Natural community is a collection of plants, animals, microorganisms adapted to living conditions in a certain territory, influencing each other and the environment. The circulation of substances is carried out and maintained in it.

We can distinguish natural communities of different scales, for example, continents, oceans, forests, meadows, taiga, steppes, deserts, ponds, and lakes. Smaller natural communities are part of larger ones. Man creates artificial communities, such as fields, gardens, aquariums, and spaceships.

Each natural community is characterized by various relationships - food, habitat, etc.

The main form of connections between organisms in a natural community is food connections. The initial, main link in any natural community, creating a supply of energy in it, are plants. Only plants using solar energy, can from minerals found in soil or water and carbon dioxide create organic matter. Herbivorous invertebrates and vertebrates feed on plants. They, in turn, feed on carnivores - predators. So in natural communities food connections arise, a food chain: plants - herbivores - carnivores (predators - website note). Sometimes this chain becomes more complicated: the first predators can feed on others, and they, in turn, feed on others. For example, caterpillars eat plants, and caterpillars are eaten by predatory insects, which, in turn, serve as food for insectivorous birds, which feed on birds of prey.

Finally, the natural community also includes various organisms that feed on waste: dead plants or their parts (branches, leaves), as well as the corpses of dead animals or their excrement. They may be some animals - gravedigger beetles, earthworms. But the main role in the process of decomposition of organic substances is played by molds and bacteria. It is they who bring the decomposition of organic substances to mineral ones, which can again be used by plants. In total, the circulation of substances occurs in natural communities.

Changes in natural communities can occur under the influence of biotic, abiotic factors and humans. The change of communities under the influence of the vital activity of organisms lasts hundreds and thousands of years. Main role Plants play a role in these processes. An example of a change in community under the influence of the vital activity of organisms is the process of overgrowing of water bodies. Most lakes gradually become shallow and decrease in size. Over time, the remains of aquatic and coastal plants and animals, as well as soil particles washed away from the slopes, accumulate at the bottom of the reservoir. Gradually, a thick layer of silt forms at the bottom. As the lake becomes shallower, its shores become overgrown with reeds and reeds, then with sedges. Organic residues accumulate even faster and form peaty deposits. Many plants and animals are replaced by species whose representatives are more adapted to life in new conditions. Over time, a different community forms in place of the lake - a swamp. But the change of communities does not stop there. Shrubs and trees that are unpretentious to the soil may appear in the swamp, and ultimately the swamp may be replaced by a forest.

Thus, a change in communities occurs because, as a result of changes in the species composition of communities of plants, animals, fungi, and microorganisms, the habitat gradually changes and conditions favorable for the habitat of other species are created.

Change of communities under the influence of human activity. If the change of communities under the influence of the life activity of the organisms themselves is a gradual and long process, covering a period of tens, hundreds and even thousands of years, then the change of communities caused by human activity occurs quickly, over several years.

So if they get into water bodies wastewater, fertilizers from fields, household waste, then oxygen dissolved in water is spent on their oxidation. As a result, it decreases species diversity, various aquatic plants(salvinia floating, amphibian knotweed) are replaced by duckweed, algae are replaced by blue-green algae, and a “water bloom” occurs. Valuable commercial fish are replaced by low-value ones, shellfish and many species of insects disappear. A rich aquatic ecosystem turns into an ecosystem of a decaying reservoir.

If the human impact that caused a change in communities stops, then, as a rule, natural process self-healing. Plants continue to play a leading role in it. Thus, after the cessation of grazing, tall grasses appear on pastures, typical forest plants appear in the forest, and the lake is cleared of dominance unicellular algae and blue-green, fish, shellfish, and crustaceans reappear in it.

If the species and trophic structure are simplified so much that the process of self-healing can no longer occur, then man is again forced to intervene in this natural community, but now for good purposes: grass is sown in pastures, new trees are planted in the forest, water bodies are cleaned and juveniles are released there fish

The community is capable of self-healing only with partial violations. Therefore the influence economic activity a person should not exceed the threshold after which self-regulation processes cannot take place.

Change of communities under the influence of abiotic factors. For the development and change of communities big influence have had and are having drastic climate changes, fluctuations in solar activity, mountain-building processes, and volcanic eruptions. These factors are called abiotic factors inanimate nature. They disrupt the stability of the habitat of living organisms.

Unfortunately, the ability of natural communities to self-heal is not unlimited: if the external impact exceeds a certain limit, the ecosystem will collapse, and the territory where it was located will itself become a source of ecological imbalance. Even if restoration of the ecosystem is possible, it will cost much more than timely measures to preserve it.

The ability of natural communities to self-regulate is achieved thanks to the natural diversity of living beings that have adapted to each other as a result of long-term joint evolution. When the number of one of the species decreases, its partially freed ecological niche temporarily occupies an ecologically close species of the same community, preventing the development of certain destabilizing processes.

The situation is completely different if a species has dropped out of the community. In this case, the system of “mutual insurance” of ecologically similar species is disrupted, and part of the resources they consume is not used, that is, an ecological imbalance arises. As the natural species composition of the community further depletes, conditions are created for excessive accumulation of organic matter, outbreaks of insect numbers, the introduction of alien species, etc.
Usually, the so-called rare species are the first to drop out of the natural community, since their rarity is due to the fact that they are the most demanding of living conditions and sensitive to their changes. In a stable community, rare species should be present among all groups of living organisms. Therefore, the presence of various rare species serves as an indicator of the preservation of natural biodiversity as a whole and, thus, the ecological usefulness of the natural community.

As is known, the biotic cycle of substances is provided by species occupying different trophic levels:

Producers that produce organic matter from inorganic matter are, first of all, green plants;
First-order consumers who consume phytomass are herbivores, both vertebrates and invertebrates;
consumers of the second and higher orders that feed on other consumers, for example, predatory insects and spiders, predatory fish, amphibians and reptiles, insectivores and birds of prey and mammals;
decomposers that decompose dead organic matter - this process is provided primarily by a variety of microorganisms, fungi, as well as rain annelids and some other soil invertebrates.

The study of full-fledged natural communities shows that rare species are present in them at all trophic levels. The most significant thing is the presence in the community of viable populations of consumers of higher orders: they are at the top of the trophic pyramid and, thus, their condition is most dependent on the state of the trophic pyramid as a whole.

An important characteristic of any species is the size of the territory, the minimum necessary for the existence of its viable population. For conservation purposes, several size classes of territories necessary for the existence of a viable population of a species can be distinguished.

In the size range from an individual plant association to the biogeocenosis inclusive, it is advisable to identify areas of the following size classes:

1 - microbiotopes, individual areas of plant associations, necessary, for example, for fungi, many plants and invertebrate animals;
2 - a combination of certain microbiotopes and plant associations, necessary, for example, for some plants, amphibians, reptiles, dragonflies, and many butterflies;
3 - biogeocenosis as a whole, necessary for small birds and mammals, the largest and most mobile insects, and among plants - for forest-forming tree species.

For the existence of populations of medium and large birds and mammals usually require territories that significantly exceed the area occupied by one biogeocenosis. For such territories we distinguish the following size classes:

4 - a group of similar biocenoses or their combinations;
5 - natural massifs consisting of various biotopes;
6 - natural massifs and their complexes at the regional level.

Under conditions of transformation natural areas The most vulnerable species are those that require territories of higher (IV-VI) size classes, especially since most of these species belong to consumers of higher orders.

Thus, an indicator of the qualitative usefulness of an ecosystem is the presence of all trophic levels, and within each trophic level there are species whose populations occupy significantly different ecological niches and territories of different size classes.

The condition for preserving the environment-forming functions of natural communities is inter-ecosystem connections that make possible the natural restoration of disturbed areas due to the migration of living organisms from neighboring areas that are better preserved. Then they protect each other in the same way as populations of similar species within the same community. Being functionally interconnected within the region, natural communities form a natural framework on which regional environmental stability rests. Therefore, preserving a system of interconnected natural communities capable of self-healing is the only real way maintaining human habitat.



Primary consumers

Primary consumers feed on primary producers, i.e. they are herbivores. On land, typical herbivores include many insects, reptiles, birds and mammals. Most important groups Herbivorous mammals are rodents and ungulates. The latter include grazing animals such as horses, sheep, large cattle, adapted for running on the tips of the fingers.

IN aquatic ecosystems(freshwater and marine) herbivorous forms are usually represented by mollusks and small crustaceans. Most of these organisms are cladocera and copepods, crab larvae, barnacles And bivalves(for example, mussels and oysters) - feed by filtering the smallest primary producers from the water. Together with protozoa, many of them form the bulk of the zooplankton that feed on phytoplankton. Life in oceans and lakes depends almost entirely on plankton, since almost all food chains begin with it.

biotic ecosystem sun food trophic

Second and third order consumers

Plant material (eg nectar) > fly > spider >

> shrew > owl

Ecology- This biological science, which studies the relationship of living organisms with their environment. All organisms on Earth interact with each other, influence each other in one way or another, they are influenced by inanimate nature, as well as humans. This also applies to animals.

Animal ecology examines the interactions between animals and their environment. At the same time, animals are highly dependent on the vegetation around them. Many can live only in certain natural communities formed by certain plants.

Relationships between animals and living organisms

In natural communities, animals play the role of consumers, since they are heterotrophs, that is, they consume ready-made organic substances.

Initially, in an ecosystem, organic substances are produced by plants (producers), which are autotrophs. Animals that eat plant foods are called herbivores or consumers first order (in animal ecology they can use the notation “consumers I”).

Second-order consumers eat animal food (eat other animals), that is, they are predators. Some animals are omnivores, that is, they are simultaneously consumers of several orders. In addition, there are third-order consumers who eat second-order consumers. In complex large natural communities (especially aquatic ones), fifth-order consumers can also be found.

In terms of mass (they say “biomass”), plants always predominate in natural communities, followed by consumers I and only then consumers II. There are always fewer predators than herbivores, since it is not during the movement of energy through food chains that it is partially dissipated in the form of heat. To feed itself, one predator needs many herbivores.

In ecosystems, animals act as not only consumers, but also decomposers. Decomposers- These are organisms that can decompose organic substances into inorganic ones. In addition to animals, bacteria and fungi are decomposers. Decomposers usually live in the soil. This includes dead parts of plants, animal feces, and dead animals. All this organic matter is decomposed by decomposers into mineral substances, which are then available to plants. Thus, the cycle of substances occurs in nature (by this we should understand the cycle chemical elements): first they find themselves enclosed in producers, then they move along a chain of consumers of several orders, and finally end up in decomposers, who ultimately release them into the external environment.

The influence of inanimate nature on animals

Animal ecology also examines how animals are adapted to environmental conditions such as temperature, humidity, diurnal and seasonal changes.

For each climate zone their animals are typical. So lions live in warm Africa, and polar bears live in cold arctic. The specific habitat is also important: some animals live in rivers, seas and oceans, while others live on land. Well, even in one ecosystem, someone walks on the ground, someone flies, and someone climbs trees or lives underground. Ecology studies all these features of animal life, their adaptation to specific conditions. abiotic environment(inanimate nature).

The change of seasons has a great impact on the life of animals. So in temperate latitudes winter and summer are very different. Many animals cannot lead an active lifestyle in winter. Therefore, they take cover and fall into torpor, hibernation; the birds fly away. Warm-blooded animals (birds and mammals) do this mainly due to lack of food in winter time of the year. Those species that can forage for food in winter do not hibernate or fly away.

Separately, it should be noted that humans have an impact on the ecology of animals. Negative influence, especially in the last century.

food chain has a certain structure. It includes producers, consumers (first, second order, etc.) and decomposers. More details about consumers will be discussed in the article. In order to thoroughly understand who consumers of the 1st order, 2nd order and beyond are, we first briefly consider the structure of the food chain.

Structure of the food chain

The next link in the chain and, accordingly, the tier of the food pyramid are consumers (of several orders). This is the name given to organisms that producers consume as food. They will be discussed in detail below.

And finally, decomposers are the final tier of the food pyramid, the last link in the chain, “orderly” organisms. This is an integral and very important component of the ecosystem. They process and decompose high molecular weight organic compounds to inorganic ones, which are then reused by autotrophs. Most of them are organisms of fairly small size: insects, worms, microorganisms, etc.

Who are consumers

As mentioned above, consumers are located on the second tier of the food pyramid. These organisms, unlike producers, do not have the ability for photo- and chemosynthesis (the latter is understood as the process by which archaea and bacteria obtain the energy necessary for the synthesis of organic substances from carbon dioxide). Therefore, they must feed on other organisms - those who have such an ability, or their own kind - other consumers.

Animals are consumers of the 1st order

This link in the food chain includes heterotrophs, which, unlike decomposers, are not capable of decomposing organic substances into inorganic ones. So called primary consumers(1st order) - those that directly feed on the biomass producers themselves, that is, producers. These are primarily herbivores - so-called phytophages.

This group includes: giant mammals, for example, elephants, and small insects - locusts, aphids, etc. It is not difficult to give examples of consumers of the 1st order. These are almost all animals bred by humans in agriculture: cattle, horses, rabbits, sheep.

Among wild animals, the beaver is a phytophagous animal. It is known that it uses tree trunks to build dams, and uses their branches for food. Some species of fish, such as grass carp, are also herbivores.

Plants are consumers of the first order

To summarize, we can draw the following conclusion: consumers are organisms that feed on plants.

Second order consumers and beyond

In turn, consumers of the 3rd order are those who eat consumers of the previous order, that is, more large predators, 4th - those who eat consumers of the third. Above the fourth level, the food pyramid, as a rule, does not exist, since energy losses from the producing organism to the consumer at the previous levels are quite large. After all, they are inevitable at every level.

It is also often difficult, and sometimes impossible, to draw a clear boundary between consumers of certain orders. After all, some animals are also consumers different levels.

Also, many of them are omnivores, for example a bear, that is, consumers of the first and second order at the same time. The same applies to a person who is omnivorous, although due to different views, traditions or living conditions, he may, for example, eat food only of plant origin.

Topic No. 4 BIOCENOSIS

The concept of biocenosis

Trophic structure of biocenosis

Spatial structure of the biocenosis

The concept of biocenosis

In nature, populations of different species are integrated into macrosystems of a higher rank - into so-called communities, or biocenoses.

Biocenosis (from the Greek bios - life, koinos - general) is an organized group of interconnected populations of plants, animals, fungi and microorganisms living together in the same environmental conditions.

The concept of “biocenosis” was proposed in 1877 by the German zoologist K. Mobius. Moebius, studying oyster banks, came to the conclusion that each of them represents a community of living beings, all members of which are closely interconnected. Biocenosis is a product natural selection. Its survival, stable existence in time and space depends on the nature of the interaction of the constituent populations and is possible only with the obligatory supply of radiant energy from the Sun from outside.

Each biocenosis has a certain structure, species composition and territory; it is characterized by a certain organization of food connections and a certain type of metabolism

But no biocenosis can develop on its own, outside and independently of the environment. As a result, certain complexes, aggregates of living and nonliving components. The complex interactions of their individual parts are supported on the basis of versatile mutual adaptability.

A space with more or less homogeneous conditions, inhabited by one or another community of organisms (biocenosis), is called a biotope.

In other words, a biotope is a place of existence, habitat, biocenosis. Therefore, a biocenosis can be considered as a historically established complex of organisms, characteristic of a specific biotope.

Any biocenosis forms a dialectical unity with a biotope, a biological macrosystem of an even higher rank - a biogeocenosis. The term “biogeocenosis” was proposed in 1940 by V. N. Sukachev. It is almost identical to the term “ecosystem”, widely used abroad, which was proposed in 1935 by A. Tansley. There is an opinion that the term “biogeocoenosis” to a much greater extent reflects the structural characteristics of the macrosystem being studied, while the concept of “ecosystem” primarily includes its functional essence. In fact, there is no difference between these terms. Undoubtedly, V.N. Sukachev, formulating the concept of “biogeocoenosis”, combined in it not only the structural, but also the functional significance of the macrosystem. According to V.N. Sukachev, biogeocenosis- This a set of homogeneous natural phenomena over a known area of ​​the earth's surface- atmosphere, rock, hydrological conditions, vegetation, fauna, microorganisms and soil. This set is distinguished by the specific interactions of its components, their special structure and a certain type of exchange of substances and energy among themselves and with other natural phenomena.

Biogeocenoses can be of very different sizes. In addition, they are characterized by great complexity - it is sometimes difficult to take into account all the elements, all the links. These are, for example, such natural groups as a forest, lake, meadow, etc. An example of a relatively simple and clear biogeocenosis is a small reservoir or pond. Its non-living components include water, substances dissolved in it (oxygen, carbon dioxide, salts, organic compounds) and soil - the bottom of a reservoir, which also contains a large number of various substances. The living components of a reservoir are divided into primary producers - producers (green plants), consumers - consumers (primary - herbivores, secondary - carnivores, etc.) and destroyers - destructors (microorganisms), which decompose organic compounds to inorganic ones. Any biogeocenosis, regardless of its size and complexity, consists of these main links: producers, consumers, destroyers and components of inanimate nature, as well as many other links. Connections of the most varied orders arise between them - parallel and intersecting, entangled and intertwined, etc.

In general, biogeocenosis represents an internal contradictory dialectical unity, in constant movement and change. “Biogeocenosis is not the sum of biocenosis and environment,” points out N.V. Dylis, “but a holistic and qualitatively isolated phenomenon of nature, acting and developing according to its own laws, the basis of which is the metabolism of its components.”

The living components of biogeocenosis, i.e., balanced animal-plant communities (biocenoses), are the highest form of existence of organisms. They are characterized by a relatively stable composition of fauna and flora and have a typical set of living organisms that retain their basic characteristics in time and space. The stability of biogeocenoses is supported by self-regulation, i.e. all elements of the system exist together, never completely destroying each other, but only limiting the number of individuals of each species to a certain limit. That is why such relationships have historically developed between species of animals, plants and microorganisms that ensure development and maintain their reproduction at a certain level. Overpopulation of one of them may arise for some reason as an outbreak of mass reproduction, and then the existing relationship between the species is temporarily disrupted.

To simplify the study of biocenosis, it can be conditionally divided into separate components: phytocenosis - vegetation, zoocenosis - animal world, microbiocenosis - microorganisms. But such fragmentation leads to an artificial and actually incorrect separation from a single natural complex of groups that cannot exist independently. In no habitat can there be dynamic system, which would consist only of plants or only of animals. Biocenosis, phytocenosis and zoocenosis must be considered as biological unities of different types and stages. This view objectively reflects the real situation in modern ecology.

In the conditions of scientific and technological progress, human activity transforms natural biogeocenoses (forests, steppes). They are being replaced by sowing and planting of cultivated plants. This is how special secondary agrobiogeocenoses, or agrocenoses, are formed, the number of which on Earth is constantly increasing. Agrocenoses are not only agricultural fields, but also shelterbelts, pastures, artificially regenerated forests in cleared areas and fires, ponds and reservoirs, canals and drained swamps. Agrobiocenoses in their structure are characterized by a small number of species, but their high abundance. Although there are many specific features in the structure and energy of natural and artificial biocenoses, there are no sharp differences between them. In a natural biogeocenosis, the quantitative ratio of individuals of different species is mutually determined, since mechanisms regulating this ratio operate in it. As a result, a stable state is established in such biogeocenoses, maintaining the most favorable quantitative proportions of its constituent components. In artificial agrocenoses there are no such mechanisms; there, man has completely taken upon himself the responsibility for regulating the relationships between species. Much attention is paid to the study of the structure and dynamics of agrocenoses, since in the foreseeable future there will be practically no primary, natural, biogeocenoses left.

Trophic structure of biocenosis

The main function of biocenoses - maintaining the cycle of substances in the biosphere - is based on the nutritional relationships of species. It is on this basis that organic substances synthesized by autotrophic organisms undergo multiple chemical transformations and ultimately return to the environment in the form of inorganic waste products, again involved in the cycle. Therefore, with all the diversity of species that make up various communities, each biocenosis necessarily includes representatives of all three fundamental ecological groups of organisms - producers, consumers and decomposers . The completeness of the trophic structure of biocenoses is an axiom of biocenology.

Groups of organisms and their relationships in biocenoses

Based on their participation in the biogenic cycle of substances in biocenoses, three groups of organisms are distinguished:

1) Producers(producers) - autotrophic organisms that create organic substances from inorganic ones. The main producers in all biocenoses are green plants. The activities of producers determine the initial accumulation of organic substances in the biocenosis;

ConsumersIorder.

This trophic level is composed of direct consumers of primary production. In the most typical cases, when the latter is created by photoautotrophs, these are herbivores (phytophagous). The species and ecological forms representing this level are very diverse and adapted to nutrition different types plant food. Due to the fact that plants are usually attached to the substrate, and their tissues are often very strong, many phytophages have evolved a gnawing type of mouthparts and various types of adaptations for grinding and grinding food. These are the dental systems of the gnawing and grinding type in various herbivorous mammals, the muscular stomach of birds, especially well expressed in granivores, etc. n. The combination of these structures determines the ability to grind solid food. Gnawing mouthparts are characteristic of many insects and others.

Some animals are adapted to feeding on plant sap or flower nectar. This food is rich in high-calorie, easily digestible substances. Oral apparatus in species that feed in this way, it is arranged in the form of a tube through which liquid food is absorbed.

Adaptations to feeding on plants are also found at the physiological level. They are especially pronounced in animals that feed on the rough tissues of the vegetative parts of plants, containing large amounts of fiber. In the body of most animals, cellulolytic enzymes are not produced, and the breakdown of fiber is carried out by symbiotic bacteria (and some protozoa of the intestinal tract).

Consumers partially use food to support life processes (“respiration costs”), and partially build their own body on its basis, thus carrying out the first, fundamental stage of transformation organic matter, synthesized by producers. The process of creation and accumulation of biomass at the level of consumers is designated as , secondary products.

ConsumersIIorder.

This level unites animals with a carnivorous type of nutrition (zoophagous). Usually, all predators are considered in this group, since their specific features practically do not depend on whether the prey is a phytophage or a carnivore. But strictly speaking, only predators that feed on herbivores and, accordingly, represent the second stage of transformation of organic matter in food chains should be considered second-order consumers. The chemical substances from which the tissues of an animal organism are built are quite homogeneous, therefore the transformation during the transition from one level of consumers to another is not as fundamental as the transformation of plant tissues into animals.

With a more careful approach, the level of consumers of the second order should be divided into sublevels according to the direction of flow of matter and energy. For example, in the trophic chain “cereals - grasshoppers - frogs - snakes - eagles”, frogs, snakes and eagles constitute successive sublevels of consumers of the second order.

Zoophages are characterized by their specific adaptations to their feeding patterns. For example, their mouthparts are often adapted to grasp and hold live prey. When feeding on animals that have dense protective coverings, adaptations are developed to destroy them.

At the physiological level, adaptations of zoophages are expressed primarily in the specificity of the action of enzymes “tuned” to digest food of animal origin.

ConsumersIIIorder.

Most important in biocenoses they have trophic connections. Based on these connections of organisms in each biocenosis, so-called food chains are distinguished, which arise as a result of complex food relationships between plant and animal organisms. Power circuits are connected directly or indirectly large group organisms into a single complex, connected to each other by the relationship: food - consumer. The food chain usually consists of several links. The organisms of the subsequent link eat the organisms of the previous link, and thus a chain transfer of energy and matter occurs, which underlies the cycle of substances in nature. With each transfer from link to link, it is lost most of(up to 80 - 90%) of potential energy dissipated in the form of heat. For this reason, the number of links (types) in the food chain is limited and usually does not exceed 4-5.

A schematic diagram of the food chain is shown in Fig. 2.

Here, the basis of the food chain is made up of species - producers - autotrophic organisms, mainly green plants that synthesize organic matter (they build their body from water, inorganic salts and carbon dioxide, assimilating the energy of solar radiation), as well as sulfur, hydrogen and other bacteria that use the energy of oxidation of chemicals to synthesize organic substances. The next links in the food chain are occupied by consumer species—heterotrophic organisms that consume organic substances. Primary consumers are herbivorous animals that feed on grass, seeds, fruits, underground parts of plants - roots, tubers, bulbs and even wood (some insects). Secondary consumers include carnivores. Carnivores, in turn, are divided into two groups: those that feed on mass small prey and active predators that often attack prey larger than the predator itself. At the same time, both herbivores and carnivores have a mixed feeding pattern. For example, even with the abundance of mammals and birds, martens and sables also eat fruits, seeds and pine nuts, and herbivores consume some amount of animal food, thus obtaining the essential amino acids of animal origin they need. Starting from the producer level, there are two new ways to use energy. Firstly, it is used by herbivores (phytophages), which directly eat living plant tissue; secondly, they consume saprophages in the form of already dead tissue (for example, during the decomposition of forest litter). Organisms called saprophages, mainly fungi and bacteria, obtain the necessary energy by decomposing dead organic matter. In accordance with this, there are two types of food chains: chains of consumption and chains of decomposition, Fig. 3.

It should be emphasized that food chains of decomposition are no less important than chains of grazing. On land, these chains begin with dead organic matter (leaves, bark, branches), in water - dead algae, fecal matter and other organic debris. Organic residues can be completely consumed by bacteria, fungi and small animals - saprophages; This releases gas and heat.

Each biocenosis usually has several food chains, which in most cases are complexly intertwined.

Ecological pyramid

All species that form the food chain exist on organic matter created by green plants. In this case, there is an important pattern associated with the efficiency of use and conversion of energy in the nutrition process. Its essence is as follows.

Only about 0.1% of the energy received from the Sun is bound through the process of photosynthesis. However, due to this energy, several thousand grams of dry organic matter per 1 m2 per year can be synthesized. More than half of the energy associated with photosynthesis is immediately consumed in the process of respiration of the plants themselves. The other part is transported through food chains by a number of organisms. But when animals eat plants, most of the energy contained in food is spent on various vital processes, turning into heat and dissipating. Only 5 - 20% of food energy passes into the newly built substance of the animal's body. The amount of plant matter that serves as the basis of the food chain is always several times greater than the total mass of herbivorous animals, and the mass of each of the subsequent links in the food chain also decreases. This very important pattern is called rule of the ecological pyramid. An ecological pyramid representing a food chain: cereals - grasshoppers - frogs - snakes - eagle is shown in Fig. 6.

The height of the pyramid corresponds to the length of the food chain.

The transition of biomass from a lower trophic level to a higher one is associated with losses of matter and energy. On average, it is believed that only about 10% of the biomass and its associated energy moves from each level to the next. Because of this, total biomass, production and energy, and often the number of individuals, progressively decrease as they ascend through trophic levels. This pattern was formulated by Ch. Elton (Ch. Elton, 1927) in the form of a rule ecological pyramids (Fig. 4) and acts as main limiter length of food chains.

Biomass And biocenosis productivity

The amount of living matter of all groups of plant and animal organisms is called biomass. The rate of biomass production is characterized by the productivity of the biocenosis. There is a distinction between primary productivity - plant biomass formed per unit time during photosynthesis, and secondary - biomass produced by animals (consumers) consuming primary products. Secondary products are formed as a result of the use of energy stored by autotrophs by heterotrophic organisms.

Productivity is usually expressed in units of mass per year on a dry matter basis per unit area or volume, which varies considerably among different plant communities. For example, 1 hectare of pine forest produces 6.5 tons of biomass per year, and a sugar cane plantation produces 34-78 tons. In general, the primary productivity of forests globe is the largest compared to other formations. A biocenosis is a historically established complex of organisms and is part of a more general natural complex - an ecosystem.

Spatial structure of biocenoses.

The definition of a biocenosis as a system of interacting species that carries out a cycle of biogenic circulation provides for the minimum spatial volume of this level of biosystems. Thus, it is incorrect to talk about “biocenosis of a stump”, “biocenosis of a gopher hole”, etc., since a complex of organisms of this level does not provide the possibility of a complete cycle of circulation. But this approach does not limit the “upper threshold” of the concept of biocenosis: the complete circulation of substances can take place within spatial boundaries of different scales. R. Hesse (R. Hesse, 1925) gave practically the first system of dividing the biosphere into subordinate zones of life. As the largest unit, he identified biocycles: land, sea bodies and sandy waters. They are divided into biochores- large spatial areas of the biocycle, covering a series of homogeneous landscape systems (desert, tundra, etc.). Later, this term was almost completely replaced by the one introduced by L.S. Berg (1913, 1931) concept "landscape zone". Both of these divisions meet the formal criteria of a biocenosis, but are not considered as such. The spatial boundaries of the biocenosis correspond to the concept biotope- a division of a biochore (landscape zone), characterized by a single type of vegetation cover (phytocenosis). In this regard, the most clear approach is manifested in the formulation introduced by V.N. Sukachev’s concept of “biogeocenosis”: “Biogeocenosis is an ecosystem within the boundaries of a phytocenosis” (E.M. Lavrenko, N.V. Dylis, 1968, p. 159). In most cases, the idea of ​​a biocenosis (ecosystem) is associated with precisely this spatial scale.

Species populations within a biocenosis are naturally located not only in area, but also vertically in accordance with the biological characteristics of each species. Thanks to this, the ecosystem always occupies a certain three-dimensional space; Accordingly, interspecific relationships have not only a functional, but also a spatial orientation.

In aquatic ecosystems, large-scale vertical structure is determined primarily by external conditions. In the pelagic zone, the determining factors are gradients of illumination, temperature, concentration of nutrients, etc. At great depths, the factor of hydrostatic pressure operates; in bottom biocenoses, the heterogeneity of soils and the hydrodynamics of near-bottom water layers are added to this. Features of the vertical structure are expressed in the specificity of species composition, changes in dominant species, biomass and production indicators. Thus, in the northwestern part of the Pacific Ocean, a vertical change in dominance in hydromedusa species is clearly visible: in the surface layer (50-300 m) Aglantha digitate, in a layer of 500-1000 m - Crossota brunea, and even deeper - Bottynema bruceu. In freshwater bodies of water, populations of mosquito larvae of the genus Chaoborus, and to the superficial - kind Sikh. Photosynthetic algae are confined to the upper, better illuminated horizons, which forms vertical flows of matter and energy, connecting communities of the euphotic zone with deep-sea biocenoses, the life of which is based on allochthonous (brought from outside) organic matter (A.S. Konstantinov, 1986).

In terrestrial ecosystems, the main factor creating vertical structure is biological in nature and is associated with the division of plant communities by height. This is especially clearly expressed in forest phytocenoses, the vertical structure of which is expressed in the form Tiering. The upper tier is represented by tree species, followed by tiers of shrubs, dwarf shrubs, herbaceous plants and ground moss cover. IN different types In forests this scheme is expressed differently. So, in deciduous forests several tree layers are distinguished, composed of species with different heights trees, as well as the undergrowth layer (shrubs and low-growing trees); herbaceous vegetation can also form 2-3 tiers. The growth of young trees forms groups that change in height as they grow. The underground parts of plants, in turn, form several tiers.

From the perspective of biogeocenology, a layer is a complex material and energy system, on the basis of which a number of elementary vertical components are differentiated (N.V. Dylis et al., 1964).

Tiering is also expressed in herbaceous phytocenoses, determining the vertical differentiation of the distribution of animals and microorganisms in the above-ground part of the community. It has already been noted that the vertical structure of terrestrial ecosystems is closely related to their functional activity: pasture chains are concentrated mainly in the aboveground part of biocenoses, and decomposition chains are concentrated in their underground part.