ions continuously flow into it from the soil. Part of the sulfur from the ocean returns to land through the atmosphere according to the scheme hydrogen sulfide - its oxidation to sulfur dioxide - dissolution of the latter in rainwater with the formation of sulfuric acid and sulfates - return of sulfur with precipitation to the soil cover of the Earth.

Cycle of inorganic cations

In addition to the basic elements that make up living organisms (carbon, oxygen, hydrogen, phosphorus and sulfur), many other macro- and microelements - inorganic cations - are vitally important. In water basins, plants receive the metal cations they need directly from the environment. On land, the main source of inorganic cations is the soil, which received them during the destruction of parent rocks. In plants, cations absorbed by root systems move to leaves and other organs; some of them (magnesium, iron, copper and a number of others) are part of biologically important molecules (chlorophyll, enzymes); others, remaining in free form, participate in maintaining the necessary colloidal properties of cell protoplasm and perform other various functions.

When living organisms die, inorganic cations return to the soil during the mineralization of organic substances. The loss of these components from the soil occurs as a result of leaching and removal of metal cations with rainwater, rejection and removal of organic matter by humans during the cultivation of agricultural plants, cutting down forests, mowing grass for livestock feed, etc.

Rational use of mineral fertilizers, soil reclamation, application organic fertilizers, correct agricultural technology will help restore and maintain the balance of inorganic cations in the biocenoses of the biosphere.

Anthropogenic cycle: cycle of xenobiotics (mercury, lead, chromium)

Humanity is part of nature and can only exist in constant interaction with it.

There are similarities and contradictions between the natural and anthropogenic cycle of substances and energy occurring in the biosphere.

The natural (biogeochemical) cycle of life has the following features:

• - the use of solar energy as a source of life and all its manifestations based on thermodynamic laws;
• - it is carried out without waste, i.e. all products of its vital activity are mineralized and again included in the next cycle of the circulation of substances. At the same time, waste, depreciated thermal energy is removed outside the biosphere. During the biogeochemical cycle of substances, waste is formed, i.e. reserves in the form of coal, oil, gas and other mineral resources. Unlike the waste-free natural cycle, the anthropogenic cycle is accompanied by increasing waste every year.

There is nothing useless or harmful in nature, even volcanic eruptions have benefits, because volcanic gases enter the air necessary elements(eg nitrogen).

There is a law of global closure of the biogeochemical cycle in the biosphere, which operates at all stages of its development, as well as the rule of increasing closure of the biogeochemical cycle during succession.

Humans play a huge role in the biogeochemical cycle, but in the opposite direction. Man disrupts the existing cycles of substances, and this manifests his geological power - destructive in relation to the biosphere. As a result of anthropogenic activity, the degree of closedness of biogeochemical cycles decreases.

The anthropogenic cycle is not limited to the energy of sunlight captured by the green plants of the planet. Humanity uses the energy of fuel, hydro and nuclear power plants.

It can be argued that anthropogenic activity at the present stage represents a huge destructive force for the biosphere.

The biosphere has a special property - significant resistance to pollutants. This sustainability is based on the natural ability of various components of the natural environment to self-purify and self-heal. But not unlimited. A possible global crisis has necessitated the construction of a mathematical model of the biosphere as a single whole (the Gaia system) in order to obtain information about the possible state of the biosphere.

Xenobiotic is a substance foreign to living organisms that appears as a result of anthropogenic activities (pesticides, drugs household chemicals and other pollutants) that can cause disruption of biotic processes, incl. disease or death of the body. Such pollutants do not undergo biodegradation, but accumulate in trophic chains.

Mercury is a very rare element. It is scattered throughout the earth's crust and only a few minerals, such as cinnabar, contain it in concentrated form. Mercury participates in the cycle of matter in the biosphere, migrating in a gaseous state and in aqueous solutions.

It enters the atmosphere from the hydrosphere during evaporation, when released from cinnabar, with volcanic gases and gases from thermal springs. Part of the gaseous mercury in the atmosphere turns into the solid phase and is removed from the air. The dropped mercury is absorbed by soils, especially clayey soils, water and rocks. Combustible minerals - oil and coal - contain up to 1 mg/kg of mercury. The water mass of the oceans contains approximately 1.6 billion tons, in bottom sediments - 500 billion tons, and in plankton - 2 million tons. River waters Every year about 40 thousand tons are removed from land, which is 10 times less than what enters the atmosphere during evaporation (400 thousand tons). About 100 thousand tons fall on the land surface annually.

Mercury has transformed from a natural component of the natural environment into one of the most dangerous man-made emissions into the biosphere for human health. It is widely used in the metallurgy, chemical, electrical, electronics, pulp and paper and pharmaceutical industries and is used in the production of explosives, varnishes and paints, as well as in medicine. Industrial effluents and atmospheric emissions, along with mercury mines, mercury production plants and thermal power plants (CHPs and boiler houses) using coal, oil and petroleum products, are the main sources of pollution of the biosphere with this toxic component. In addition, mercury is part of organomercury pesticides used in agriculture to treat seeds and protect crops from pests. It enters the human body with food (eggs, pickled grain, meat of animals and birds, milk, fish).

Mercury in water and river sediments

It has been established that about 80% of mercury entering natural water bodies is in dissolved form, which ultimately contributes to its distribution over long distances along with water flows. The pure element is non-toxic.

Mercury is often found in bottom silt water in relatively harmless concentrations. Inorganic mercury compounds are converted into toxic organic mercury compounds, such as methylmercury CH?Hg and ethylmercury C?H?Hg, by bacteria living in detritus and sediments, in the bottom mud of lakes and rivers, in the mucus covering the bodies of fish, and in fish stomach mucus. These compounds are easily soluble, mobile and very poisonous. The chemical basis for the aggressive action of mercury is its affinity with sulfur, in particular with the hydrogen sulfide group in proteins. These molecules bind to chromosomes and brain cells. Fish and shellfish can accumulate them to concentrations that are dangerous for humans who eat them, causing Minamata disease.

Metallic mercury and its inorganic compounds act mainly on the liver, kidneys and intestinal tract, but under normal conditions they are removed from the body relatively quickly and a dangerous amount for the human body does not have time to accumulate. Methylmercury and other alkyl mercury compounds are much more dangerous because accumulation occurs - the toxin enters the body faster than it is eliminated from the body, affecting the central nervous system.

Bottom sediments are important characteristic aquatic ecosystems. Accumulating heavy metals, radionuclides and highly toxic organic substances, bottom sediments, on the one hand, contribute to the self-purification of aquatic environments, and on the other hand, they represent a constant source of secondary pollution of water bodies. Bottom sediments are a promising object of analysis, reflecting a long-term pattern of pollution (especially in low-flow water bodies). Moreover, the accumulation of inorganic mercury in bottom sediments is observed especially at river mouths. A tense situation may arise when the adsorption capacity of sediments (silt, sediment) is exhausted. When the adsorption capacity is reached, heavy metals, incl. mercury will begin to enter the water.

It is known that under marine anaerobic conditions in sediments of dead algae, mercury attaches hydrogen and turns into volatile compounds.

With the participation of microorganisms, metallic mercury can be methylated in two stages:

CH?Hg+ ? (CH?)?Hg

Methylmercury appears in the environment almost exclusively through the methylation of inorganic mercury.

The biological half-life of mercury is long; for most tissues of the human body it is 70-80 days.

It is known that large fish, such as swordfish and tuna, are contaminated with mercury at the beginning of the food chain. It is not without interest to note that, to an even greater extent than in fish, mercury accumulates (accumulates) in oysters.

Mercury enters the human body through breathing, food and through the skin according to the following scheme:

Firstly, mercury is transformed. This element occurs naturally in several forms.

Metallic mercury, used in thermometers, and its inorganic salts (for example, chloride) are eliminated from the body relatively quickly.

Much more toxic are alkyl mercury compounds, in particular methyl and ethyl mercury. These compounds are eliminated from the body very slowly - only about 1% of the total amount per day. Although most of the mercury entering natural waters, is contained there in the form of inorganic compounds; in fish it always appears in the form of much poisonous methylmercury. Bacteria in the bottom silt of lakes and rivers, in the mucus covering the bodies of fish, as well as in the mucus of fish stomachs are capable of converting inorganic mercury compounds into methylmercury.

Second, selective accumulation, or biological accumulation (concentration), increases mercury levels in fish and shellfish to levels many times higher than in bay waters. Fish and shellfish living in the river accumulate methylmercury to concentrations that are dangerous for humans who use them as food.

% of the world's fish catch contains mercury in quantities of no more than 0.5 mg/kg, and 95% contain less than 0.3 mg/kg. Almost all the mercury in fish is in the form of methylmercury.

Taking into account the different toxicity of mercury compounds for humans in food products, it is necessary to determine inorganic (total) and organically bound mercury. We only determine the total mercury content. According to medical and biological requirements, the mercury content in freshwater predatory fish is allowed 0.6 mg/kg, in sea fish - 0.4 mg/kg, in freshwater non-predatory fish only 0.3 mg/kg, and in tuna fish up to 0.7 mg/kg kg. In baby food products, the mercury content should not exceed 0.02 mg/kg in canned meat, 0.15 mg/kg in canned fish, and 0.01 mg/kg in others.

Lead is present in almost all components of the natural environment. The earth's crust contains 0.0016%. The natural level of lead in the atmosphere is 0.0005 mg/m3. Most of it is deposited with dust, approximately 40% falls with precipitation. Plants obtain lead from soil, water and atmospheric deposition, and animals receive lead from consuming plants and water. Metal enters the human body along with food, water and dust.

The main sources of lead pollution in the biosphere are gasoline engines, the exhaust gases of which contain triethyl lead, and thermal power plants that burn coal, mining, metallurgical and chemical industry. Significant amounts of lead are introduced into the soil along with wastewater used as fertilizer. To extinguish the burning reactor of the Chernobyl nuclear power plant, lead was also used, which entered the air basin and was dispersed over vast areas. With increasing environmental pollution by lead, its deposition in bones, hair, and liver increases.

Chromium. The most dangerous is toxic chromium (6+), which is mobilized in acidic and alkaline soils, in fresh and sea waters. In sea water, chromium is 10 - 20% represented by the Cr (3+) form, 25 - 40% by Cr (6+), and 45 - 65% by the organic form. In the pH range 5 - 7, Cr (3+) predominates, and at pH > 7, Cr (6+) predominates. It is known that Cr(6+) and organic chromium compounds do not coprecipitate with iron hydroxide in seawater.

Natural cycles of substances are practically closed. In natural ecosystems, matter and energy are used sparingly and the waste of some organisms serves an important condition the existence of others. The anthropogenic cycle of substances is accompanied by a huge consumption of natural resources and a large amount of waste, causing pollution environment. The creation of even the most advanced treatment facilities does not solve the problem, so it is necessary to develop low- and waste-free technologies that make the anthropogenic cycle as closed as possible. Theoretically, it is possible to create a waste-free technology, but low-waste technologies are real.

Adaptation to natural phenomena

Adaptations are various adaptations to the environment developed in organisms (from the simplest to the highest) in the process of evolution. The ability to adapt is one of the main properties of living things, ensuring the possibility of their existence.

The main factors developing the adaptation process include: heredity, variability, natural (and artificial) selection.

Tolerance may change if the body is exposed to other external conditions. Finding himself in such conditions, after some time he gets used to it, adapts to them (from the Latin adaptation - to adapt). The consequence of this is a change in the position of the physiological optimum.

The property of organisms to adapt to existence in a particular range environmental factor called ecological plasticity.

The wider the range of environmental factors within which a given organism can live, the greater its ecological plasticity. According to the degree of plasticity, two types of organisms are distinguished: stenobiont (stenoeki) and eurybiont (euryek). Thus, stenobionts are ecologically non-plastic (for example, flounder lives only in salt water, and crucian carp only in fresh water), i.e. are not hardy, and eurybionts are ecologically plastic, i.e. more hardy (for example, three-spined stickleback can live in both fresh and salt waters).

Adaptations are multidimensional, since the organism must simultaneously comply with many different environmental factors.

There are three main ways of adaptation of organisms to environmental conditions: active; passive; avoidance of adverse effects.

The active path of adaptation is strengthening resistance, developing regulatory processes that allow all vital functions of the body to be carried out, despite deviations of the factor from the optimum. For example, warm-blooded animals support constant temperature body - optimal for the biochemical processes occurring in it.

The passive path of adaptation is the subordination of the vital functions of organisms to changes in environmental factors. For example, under unfavorable environmental conditions, many organisms go into a state of suspended animation (hidden life), in which the metabolism in the body practically stops (state of winter dormancy, torpor of insects, hibernation, preservation of spores in the soil in the form of spores and seeds).

Avoidance of adverse effects - the development of adaptations, behavior of organisms (adaptation), which help to avoid unfavorable conditions. In this case, adaptations can be: morphological (the structure of the body changes: modification of the leaves of a cactus), physiological (the camel provides itself with moisture due to the oxidation of fat reserves), ethological (behavior changes: seasonal migrations of birds, hibernation in winter).

Living organisms are well adapted to periodic factors. Non-periodic factors can cause illness and even death of the organism (for example, medications, pesticides). However, with prolonged exposure to them, adaptation to them may also occur.

Organisms adapted to daily, seasonal, tidal rhythms, rhythms of solar activity, lunar phases and other strictly periodic phenomena. Thus, seasonal adaptation is distinguished as seasonality in nature and a state of winter dormancy.

Seasonality in nature. The leading significance for plants and animals in the adaptation of organisms is the annual variation of temperature. The period favorable for life, on average for our country, lasts about six months (spring, summer). Even before the arrival of stable frosts, a period of winter dormancy begins in nature.

State of winter dormancy. Winter dormancy is not just a cessation of development as a result of low temperatures, but a complex physiological adaptation, which occurs only at a certain stage of development. For example, the malaria mosquito and the urticaria butterfly overwinter in the adult insect stage, the cabbage moth in the pupal stage, and the gypsy moth in the egg stage.

Biorhythms. In the process of evolution, each species has developed a characteristic annual cycle of intensive growth and development, reproduction, preparation for winter and wintering. This phenomenon is called biological rhythm. Match every period life cycle with the appropriate time of year is crucial for the existence of the species.

The main factor in the regulation of seasonal cycles in most plants and animals is the change in day length.

Biorhythms are:

exogenous (external) rhythms (arise as a reaction to periodic changes in the environment (change of day and night, seasons, solar activity) endogenous (internal rhythms) are generated by the body itself

In turn, endogenous are divided into:

Physiological rhythms (heartbeat, breathing, work of endocrine glands, synthesis of DNA, RNA, proteins, work of enzymes, cell division, etc.)

Ecological rhythms (daily, annual, tidal, lunar, etc.)

The processes of DNA, RNA, protein synthesis, cell division, heartbeat, breathing, etc. have rhythm. External influences can shift the phases of these rhythms and change their amplitude.

Physiological rhythms vary depending on the state of the body, environmental rhythms are more stable and correspond to external rhythms. With endogenous rhythms, the body can orient itself in time and prepare in advance for upcoming environmental changes - this is the body’s biological clock. Many living organisms are characterized by circadian and circan rhythms.

Circadian rhythms (circadian) - repeating intensities and nature of biological processes and phenomena with a period of 20 to 28 hours. Circadian rhythms are associated with the activity of animals and plants during the day and, as a rule, depend on temperature and light intensity. For example, bats fly at dusk and rest during the day; many planktonic organisms stay near the surface of the water at night and descend into the depths during the day.

Seasonal biological rhythms are associated with the influence of light - photoperiod. The response of organisms to day length is called photoperiodism. Photoperiodism is a general, important adaptation that regulates seasonal phenomena in a wide variety of organisms. The study of photoperiodism in plants and animals has shown that the reaction of organisms to light is based on alternating periods of light and darkness of a certain duration during the day. The response of organisms (from single-celled organisms to humans) to the length of day and night shows that they are able to measure time, i.e. They have some kind of biological clock. Biological clocks, in addition to seasonal cycles, control many other biological phenomena and determine the correct daily rhythm of both the activity of entire organisms and processes occurring even at the cellular level, in particular, cell division.

A universal property of all living things, from viruses and microorganisms to higher plants and animals, is the ability to produce mutations - sudden, natural and artificially induced, inherited changes in genetic material, leading to changes in certain characteristics of the organism. Mutational variability does not meet environmental conditions and, as a rule, disrupts existing adaptations.

Many insects enter diapause (a long stop in development) at a certain stage of development, which should not be confused with a state of rest in unfavorable conditions. The reproduction of many marine animals is influenced by lunar rhythms.

Circanian (annual) rhythms are repeated changes in the intensity and nature of biological processes and phenomena with a period of 10 to 13 months.

The physical and psychological state of a person also has a rhythmic character.

The disrupted rhythm of work and rest reduces performance and has an adverse effect on human health. A person’s condition in extreme conditions will depend on the degree of his preparedness for these conditions, since there is practically no time for adaptation and recovery.

Trophic network

Usually, for each link in the chain, you can specify not one, but several other links connected to it by the “food-consumer” relationship. So, not only cows, but also other animals eat grass, and cows are food not only for humans. The establishment of such connections turns the food chain into a more complex structure - food web.

Trophic level

Trophic level is a conventional unit indicating the distance from producers in the trophic chain of a given ecosystem. In some cases, in a trophic network, it is possible to group individual links into levels in such a way that links at one level act only as food for the next level. This grouping is called a trophic level.

Cycle of substances and energy flows in ecosystems

Nutrition is the main way of movement of substances and energy. Organisms in an ecosystem are connected by a commonality of energy and nutrients that are necessary to sustain life. The main source of energy for the vast majority of living organisms on Earth is the Sun. Photosynthetic organisms (green plants, cyanobacteria, some bacteria) directly use the energy of sunlight. In this case, complex organic substances are formed from carbon dioxide and water, in which part of the solar energy is accumulated in the form of chemical energy. Organic substances serve as a source of energy not only for the plant itself, but also for other organisms in the ecosystem. The release of energy contained in food occurs during the process of breathing. Respiration products - carbon dioxide, water and inorganic substances - can be reused by green plants. As a result, substances in this ecosystem undergo an endless cycle. At the same time, the energy contained in food does not cycle, but gradually turns into thermal energy and leaves the ecosystem. Therefore, a necessary condition for the existence of an ecosystem is a constant flow of energy from outside. Thus, the basis of the ecosystem is made up of autotrophic organisms - producers (producers, creators), which, through the process of photosynthesis, create energy-rich food - primary organic matter. In terrestrial ecosystems, the most important role belongs to higher plants, which, forming organic substances, give rise to all trophic relationships in the ecosystem, serve as a substrate for many animals, fungi and microorganisms, and actively influence the microclimate of the biotope. In aquatic ecosystems, the main producers of primary organic matter are algae. Ready-made organic substances are used to obtain and accumulate energy by heterotrophs, or consumers. Heterotrophs include herbivores (consumers of the 1st order), carnivores that live off herbivorous forms (consumers of the 2nd order), consuming other carnivores (consumers of the 3rd order), etc. A special group of consumers consists of decomposers (destroyers, or destructors), decomposing organic remains of producers and consumers to simple inorganic compounds, which are then used by producers. Decomposers include mainly microorganisms - bacteria and fungi. In terrestrial ecosystems, soil decomposers are especially important, drawing organic matter from dead plants into the general cycle (they consume up to 90% of the primary forest production). Thus, each living organism within an ecosystem occupies a certain ecological niche(place) in a complex system of ecological relationships with other organisms and abiotic environmental conditions.

Biological and geological cycles.

The processes of photosynthesis of organic matter from inorganic components last for millions of years, and during this time the chemical elements must have passed from one form to another. However, this does not happen due to their circulation in the biosphere. Every year, photosynthetic organisms assimilate about 350 billion tons of carbon dioxide, release about 250 billion tons of oxygen into the atmosphere and break down 140 billion tons of water, forming more than 230 billion tons of organic matter (calculated by dry weight). Enormous quantities of water pass through plants and algae during transport and evaporation. This leads to the fact that the water of the surface layer of the ocean is filtered by plankton in 40 days, and the rest of the ocean water is filtered in about a year. All carbon dioxide in the atmosphere is renewed in several hundred years, and oxygen in several thousand years. Every year, photosynthesis includes 6 billion tons of nitrogen, 210 billion tons of phosphorus and a large number of other elements (potassium, sodium, calcium, magnesium, sulfur, iron, etc.) into the cycle. The existence of these cycles gives the ecosystem a certain stability.

There are two main cycles: large (geological) and small (biotic). The great cycle, which continues for millions of years, consists in the fact that rocks are destroyed, and weathering products (including water-soluble nutrients) are carried by water flows into the World Ocean, where they form marine strata and only partially return to land with precipitation . Geotectonic changes, the processes of continental subsidence and seabed rise, the movement of seas and oceans over a long period of time lead to the fact that these strata return to land and the process begins again. The small cycle (part of the large one) occurs at the ecosystem level and consists in the fact that nutrients, water and carbon accumulate in the substance of plants, are spent on building the body and on the life processes of both these plants themselves and other organisms (usually animals), that eat these plants (consumers). The decay products of organic matter under the influence of decomposers and microorganisms (bacteria, fungi, worms) again decompose into mineral components that are accessible to plants and are drawn into the flow of matter by them. The circulation of chemicals from the inorganic environment through plant and animal organisms back into the inorganic environment using solar energy and the energy of chemical reactions is called the biogeochemical cycle. Almost all chemical elements are involved in such cycles, and primarily those that participate in the construction of a living cell. Thus, the human body consists of oxygen (62.8%), carbon (19.37%), hydrogen (9.31%), nitrogen (5.14%), calcium (1.38%), phosphorus (0. 64%) and about 30 more elements.

The role of Man.

A person has the power to change the strength of action and the number of limiting factors, as well as expand or, conversely, narrow the boundaries of the optimal values ​​of environmental factors. For example, harvesting is inevitably associated with the depletion of soil elements of mineral nutrition of plants and the transfer of some of them to the category of limiting factors. Various types of land reclamation (watering, drainage, fertilization, etc.) optimize factors and remove their limiting effect. Man has immeasurably expanded his adaptive capabilities by conditioning the conditions of his environment (clothing, housing, new materials, etc.) and thereby sharply reduced his dependence on the natural environment and the resources it represents. For example, in the human diet, wild food resources make up only 10-15%. The remaining food needs are met through cultural farming. The consequence of reducing dependence on environmental factors is the expansion of man’s range to the entire planet and the removal of natural mechanisms for regulating population numbers.

Man has changed this principle of food chains and ecological pyramids in relation to both his own population and other species (varieties, breeds), especially those grown in cultural farming. This discrepancy with natural ecosystems is made possible by the appropriation and investment of additional energy into systems. Violating the rules of ecological pyramids turns out to be unreasonably expensive. It is inevitably accompanied by changes in the cycles of substances, the accumulation of waste and environmental pollution. As an example, we can name livestock complexes with their environmental problems. Violation of the rules of the pyramids is also due to the fact that human consumer interests have gone beyond the limits of biological resources as a whole. Its interests include products (resources) of previous geological eras, and many of the products produced become dead ends (waste and pollutants). The people of Earth alone, as a biological species, require about 2 million tons of food and 10 billion m3 of oxygen every day. In addition, almost 30 million tons of substances are extracted and processed, about 30 million tons of fuel are burned, 2 billion m3 of water and 65 billion m3 of oxygen are used for technical needs

Due to their omnivorous nature, people begin to eat more and more diverse organisms, which requires a variety of methods of catching prey or searching for plants. Of course, you also have to come up with ways to make the prey edible. It's one thing to fry a rabbit and quite another to cook a jellyfish for dinner. Only a sophisticated mind could think of eating, for example, cassava, the tubers of which are bitter and also contain hydrocyanic acid. However, throughout Brazil, and not only there, cassava is grown and eaten in quantities comparable to potatoes eaten in Russia. But coming up with a technology for processing it was a very difficult task.

By eating a wide variety of organisms, a person becomes involved in many food chains, removing additional organic matter and ending these chains with himself. He turns out to be an apex predator everywhere. So man began to shorten food chains in many ecosystems, and the shorter such a chain, the faster the turnover of matter and energy.

Also, human activity is associated with a strong transformation of natural habitats. Modern man prefers not to change in accordance with environmental conditions, but to change these conditions themselves. Therefore, he devotes considerable intellectual and technical effort to transforming the environment. Having plowed the meadow space and sowed it the right plants, the plowman has already radically changed the environment. Of the many plants in the meadow, he left only one, and even then, most often, it was alien. He transformed the soil and its fauna, formed here over many hundreds of years, in a few hours. As a result, the resource of almost all animal species was eliminated, and their food plants disappeared. The converted space became unsuitable for many native plants and unattainable for others. The owner of the crop protects his field, waters it with herbicides, and fights with competing consumers.

As we remember, in ecosystems a person lives not alone, but with a huge number of neighbors - plant and animal organisms. This transformed environment is not suitable for all of them. Many, especially primitive forms of life, easily adapt to changing conditions. For the vast majority of complex organisms, the new environment is not suitable. They leave these places or die. So any transformation of nature always leads to the death of many organisms.

Eating. The range of food for this zoological species is probably the widest on the planet. Man is an amazing euryphage (polyphagous) and eats almost everything. The list of animals on his menu is huge, which, along with the traditional cows, sheep and poultry, includes termites, locusts, locusts and centipedes, and some spiders. The larvae of various insects - bees, tree beetles - are eaten by many peoples as a delicacy. Residents of Africa eagerly eat the huge larvae of the goliath beetle, where it is found. A variety of lizards, snakes, turtles and frogs are also firmly established in human diets. The inhabitants of the water - fish and shellfish - have been traditional food since the time of the Cro-Magnon man. However, here too the diet of the species expanded, including a huge number of animals from whales to some jellyfish and euphausids.

Ecologists, studying the diets of animals, especially those that are food competitors of humans, note in many of them a striking diversity of food. For example, a typical polyphagous water vole, which destroys the crops of peasants in the southern part of Western Siberia, is capable of eating more than 300 species of plants. As this animal is studied, ever longer lists of food suitable for it are compiled. Man, in the role of a herbivorous animal (the primary consumer), has far surpassed all other species. Full lists No one has yet compiled its food plants on the planet, but their length is easy to guess. So, in Japanese cuisine The flower buds of about 300 plant species are used to prepare various dishes. Chinese cuisine is even more sophisticated and varied. And if you add lists here food species plants from tropical cookbooks!?

People use both animals and plants for food purposes with increasing intensity. If he does not eat some animals directly, he feeds them to his food animals or fertilizes the fields with them. Man is wasteful and often uses even delicious species, along with food, as feed and even as fertilizer. For example, the history of fishing for sea striped bass - fish almost 2 meters in length and 50 - 70 kg in weight. It is superior in taste to Atlantic salmon. This perch was caught in huge quantities at the beginning of the 17th century off the coast of New England. Most of these catches were used for fertilizer land plots local residents. Colonial farmers buried hundreds of tons of this fish in their corn fields. In the Newfoundland area, many tons of Atlantic salmon early XIX centuries used to fertilize fields. The same thing happened with overfishing of cod and sturgeon. Huge factories were built to process mackerel, herring, capelin and other marine fish into fertilizers and animal feed. In Newfoundland at the beginning of the 18th century, the meat of huge lobster sea crayfish (they weighed up to 10 - 12 kg) was used for bait when fishing for cod, as well as for fattening domestic animals. Each potato field was strewn with the shells of these crustaceans, because 2-3 lobsters were placed under each potato bush for fertilizer. Until the mid-20th century, these giant and very tasty crayfish were fed to livestock in some areas of Newfoundland. Even such an enlightened country as Russia acted wastefully until the very end of the 20th century. In 1998, on television, its not very well-fed population was shown how in Russian Far East Bulldozers buried hundreds of tons of delicious salmon fish into the ground. People were unable to dispose of their catches!

Man ensured his transformation into a hypereurybiont not through biological mechanisms, but through technical means, and therefore he has largely lost the potential for biological adaptation. This is the reason that a person is among the first candidates for leaving the arena of life as a result of environmental changes caused by him. Hence an important conclusion: if the modern niche of man is primarily the result of intelligent activity, power over the environment, therefore, the mind must be the main driving force behind its change.

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All substances on the planet are in the process of circulation. Solar energy causes two cycles of substances on Earth: large (geological, biosphere) And small (biological).

The large cycle of substances in the biosphere is characterized by two important points: it occurs throughout the entire geological development of the Earth and is a modern planetary process that takes a leading part in the further development of the biosphere.

The geological cycle is associated with the formation and destruction of rocks and the subsequent movement of destruction products - clastic material and chemical elements. The thermal properties of the surface of land and water played and continue to play a significant role in these processes: absorption and reflection of solar rays, thermal conductivity and heat capacity. The unstable hydrothermal regime of the Earth's surface, together with the planetary atmospheric circulation system, determined the geological circulation of substances, which at the initial stage of the Earth's development, along with endogenous processes, was associated with the formation of continents, oceans and modern geospheres. With the formation of the biosphere, the waste products of organisms were included in the large cycle. The geological cycle supplies living organisms with nutrients and largely determines the conditions of their existence.

Main chemical elements lithosphere: oxygen, silicon, aluminum, iron, magnesium, sodium, potassium and others - participate in a large cycle, passing from the deep parts of the upper mantle to the surface of the lithosphere. Igneous rock that arose during the crystallization of magma, arriving on the surface of the lithosphere from the depths of the Earth, undergoes decomposition and weathering in the biosphere. Weathering products enter a mobile state, are carried by water and wind to low areas of the relief, enter rivers, the ocean and form thick layers of sedimentary rocks, which over time, plunging to depth in areas with increased temperature and pressure, undergo metamorphosis, i.e. "remelted". During this melting, a new metamorphic rock appears, entering the upper horizons of the earth's crust and again entering the cycle of substances (rice.).

Easily mobile substances - gases and natural waters that make up the atmosphere and hydrosphere of the planet - undergo the most intense and rapid circulation. The lithosphere material cycles much more slowly. In general, each cycle of any chemical element is part of the general large cycle of substances on Earth, and they are all closely interconnected. The living matter of the biosphere in this cycle performs a tremendous job of redistributing chemical elements continuously circulating in the biosphere, moving from external environment into organisms and again into the external environment.

Small, or biological, cycle of substances- This

circulation of substances between plants, animals, fungi, microorganisms and soil. The essence of the biological cycle lies in the occurrence of two opposite but interconnected processes - the creation of organic substances and their destruction. First stage the emergence of organic substances is due to photosynthesis of green plants, i.e., the formation of living matter from carbon dioxide, water and simple mineral compounds using solar energy. Plants (producers) extract molecules of sulfur, phosphorus, calcium, potassium, magnesium, manganese, silicon, aluminum, zinc, copper and other elements from the soil in solution. Herbivorous animals (consumers of the first order) absorb compounds of these elements in the form of food of plant origin. Predators (II-order consumers) feed on herbivores, consuming food of a more complex composition, including proteins, fats, amino acids and other substances. In the process of destruction by microorganisms (decomposers) of organic substances of dead plants and animal remains, into the soil and aquatic environment simple mineral compounds arrive that are available for assimilation by plants, and the next round of the biological cycle begins (Fig. 33).

The emergence and development of the noosphere

Evolution organic world on Earth went through several stages. The first is associated with the emergence of the biological cycle of substances in the biosphere. The second was accompanied by the formation of multicellular organisms. These two stages are called biogenesis. The third stage is associated with the emergence of human society, under the influence of which, in modern conditions, the evolution of the biosphere occurs and its transformation into the sphere of reason - the noosphere (from the Greek - mind, - ball). Noosphere is a new state of the biosphere, when intelligent human activity becomes the main factor determining its development. The term “noosphere” was introduced by E. Leroy. V.I. Vernadsky deepened and developed the doctrine of the noosphere. He wrote: “The noosphere is a new geological phenomenon on our planet. In it, man becomes a major geological force.” V.I. Vernadsky identified the necessary prerequisites for the creation of the noosphere: 1. Humanity has become a single whole. 2. The possibility of instant exchange of information. 3. Real equality of people. 4. Growth of the general standard of living. 5. Use of new types of energy. 6. Elimination of wars from the life of society. The creation of these prerequisites becomes possible as a result of the explosion of scientific thought in the twentieth century.

Topic – 6. Nature – man: a systematic approach. Purpose of the lecture: To form a holistic understanding of the systemic postulates of ecology.

Main questions: 1. The concept of a system and complex biosystems. 2. Features of biological systems. 3. System postulates: the law of universal connection, B. Commoner’s ecological laws, the Law of large numbers, Le Chatelier’s Principle, the Law of feedback in nature and the law of constancy amount of living matter. 4. Models of interactions in the “nature-human” and “human-economy-biota-environment” systems.

Ecological system- the main object of ecology. Ecology is systemic in its essence and in its theoretical form is close to the general theory of systems. According to the general theory of systems, a system is a real or conceivable collection of parts, the integral properties of which are determined by the interaction between the parts (elements) of the system. In real life, a system is defined as a collection of objects united by some form of regular interaction or interdependence to perform a given function. In the material there are certain hierarchies - ordered sequences of spatio-temporal subordination and complication of systems. Present all the diversity of our world in the form of three successively emerged hierarchies. This is the main, natural, physico-chemical-biological (F, X, B) hierarchy and two secondary hierarchies that arose on its basis, the social (S) and technical (T) hierarchies. The existence of the last in the totality of feedbacks influences the main hierarchy in a certain way. Combining systems from different hierarchies leads to “mixed” classes of systems. Thus, the combination of systems from the physicochemical part of the hierarchy (F, X - “environment”) with living systems of the biological part of the hierarchy (B - “biota”) leads to a mixed class of systems called environmental. A combination of systems from hierarchies C

(“man”) and T (“technology”) leads to the class of economic, or technical and economic, systems

Rice. . Hierarchies of material systems:

F, X - physical and chemical, B - biological, S - social, T - technical

It should be clear that the impact of human society on nature, mediated by technology and technology (technogenesis), shown in the diagram, applies to the entire hierarchy of natural systems: the lower branch - to the abiotic environment, the upper - to the biota of the biosphere. Below we will consider the connection between the environmental and technical and economic aspects of this interaction.

All systems have some common properties:

1. Each system has a specific structure, determined by the form of spatiotemporal connections or interactions between elements of the system. Structural ordering in itself does not determine the organization of the system. The system can be called organized, if its existence is either necessary to maintain some functional (performing a certain job) structure, or, on the contrary, depends on the activity of such a structure.

2. According to principle of necessary diversity the system cannot consist of identical elements devoid of individuality. The lower limit of diversity is at least two elements (proton and electron, protein and nucleic acid, “he” and “she”), the upper limit is infinity. Diversity is the most important information characteristic of the system. It differs from the number of varieties of elements and can be measured. 3. The properties of a system cannot be understood only on the basis of the properties of its parts. It is the interaction between the elements that is decisive. It is impossible to judge its operation by looking at individual parts of a machine before assembly. By studying separately some forms of fungi and algae, it is impossible to predict the existence of their symbiosis in the form of a lichen. The combined effect of two or more different factors on the body is almost always different from the sum of their separate effects. The degree of irreducibility of the properties of a system to the sum of the properties of the individual elements of which it consists determines emergence systems.

4. Isolating a system divides its world into two parts - the system itself and its environment. Depending on the presence (absence) of exchange of matter, energy and information with the environment, the following are fundamentally possible: isolated systems (no exchange is possible); closed systems (metabolism is impossible); open systems (exchange of matter and energy is possible). The exchange of energy determines the exchange of information. In living nature there are only open dynamic systems, between the internal elements of which and the elements of the environment there are transfers of matter, energy and information. Any living system - from a virus to the biosphere - is an open dynamic system.

5. The predominance of internal interactions in the system over external ones and the lability of the system in relation to external factors
actions determine it self-preservation ability thanks to the qualities of organization, endurance and stability. External influence on the system, exceeding the strength and flexibility of its internal interactions, leads to irreversible changes
and the death of the system. The stability of a dynamic system is maintained by the external cyclic work it continuously performs. This requires the flow and transformation of energy into this. topic. The probability of achieving the main goal of the system - self-preservation (including through self-reproduction) is determined as its potential effectiveness.

6. The action of a system in time is called its behavior. A change in behavior caused by an external factor is referred to as reaction system, and a change in the system’s reaction associated with a change in structure and aimed at stabilizing behavior is. device, or adaptation. Consolidation of adaptive changes in the structure and connections of the system over time, in which its potential efficiency increases, is considered as development, or evolution, systems. The emergence and existence of all material systems in nature is due to evolution. Dynamic systems evolve in the direction from more probable to less probable organization, i.e. development follows the path of increasing complexity of organization and formation of subsystems in the structure of the system. In nature, all forms of behavior of systems - from elementary reactions to global evolution - are significantly nonlinear. An important feature of the evolution of complex systems is
unevenness, lack of monotony. Periods of gradual accumulation of minor changes are sometimes interrupted by sharp qualitative leaps that significantly change the properties of the system. They are usually associated with the so-called bifurcation points- bifurcation, splitting of the previous path of evolution. The choice of one or another continuation of the path at the bifurcation point depends on a lot, up to the emergence and prosperity of a new world of particles, substances, organisms, societies, or, conversely, the death of the system. Even for decisive systems, the result of the choice is often unpredictable, and the choice itself at the bifurcation point can be determined by a random impulse. Any real system can be represented in the form of some material resemblance or symbolic image, i.e. respectively analog or sign model of the system. Modeling is inevitably accompanied by some simplification and formalization of the relationships in the system. This formalization can be
implemented in the form of logical (cause-and-effect) and/or mathematical (functional) relationships. As the complexity of systems increases, they acquire new emergent qualities. At the same time, the qualities of simpler systems are preserved. Therefore, the overall variety of system qualities increases as it becomes more complex (Fig. 2.2).

Rice. 2.2. Patterns of changes in the properties of system hierarchies with an increase in their level (according to Fleishman, 1982):

1 - diversity, 2 - stability, 3 - emergence, 4 - complexity, 5 - non-identity, 6 - prevalence

In order of increasing activity in relation to external influences, the qualities of the system can be ordered in the following sequence: 1 - stability, 2 - reliability due to awareness of the environment (noise immunity), 3 - controllability, 4 - self-organization. In this series, each subsequent quality makes sense if the previous one is present.

Par Difficulty the structure of the system is determined by the number P its elements and number T

connections between them. If in any system the number of particular discrete states is studied, then the complexity of the system WITH is determined by the logarithm of the number of connections:

C=lgm.(2.1)

Systems are conventionally classified by complexity as follows: 1) systems with up to a thousand states (O <С < 3), относятся к simple; 2) systems with up to a million states (3< С < 6), являют собой complex systems; 3) systems with the number of states over a million (C > 6) are identified as very complex.

All real natural biosystems are very complex. Even in the structure of a single virus, the number of biologically significant molecular states exceeds the latter value.

Geological circulation substances have the highest speed in the horizontal direction between land and sea. The meaning of the large circulation is that rocks are subject to destruction, weathering, and weathering products, including water-soluble nutrients, are carried by water flows into the World Ocean with the formation of marine strata and return to land only partially, for example, with precipitation or organisms extracted from water by humans. Then, over a long period of time, slow geotectonic changes occur - the movement of continents, the rise and fall of the seabed, volcanic eruptions, etc., as a result of which the formed strata return to the land and the process begins again.

Large geological cycle of matter. Under the influence of denudation processes, rock destruction and sedimentation occur. Sedimentary rocks are formed. In areas of stable subsidence (usually the ocean floor), the material of the geographic shell enters the deep layers of the Earth. Further, under the influence of temperature and pressure, metamorphic processes occur, as a result of which rocks are formed, the substance moves closer to the center of the Earth. In the depths of the Earth, under conditions of very high temperatures, magmatism occurs: rocks melt, rise in the form of magma along faults to the earth's surface and spill out to the surface during eruptions. Thus, the cycle of matter occurs. The geological cycle becomes more complicated if we take into account the exchange of matter with outer space. The great geological cycle is not closed in the sense that some particle of matter that falls into the bowels of the Earth does not necessarily come to the surface, and vice versa, a particle rising during an eruption may never have been on the earth's surface before

The main sources of energy for natural processes on Earth

Radiation from the Sun is the main source of energy on Earth. Its power is characterized by the solar constant - the amount of energy passing through a unit area area perpendicular to the sun's rays. At a distance of one astronomical unit (that is, in Earth's orbit), this constant is approximately 1370 W/m².

Living organisms use the energy of the Sun (photosynthesis) and the energy of chemical bonds (chemosynthesis). This energy can be used in various natural and artificial processes. A third of all energy is reflected by the atmosphere, 0.02% is used by plants for photosynthesis, and the rest is used to maintain many natural processes - heating the earth, ocean, atmosphere, air movement. wt. Direct heating by the sun's rays or energy conversion using photocells can be used to generate electricity (solar power plants) or perform other useful work. In the distant past, energy stored in oil and other types of fossil fuels was also obtained through photosynthesis.

This enormous energy leads to global warming, because after it has gone through natural processes it is radiated back and the atmosphere does not allow it to go back.

2. Internal energy Earth; manifestation – volcanoes, hot springs

18. Energy transformations of biotic and abiotic origin

In a functioning natural ecosystem, waste does not exist. All organisms, living or dead, are potentially food for other organisms: a caterpillar eats foliage, a thrush eats caterpillars, a hawk can eat a blackbird. When plants, caterpillars, thrushes and hawks die, they are in turn processed by decomposers.

All organisms that use the same type of food belong to the same trophic level.

Organisms in natural ecosystems are involved in a complex network of many interconnected food chains. Such a network is called food web.

Pyramids of energy flows: With each transition from one trophic level to another within a food chain or network, work is done and thermal energy is released into the environment, and the amount of energy High Quality, used by organisms of the next trophic level, decreases.

10% rule: When moving from one trophic level to another, 90% of energy is lost and 10% is transferred to the next level.

The longer the food chain, the more useful energy is lost. Therefore, the length of the food chain usually does not exceed 4 - 5 links.

Energy of the Earth's landscape sphere:

1) solar energy: thermal, radiant

2) the flow of thermal energy from the bowels of the Earth

3) energy tidal currents

4) tectonic energy

5) energy assimilation during photosynthesis

Water cycle in nature

The water cycle in nature is the process of cyclic movement of water in the earth's biosphere. It consists of evaporation, condensation and precipitation (atmospheric precipitation partially evaporates, partially forms temporary and permanent drains and reservoirs, partially seeps into the ground and forms groundwater), as well as the processes of degassing of the mantle: water continuously flows from the mantle. water has been found even at great depths.

The seas lose more water due to evaporation than they receive through precipitation; on land the situation is the opposite. Water continuously circulates on the globe, while its total remains unchanged.

75% of the Earth's surface is covered with water. The water shell of the Earth is the hydrosphere. Most of it is salt water from seas and oceans, and a smaller part is fresh water from lakes, rivers, glaciers, groundwater and water vapor.

On earth, water exists in three states of aggregation: liquid, solid and gaseous. Without water, living organisms cannot exist. In any organism, water is the medium in which chemical reactions, without which living organisms cannot live. Water is the most valuable and essential substance for the life of living organisms.

There are several types of water cycles in nature:

The Great, or Global, Cycle - water vapor formed above the surface of the oceans is carried by winds to the continents, falls there in the form of precipitation and returns to the ocean in the form of runoff. In this process, the quality of water changes: with evaporation, salty sea water turns into fresh water, and polluted water is purified.

Small, or oceanic, cycle - water vapor formed above the surface of the ocean condenses and falls as precipitation back into the ocean.

The intracontinental cycle - water that has evaporated over the land surface again falls on land in the form of precipitation.

In the end, the sediments in the process of movement again reach the World Ocean.

The rate of transfer of different types of water varies widely, and the periods of flow and periods of water renewal are also different. They vary from several hours to several tens of thousands of years. Atmospheric moisture, which is formed by the evaporation of water from the oceans, seas and land and exists in the form of clouds, is renewed on average every eight days.

The waters that make up living organisms are restored within a few hours. This is the most active form of water exchange. The period of renewal of water reserves in mountain glaciers is about 1,600 years, in the glaciers of polar countries it is much longer - about 9,700 years.

Complete renewal of the waters of the World Ocean occurs in approximately 2,700 years.

Effects of interaction between solar radiation, moving and rotating earth.

In this matter, seasonal variability should be considered: winter/summer. Describe that due to the rotation and movement of the Earth, solar radiation arrives unevenly, which means that climatic conditions change with latitude.

The Earth is inclined to the ecliptic plane by 23.5 degrees.

The rays pass at different angles. Radiation balance. It is important not only how much it receives, but also how much it loses, and how much remains, taking into account the albedo.

Centers of action of the atmosphere

Large areas of persistent high or low pressure, associated with the general circulation of the atmosphere – centers of atmospheric action. They determine the dominant direction of the winds and serve as centers for the formation of geographical types of air masses. On synoptic maps they are expressed as closed lines - isobars.

Causes: 1) heterogeneity of the Earth;

2) difference in physical properties of land and water (heat capacity)

3) difference in surface albedo (R/Q): water – 6%, eq. forests – 10-12%, broad forests – 18%, meadow – 22-23%, snow – 92%;

4) Coriolis F

This causes OCA.

Centers of action of the atmosphere:

● permanent– they have high or low pressure all year round:

1. equatorial low band pressure, the axis of which migrates somewhat from the equator following the Sun towards the summer hemisphere - Equatorial depression (reasons: a large amount of Q and the oceans);

2. along one subtropical strip of elevation. pressure in the North and Yuzh. hemispheres; a few migrate in summer to higher subtropical areas. latitudes, in winter - to lower ones; break up into a series of oceanic anticyclones: in the North. hemispheres - Azores anticyclone (especially in summer) and Hawaiian; in the South - South Indian, South Pacific and South Atlantic;

3. areas of decline. pressure over the oceans in high latitudes of temperate zones: in the North. hemispheres - Icelandic (especially in winter) and Aleutian minimums, in the South - a continuous ring of low pressure surrounding Antarctica (50 0 S);

4. areas of increased pressure over the Arctic (especially in winter) and Antarctica - anticyclones;

● seasonal– can be traced as areas of high or low pressure during one season, changing in another season to the center of action of the atmosphere of the opposite sign. Their existence is associated with a sharp change during the year in the temperature of the land surface in relation to the temperature of the surface of the oceans; summer overheating of the land creates favorable conditions for the formation of low areas here. pressure, winter hypothermia - for areas of higher pressure. All in. hemispheres to higher winter areas. pressures include the Asian (Siberian) centered in Mongolia and the Canadian highs, and the South Australian, South American and South African highs. Summer low areas pressure: in North. hemispheres - South Asian (or Western Asian) and North American minimums, in the South. - Australian, South American and South African lows).

The centers of action of the atmosphere are characterized by a certain type of weather. Therefore, the air here relatively quickly acquires the properties of the underlying surface - hot and humid in the Equatorial Depression, cold and dry in the Mongolian Anticyclone, cool and humid in the Icelandic Low, etc.

Planetary heat exchange and its causes

Main features of planetary heat exchange. Solar energy absorbed by the surface of the globe is then spent on evaporation and heat transfer by turbulent flows. On average, about 80% of the entire planet goes to evaporation, and the remaining 20% ​​of the total heat goes to turbulent heat exchange.

Heat transfer processes and changes with geographical latitude its components in the ocean and on land are very unique. All the heat absorbed by land in spring and summer is completely lost in autumn and winter; with a balanced annual heat budget, it therefore turns out to be equal to zero everywhere.

In the World Ocean, due to the high heat capacity of water and its mobility, heat accumulates in low latitudes, from where it is transferred by currents to high latitudes, where its consumption exceeds its supply. In this way, the deficit created in the heat exchange of water with air is covered.

In the equatorial zone of the World Ocean, with a large amount of absorbed solar radiation and reduced energy consumption, the annual heat budget has maximum positive values. With distance from the equator, the positive annual heat budget decreases due to an increase in the consumption components of heat exchange, mainly evaporation. With the transition from the tropics to temperate latitudes, the heat budget becomes negative.

Within the land, all the heat received in the spring-summer period is spent in the autumn-winter period. In the waters of the World Ocean over the long history of the Earth, great amount heat equal to 7.6 * 10^21 kcal. The accumulation of such a large mass is explained by the high heat capacity of water and its intense mixing, during which a rather complex redistribution of heat occurs in the thickness of the oceanosphere. The heat capacity of the entire atmosphere is 4 times less than that of a ten-meter layer of water in the World Ocean.

Although specific gravity The solar energy used for turbulent heat exchange between the Earth's surface and the air is relatively small; it is the main source of heating of the surface part of the atmosphere. The intensity of this heat exchange depends on the temperature difference between the air and the underlying surface (water or land). In the low latitudes of the planet (from the equator to approximately the fortieth latitude of both hemispheres), the air is heated mainly by land, which is unable to accumulate solar energy and gives up all the heat it receives to the atmosphere. Due to turbulent heat exchange, the air shell receives from 20 to 40 kcal/cm^2 per year, and in areas with low humidity (Sahara, Arabia, etc.) - even more than 60 kcal/cm^2. The waters in these latitudes accumulate heat, releasing only 5-10 kcal/cm^2 per year or less to the air in the process of turbulent heat exchange. Only in certain areas (limited area) is the water colder on average per year and therefore receives heat from the air (in the equatorial zone, in the northwest Indian Ocean, as well as off the west coast of Africa and South America).