Underwater vegetation can be no less beautiful than terrestrial

The very name "Water Ecosystems" suggests that this is a kind of ecological systems, the place of existence of which is the aquatic environment. The structure, physical and chemical properties of the aquatic environment predetermine the species composition of the flora and fauna, the characteristics of trophic chains, its complexity and stability.

Depending on these indicators, aquatic ecosystems are divided into two types: marine and freshwater. The basis of this division is the indicator of the amount of salts contained in the water. This indicator is measured in ppm, that is, in thousandths. It shows how many grams of salts are contained in a thousand grams of water or one kilogram.

In addition to "salinity", aquatic ecosystems are influenced by two more factors. The amount of incoming sunlight and the oxygen content of the water.

Sunlight hits the surface of the planet, and hence the water spaces, unevenly. Its amount is greater towards the equator and less towards the poles. With the content of oxygen, the situation is somewhat different. It is more dissolved in polar waters.

Marine

Sea coral colors

Marine ecosystems include those that have formed in the aquatic environment, with the amount of salt dissolved in it about 35% or ppm. It is mainly sodium and chlorine. Marine ecosystems occupy almost 71% of the surface of our planet and are part of the global system of the World Ocean and the structure of the Earth's hydrosphere.

Marine ecosystems are part of the biosphere, producing 32% of all net primary production. They can be divided into zones, depending on the depth and coastline. Oceanic have great depth and surface area. The open ocean is sparsely populated. It is inhabited mainly by whales, sharks and tuna, as well as benthic invertebrates.

marine flora ecosystem

Water areas near the coast are called ebbs and flows or coastal. They also include:

• estuaries;
• salt marshes;
• Coral reefs;
• lagoons;
• mangrove swamps.

Animal and plant world here it is more diverse and its bulk is concentrated at depths up to 100 m from the surface. This is:

• brown algae;
• corals;
• shellfish;
• echinoderms;
• various types of fish;
• mammals;
• sharks, etc.

in bottom layers and there is no vegetation on the bottom. Some species of fish, invertebrates live there, and where a large amount of hydrogen sulfide accumulates, there are only chemosynthetic sulfur bacteria.

Marine ecosystems have a significant impact on climate formation. Evaporation from their surface is the main source of water in the atmosphere, and currents are the temperature regulator.

Variety of living things underwater

Marine ecosystems, due to their great biological diversity, are resilient to many types of pressures. They successfully resist the aggressive species of living organisms introduced by man, natural pests and anthropogenic influence.

- This is a shallow line along the coast and to the edge of the continental shelf with warm and nutrient-rich water. Its area is less than 10% of the ocean, but 90% of its biomass lives here. Places on the coast where salt and fresh river waters mix are called estuaries. Here the biomass is maximum and comparable to tropical forests. Coral reefs are also located in the coastal zones of tropical and subtropical latitudes with a water temperature of more than 20 0 C. Red and green algae are their producers. The world of consumers is extremely diverse. A third of all marine fish species live here.

Shallow water along the shore in the coastal zone

Marine ecosystems include the open ocean zone. Although it exceeds all others combined in terms of area and volume of water, it cannot boast of the quantity and diversity of flora and fauna. It accounts for only 10% of the total biomass. Its main function is different - it is the supplier of the primary biological product.

Fresh

Rocky terrain fills the water with oxygen

Freshwater ecosystems occupy only 0.8% of the land and contain 0.009% of the total water resources of the Earth. They produce only 3% of pure primary production. Although about 41% of the fish species known to science today live in fresh water. The main criterion for their difference is the speed of water in them. There are stagnant types of aquatic ecosystems. These include ponds and lakes, that is, those objects where water moves very slowly. In rivers and streams, water sometimes moves at great speed, and these types of ecosystems are called flowing. They are also classified as a separate category of swamps. These are places where the presence of water is variable, as a result of which the soil is watered or saturated with water.

Standing ponds are deep and shallow. Their ecosystems are built depending on how much sunlight and how deep it penetrates the water column. Deep-sea lakes are divided into three zones.

Water in stagnant reservoirs requires constant feeding with oxygen

Near the coast - shallow water or littoral zone. Further zone of open water and deep water. In them, light penetrates to a certain depth and creates an illuminated area. It contains photosynthetic plants, primarily algae, and everything that feeds on them. In deep water, an unlit layer of water, a near-bottom area and a bottom are formed. Light does not penetrate to them. This is a pelagic zone.

Water filled with oxygen contains many living organisms.

Ponds are shallow or shallow bodies of water. Their size and depth varies depending on the season. The flora and fauna of the ponds is diverse. Ponds are classified as reservoirs of artificial origin, but they are not always created by man. May be formed as a result of the construction activities of beavers or due to crocodile holes.

The main difference between flowing ecosystems is in the direction and speed of their flow. The higher the speed, the greater the concentration of dissolved oxygen in the water and, accordingly, the greater the species diversity. There are mountain and lowland rivers. For some, the source of nutrition comes from trees, for others from algae. Rivers and streams have zones of shallow rifts and deep-water reaches.

The current fills the mountain river with oxygen

The greatest danger to the existence of flowing ecosystems is borne by hydraulic structures built on rivers that regulate the flow of water.

Forced deceleration of the flow by hydraulic structures

As a result of such construction and regulation, aquatic ecosystems may die.

Land areas covered with water or waterlogged and filled with a significant amount of undecomposed organic, mainly of plant origin, remains are a swamp. This is an area where the peat layer is more than 0.3 m, if less - wetland. Wetlands are a natural reservoir of excess carbon. It plays an important role in sedum waters and often becomes the source of rivers.

In the aquatic ecosystem, the structure practically does not differ from the terrestrial one. Autotrophic and heterotrophic organisms coexist in it, which are distributed along vertical levels and in a horizontal plane.

Structure

autotrophic synthesize organic compounds from inorganic. Being in the aquatic environment and using the energy of sunlight, they are made of carbon dioxide produce oxygen and increase their biomass. The rapid growth of biomass does not always have a positive effect on the development and existence of the ecosystem as a whole. By increasing their volume, plants can block the access of light deep into the reservoir, slow down its internal metabolism of nutrients and reduce the oxygen content in the water. Why the species composition of the ecosystem will change in the direction of increasing the number of chemosynthetic bacteria. These are microorganisms that feed on hydrogen sulfide.

In the depths of the ocean, these bacteria are the source of food for other living organisms. For example, giant tube worms. In other water bodies, they do not find their consumer. Therefore, quite quickly they turn the reservoir into a swamp, and then into peat deposits.

Many living things can live at the bottom of the ocean

Autotrophic organisms feed on heterotrophic ones. For them, it is a source of energy and "material for building" their own biomass.

The sea ecosystem differs from the freshwater one in that marine organisms or eurygans do not live in fresh water, but stenohaline, that is, intolerant of salt, on the contrary. Although, there are exceptions to this rule. Some species of fish spend most of their lives in ocean water, but come to freshwater rivers to spawn. For example: salmon or Black Sea pike perch. There are also some species of sharks and crocodiles that thrive in both salt and fresh water.

Pollution

Pollution of aquatic ecosystems is any change in the properties of water:

• chemical;
• physical;
• biological.

In this case, pollutants can be in a solid, liquid and gaseous state.

Sources of pollution are any objects and processes as a result of which pollutants are discharged or otherwise enter the water. Which include the excess concentration of natural elements and artificially synthesized substances.

Pure mountain river, which are already very few

Pollution of aquatic ecosystems can be divided into types.

The first is mechanical pollution. This is an increase in the content of mechanical impurities in water. It can be classified as superficial.

The second is chemical, substances of organic or inorganic origin.

The third is bacteriological or biological. This is pollution by pathogenic microorganisms, fungi and algae. And the last one for today is radioactive. This is natural radioactive radiation and the consequences of the operation of nuclear reactors.

Accident: oil spill into the open sea

There are over 400 substances that can cause water pollution. Chemical pollutants include oil and oil products, surfactants, phenol, naphthenic acids, pesticides, inorganic salts, acids and alkalis, arsenic, mercury, lead and cadmium compounds. This type of pollution is persistent and spreads over long distances.

To bacterial Only more than 700 types of viruses are classified as contaminants.

radioactive contaminants stay in the water longer than any other. These are strontium-90, uranium, radium-226, cesium and so on.

They concentrate in the smallest plankton and are transferred further along the food chain with an accumulation effect.

The tide throws garbage on the shore

Mechanical pollutants - sand, sludge, silt, solid household and industrial waste, and the like. Changes the properties and structure of water by increasing its temperature, technological waters of thermal and power plants.

Water pollution occurs as a result of the following processes:

• discharge of raw sewage;
• flushing pesticides from agricultural fields;
• emissions of gas and smoke;
• leakage of oil and oil products.

Peculiarities

marine fauna

Marine or freshwater ecosystems, like terrestrial ones, are built according to their own rules of formation. The main thing is that in the ecosystem there are as many species of living organisms as necessary for the assimilation and processing of the incoming solar energy. The peculiarities of aquatic ecosystems are that they have internal complexity and non-linearity of relationships, are subject to various external influences and are not closed, a large number of heterotrophic organisms and a fast biotic cycle, high stability, resistance and adaptability, population regulation is carried out by limiting resources or by the activity of predators.

In addition, the World Ocean ecosystem preserves significant amounts of excess carbon dioxide inside. It is a global system with signs of continuity.

Video - Water is the source of life. Habitat

Ecosystem, or ecological system (from other Greekοἶκος - dwelling, residence and σύστημα - system) - a biological system consisting of a community of living organisms ( biocenosis), their habitats ( biotope), a system of connections that exchanges matter and energy between them. One of the basic concepts ecology.Ecosystem example - pond with those who live in it plants, fish, invertebrates, microorganisms, constituting the living component of the system, biocenosis. A pond as an ecosystem is characterized by bottom sediments of a certain composition, chemical composition ( ionic compound, concentration dissolved gases) and physical parameters ( water transparency, trend annual changes temperature), as well as certain indicators biological productivity, trophic status reservoir and specific conditions of this reservoir. Another example of an ecological system is deciduous forest in central Russia with a certain composition of forest litter, characteristic of this type of forest soil and sustainable plant community, and, as a result, with strictly defined indicators microclimate(temperature, humidity, illumination) and corresponding to such environmental conditions complex of animal organisms. An important aspect that makes it possible to determine the types and boundaries of ecosystems is the trophic structure of the community and the ratio biomass producers, its consumers and biomass-destroying organisms, as well as indicators of productivity and metabolism and energy.

Ecosystem classification:

microecosystems(a lichen pillow, a drop of water from a lake, a drop of blood with cells, etc., Fig. 53);

mesoecosystems(pond, lake, steppe, etc.);

macroecosystems(continent, ocean);

global ecosystem(biosphere of the Earth), or ecosphere, integration of all ecosystems of the world.

39. Composition and structure of ecosystems. The spatial structure of the ecosystem.

The structure of ecosystems. Ecosystems consist of living and non-living components, called respectively biotic and abiotic. The totality of living organisms of the biotic component is called a community. The study of ecosystems includes, in particular, the elucidation and description of the close relationships that exist between the community and the abiotic component. It is useful to divide the biotic component into autotrophic and heterotrophic organisms. Thus, all living organisms will fall into one of two groups. Autotrophs synthesize the organic substances they need from simple inorganic substances and, with the exception of chemotrophic bacteria, do it through photosynthesis, using light as an energy source. Heterotrophs need a source of organic matter and (with the exception of some bacteria) use the chemical energy contained in the food they eat. Heterotrophs depend on autotrophs for their existence, and understanding this dependence is essential to understanding ecosystems. The non-living, or abiotic, component of an ecosystem mainly includes 1) soil or water and 2) climate. Soil and water contain a mixture of inorganic and organic substances. Soil properties depend on the parent rock on which it lies and from which it is partially formed. The concept of climate includes such parameters as illumination, temperature and humidity, which to a large extent determines the species composition of organisms successfully developing in a given ecosystem. For aquatic ecosystems, the degree of salinity is also very significant.

The composition of the ecosystem. The ecosystem includes living organisms (their totality is called biogeocenosis or biota of the ecosystem), and non-living (abiotic) factors - the atmosphere, water, nutrients, light and dead organic matter - detritus.

The spatial structure of most ecosystems is determined by the tiered arrangement of vegetation

Biogeocenosis and ecological systems: composition, structure, properties

test

Features of aquatic ecosystems

Unlike terrestrial biogeocenoses, which are easy to distinguish through phytocenoses, the aquatic environment, as an environment-forming factor, is characterized by smooth transitions from one set of conditions to another. Therefore, it is more difficult to distinguish boundaries for marine and freshwater biogeocenoses. Most often, in this case, the main physical and geochemical features of the water column are used.

Aquatic ecosystems are divided into two groups:

non-flowing reservoirs (lentic environment - from lat. lentus - calm), these are lakes, ponds, swamps, flowing reservoirs (lotic - from lat. lotus - washing).

The specificity of water systems is determined by many factors, primarily the thermodynamic characteristics of water. The waters of various reservoirs are also characterized by transparency, mixing rate, salinity, content of dissolved gases.

Water pressure increases with depth, different parts of the reservoirs are differently removed from the coast. These and many other circumstances affect the distribution and distribution of living organisms inhabiting the water.

Three main zones are distinguished in the ribbon reservoir:

littoral (small areas where light penetrates to the bottom and usually

higher plants and some algae are located),

limnic (thickness of water, to the depth of which active light penetrates,

not necessarily in shallow water),

profundal (zone into which light does not penetrate).

Below the limnic zone, the accumulation of biomass is impossible, since here the processes of photosynthesis and respiration are aligned.

The lower boundary of the limnic zone is called the compensation horizon. About 1% of sunlight penetrates to this boundary. Usually these are depths of the order of 100 m.

In aquatic ecosystems (as in any other) there are autotrophic organisms (producers), phagotrophs (macroconsumers) and saprotrophs (microconsumers), which mainly play the role of destroyers of organic matter.

In rivers and streams, two zones are mainly distinguished:

shallow waters,

deep seas.

Each of these zones has its own inhabitants and its own communities of organisms (biocenoses).

Lentic and lotic reservoirs are very diverse in their structure. Each of them is characterized by complex seasonal temperature dynamics, which determines the location of ecological niches. The movement of water, especially in lotic reservoirs, associated with its speed, turbulence, determines the movement and localization of emitted substances, the specifics of their sedimentation, decomposition, self-purification processes, and eutrophication patterns.

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Aquatic ecosystems

Aquatic ecosystems differ from land ecosystems primarily in their physical and chemical properties. When considering aquatic ecosystems, they are divided into freshwater and ocean ecosystems.

freshwater ecosystems.

Freshwater ecosystems are widely represented on all continents. The rivers and lakes of the Earth contain the bulk of fresh water, although in some inland waters the water is salty (this is typical for a hot and dry climate).

In freshwater lakes, three parts are always distinguished, which can be considered as separate ecosystems:

coastal part - littoral;

deep-water part - profundal;

the main water column is pelagial.

The littoral is the most populated by living organisms. The coastal zones of any water bodies are their main trophic areas. In addition to semi-submerged plants, benthic organisms live in water bodies, which make up benthos and plankton, which

floats in the water column. The production of most water bodies is often limited by a lack of biogenic minerals. The fact is that life is concentrated in the upper layers of the water, where there is enough sunlight, and minerals come from the bottom layers. The upper and lower layers of water are separated by the so-called thermocline, which is especially clearly manifested in water bodies of the subtropical and tropical zones. Thermocline prevents vertical water exchange and leads to a deficiency of minerals in the surface layers of water.

The littoral is characterized by the presence of a large number of attached plants - macrophytes. The fauna is represented by insects and their larvae.

Rich fauna and predators. In the coastal part of the lakes, such species of fish as roach, rudd, tench, wild carp, and smelt are common. Predatory fish are represented by pike, perch and zander. The near-bottom part of the lakes has almost no plants, the water is inactive and retains a temperature of +4 ° C for almost the entire year. The fauna of such places is depleted. It is represented mainly by larvae of bell mosquitoes and mollusks.

In the pelagic zone, plants are represented by plankton from blue-green, diatoms and green algae, macrophytes, floating (elodea, pondweeds). All living organisms have various adaptations that help them stay in the water column. In plants, it is parashutopodibni to grow, droplets of fat in the body, animals actively swim. Lake trout and whitefish are found in the pelagic zone. There are many predatory rotifers, copepods and cyclops.

The flora and fauna of lakes in many cases is determined by the presence of nutrients in the water. On this basis, lakes are divided into eutrophic, rich in nitrogen, phosphorus, oligotrophic, poor in nitrogen and phosphorus (nitrates less than 1 mg / l) and lakes intermediate between them are mesotrophic. The fish fauna differs significantly in these three types of lakes. Oligotrophic lakes are characterized by whitefish, loach, perch, pike and roach. Eutrophic lakes are inhabited by species that are resistant to the frequent oxygen deficiency here - carp, tench, crucian carp, roach and bream. In the development of river ecosystems, the character of the bottom and banks, water temperature and flow velocity play a key role. In the coastal part of streams and rivers, reeds, reeds, flatbread and arrowheads, common for these places, grow. Elodea and water lilies float in the water column. With an increase in the current velocity to 0.3-0.6 m / s and more, the water column no longer grows. For rivers, plankton is not typical, since it is carried away by the current. River entomofauna is very diverse. There are many aquatic insects and their larvae. Amphipods are often found. Along the course of the rivers, there is a regular pattern in the distribution of the ichthyofauna. Trout lives in the sources of clean water with clear water. In the middle reaches, the main species are grayling and barbel, here the usual tench and chub. In the lower part of the year, where the current slows down, the ichthyofauna includes bream, carp, pike and perch.

The trophic chains of freshwater ecosystems and especially rivers are short due to the lack of a rich food supply. They start with autotrophic plants and end in grazing trophic chains with predatory fish, and in detrital trophic chains with microorganisms. On the territory of Ukraine, 71,000 rivers are registered, with a total length of 243 thousand km. Most of the rivers belong to the basins of the Black and Azov Seas. There are 3,000 lakes in Ukraine with a total water surface area of ​​2,000 sq. m. km. In addition, the country has 23,000 ponds and reservoirs, especially in the region of the middle and lower Dnieper.

The rivers and lakes of Ukraine include 195 species of aquatic macrophytes, as well as many species of algae. There are 57 aquatic plant formations in Ukraine. Water ecosystems are an important national wealth. These are fresh water storage facilities, sources of various products, and places of recreation for the population.

Ecosystems of the World Ocean. A characteristic feature of ocean ecosystems:

global dimensions and vast depths filled with life;

continuity (all oceans are connected to each other);

constant circulation (the presence of strong winds that blow throughout the year in the same direction, the presence of deep currents)

the dominance of different waves and tides, which leads to a noticeable periodicity in the life of groups, especially in coastal zones;

salinity and strong buffering;

The presence of dissolved nutrients, which are the limiting factors that determine the size of the population.

Living conditions in ocean water are at a higher level than on land. Vegetation is poorer - mostly algae. The animal world is rich. It is presented to the following groups:

Benthos - natural organisms (algae, sponges, bryozoans, ascidians), crawling (echinoderms, crustaceans), fish, molluscs.

Plankton are diatoms and other algae suspended in water.

Temporary components - larvae of worms, mollusks, crustaceans, echinoderms, fish fry. From the constant component - the simplest, gastropods, copepods. They are food for seabirds.

Nekton - a group of active organisms is thicker. Fish, cephalopods, cetaceans, pinnipeds. The main ecological parts of the ocean:

the littoral, or shelf (up to 200 m), occupies 7-8%, lives here up to 80% of all marine organisms;

the continental slope (200-2000 m) occupies 8.1%;

Abesalom - 82.2%;

deep-water trenches - 2.1%.

The entire population of aquatic ecosystems (about 200,000 species), as well as terrestrial ones, is divided into producers, consumers and reducers. The ecosystems of the oceans are highly productive and play an important role as giant regulators of the Earth's climate.

Questions for self-examination

What types are the ecosystems of planet Earth divided into?

1. Natural.

2. Artificial.

3. Water.

4. Ground.

5. Near-Earth.

What underlies the division of ecosystems into types?

1. Origin.

2. The volume of manufactured products.

3. Type of environment.

4. Differences in the functioning of various ecosystems.

5. Coefficient of similarity between different ecosystems.

Which of the proposed answers correspond to the characteristics of tundra ecosystems?

1. The relief is even.

3. Soils are always acidic.

4. The vegetation cover is dominated by low-growing shrubs.

5. Rich composition of the fauna.

Which of the proposed answers correspond to the characteristics of taiga ecosystems?

1. The relief is even.

2. Soils are underdeveloped, humification is slow.

3. Soils are podzolic.

5. The composition of the fauna is stable in relation to the composition of the fauna of the tundra.

Which of the proposed answers correspond to the characteristics of tropical ecosystems?

1. The relief is even.

3. Soils are gley.

4. The vegetation cover is dominated by evergreens.

Which of the proposed answers correspond to the characteristics of steppe ecosystems?

1. The relief is even.

2. Soils are underdeveloped, humification is fast.

3. Soils are powerful chernozems, humification is fast.

4. The vegetation cover is dominated by perennial grasses.

5. 50 percent of the world's gene pool is represented here.

Which of the proposed answers correspond to the characteristics of desert ecosystems?

1. The relief is even.

2. Soils are underdeveloped, humification is fast.

3. Soils are thin.

4. The vegetation cover is highly liquefied.

5. Here you can see significant daily fluctuations in air temperature.

What are the types of swamp ecosystems?

1. Lowland swamps.

2. Raised swamps.

3. Transitional swamps.

4. Coastal swamps.

5. Medium swamps.

Which of the proposed answers correspond to the characteristics of swamp ecosystems?

1. Ecosystems of swamps are azonal.

2. Arise in places of strong waterlogging.

3. detrital food chain lengthens.

4. detrital food chain is greatly shortened.

5. Formation of humus is impossible.

How do aquatic ecosystems differ from each other?

1. salinity of water.

2. depth.

3. The presence or absence of flow.

4. The composition of the flora.

5. The composition of the fauna.

Which of the proposed options reflect the characteristics of the ecosystems of the World Ocean?

1. Globality.

2. Continuity.

3. Constant circulation.

4. Strong buffering.

The composition of the ecosystem includes living organisms (their totality is called biocenosis, or biota, ecosystems), inanimate factors (abiotic) - atmosphere, water, nutrients, light and dead organic matter - detritus.

All living organisms are divided into two groups according to the method of nutrition (according to the functional role) - autotrophs(from the Greek words autos - itself and tropho - nutrition) and heterotrophs(from the Greek word heteros - another).

Autotrophs. These organisms use inorganic carbon to synthesize organic matter, this is producers ecosystems. According to the energy source used, they, in turn, are also divided into two groups.

Photoautotrophs use light. These are green plants, cyanobacteria, as well as many colored bacteria that have chlorophyll (and other pigments) and absorb solar energy. The process by which it is digested is called photosynthesis.

Chemoautotrophs use the chemical energy of the oxidation of inorganic substances (sulfur, hydrogen sulfide, ammonia, iron, etc.). These are sulfur bacteria, hydrogen bacteria, iron bacteria, nitrifying bacteria, etc. Chemoautotrophs play a major role in groundwater ecosystems, as well as in special ecosystems of rift zones of the ocean floor, where hydrogen sulfide is released from plate faults, which is oxidized by sulfur bacteria. Nitrifying bacteria play an important role in terrestrial ecosystems.

Heterotrophs. These organisms feed on ready-made organic substances that are synthesized by producers, and together with these substances they receive energy. Heterotrophs in an ecosystem are consumers(from the Latin word consumo - I consume), consuming organic matter, and decomposers, decomposing it to simple compounds. There are several consumer groups.

Phytophages(herbivores). These include animals that feed on living plants. Among phytophages there are both small organisms, such as aphids or grasshoppers, and giants, such as elephants. Almost all agricultural animals are phytophages: cow, horse, sheep, rabbit. The main phytophages in aquatic ecosystems are microscopic organisms of herbivorous plankton that feed on algae. There are also large phytophages in these ecosystems, for example, grass carp, eating plants that overgrow irrigation canals. An important phytophage is the beaver. It feeds on tree branches, and from the trunks it builds dams that regulate the water regime of the territory.

Zoophages(predators, carnivores). Zoophages are very diverse. These are small animals that feed on amoebas, worms or crustaceans. And big ones, like a wolf. Predators that feed on smaller predators are called second-order predators. Zoophages are widespread in aquatic ecosystems. filter feeders, this group includes both microscopic crustaceans and a whale. Filter feeders play a huge role in the self-purification of polluted waters (Fig. 30). Only planktonic marine copepods from the genus Calanus are able to filter the waters of the entire World Ocean in a few years!

There are predatory plants (dew, pemphigus) that use insects as food. True, their way of feeding differs from animal predators. They “catch” small insects, but do not swallow them, but “digest” them, releasing enzymes on their surface. There are also predators among soil fungi that "catch" microscopic round nematode worms.

Symbiotrophs. These are bacteria and fungi that feed on the root secretions of plants. Symbiotrophs are very important for the life of the ecosystem. Threads of fungi that entangle the roots of plants help the absorption of water and minerals. Symbiotrophic bacteria absorb gaseous nitrogen from the atmosphere and bind it into compounds available to plants (ammonia, nitrates). This nitrogen is called biological (in contrast to the nitrogen of mineral fertilizers).

Symbiotrophs also include microorganisms (bacteria, unicellular animals) that live in the digestive tract of phytophagous animals and help them digest food. Animals such as cows, without the help of symbiotrophs, are not able to digest the grass they eat.

Detritivores organisms that feed on dead organic matter. These are centipedes, earthworms, dung beetles, crayfish, crabs, jackals and many others. A significant diversity of detritivorous species is associated with the soil. There are numerous detritophages that destroy wood (Fig. 31).

Organisms that feed on excrement are called coprophages. Some organisms use both plants and animals as food, and even detritus, and are classified as euryphages(omnivorous) - bear, fox, pig, rat, chicken, crow, cockroaches. Euryphage is also a man.

decomposers- organisms that, by their position in the ecosystem, are close to detritophages, since they also feed on dead organic matter. However, decomposers - bacteria and fungi - break down organic matter to mineral compounds, which return to the soil solution and are again used by plants.

Decomposers need time to process dead organic matter. Therefore, in the ecosystem there is always a reserve of this substance - detritus. Detritus is leaf litter on the surface of forest soil (remains for 2–3 years), the trunk of a fallen tree (remains for 5–10 years), soil humus (remains for hundreds of years), deposits of organic matter on the bottom of the lake - sapropel and peat in the swamp (remains thousands years). The longest lasting detritus are coal and oil.

Producers, phytophages, predators are connected in the process of ecosystem "work", that is, the assimilation and expenditure of energy in the production of organic matter and, as it were, participate in the "relay race" of energy transfer. The number of the relay participant is his trophic level. The first trophic level - producers, the second - phytophages, the third - predators of the first order, the fourth - predators of the second order. In some ecosystems, for example in a lake, the number of trophic levels can reach 5-6.

On fig. 32 shows the structure of the ecosystem, which is based on plants - photoautotrophs, and in table. 1 shows examples of representatives of different trophic groups for some ecosystems.

Table 1

Representatives of different trophic groups in some ecosystems