What organisms of the biosphere are involved in the circulation of substances. The biological cycle

Back forward

Attention! Slide previews are for informational purposes only and may not represent all the presentation options. If you are interested in this work, please download the full version.

The purpose of the lesson:to give the concept of the circulation of substances, the relationship of substances in the biosphere, compliance with the uniform laws of nature.

Lesson Objectives:

Expand knowledge about the circulation of substances.
Show the movement of substances in the biosphere.
Show the role of the circulation of substances in the biosphere.

Equipment: tables "Boundaries of the biosphere and the density of life in it", a diagram of the cycle of substances, PC, projector, presentation.

Lesson plan.

I. Statement of the problematic question.

II. Check of knowledge.

III. New material.

3.1. Problematic question.

3.2. Definition of the biosphere according to V.I. Vernadsky.

3.3. Characteristics of the biosphere.

3.4. Slide 4. The role of living organisms in the biosphere.

3.5. The cycle of substances in the ecosystem.

IV. Slide 8. Working with the scheme is involved in a cycle.

V. Slide 9. Working with the water cycle diagram.

Vi. Slide 10. Working with the oxygen cycle.

Vii. Slide 12. Working with the carbon cycle diagram.

VIII. Slide 13. The nitrogen cycle.

IX. Slide 14. The sulfur cycle.

H. Slide 15. The phosphorus cycle.

XI. Recording the output on the topic of the lesson.

During the classes

I. Organizing time... The mood of the class for work.

II. Check of knowledge.

Executing a test by options. The tests are printed.

Option 1

1. The most constant factor affecting the atmosphere is:

a) pressure b) transparency c) gas composition d) its temperature

2. The functions of the biosphere due to the processes of photosynthesis include:

a) gas b) redox c) concentration

d) all the listed functions e) gas and redox

3. All oxygen in the atmosphere is formed due to the activity:

a) cyanobacteria of blue-green algae b) heterotrophic organisms c) colonial protozoa c) autotrophic organisms

4. In the transformation of the biosphere, the main role is played by:

a) living organisms b) biorhythms

c) circulation of mineral substances c) self-regulation processes.

Option 2

1. Life can be discovered:

a) any point in the biosphere

b) Any point on Earth

c) any point in the biosphere

d) any point in the biosphere, except Antarctica and the Arctic

e) only geological evolution occurs in the biosphere

2. The influx of energy into the biosphere from the outside is necessary because:

a) carbohydrates formed in the plant serve as a source of energy for other organisms

b) oxidative processes occur in organisms

c) organisms destroy the remains of biomass

d) no species of organisms creates energy reserves

3. Select the main environmental factors that affect the prosperity of organisms in the ocean:

a) water availability b) rainfall

c) transparency of the medium d) pH of the medium

e) water salinity f) water evaporation rate

g) concentration of carbon dioxide

4. Biosphere is a global ecosystem, the structural components of which are:

a) classes and divisions of plants b) populations

c) biogeocenoses d) classes and types.

III. New material.

3.1. Problematic question

Remember the law of conservation of substances from chemistry. How can this law be related to the biosphere?

3.2. Definition of the biosphere

Biosphere, according to V.I. Vernadsky, is a general planetary shell, that area of \u200b\u200bthe Earth where life exists or existed and which is or has been exposed to it. The biosphere covers the entire surface of the land, seas and oceans, as well as that part of the Earth's interior where the rocks created by the activity of living organisms are located.

V. I. Vernadsky
(1863-1945)

Outstanding Russian scientist
Academician, founder of the science of geochemistry
Created the doctrine of the Earth's biosphere.

3.3. Characteristics of the biosphere

Biosphere covers the entire surface of land, seas and oceans, as well as that part of the Earth's interior where the rocks created by the activity of living organisms are located. In the atmosphere, the upper limits of life are determined ozone screen - a thin layer of ozone gas at an altitude of 16–20 km. It blocks the sun's harmful ultraviolet rays. The ocean is full of life as a whole, to the bottom of the deepest depressions in the 10-11 km. In the depths of the solid part of the Earth, active life penetrates in places up to 3 km (bacteria in oil fields). The results of the vital activity of organisms in the form of sedimentary rocks can be traced even deeper.

Reproduction, growth, metabolism and activity of living organisms have completely transformed this part of our planet over billions of years.

The whole mass of organisms of all types V.I. Vernadsky named living matter Earth.

The chemical composition of living matter includes the same atoms that make up inanimate nature, but in a different ratio. In the course of metabolism, living things constantly redistribute chemical elements in nature. Thus, the chemistry of the biosphere is changing.

IN AND. Vernadsky wrote that there is no chemical force on the earth's surface that is more constantly acting, and therefore more powerful in its consequences, than living organisms taken as a whole. Over billions of years, photosynthetic organisms (Fig. 1) have linked and converted vast amounts of solar energy into chemical work. Part of its reserves in the course of geological history has accumulated in the form of deposits of coal and other fossil organic substances - oil, peat, etc.

Fig. 1. The first land plants (400 million years ago)

Slide 4.

3.4. The role of living organisms in the biosphere

Living organisms create in the biosphere the cycles of the most important nutrients, which alternately pass from living matter to inorganic matter. These cycles are divided into two main groups: gas cycles and sedimentary cycles. In the first case, the main supplier of elements is the atmosphere (carbon, oxygen, nitrogen), in the second, sedimentary rocks (phosphorus, sulfur, etc.).

Thanks to living creatures, many rocks have arisen on Earth. Organisms have the ability to selectively absorb and accumulate individual elements in themselves in much larger quantities than they are in the environment.

Making a giant biological circulation in the biosphere, life maintains stable conditions for its existence and the existence of a person in it.

Living organisms play an important role in the destruction and weathering of rocks on land. They are the main destroyers of dead organic matter.

V. V. Dokuchaev
(1846 - 1903)
The founder of modern soil science,
based on the idea of \u200b\u200ba deep relationship between animate and inanimate nature

Thus, during the period of its existence, life has transformed the Earth's atmosphere, the composition of the ocean waters, created an ozone screen, soils, and many rocks. The conditions of weathering of rocks have changed, the microclimate created by vegetation has begun to play an important role, and the climate of the Earth has also changed.

3.5. The cycle of substances in the ecosystem

IV. Work with the scheme is involved in a cycle

In each ecosystem, a cycle of matter occurs as a result of the ecophysiological relationship of autotrophs and heterotrophs.

Carbon, hydrogen, nitrogen, sulfur, phosphorus and about 30 other simple substances necessary to create cell life are continuously converted into organic substances (glycides, lipids, amino acids ...) or absorbed in the form of inorganic ions by autotrophic organisms, subsequently used by heterotrophic organisms, and then - microorganisms-destructors. The latter decompose waste, animal and plant residues into soluble mineral elements or gaseous compounds, which are returned to the soil, water and atmosphere.

V. Working with the water cycle diagram

Fig. 6. Water cycle in the biosphere

Vi. Working with the oxygen cycle

Slide 10

Oxygen cycle.

The cycle of oxygen on Earth takes about 2000 years, water cycle - about 2 million years (Fig. 6). This means that the atoms of these substances in the history of the Earth have repeatedly passed through living matter, having visited the bodies of ancient bacteria, algae, tree ferns, dinosaurs and mammoths.

The biosphere went through a long period of development, during which life changed forms, spread from water to land, changed the system of cycles. The oxygen content in the atmosphere gradually increased (see Fig. 2).

Over the past 600 million years, the speed and nature of the gyres have approached modern ones. The biosphere functions as a gigantic well-coordinated ecosystem, where organisms not only adapt to the environment, but also create and maintain conditions on Earth that are favorable for life.

Vii. Working with the carbon cycle

Questions to students:

1. Remember the role of photosynthesis in nature?

2. What conditions are necessary for photosynthesis?

The carbon cycle (fig. 4). Its source for photosynthesis serves as carbon dioxide (carbon dioxide) in the atmosphere or dissolved in water. Carbon bound in rocks is involved in the cycle much more slowly. As part of the organic substances synthesized by the plant, carbon enters, then into power circuits through living or dead plant tissues and returns to the atmosphere again in the form of carbon dioxide as a result of respiration, fermentation or combustion of fuel (wood, oil, coal, etc.). The carbon cycle is three to four centuries long.

Fig. 4. Carbon cycle in the biosphere

VIII. Working with the Nitrogen Cycle scheme.

Remember the role they play in nitrogen accumulation?

The nitrogen cycle (Fig. 5). Plants obtain nitrogen mainly from decaying dead organic matter through the activity of bacteria, which convert the nitrogen of proteins into a form that plants can absorb. Another source - free nitrogen of the atmosphere - is not directly available to plants. But they bind him, i.e. transform into other chemical forms, some groups of bacteria and blue-green algae, they enrich the soil with it. Many plants are in symbiosis with nitrogen-fixing bacteria that form nodules on their roots. From dead plants or animal corpses, part of the nitrogen, due to the activity of other groups of bacteria, turns into a free form and re-enters the atmosphere.

Fig. 5. The cycle of nitrogen in the biosphere

IX. The sulfur cycle

Slide 14

The cycle of phosphorus and sulfur. (fig. 6, 7). Phosphorus and sulfur are found in rocks. When they are destroyed and eroded, they enter the soil, from there they are used by plants. The activity of organisms - decomposers returns them to the soil again. Some of the compounds of nitrogen and phosphorus are washed off by rains into rivers, and from there into the seas and oceans and used by algae. But, in the end, in the composition of dead organic matter, they settle to the bottom and are again included in the composition of rocks.

X. The phosphorus cycle

Over the past 600 million years, the speed and nature of the gyres have approached modern ones. The biosphere functions as a giant well-coordinated ecosystem, where organisms not only adapt to the environment, but also create and maintain conditions on Earth that are favorable for life.

XI. Recording the output in a notebook

1. The biosphere is an energetically open system

2. The accumulation of substances in the biosphere is due to plants capable of converting the energy of sunlight.

3. The circulation of substances is a necessary condition for the existence of life on Earth.

4. In the course of evolution in the biosphere, an equilibrium has been established between organisms.

Review questions:

1. What organisms of the biosphere are involved in the cycle of substances?

2. What determines the amount of biomass in the biosphere?

3. What is the role of photosynthesis in the cycle of substances?

4. What is the role of the carbon cycle in the biosphere?

5. What organisms are involved in the nitrogen cycle?

Homework: Learn paragraphs 76, 77.

Advance Learning: Pick up material on the main environmental issues of our time.

G.I. Lerner General biology: preparation for the exam. Control and independent work - M .: Eksmo, 2007. - 240 p.
E.A. Carvers Ecology: Textbook. 2nd ed. rev. and add. - M .: MGIU, 2000 - 96 p.
Internet library: http://allbest.ru/nauch.htm
Ecology website: http://www.anriintern.com/ecology/spisok.htm
Electronic journal "Ecology and Life" .: http://www.ecolife.ru/index.shtml

All substances on our planet are in a state of constant circulation. causes two cycles of substances on Earth: one, large, covering the whole, is called biosphere, and the other - small - flows inside and is called biological.

The biospheric cycle of substances is preceded by a geological one, which determines the destruction, migration and accumulation of chemical compounds and substances. In such migration, the leading role belongs to solar energy, on which the speed and scale of development of exogenous processes depend. In them, the dominant role belongs to the gravitational and especially thermal properties of the land surface and water shell, which absorb and reflect the sun's rays, have thermal conductivity and heat capacity. The unstable hydrothermal regime, together with the planetary atmospheric circulation system, caused the geological circulation of substances, which, together with endogenous processes - spreading, subduction, volcanism, tectonic movements - causes the formation and development of oceans and continents. Weathering products are transported by air masses and water currents. With the emergence of the biosphere, the waste products of organisms were included in the great circulation of substances, and, thus, the geological circulation acquired completely new features. It becomes a supplier of nutrients to living organisms, largely determines the conditions of their existence, and at the same time, along with mechanical and chemical differentiation and accumulation of matter, biological disintegration and biological accumulation of matter began to take place.

The large cycle of substances in the biosphere is characterized by two important features. First, it has been carried out throughout the entire history of the biosphere, i.e., starting at least from 3.8-4.0 billion years ago. Secondly, it is a modern planetary process that plays an important role in the further existence and development of the biosphere.

Moving in the geological cycle inorganic substance is a kind of reserve fund for the biological branch of the biosphere cycle. This reserve fund is concentrated in the atmosphere in the form of gases and thermodynamically active substances, in the form of dissolved chemicals and their compounds, in the lithosphere in the form of mineral and organomineral substances, some of which are located in the upper horizons and soils. The transit cycle of the gyre is mainly associated with the atmosphere and hydrosphere, and accumulative, or sedimentary, with the lithosphere and partly with the hydrosphere.

Small, or biological, circulation of substances develops against a geological background, covering the entire biosphere. Although it occurs within individual ecosystems, it is not closed, and this is due to the fact that matter comes into the ecosystem from the outside.

Plants, animals and soil cover on land form a complex global system that forms biomass, binds and redistributes solar energy, atmospheric carbon, moisture, oxygen, nitrogen, phosphorus, sulfur, calcium and other elements involved in the life of organisms, which are called biogenic elements ... Plants, animals and microorganisms of the aquatic environment, which perform the same function of binding and redistributing solar energy and biological circulation of substances, form another global system.

The peculiarity of the biological cycle lies in the course of three opposite, but interrelated processes: the formation of organic matter, its destruction and redistribution. The initial stage of the emergence of organic matter is due to the vital activity of producers and is associated with the photosynthesis of plants, i.e., with the formation of organic matter from carbon dioxide, water and simple minerals using solar energy. Plants extract sulfur, phosphorus, calcium, potassium, magnesium, manganese, silicon, aluminum, copper, zinc and other vital elements and trace elements from the soil in dissolved form. First-order consumables, that is, herbivorous animals, absorb the created organic matter and, together with food of plant origin, assimilate the biogenic elements necessary for life. Second-order consumables - predators - feed on herbivorous animals and thus consume organic substances of a more complex composition, including fats, amino acids, and along with them also trace elements necessary for subsequent vital activity.

In the process of destruction by microorganisms of organic matter of plant or animal origin, simple mineral compounds that are available for assimilation by plants enter the soil and aquatic environment. Thus, a new cycle of biological circulation begins.

In contrast to the large cycle, the small cycle has undoubtedly a shorter, but unequal duration. Distinguish between seasonal, annual, perennial and secular small gyres. When considering the biological cycle of substances, the main attention is paid to the annual rhythm, determined by the annual dynamics of the development of the vegetation cover.

The exchange of matter and energy, which takes place between different structural parts of the biosphere and is determined by the vital activity of microorganisms, is called a biogeochemical cycle. This concept was introduced into world science by V. I. Vernadsky, and only after that the idea of \u200b\u200bthe circulation of substances as a closed system ceased to exist. All biogeochemical cycles constitute the modern dynamic basis for the existence of life. They are interconnected, and at the same time, each of them plays its own unique role in the evolution of the biosphere.

Separate cyclical processes, however, are not completely reversible. One part of the elements and compounds in the process of migration and transformation scatters or binds in new systems and, therefore, falls out of the cycle. Another part of the substances is able to return to the cycle, but quite often it acquires new qualities, and at the same time the quantitative composition of the substances participating in the cycle changes. Part of the substances due to geological processes, in particular subduction, can be removed from the circulation and, moving to the lower horizons of the lithosphere, modified, and part, mainly in a gaseous state, can be removed from the atmosphere into outer space.

The duration of the cycles of certain substances in different systems is extremely different. It has been established that the total turnover of carbon dioxide in the atmosphere through photosynthesis is about 300 years, atmospheric oxygen and also through photosynthesis - 2000-2500 years, atmospheric nitrogen through biological fixation and photochemistry - about 100 million years, and water through evaporation - about 1 million years.

A huge number of chemical elements and compounds are involved in the biosphere and biological cycles, but the most important of them are those that determine the modern stage of the development of the biosphere associated with human economic activity. These include the cycles of carbon, sulfur, nitrogen and phosphorus. The oxides of the first three are the main pollutants of the atmosphere, and phosphates are the pollutants of water bodies. Knowledge of the cycles of a number of toxic elements and, in particular, mercury (a food contaminant) and lead (a component of gasoline that acts as a soil and air pollutant) is of great importance. Many substances of anthropogenic origin (DDT, pesticides, radionuclides, etc.) are involved in the circulation, which harm the biota and human health.

The carbon cycle

This cycle is one of the most important cycles of matter in the biosphere. Changes in the global scale of the carbon cycle caused by anthropogenic activities lead to adverse consequences for the biosphere. The process of the carbon cycle is directly related to the oxygen content in the atmosphere and its cycle in the biosphere, changes in climate and weather conditions on the earth's surface, etc.

Carbon participates in the large and small cycles of matter. Its compounds in the biosphere constantly arise, undergo transformations and decompose. The main route of carbon migration is from carbon dioxide in the atmosphere to living matter and from living matter to atmospheric carbon dioxide. In this case, part of the carbon leaves the cycle, dissolving in the hydrosphere and precipitating in the form of carbonate rocks, and part of it remains in the soil.

There are three stages in the biological carbon cycle. At the first stage, green plants absorb carbon dioxide from the air, create organic matter, the main component of which is carbon. Subsequently, animals, feeding on plants, from the compounds contained in organic matter, including carbon compounds, produce other compounds. At the final stage, after the death of organisms of plant or animal origin, their dead are destroyed by microorganisms that release carbon. It enters the atmosphere again in the form of carbon dioxide. In addition, the source of carbon is carbon dioxide released into the atmosphere during the respiration of plants at night, released during the respiration of animals and humans, and also released into the atmosphere as a result of volcanic eruptions and during the weathering of rocks containing carbon in a bound form.

Part of the carbon accumulates in the form of dead organic matter and where there are no conditions for their decomposition, i.e., under reducing conditions. In this case, organic carbon goes into a fossil state and accumulates in the form of peat and gas, and is further processed into coal and oil shale, and with metamorphism transforms into graphite.

Considering the global transformation of organic carbon and its intensive burial in bogs, floodplain-old conditions, lagoons, mangroves, sea basins and freshwater bodies, it must be admitted that this process was carried out on Earth during the entire biological evolution of the biosphere, and this process over a long geological time passed with great intensity, but at different rates. In the geological past, when there was a landscape and climatic situation favorable to the development of vegetation, and the concentration of carbon dioxide in the atmosphere was almost an order of magnitude higher than the modern one, the excess of organic carbon was buried in the bowels of the Earth, forming mineral deposits. The total mass of carbon that is buried in the form of fossil fuels is estimated at more than 100,000 trillion. t.

Modern vegetation, including algae, produces about 1.5 trillion annually. T. carbon. According to MI Budyko's calculations, the entire supply of carbon dioxide in the atmosphere, if it were not renewed, would have been depleted by plants in eight years.

In addition to the biosphere, carbon dioxide is produced by inert systems, in particular volcanic eruptions. A very significant source and consumer of carbon dioxide is the water masses of the hydrosphere. Carbon dioxide is presented in it in the form of dilute solutions of carbonic acid and mainly in the form of bicarbonates. There is a global exchange between the atmosphere and the hydrosphere, not only energy, but also matter in the form of gases. An increase in the concentration and partial pressure of CO 2 in the atmosphere, regional or seasonal cooling of waters - all this is accompanied by an immediate increase in the concentration of carbon dioxide in water and calcium bicarbonate solutions. The required amounts of carbon dioxide are removed from the atmosphere.

It is known that many aquatic organisms, absorbing calcium carbonate, build their skeletons, and after death they form bottom calcareous deposits, which are further transformed in the process of lithogenesis in the strata of organogenic limestones. When settling, calcium carbonate binds part of the carbon dioxide in the form of lime sediments at the bottom of the World Ocean and freshwater bodies, but at the same time part of the carbon dioxide returns to the atmosphere.

There is an equilibrium between atmospheric carbon dioxide and carbon dioxide dissolved in the oceans. A decrease in carbon dioxide in the atmosphere inevitably causes the degassing of ocean waters and leads to the release of carbon dioxide into the atmosphere. The temperature factor often acts as a disturbance to the equilibrium process.

Photosynthesis in the hydrosphere is a permanent factor in the absorption of carbon dioxide from the atmosphere, as well as gases dissolved in the aquatic environment. Moreover, this process proceeds with the corresponding release of oxygen.

Thus, they represent a single system that regulates the mutual distribution of carbon dioxide. A number of researchers believe that in the modern era, despite the increase in the concentration of carbon dioxide in the atmosphere, the World Ocean continues to effectively perform the function of capturing and binding excess amounts of carbon dioxide, converting it into soluble bicarbonates and precipitating in the form of calcium carbonate, as well as through the formation of biomass of living substances with a carbonate skeleton.

The carbon cycle continues to control the oxygen content in the atmosphere. At the same time, MI Budyko and AB Ronov estimate the total mass of oxygen at 1.2 * 10 6 billion tons. The planetary oxygen consumption for the combustion of fossil fuel is about 15 billion tons annually. This is almost an order of magnitude less than the annual input into the atmosphere of oxygen released during photosynthesis (140-200 billion tons). The released oxygen is almost completely used in the respiration of organisms and the mineralization of dead organic matter, and is also partially preserved in the lithosphere in the form of metal oxides and compounds.

For the combustion of mineral fuel, oxygen is used, already accumulated in the atmosphere, and its annual decrease is approximately one ten thousandth of its mass in the atmosphere. Complete combustion of carbon fuels reduces the oxygen content in the atmosphere by only a fraction of a percent. Significant changes in the mass of oxygen can manifest themselves over very long periods of time, estimated at millions of years. Based on this, it is believed that the greatest danger to the biosphere is a violation of the carbon cycle.

In the modern era, in contrast to past geological periods, the flow of carbon into the atmosphere has increased due to anthropogenic emissions, and the vegetation has been unable to fully assimilate it. As a result, the self-cleaning of the atmosphere from carbon monoxide decreased, i.e. from carbon monoxide.

Self-purification of air from carbon monoxide occurs as a result of CO migration to the upper atmosphere, where it is oxidized to CO 2 in the presence of nitrogen dioxide and ozone. It has been established that if the constant supply of technogenic carbon monoxide to the atmosphere ceased, it would be cleared of it within several years.

The nitrogen cycle

Nitrogen, like carbon, participates in the large and small cycles. The source of nitrogen in the biological cycle are nitrates and nitrites, which are absorbed by plants from soil and water. Plants do not have the ability to extract nitrogen directly from the atmosphere. Herbivorous animals create the protoplasm of their cells from the amino acids of plant proteins. Putrefactive bacteria convert nitrogen compounds in dead plant and animal remains into ammonia. The nitrifying bacteria then convert the ammonia to nitrite and nitrate. Part of the nitrogen, due to denitrifying bacteria, re-enters the atmosphere. If there was no additional source of replenishment of nitrogen reserves in the soil, nitrogen starvation of plants would occur and, as a consequence, the destruction of the biosphere, since in the process of denitrification, free nitrogen is removed from the biological cycle.

There are two ways to involve atmospheric nitrogen in the biological cycle. One of them is associated with atmospheric precipitation, and the second is associated with biological nitrogen fixation by prokaryotic organisms.

As a result of volcanic eruptions, as well as ongoing photos chemical reactions and arising from lightning discharges and ionization of electrical oxidation of nitrogen in the atmosphere, nitrogen oxides are always present, which, together with atmospheric precipitation, enter the soil layers. In addition, the atmospheric air always contains ammonia. In a normal state, it is 0.02-0.04 mg / m 3, but its amount increases with lightning discharges. It is estimated that the total nitrogen input into the soil in this way is 10-15 kg / ha.

Biological nitrogen fixation is associated with the activity of prokaryotes. They are able to convert biologically useless nitrogen gas into compounds necessary for plant root nutrition. The fixation of nitrogen requires a large expenditure of energy, which is spent mainly on breaking the triple bond in the nitrogen molecule, then, with the addition of hydrogen from water, to convert it into two ammonia molecules.

Nitrogen is fixed by free-living aerobic (Asotobacter) and anaerobic (Clostridium) bacteria, some blue-green algae (Anabaena, Nostos), symbiotic nodule bacteria of legumes (Rhizobium) and other microorganisms. The root nodule bacteria are especially active. The total amount of nitrogen fixed by them can reach 350 kg / ha, which is 100 times higher than that of free-living nitrogen-fixing organisms.

Most of the fixed nitrogen in the soil is absorbed by plants, but some of its compounds are carried out into rivers and enter water bodies, including the seas. Most of the ammonium salts, nitrates and nitrites are found in the waters of river estuaries and off the coast of the seas, in the deep parts of water bodies of land, where they enter in the process of decay of organic matter. The nitrogen found in surface waters is consumed by plant microorganisms. The loss of nitrogen is continuously replenished by its supply from land, as a result of constant mixing of waters, the fallout of ammonia from the atmosphere and the decomposition of plant and animal residues in the surface parts of water bodies.

Anthropogenic disturbances of the nitrogen cycle in the biosphere are associated with the combustion of mineral fuels in land and air transport, at thermal power plants and with the production of nitrogen fertilizers. Entering the atmosphere of nitrogen of anthropogenic origin in the 70s of the XX century. was 15 times, and in the 80s - 12 times less than from natural sources. However, due to the development of industry and transport, the amount of technogenic nitrogen in the atmosphere tends to increase.

When fuel is burned, an additional amount of nitrogen oxides enters the atmosphere, which are involved in photochemical reactions. One of these reactions leads to the formation of photochemical smog containing formaldehyde and other toxic components.

Stratospheric pollution with nitrogen oxides as a result of flights of airplanes, space and simple rockets disrupts the natural nitrogen cycle and leads to the growing destruction of the ozone screen. In the troposphere, nitrogen oxides, in contact with water vapor, form nitric acid aerosols, which together with sulfuric acid aerosols fall out in the form of acid rain.

The production and use of nitrogen fertilizers make significant changes in the nitrogen cycle. In the XX century. chemical synthesis of nitrogen fertilizers based on the binding of atmospheric nitrogen has become the main source of nutrition for cultivated plants. Over 40 million tons of nitrogen are applied annually in the world in the form of mineral fertilizers. In addition, difficult to account for nitrogen from livestock complexes and farms enters the soil cover and water systems.

Phosphorus cycle

The biological significance of phosphorus in the life of organisms is extremely high. Its compounds are included in nucleic acids, cell membranes, energy transfer systems, in the brain and bone tissue. The phosphorus content in plant tissues is 250-350, marine animals - 400-1800, land animals - 170-4400, bacteria - about 3000 mg per 100 g of dry matter. Like carbon, phosphorus participates in the biological and geological cycle of matter.

The lithosphere, in particular, phosphorus-containing rocks, such as phosphorites, apatites, and nepheline syenites, serves as a reservoir of phosphorus in the biological cycle. In the process of weathering, phosphorus compounds enter the soil cover, are carried out by surface waters into the final runoff basins, where they either slowly settle to the bottom and lithify, or are dispersed by deep waters.

Phosphorus is extracted from the soil by plants in the form of soluble phosphates, which are absorbed with soil solutions and converted into PO 4 -2 ions. The rate of assimilation of phosphorus by plants depends on the acidity of the soil solution. In an alkaline medium, calcium and sodium phosphates are practically insoluble, and in a neutral medium, they are slightly soluble. As the acidity increases, they turn into highly soluble phosphoric acid. Phosphorus found in vegetation is transferred to animals that consume plant food.

Organic phosphorus found in plant litter, dead plant and animal residues as a result of bacterial transformations in the soil is transformed into phosphates. The phosphate-destroying bacteria acting on them continue the biological cycle of phosphorus, converting it into a soluble form, which, getting into the aquatic environment, takes part in the geological cycle.

The phosphorus cycle in the biosphere is not closed, as part of it enters the lithosphere. Only a small amount of phosphorus is irretrievably lost during geological processes, and part of it is accumulated along with precipitation. With river flows, according to the calculations made, about 3-4 million tons of phosphorus enter the World Ocean annually, which is excluded from the cycle.

In the seas and oceans, phosphorus is concentrated in the form of phosphate nodules, which, in the course of sedimentation over time, are converted into phosphorites. In the upwelling zone, when deep waters rise, phosphorus, along with other biogenic elements and nutrients, is carried to the surface, and therefore the upwelling zones are unusually rich in organisms.

Phosphorus is always in short supply in soil and natural waters. The ratio of phosphorus and nitrogen in natural waters is on average 1:23 (in rivers and streams 1:28), in biomass 1:16. This in a certain way inhibits the biological productivity of the Earth. Although a part of phosphorus from the World Ocean naturally returns to land by birds and with caught fish, the total volume of phosphorus return is clearly less than the amount carried out into the hydrosphere.

During the XX century. as a result of human economic activity, the chain of phosphorus circulation in the biosphere was disrupted. This was facilitated by the production of phosphorus fertilizers and their widespread use in agriculture, the production of various phosphorus-containing preparations on an industrial scale, the production of food and feed, the development of fisheries, the extraction of sea and algae. These actions directly affected the phosphorus cycle and led to the redistribution of the phosphate content on land and in the hydrosphere. There is also an extremely uneven concentration of phosphorus on the earth's surface. It is more in places where agriculture is developed, where there is a low-reversible accumulation of organic phosphorus compounds. Soil erosion, washout of fertilizers, organic waste and excrement by surface waters, and sewage discharges lead to severe phosphorus pollution of rivers, lakes and coastal areas of the World Ocean. Phosphatization of soils, rivers, water bodies of land, coastal areas of the seas occurs, especially in the area of \u200b\u200bdeltas, bays and estuaries.

The sulfur cycle

Sulfur is of great biological importance, as it is a constituent of amino acids, proteins and other complex organic compounds. In terms of dry matter, the sulfur content in terrestrial plants is 0.3%, in terrestrial animals - 0.5%, in marine plants - 1.2%, in marine animals - up to 2%.

In a large geological cycle, sulfur is transported from the ocean to the continents by atmospheric precipitation and returns with river runoff back to the World Ocean. At the same time, its reserves are replenished due to volcanic activity and during weathering processes. sulfur is emitted in the form of trioxide (sulfuric anhydride SO 3), dioxide (sulfur dioxide SO 2), hydrogen sulfide H 2 S and elemental sulfur. The lithosphere contains a large amount of sulfides of various metals: iron, zinc, lead, copper, etc. In the biosphere, sulfide sulfur with the participation of numerous microorganisms is oxidized to sulfate sulfur SO 4 -2, which is found in soil and water bodies. In the small cycle, sulphates are absorbed by plants. Herbivorous animals receive the sulfur necessary for life. As a result of complex transformations and modifications during the destruction of the remains of organisms, plant waste, sulfur enters the soil water and into the silts of land, seas and oceans. When proteins are destroyed with the participation of microorganisms, hydrogen sulfide is formed, which is further oxidized either to elemental sulfur or to sulfates. In the first case, deposits of pure sulfur are formed, and in the second, deposits of gypsum. When the latter are destroyed during mining or weathering, sulfur is again involved in the cycle.

Hydrogen sulfide contamination of the Black Sea waters is the result of the vital activity of sulfur-decomposing bacteria under anaerobic conditions. Hydrogen sulfide often occurs in freshwater bodies of water polluted by industrial effluents. At the final stage of the geological cycle, sulfur precipitates under anaerobic conditions in the presence of iron and other metals and slowly accumulates in the form of nodules or finely dispersed matter in the earth's interior.

Industrial pollution leads to disruption of the sulfur cycle, as well as the other elements listed above, participating in other cycles. An additional supplier of sulfur to the big cycle is thermal power plants, which, when burning mineral fuel, emit sulfur dioxide.

The Earth's atmosphere is capable of self-cleaning from sulfur dioxide when atmospheric precipitation falls: it is transformed by gaseous emissions of vegetation or precipitated in the form of sulfate aerosols.

The environmental hazard of sulfur dioxide is that during photochemical oxidation in the presence of nitrogen dioxide and hydrocarbons, sulfuric anhydride SO 3 is first formed, which, when combined with water vapor, turns into aerosols of sulfuric acid Н 2 SO 4. The duration of the entire cycle from the moment of natural or man-made emissions of SO 2 to the removal of sulfuric acid vapors from the atmosphere is up to 14 days. With air currents, sulfuric acid aerosols are carried over considerable distances from the source of emission and fall out in the form of acid rain. This is described in more detail in the sections concerning the asidification of the atmosphere and hydrosphere.

The mercury cycle

This rare chemical element is highly toxic. Mercury compounds are also highly toxic. In nature, mercury is dispersed in earth crust and is very rare in minerals such as cinnabar, where it is found in concentrated form. Mercury participates in the circulation of substances, migrating in a gaseous state and in aqueous solutions.

Mercury enters the atmosphere from the hydrosphere during evaporation, together with volcanic gases and gases from thermal springs. Part of the gaseous mercury goes into the solid phase and is removed from the air. The mercury precipitated together with atmospheric precipitation is absorbed by soil solutions and clay rocks. Mercury is found in small amounts in oil and coal (up to 1 mg / kg). In the water mass of the oceans, its amount is about 1.6 billion tons, bottom sediments contain about 500 billion tons, and planktonic organisms contain up to 2 million tons of mercury and its compounds. River waters annually carry out about 40 thousand tons of mercury from the land, which is an order of magnitude less than enters the atmosphere during evaporation.

As a result of the increased technogenic emissions into the atmosphere and the hydrosphere, mercury from a natural component of the natural environment participating in all cycles has turned into a very dangerous component for human health and living matter. Mercury is used in the metallurgical, chemical, electrical, electronic, pulp and paper and pharmaceutical industries; it is used for the production of explosives, fluorescent lamps, varnishes and paints. Industrial effluents and atmospheric emissions, mining and processing plants at mercury mines, thermal power plants using mineral fuels are the main sources of pollution of the biosphere with this toxic component. In addition, mercury is part of some pesticides used in agriculture to treat seeds and protect them from pests. Mercury and its compounds enter the human body together with food.

Lead cycle

Despite the fact that lead in the earth's crust contains only 0.0016%, it is present in all components of the natural environment. The most important in the cycle of lead is its atmospheric-hydrospheric transport. Lead in the atmosphere, together with dust, is precipitated by atmospheric precipitation and begins to concentrate in soils. Plants get lead from soil, natural waters and atmospheric fallout, while animals get lead from plants and water. Lead enters the human body through food, water and dust.

The main sources of lead pollution of the biosphere are various, the exhaust gases of which contain tetraethyl lead, thermal power plants that burn coal, mining, metallurgical and chemical industries. A significant amount of lead is introduced into the soil by wastewater.

Residents of industrialized countries have several times more lead content in their bodies than residents of agrarian countries, and urban dwellers have higher levels of lead than rural residents. An increase in the concentration of lead in natural environments leads to irreversible processes in the bones and liver of people.

The biosphere is the area of \u200b\u200bdistribution of living matter. There are important milestones in its history, testifying to the influence of various geospheric factors on its development and evolution. Living matter has very peculiar ecological functions. Energy, gas, soil-eluvial, water purification, water regulation, concentration, transport and destructive functions are of great geoecological importance. The biosphere is multifaceted as a result of an exceptionally great taxonomic diversity. Each organism or group of organisms, due to their physiological characteristics and conditions of existence, can serve as a tool for indicating the pollution of the natural environment. There is a cycle of substances in the biosphere, which is preceded by a geological cycle, which prepares substances for the vital activity of organisms. The lower level of the biosphere cycle is the biological cycle. In nature, there are cycles of carbon, nitrogen, phosphorus, sulfur, mercury, lead and other chemical elements and compounds.

Many enzymatic reactions take place in living cells. We combine the entire set of these reactions with the general concept of metabolism, but it would be wrong to think that a cell is nothing more than a membrane bag in which enzymes act in a random, disordered manner. Metabolism is a highly coordinated and targeted cellular activity mediated by the participation of many interconnected multienzyme systems. It has four specific functions: 1) supplying chemical energy, which is obtained by breaking down energy-rich nutrients that enter the body from the environment, or by converting the captured energy of sunlight; 2) the transformation of molecules of nutrients into building blocks, which are used in the future by the cell to build macromolecules; 3) assembly of proteins, nucleic acids, lipids, polysaccharides and other cellular components from these building blocks; 4) synthesis and destruction of those biomolecules that are necessary for the performance of any specific functions of a given cell.

Although metabolism is composed of hundreds of different enzymatic reactions, the central metabolic pathways that we are usually most interested in are few and far between all living forms are basically the same. In this overview chapter, we will look at the sources of substances and energy for metabolism, the central metabolic pathways used for the synthesis and breakdown of the main cellular components, the mechanisms involved in the transfer of chemical energy, and, finally, those experimental approaches that are used to study metabolic pathways.

13.1. Living organisms take part in the carbon and oxygen cycle

We will begin our consideration with the macroscopic aspects of metabolism, with the general metabolic interaction between living organisms of the biosphere. All living organisms can be divided into two large groups depending on the chemical form in which they are able to assimilate carbon coming from the environment. Autotrophic cells (“feeding themselves”) can use atmospheric carbon as the only source of carbon, from which they build all their carbon-containing biomolecules.

This group includes photosynthetic bacteria and leaf cells of green plants. Some autotrophs, such as cyanobacteria, can also use atmospheric nitrogen to synthesize all of their nitrogen-containing components. Heterotrophic cells ("eating at the expense of others") do not have the ability to assimilate atmospheric; they must receive carbon in the form of fairly complex organic compounds, such as, for example, glucose. Heterotrophs include cells of higher animals and most microorganisms. Autotrophs, which provide themselves with everything necessary for life, have a certain independence, while heterotrophs, which require complex carbon sources, feed on the waste products of other cells.

There is another important difference between the two groups. Many autotrophic organisms carry out photosynthesis, that is, they have the ability to use the energy of sunlight, while heterotrophic cells extract the energy they need by breaking down organic compounds produced by autotrophs. In the biosphere, autotrophs and heterotrophs coexist as participants in a single giant cycle in which autotrophic organisms build organic biomolecules from the atmosphere and some of them release oxygen into the atmosphere. Heterotrophs use organic products produced by autotrophs as food and return them to the atmosphere. In this way, there is a continuous cycle of carbon and oxygen between the animal and plant world. The energy source for this colossal process is sunlight (Figure 13-1).

Autotrophic and heterotrophic organisms can, in turn, be divided into subclasses. There are, for example, two large subclasses of heterotrophs: aerobes and anaerobes. Aerobes live in an oxygen-containing environment and oxidize organic nutrients with molecular oxygen.

Fig. 13-1. The cycle of carbon dioxide and the cycle of oxygen between the two regions of the Earth's biosphere, photosynthetic and heterotrophic. The scale of this cycle is enormous. Over the course of a year, the biosphere makes a cycle of more than carbon. The balance between education and consumption is one of the important factors that determine the climate on Earth. The content in the atmosphere has increased by about 25% over the past 100 years due to the increasing burning of coal and oil. Some scientists argue that a further increase in the amount of atmospheric will lead to an increase in average temperature atmosphere (greenhouse); not everyone, however, agrees with this, since it is difficult to determine precisely the amount generated and recirculated in the biosphere, as well as absorbed by the oceans. It takes about 300 years for all the atmosphere to be passed through the plants.

Anaerobes do not need oxygen to oxidize nutrients; they live in an oxygen-free environment. Many cells, such as yeast cells, can exist under both aerobic and anaerobic conditions. Such organisms are called facultative anaerobes. However, for obligate anaerobes, which are not able to use oxygen, the latter is a poison. These are, for example, organisms that live deep in the soil or on the seabed. Most heterotrophic cells, especially higher cells, are facultative anaerobes, but in the presence of oxygen, they use aerobic metabolic pathways to oxidize nutrients.

In the same organism, different groups of cells can belong to different classes.

For example, in higher plants, green chlorophyll-containing leaf cells are photosynthetic autotrophs, and chlorophyll-free root cells are heterotrophs. Moreover, green leaf cells lead an autotrophic existence only during the day. In the dark, they function as heterotrophs and extract the energy they need by oxidizing the carbohydrates they synthesize in the light.

Question 1. What is the main function of the biosphere?

The main function of the biosphere is to ensure the circulation of chemical elements, which is expressed in the circulation of substances between the atmosphere, soil, hydrosphere and living organisms.

Question 2. Tell us about the water cycle in nature.

Water evaporates and is carried over long distances by air currents. Falling on the land surface in the form of precipitation, it contributes to the destruction of rocks, makes them accessible to plants and microorganisms, erodes the upper soil layer and goes along with dissolved chemical compounds and suspended organic particles into the seas and oceans. The circulation of water between the ocean and land is an essential link in the maintenance of life on Earth.

Question 3. Do living organisms participate in the water cycle? If yes, then supplement the scheme shown in Figure 113, indicating the participation of living organisms in the cycle.

Plants participate in the water cycle in two ways: they extract it from the soil and evaporate it into the atmosphere; some of the water in plant cells is split during photosynthesis. In this case, hydrogen is fixed in the form of organic compounds, and oxygen enters the atmosphere.

Animals consume water to maintain osmotic and salt balance in the body and excrete it into the external environment along with metabolic products.

Question 4. What organisms absorb carbon dioxide from the atmosphere?

In the process of photosynthesis, green plants use the carbon of carbon dioxide and hydrogen in water to synthesize organic compounds, and the liberated oxygen enters the atmosphere.

Question 5. How is the bound carbon returned to the atmosphere?

Various animals and plants breathe oxygen, and the end product of respiration - CO2 - is released into the atmosphere.

Question 6. Draw a schematic diagram of the nitrogen cycle in nature.

Question 7. Consider and provide examples that show that microorganisms play an important role in the sulfur cycle.

Found deep in the soil and in marine sedimentary rocks, sulfur compounds with metals - sulfides - are converted by microorganisms into an accessible form - sulfates, which are absorbed by plants. With the help of bacteria, separate oxidation-reduction reactions are carried out. Deep-seated sulfates are reduced to H2S, which rises and is oxidized by aerobic bacteria to sulfates. The decomposition of the carcasses of animals or plants ensures the return of sulfur to the cycle.

Question 8. Every person's diet must include fish dishes. Explain why this is important.

Together with the fish caught, about 60 thousand tons of elemental phosphorus are returned to land. 70% of all phosphorus contained in our body is concentrated in bones and teeth. Together with calcium, it forms the correct structure of bones and ensures their mechanical strength. The ideal ratio of the amount of phosphorus and calcium is considered 1 to 2 or 3 to 4. And if there are, say, equal parts, then the bone, gradually losing calcium, will become hard, but fragile, like glass, at first glance it is quite hard, although at the same time it's easy to break.

Phosphorus is the main energy carrier, it is part of adenosine triphosphate (abbreviated as ATP), which is absorbed into the blood and delivers energy to all cells that need it.

Question 9. Discuss in class how the circulation of substances in nature would change if all living organisms disappeared on the planet.

All living organisms take part in the circulation of substances, absorbing some substances from the external environment and releasing others into it. Thus, plants consume carbon dioxide, water and mineral salts from the external environment and release oxygen into it. Animals inhale the oxygen released by plants, and by eating them, they assimilate organic substances synthesized from water and carbon dioxide and release carbon dioxide, water and substances from the undigested part of food. When bacteria and fungi decompose dead plants and animals, an additional amount of carbon dioxide is formed, and organic substances are converted into minerals, which enter the soil and are again absorbed by plants. Thus, the atoms of the main chemical elements constantly migrate from one organism to another, from the soil, atmosphere and hydrosphere to living organisms, and from them to the environment, thus replenishing the inanimate matter of the biosphere. These processes are repeated an infinite number of times. So, for example, all atmospheric oxygen passes through living matter in 2 thousand years, all carbon dioxide - in 200-300 years.

The continuous circulation of chemical elements in the biosphere along more or less closed paths is called a biogeochemical cycle. The need for such circulation is explained by the limited supply of their resources on the planet. To ensure the infinity of life, chemical elements must move in a circle. With the disappearance of living organisms, there would be a failure in the circulation of substances and energy, and, as a consequence, the death of the biosphere.

The cycle of substances in the biosphere is a "journey" of certain chemical elements along the food chain of living organisms, thanks to the energy of the Sun. During the "journey" some element, for various reasons, drops out and remains as a rule, in the ground. Their place is taken by the same ones that usually come from the atmosphere. This is the most simplified description of what is the guarantee of life on planet Earth. If for some reason such a journey is interrupted, then the existence of all living things will cease.

To describe briefly the cycle of substances in the biosphere, it is necessary to set several starting points. First, out of more than ninety chemical elements known and found in nature, living organisms need about forty. Secondly, the amount of these substances is limited. Thirdly, we are talking only about the biosphere, that is, about the life-containing shell of the earth, and, therefore, about the interactions between living organisms. Fourth, the energy that contributes to the circulation is the energy coming from the sun. The energy generated in the bowels of the Earth as a result of various reactions does not take part in the process under consideration. And the last thing. It is necessary to get ahead of the starting point of this "journey". It is conditional, since there can be no end and beginning of a circle, but this is necessary in order to start describing the process from somewhere. Let's start with the lowest link in the trophic chain - with decomposers or gravediggers.

Crustaceans, worms, larvae, microorganisms, bacteria and other gravediggers, consuming oxygen and using energy, process inorganic chemical elements into an organic substance suitable for feeding living organisms and its further movement along the food chain. Further, these, already organic substances, are eaten by consumers or consumers, which include not only animals, birds, fish and the like, but also plants. The latter are producers or producers. Using these nutrients and energy, they produce oxygen, which is the main element suitable for breathing all life on the planet. Consumers, producers and even decomposers perish. Their remains, along with the organic matter in them, "fall" at the disposal of the gravediggers.

And everything is repeated again. For example, all oxygen existing in the biosphere makes its turnover in 2000 years, and carbon dioxide in 300. Such a circulation is usually called a biogeochemical cycle.

Some organic substances in the course of their "journey" enter into reactions and interactions with other substances. As a result, mixtures are formed that, as they are, cannot be processed by reducers. Such mixtures remain “stored” in the ground. Not all organic substances that fall on the "table" of the gravediggers cannot be processed by them. Not everyone can rot with bacteria. Such non-rotted residues are stored. Everything that remains in storage or in reserve is eliminated from the process and does not enter the cycle of substances in the biosphere.

Thus, in the biosphere, the circulation of substances, the driving force of which is the activity of living organisms, can be divided into two components. One - the reserve fund - is a part of a substance that is not associated with the activity of living organisms and does not participate in circulation until some time. And the second is the revolving fund. It is only a small part of the substance that is actively used by living organisms.

What are the atoms of the main chemical elements that are so necessary for life on Earth? These are: oxygen, carbon, nitrogen, phosphorus and some others. Of the compounds, the main one in the circuit, water can be called.

Oxygen

The oxygen cycle in the biosphere should begin with the process of photosynthesis, as a result of which it appeared billions of years ago. It is released from water molecules by plants when exposed to solar energy. Oxygen is also formed in the upper atmosphere during chemical reactions in water vapor, where chemical compounds are decomposed by electromagnetic radiation. But this is a negligible source of oxygen. The main thing is photosynthesis. Oxygen is also found in water. Although it is there, 21 times less than in the atmosphere.

The resulting oxygen is used by living organisms for breathing. It is also an oxidizing agent for various mineral salts.

And a person is a consumer of oxygen. But with the beginning of the scientific and technological revolution, this consumption has increased many times over, since oxygen is burned or bound during the operation of numerous industrial industries, transport, to meet household and other needs in the course of human life. The previously existing so-called exchangeable oxygen fund in the atmosphere in the amount of 5% of its total volume, that is, as much oxygen was produced in the process of photosynthesis as it was consumed. Now this volume is becoming catastrophically small. Oxygen is consumed, so to speak, from the emergency supply. From there, where there is no one to add it.

This problem is slightly mitigated by the fact that some of the organic waste is not processed and does not fall under the influence of putrefactive bacteria, but remains in sedimentary rocks, forming peat, coal and similar fossils.

If the result of photosynthesis is oxygen, then its raw material is carbon.

Nitrogen

The nitrogen cycle in the biosphere is associated with the formation of such important organic compounds as proteins, nucleic acids, lipoproteins, ATP, chlorophyll and others. Nitrogen, in molecular form, is found in the atmosphere. Together with living organisms, this is only about 2% of all nitrogen on Earth. In this form, it can only be consumed by bacteria and blue-green algae. For the rest of the plant world in molecular form, nitrogen cannot serve as food, but can be processed only in the form of inorganic compounds. Some types of such compounds are formed during thunderstorms and get into water and soil with rainfall.

The most active "processors" of nitrogen or nitrogen fixers are nodule bacteria. They take up residence in the root cells of legumes and convert molecular nitrogen into compounds suitable for plants. After they die off, the soil is also enriched with nitrogen.

Putrefactive bacteria break down nitrogen-containing organic compounds to ammonia. Part of it escapes into the atmosphere, while the other is oxidized by other types of bacteria to nitrites and nitrates. These, in turn, are supplied as food for plants and are reduced by nitrifying bacteria to oxides and molecular nitrogen. Which re-enter the atmosphere.

Thus, it can be seen that the main role in the nitrogen cycle is played by various types of bacteria. And if you destroy at least 20 of these species, then life on the planet will stop.

And again the established circuit was broken by man. For the purpose of increasing the yield of agricultural crops, he began to actively use nitrogen-containing fertilizers.

Carbon

The carbon cycle in the biosphere is inextricably linked with the cycle of oxygen and nitrogen.

In the biosphere, the carbon cycle is based on the vital activity of green plants and their ability to convert carbon dioxide into oxygen, that is, photosynthesis.

Carbon interacts with other elements different ways and is part of almost all classes of organic compounds. For example, it is part of carbon dioxide, methane. It is dissolved in water, where its content is much higher than in the atmosphere.

Although carbon is not in the top ten in terms of abundance, in living organisms it makes up from 18 to 45% of dry mass.

The oceans serve as a regulator of carbon dioxide content. As soon as its share in the air rises, the water levels out by absorbing carbon dioxide. Another consumer of carbon in the ocean is marine organisms, which use it to build shells.

The carbon cycle in the biosphere is based on the presence of carbon dioxide in the atmosphere and hydrosphere, which is a kind of exchange fund. It is replenished by the respiration of living organisms. Bacteria, fungi and other microorganisms that take part in the decomposition of organic residues in the soil also participate in the replenishment of the atmosphere with carbon dioxide. Carbon is "conserved" in mineralized non-rotten organic residues. In coal and brown coal, peat, oil shale and similar deposits. But the main reserve fund of carbon is limestone and dolomite. The carbon contained in them is "safely hidden" in the depths of the planet and is released only during tectonic shifts and emissions of volcanic gases during eruptions.

Due to the fact that the process of respiration with the release of carbon and the process of photosynthesis with its absorption passes through living organisms very quickly, only a small fraction of the total carbon of the planet participates in the cycle. If this process were non-reciprocal, then only sushi plants would use all the carbon for only 4-5 years.

Currently, thanks to human activities, vegetable world has no shortage of carbon dioxide. It is replenished immediately and simultaneously from two sources. By burning oxygen during the work of the industry of production and transport, as well as in connection with the use of those "canned food" for the work of these types of human activity - coal, peat, shale and so on. As a result, the content of carbon dioxide in the atmosphere increased by 25%.

Phosphorus

The phosphorus cycle in the biosphere is inextricably linked with the synthesis of such organic substances as: ATP, DNA, RNA and others.

The phosphorus content in soil and water is very low. Its main reserves are in rocks formed in the distant past. With the weathering of these rocks, the phosphorus cycle begins.

Plants assimilate phosphorus only in the form of phosphoric acid ions. Basically, it is a product of processing organic residues by gravediggers. But if the soils have an increased alkaline or acidic factor, then phosphates practically do not dissolve in them.

Phosphorus is an excellent nutrient for various types of bacteria. Especially blue-green algae, which develops rapidly with an increased phosphorus content.

Nevertheless, most of the phosphorus is carried away with river and other waters into the ocean. There it is actively eaten by phytoplankton, and with it seabirds and other species of animals. Subsequently, phosphorus enters the ocean floor and forms sedimentary rocks. That is, it returns to the ground, only under a layer of sea water.

As you can see, the phosphorus cycle is specific. It is difficult to call it a circuit, since it is not closed.

Sulfur

In the biosphere, the sulfur cycle is necessary for the formation of amino acids. It creates the three-dimensional structure of proteins. It involves bacteria and organisms that consume oxygen to synthesize energy. They oxidize sulfur to sulfates, and unicellular prenuclear living organisms reduce sulfates to hydrogen sulfide. In addition to them, whole groups of sulfur bacteria oxidize hydrogen sulfide to sulfur and further to sulfates. Plants can consume from the soil only the sulfur ion - SO 2 - 4. Thus, some microorganisms are oxidizing agents, while others are reducing agents.

The places of accumulation of sulfur and its derivatives in the biosphere are the ocean and the atmosphere. Sulfur enters the atmosphere with the release of hydrogen sulfide from water. In addition, sulfur enters the atmosphere in the form of dioxide when combustible fossil fuels are burned in production and for domestic needs. Primarily coal. There it is oxidized and, turning into sulfuric acid in rainwater, it falls to the ground with it. Acid rains by themselves cause significant harm to the entire flora and fauna, and besides this, with storm and melt waters, they fall into rivers. Rivers carry sulfur sulfate ions into the ocean.

Sulfur is also contained in rocks in the form of sulfides, in gaseous form - hydrogen sulfide and sulfur dioxide. At the bottom of the seas, there are deposits of native sulfur. But this is all "reserve".

Water

There is no more abundant substance in the biosphere. Its reserves are mainly in the salty-bitter form of the waters of the seas and oceans - about 97%. The rest is fresh water, glaciers and groundwater and groundwater.

The water cycle in the biosphere conventionally begins with its evaporation from the surface of water bodies and plant leaves and amounts to approximately 500,000 cubic meters. km. It returns back in the form of precipitation, which falls either directly back into water bodies, or, passing through the soil and groundwater.

The role of water in the biosphere and the history of its evolution is such that all life since its inception has been completely dependent on water. In the biosphere, water has gone through the cycles of decomposition and birth many times through living organisms.

The water cycle has a largely physical process underneath it. However, the animal and, especially, the plant world takes an important part in this. Evaporation of water from the surface areas of tree leaves is such that, for example, a hectare of forest evaporates up to 50 tons of water per day.

If the evaporation of water from the surfaces of reservoirs is natural for its circulation, then for continents with their forest zones, such a process is the only and main way of preserving it. Here the circuit goes on as if in a closed cycle. Precipitation is formed from evaporation from soil and plant surfaces.

In the process of photosynthesis, plants use the hydrogen contained in a water molecule to create a new organic compound and release oxygen. And, conversely, in the process of respiration, living organisms, the oxidation process occurs and water is formed again.

Describing the circulation of various types of chemicals, we are faced with a more active human influence on these processes. At present, nature, due to its multibillion-dollar history of survival, is coping with the regulation and restoration of disturbed balances. But the first symptoms of the "disease" are already there. And this is the "greenhouse effect". When two energies: solar and reflected by the Earth, do not protect living organisms, but, on the contrary, strengthen each other. As a result, the ambient temperature rises. What are the consequences of such an increase, except for the accelerated melting of glaciers, evaporation of water from the surfaces of the ocean, land and plants?