Studying the biotic structures of various ecosystems, scientists noticed that all the organisms in them are built in. And there are a lot of such chains in each such ecosystem. According to them, a substance that is a source of energy, as well as building material, moves from one organism to another. That is, one organism eats another, and a third in turn eats it. Here is a simple example of such a chain: grass - cow - man.

And all these chains are rarely isolated from each other - they are all combined into one food network. The relationships on this network are quite complex. For example, herbivores feed on plants of several species. And predators are also not very picky in choosing meat for their diet. But, despite the fact that there are many of them and they are all quite diverse - they can be entered into one scheme. But this scheme looks like this: green plants - primary consumers - secondary consumers - tertiary consumers - reproducers. Moreover, reproducers are always at the end and there may be several reasons for it. All these links are called trophic levels.

That is, from a scientific point of view, the trophic level is the entire set of organisms that occupy a certain place in the food web. And in an ordinary ecosystem, no more than 3-4 such levels can be counted. The first trophic level is, of course, plants. Everything begins with them. The second trophic level is occupied by phytophages, that is, herbivorous. This is what they eat only flora.

The third trophic level is occupied by second-order consumers. They are predators that feed only on herbivores. Also here can be euriphages, that is, omnivores. They can equally eat both plant and animal food. These include pigs, foxes, rats, cockroaches, and the like. Man, in essence, is also a euryphage. Also at this level there may be third-order consumers - such predators that feed only on carnivores.

And the last trophic level is usually occupied by reducers, that is, heterotrophic organisms. They destroy, mineralize and degrade ecosystem waste. After their “work” simple mineral compounds are obtained. And reducers, in turn, are divided into two classes. These are detritophages - animals that directly feed on organic debris and dead organisms. These include vultures, vultures, jackals, hyenas, earthworms and other scavengers.

Reducers also include destructors. They already decompose dead "organic" into inorganic compounds. Simply put, they support decay and decay processes. These include bacteria and fungi. And all these are arranged in such a way that producers, consumers and reducers closely interact through them. They maintain the integrity and structure of biocenoses, while coordinating the flow of matter and energy. This contributes to environmental regulation.

Graphically, such a trophic structure of an ecological system can be depicted as a pyramid of energy flows. Its basis is producers or the 1st trophic level. And all subsequent levels are the floors and the top of this pyramid. And through each of these levels there is a flow of energy. In this case, the energy leaving one level is the input energy for the next. And the main reason for such a small number of trophic levels in each ecosystem is that a significant part of the energy is lost during these transitions. Here the 10% rule applies, and according to it only such an amount of useful energy is transferred to the next level. And 10% is the maximum figure. In some ecosystems, this efficiency is only one percent.

Stable biogeochemical cycles of matter and energy in the biosphere of our planet are formed due to the biological diversity of the set of substances consumed by organisms and waste products released into the natural environment. The base of the biological cycle of substances is trophic levels, which are represented by specific types of living organisms, divided into three main groups: producers, consumers and reducers. The trophic level consists of populations of organisms that perform the same trophic functions in the ecosystem and have different species composition (from the Greek. Trophe - "nutrition").

The first trophic level is primary production level - form autotrophs. These are organisms that synthesize organic substances (carbohydrates, fats, proteins, nucleic acids) from inorganic compounds using the energy of the sun. Primary production is the biomass of plant tissue. Primary producers are plants, photoautotrophic bacteria and chemosynthetic bacteria (chemotrophs). Chemotrophs are microorganisms that synthesize organic matter due to the oxidation energy of ammonia, hydrogen sulfide and other substances found in water and soil.

The second trophic level represent consumers (heterotrophs):

1) the first order - phytophages - use plants as food;

2) second order - eat animal food.

At the third trophic level - reducers. These are organisms that decompose waste products and dead organisms into minerals, carbon dioxide and water. Consumptions are also involved in the mineralization of organic substances.

All organisms use the biomass of previous trophic levels for food, losing energy with loss of respiration, heating the body, various forms of activity, excreting excrement.

Between species of different trophic levels, there are relationships that form a system of trophic chains (food chains). The use of resources at each trophic level depends on the species diversity of the ecosystem.

Species diversity may decrease in pollution zones, causing a simplification of the trophic structure.

Today, violations of the structure of biocenoses due to environmental pollution are recorded. Toxicants are transmitted through the food chain and contribute to the death of animals, birds, aquatic organisms, and also accumulate in foods consumed by humans.

Food chains and trophic levels are considered integral components of the biological cycle. It involves many elements. Next, we consider in more detail the trophic levels of the ecosystem.

Terminology

The food chain is the movement of energy that is contained in plant foods through a number of organisms due to their eating each other. Only plants form organic matter from inorganic matter. The trophic level is a complex of organisms. Between them there is an interaction in the process of transfer of nutrients and energy from the source. Trophic chains (trophic level) suggest a certain position of organisms at one or another stage (link) during this movement. Marine and land biological structures have many differences. One of the main ones is that in the first food chains are longer than in the second.

Steps

The first trophic level is represented by autotrophs. They are also called producers. The second trophic level consists of the initial consumers. At the next stage are consumers who consume herbivorous organisms. These consumers are called secondary. These, for example, include primary predators, carnivores. Also in the 3rd trophic level are consumers of the 3rd order. They consume, in turn, weaker predators. As a rule, there is a limited number of trophic levels - 4 or 5. Rarely more than six. This food chain is usually closed by reducers or destructors. They are bacteria, microorganisms that decompose organic residues.

Consumers: general information

They are not just “eaters” that the food chain contains. Satisfaction of their needs by them is carried out through a feedback system (positive). Consumers influence the trophic levels of the ecosystem above. So, for example, the consumption of vegetation in the African savannahs by large herds of antelopes, along with fires in the dry period, increases the rate of nutrient return to the soil. Subsequently, during the rainy season, the restoration of grassy plants and their production increases.

An interesting example is Odum. It describes the impact of consumers on producers in the marine ecosystem. Crabs that consume detritus and algae "look after" their herbs in several ways. They break the soil, thus enhancing the circulation of water near the roots and introducing oxygen and necessary elements into the anaerobic coastal zone. In the process of continuous processing of bottom silts, rich in organic matter, crabs contribute to improving the conditions for the development and growth of benthic algae. One trophic level is composed of organisms that receive energy through the same number of steps.

Structure

Food consumed at each trophic level is not fully assimilated. This is due to its significant losses at the stages of metabolic processes. In this regard, the production of organisms included in the next trophic level is less than in the previous one. Inside a biological system, organic compounds containing energy are formed by autotrophic organisms. These substances are a source of energy and necessary components for heterotrophs. The following example is simple: an animal consumes plants. In turn, the beast can be eaten by another larger representative of the fauna. Thus, energy transfer through several organisms can take place. The next one uses the previous one, supplying energy and nutrients. It is this sequence that forms the food chain, in which the trophic level acts as a link.

1st order producers

The initial trophic level contains autotrophic organisms. They mainly include green spaces. Some prokaryotes, in particular blue-green algae, as well as a few species of bacteria, also have the ability to photosynthesis. However, their contribution to the trophic level is insignificant.

Thanks to the activity of photosynthetics, solar energy is converted into chemical energy. It lies in organic molecules, from which, in turn, tissues are built. A relatively small contribution to the production of organic matter is made by chemosynthetic bacteria. They extract energy from inorganic compounds. Algae act as the main producers in aquatic ecosystems. Often they are represented by small unicellular organisms that form phytoplankton in the surface layers of lakes and oceans. Most of the primary production on land comes in more highly organized forms. They relate to gymnosperms and angiosperms. Due to them, meadows and forests are formed.

Consumers 2, 3 orders

Food chains can be of two types. In particular, detrital and pasture structures are distinguished. The examples of the latter are described above. In them, on the first level there are green plants, on the second - pasture animals, on the third - predators. However, the bodies of dead plants and animals still contain energy and "building material" along with intravital secretions (urine and feces). All these organic materials are decomposed due to the activity of microorganisms - bacteria and fungi. They live on organic debris as saprophytes.

Organisms of this type are called reducers. They secrete digestive enzymes to waste products or to dead bodies, and then digestion products are absorbed. Decomposition can occur at different rates. The consumption of organic compounds of feces, urine, animal corpses is carried out for several weeks. At the same time, fallen branches or trees can decompose for years.

Detritophages

A significant role in the process of rotting wood belongs to mushrooms. They secrete the enzyme cellulase. It has a softening effect on wood, which makes it possible for small animals to penetrate and absorb material. Fragments of the decomposed material are called detritus. It feeds on many small living organisms (detritophages) and accelerate the destruction process.

Since the decomposition involves two types of organisms (fungi and bacteria, as well as animals), they are often combined under the same name - "reducers". But in reality, this term applies only to saprophytes. Detritophages, in turn, can be absorbed by larger organisms. In this case, a different type of chain is formed - starting with detritus. Detritophages of coastal and forest communities include wood lice, earthworm, carrion fly larva, purplish, holothuria, and polychaete.

Food network

In systems diagrams, each organism can be represented as consuming others belonging to a certain type. But the nutritional relationships that exist in the biological structure have a much more complex structure. This is due to the fact that the animal can consume organisms of various types. Moreover, they can belong to the same food chain or belong to different ones. This is especially evident among predators at high levels of the biological cycle. There are animals that consume other representatives of the fauna and plants at the same time. Such individuals belong to the category of omnivores. In particular, such is man. In the existing biological system, the interweaving of food chains is quite common. As a result, a new multicomponent structure is formed - the network. Only some of all possible relationships can be reflected in the diagram. As a rule, it contains only one or two predators belonging to the upper trophic levels. In the flow of energy and the cycle within the framework of a typical structure, there can be two ways of exchange. On the one hand, the interaction is between predators, and on the other, between reducents and detritus. The latter can consume dead animals. At the same time, living reducers and child-eaters can act as food for predators.

TROPHIC LEVEL TROPHIC LEVEL

a set of organisms united by a type of nutrition. Representation about T. at. allows you to understand the dynamics of the energy flow and its determining trophic. structure. Autotrophic organisms (predominantly green plants) occupy the first T. at. - (producers), herbivorous animals - the second (first order consumers), predators feeding on herbivorous animals - the third (second order consumers), secondary predators - the fourth (third order consumers). Organisms of different trophic. chains, but receiving food through an equal number of links in the trophic. chains, are on one T. at. So, the cow and beetle weevil of the genus siton feeding on alfalfa leaves are first-class consumers. Real relationships between T. at. the community is very complex. Populations of the same species, participating in decomp. trophic chains, can be on different T. at., depending on a source of the used energy. On each T. at. the consumed food is not fully assimilated, because it means that part of it is spent on exchange. Therefore, the production of organisms of each subsequent T. at. always less than the products of the previous T. at., an average of 10 times. Relates, the amount of energy transmitted from one T. at. to another, called ecology, community efficiency or trophic efficiency. chains. The ratio of dec. T. at. (trophic structure) can be depicted graphically in the form of an ecological pyramid, the basis of which is the first level (the level of producers). Ecological a pyramid can be of three types: 1) a pyramid of numbers - reflects the number of det. organisms at every level; 2) biomass pyramid - total dry weight, energy content or other measure of the total number of living matter; 3) energy pyramid - the magnitude of the energy flow. The base in the pyramids of numbers and biomass may be less than subsequent levels (depending on the size ratio of producers and consumers). The pyramid of energy always tapers up. In terrestrial ecosystems, a decrease in the amount of available energy is usually accompanied by a decrease in the biomass and number of individuals on each T.

.(Source: “Biological Encyclopedic Dictionary.” Edited by M. S. Gilyarov; Editorial: A. A. Babaev, G. G. Vinberg, G. A. Zavarzin et al. - 2nd ed., Corrected . - M .: Sov. Encyclopedia, 1986.)

See what the "TROPHIC LEVEL" is in other dictionaries:

The set of organisms that occupy a certain position in the general food chain. The remoteness of organisms from producers is the same. They are characterized by a certain form of organization and utilization of energy. Organisms of different trophic chains, ... ... Ecological Dictionary

trophic level  - 1. The level at which energy in the form of food is transmitted from one organism to another as part of a trophic chain. 2. The level of distribution of nutrients in the reservoir, especially in relation to the content of nitrates and phosphates in the water ... Geography Dictionary

TROPHIC LEVEL, the position that the body occupies in the FOOD CHAIN. It is usually determined by the boundaries at which nutrition is provided. The first trophic link is the PRIMARY MANUFACTURERS of green plants that use photosynthesis to ... ... Scientific and technical encyclopedic dictionary

trophic level  - The set of organisms of one ecosystem, united by the type of food Biotechnology topics EN trophic level ... Technical Translator Reference

trophic level  - 3.23 trophic level: An element of the functional classification of organisms within a community based on the food used.

The processes of nitrification and denitrification were balanced until the beginning of the intensive use by man of nitrogen fertilizers in order to obtain large yields of agricultural plants. Currently, due to the use of huge volumes of such fertilizers, an accumulation of nitrogen compounds in soil, plants, and groundwater is observed. Thus, the role of living organisms in the nitrogen cycle is fundamental.

The cycle of substances is the basis of the infinity of life on our planet. All living organisms take part in it, carrying out the processes of nutrition, respiration, excretion, reproduction. The basis of the biogenic cycle is solar energy, which is absorbed by phototrophic organisms and converted by them into the primary organic matter available to consumers. In the course of further transformation by consumers of various orders, the energy of food is gradually wasted, reduced. Therefore, the stability of the biosphere is directly related to the constant influx of solar energy. In the biogeochemical cycles of carbon and nitrogen, living organisms play the main role, while physical processes provide the basis for the global water cycle in the biosphere.

IN AND. Vernadsky came to the conclusion that in order to ensure his stability, life must certainly be presented in various forms. Indeed, if we assume that life originated somewhere in the ocean in the form of only one biological species, then after a while he will extract everything he needs from the environment, isolate the waste of his activities, dot the entire bottom of the seas with his remains, and on this life will stop: there will be no one to turn these remains into minerals. That is why life as a stable planetary phenomenon is possible only when it is of different quality. This diversity in the existing biosphere on Earth is characterized by the presence of three components: producers, consumers and reducers.

The trophic hierarchy of the biosphere is expressed in complex food relationships between its constituent species; it is a set of organisms united by the type of nutrition. Autotrophic organisms (mainly green plants) occupy the first trophic level (producers), followed by heterotrophs: on the second level, herbivorous animals (first-order consumers); predators feeding on herbivorous animals - on the third (second order consumers); secondary predators - in the fourth (3rd order consumers). Saprotrophic organisms (reducers) can occupy all levels, starting from the second. Organisms of various trophic chains that receive food through an equal number of links are on the same trophic level. The ratio of the various trophy levels can be graphically depicted as a pyramid.

Fig. 1: Biomass pyramid and trophic levels in the ecosystem

The ecological pyramids of numbers, biomass and energy, depicted in the form of graphic models, express the quantitative proportions of organisms different in the way they are fed: producers, consumers and reducers. Producers are called organisms that are capable of photo- and chemosynthesis and are the first link in the food chain of substances, the creator of organic substances from inorganic ones. Almost all plants belong to producers.

Consumables are called organisms that are consumers of organic matter in the food chain. Consumers feed on plants, animals, or both plants and animals. Distinguish between consumers of the first and second order. First-order animals include all herbivorous animals, and second-order animals are predators. Reducers are called organisms that decompose dead organic substances (corpses, garbage) and turn them into inorganic substances that can be assimilated again. Reducers include bacteria and fungi. In the food chain, reducers are consumers. The interaction of producers, consumers and reducers ensures the constancy, stability of the biological cycle. As a result of this cycle, various life forms affect the environment, organize its chemistry, change the terrain and microclimatic conditions. The zones in which the biogenic cycle takes place are called ecosystems or, as V.N. Sukachev, biogeocenoses. They represent homogeneous sections of the earth's surface with the established compositions of living creatures (biocenoses) and inert components (soils, surface layers of the atmosphere, solar energy) in interaction. The latter is associated with the metabolism and energy. The whole set of biogeocenoses available on Earth and carrying out the biogenic cycle of substances makes up the biosphere as a whole.

In all biogeocenoses, producers, consumers, and reducers make up diverse sets. This is a guarantee that if something happens to one of the species, then other species will take its share of the influence on the biosphere, and the biogeocenosis will not be destroyed. The interconnection of biogeocenoses ensures the sustainability of life processes on the planet as a whole. This guarantee is also ensured by the fact that there are many different biogeocenoses: if some cataclysm occurs somewhere on the Earth (volcanic eruption, lowering of the earth's crust, sea advance / retreat, geological shift, cooling, etc.), other biogeocenoses will support the existence of life and eventually restore balance. For example, after all living things were completely destroyed on the island of Krakatau as a result of the volcanic eruption in 1883, after half a century life on the island was restored.

So, the biosphere is a system of biogeocenoses. Each of them is an independent biological system, or rather a subsystem. It ensures the maintenance of the nutrient cycle in specific geographical conditions. Each biogeocenosis has its own set of species associated with each other. But relationships in biogeocenoses are built not at the species level (because their representatives can live not only in this biogeocenosis) and not at the level of individuals (because here they are mainly food and therefore short-lived), but at the level of species populations. A population is understood as an aggregate of individuals of one species, occupying a certain space for a long time and reproducing itself for a large number of generations. During the joint evolution of species, populations within the biogeocenosis adapt to each other and strive to sustainably maintain the corresponding trophic chains.

Food (trophic) chain - a series of species of plants, animals, fungi and microorganisms that are related to each other by relationships: food is a consumer. Organisms of the next link eat up the organisms of the previous link, and thus the chain transfer of energy and matter is carried out, which underlies the cycle of matter in nature. With each transfer from link to link, a large part (up to 80-90%) of potential energy is lost, dissipated in the form of heat. For this reason, the number of links (species) in the food chain is limited and usually does not exceed 4-5.

As a result of the sequence of energy transformations in food chains, each community of living organisms in an ecosystem acquires a certain trophic structure. The trophic structure of the community reflects the ratio between producers, consumers (first, second, etc. orders separately) and reducers, expressed either by the number of individuals of living organisms, or ph  biomass, or the energy enclosed in them, calculated per unit area per unit time.

The trophic structure is usually depicted as ecological pyramids. This graphic model was developed in 1927 by the American zoologist Charles Elton. The basis of the pyramid is the first trophic level - the level of producers, and the next floors of the pyramid are formed by subsequent levels - consumers of various orders. The height of all blocks is the same, and the length is proportional to the number, biomass or energy at the corresponding level. There are three ways to build ecological pyramids.

The energy pyramid reflects the magnitude of the energy flow, the speed of passage of the mass of food through the food chain. The structure of the biocenosis to a greater extent is affected not by the amount of fixed energy, but by the rate of food production. It has been established that the maximum amount of energy transferred to the next trophic level can in some cases be 30% of the previous one, and this is in the best case. In many biocenoses, food chains, the amount of transmitted energy can be as little as 1%.

In 1942, the American ecologist R. Lindeman formulated energy pyramid law (10 percent law),  according to which, on average, about 10% of the energy delivered to the previous level of the ecological pyramid passes from one trophic level through food chains to another trophic level. The rest of the energy is lost in the form of thermal radiation, in motion, etc. Organisms as a result of metabolic processes lose about 90% of all energy that is spent on maintaining their vital activity in each link of the food chain.

If the hare ate 10 kg of plant mass, then its own weight may increase by 1 kg. A fox or a wolf, eating 1 kg of hare, increases its mass by only 100 g. For woody plants, this proportion is much lower due to the fact that wood is poorly absorbed by organisms. For herbs and algae, this value is much larger, since they lack hard-to-digest tissues. However, the general regularity of the energy transfer process remains: much less passes through the upper trophic levels than through the lower ones. That is why food chains usually cannot have more than 3-5 (rarely 6) links, and ecological pyramids cannot consist of a large number of floors. To the final link of the food chain, as well as to the upper floor of the ecological pyramid, so little energy will flow that it will not be enough if the number of organisms increases.

This statement can be explained by tracing where the energy of consumed food is spent (C). Part of it goes to the construction of new cells, i.e. on growth (P). Part of the energy of the food is spent on providing energy metabolism or on breathing. Since the digestibility of food cannot be complete, i.e. 100%, some of the undigested food in the form of excrement is removed from the body (F). The balance sheet will look like this:

C \u003d P + R + F.

Given that the energy spent on breathing is not transferred to the next trophic level and leaves the ecosystem, it becomes clear why each subsequent level will always be less than the previous one. That is why large predatory animals are always rare. Therefore, there are also no predators that would eat wolves. In this case, they simply would not be fed, since wolves are few in number.

The biomass pyramid is the ratio of the masses of organisms of different trophic levels. Typically, in terrestrial biocenoses, the total mass of producers is greater than each subsequent link. In turn, the total mass of first-order consumers is greater than second-order consumers, etc. If organisms do not vary too much in size, then a graph usually turns out to be a step pyramid with a tapering apex. So, for the formation of 1 kg of beef, you need 70-90 kg of fresh grass.

In aquatic ecosystems, you can also get a reversed, or inverted, pyramid of biomass, when the biomass of producers is smaller than consumers, and sometimes reducers. For example, in the ocean, at a relatively high productivity of phytoplankton, the total mass at the moment may be less than that of consumer consumers (whales, large fish, mollusks).

Pyramids of numbers and biomass reflect statics  systems i.e. characterize the number or biomass of organisms in a certain period of time. They do not provide complete information on the trophic structure of the ecosystem, although they make it possible to solve a number of practical problems, especially those related to maintaining ecosystem stability. The pyramid of numbers allows, for example, to calculate the allowable value of fish catch or shooting animals during the hunting period without consequences for their normal reproduction.

Pyramid of numbers (  abundance) reflects the abundance of individual organisms at each level. For example, in order to feed one wolf, it is necessary at least a few rabbits, which he could hunt; To feed these hares, you need a fairly large number of different plants. Sometimes pyramids of numbers can be reversed or inverted. This applies to the food chains of the forest, when the producers are trees, and the primary consumers are insects. In this case, the level of primary consumers is numerically richer than the level of producers (a large number of insects feed on one tree).

A species that is a consumer cannot completely destroy the entire population of its potential victims: otherwise it will die itself. In turn, the fertility level of the victims evolves evolutionally, taking into account the fact that part of the population will be destroyed by predators. But naturally, there are always restrictions on the number of predators themselves. This maintains the balance of the system.

Any population in itself is also a sustainable biological system. To ensure this, it continuously reproduces its appearance in the biogeocenosis in which it exists. The laws of self-organization of the biosphere are such that relationships between individuals of a population are formed, aimed at organizing the implementation of this function. In particular, under favorable conditions for the existence of a population, its individuals begin to multiply more intensively. This leads to the fact that between individual individuals there is competition (due to territory, females, etc.). It becomes beneficial for the population that part of the individuals cease to reproduce and the population growth slows down. It is clear that for an individual the refusal to create offspring is abnormal, but for a population this is a necessary reaction to its excessive numbers. For example, at a certain density within the rodent community, internal relationships begin to aggravate. At the same time, aggressive forms of relationships begin to prevail over communicative ones, and a stressful situation arises. The latter leads to the death of individual individuals or to the blocking in some of them of the release of sex hormones into the blood.

With a sharp deterioration in the conditions of existence (predators have proliferated excessively, climatic conditions have worsened, food has become scarce, etc.), the population begins to decline. Then the natural mechanisms that stimulate reproduction are included. But the population always strives for the optimal level of its number, and, therefore, the process of self-regulation is characteristic of any population. Thus, the biosphere is a system in which biogeocenoses act as a subsystem. Each biogeocenosis, in turn, is an independent system in which populations act as a subsystem. In them, the subsystems are individual organisms. Each organism, of course, is a separate biological system. The latter is the main unit of metabolism. The biogenic cycle of substances on a planetary scale is possible only because all organisms carry it out with the environment continuously. It is with the body that the chain of relationships between the components of living matter begins. And at no level can this chain be interrupted, for they are all functionally related. This means that the biosphere, being an integral hierarchy, is subordinate to this regularity.