2nd and 3rd order consumers are examples. Consumers of the third order

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. Moebius. 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 of 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, collections of living and nonliving components, develop in nature. 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 - fauna, 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 a dynamic system that consists 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.

Phytophagous and carnivorous

The structure of living matter in an ecosystem. Biotic structure. Autotrophs and heterotrophs

Ecosystem. Signs of an ecosystem

Ecosystem homeostasis. Ecological succession. Types of natural and anthropogenic successions. Concepts of climax, stability and variability of ecosystems.

Populations in an ecosystem.

Producers. Consumers of the 1st and 2nd order. Detritivores. Decomposers.

Phytophagous and carnivorous.

The structure of living matter in an ecosystem. Biotic structure. Autotrophs and heterotrophs.

Ecosystem. Signs of an ecosystem.

Topic 3. Ecosystem. Ecosystem structure

Bioconsumption. Population and stability of the biosphere

Concepts of noosphere and technosphere

The term “ecosystem” was proposed by the English ecologist A. Tansley in 1935.

Ecosystem is any set of interacting living organisms and environmental conditions.

“Any unit (biosystem) that includes all the co-functioning organisms (biotic community) in a given area and interacts with the physical environment in such a way that the flow of energy creates well-defined biotic structures and the circulation of substances between living and nonliving parts is ecological system, or ecosystem"(Y. Odum, 1986).

Ecosystems are, for example, anthills, a patch of forest, a farm area, a spaceship cabin, a geographic landscape, or even the entire globe.

Ecologists also use the term “biogeocenosis”, proposed by the Russian scientist V.N. Sukachev. This term refers to the collection of plants, animals, microorganisms, soil and atmosphere on a homogeneous land area. Biogeocenosis is one of the variants of an ecosystem.

Between ecosystems, as well as between biogeocenoses, there are usually no clear boundaries, and one ecosystem gradually passes into another. Large ecosystems are made up of smaller ecosystems.

Rice. "Matryoshka" of ecosystems

In Fig. a “matryoshka” of ecosystems is shown. The smaller the size of the ecosystem, the more closely its constituent organisms interact. An organized group of ants lives in an anthill, in which all responsibilities are distributed. There are ants-hunters, guards, builders.

The anthill ecosystem is part of the forest biogeocenosis, and the forest biogeocenosis is part of the geographical landscape. The composition of the forest ecosystem is more complex; representatives of many species of animals, plants, fungi, and bacteria live together in the forest. The connections between them are not as close as those of ants in an anthill. Many animals spend only part of their time in the forest ecosystem.

Within the landscape, different biogeocenoses are connected by aboveground and underground movement of water in which minerals are dissolved. Water with minerals moves most intensively within a drainage basin - a reservoir (lake, river) and adjacent slopes, from which above-ground and underground waters flow into this reservoir. The ecosystem of the drainage basin includes several different ecosystems - forest, meadow, and arable land. The organisms of all these ecosystems may not have direct relationships and are connected through underground and aboveground water flows that move to the reservoir.

Within the landscape, plant seeds are transferred and animals move. A fox's hole or a wolf's lair are located in one biogeocenosis, and these predators hunt over a large territory consisting of several biogeocenoses.

Landscapes are united into physical-geographical regions (for example, the Russian Plain, the West Siberian Lowland), where different biogeocenoses are connected by a common climate, the geological structure of the territory and the possibility of settlement of animals and plants. Connections between organisms, including humans, in the ecosystems of a physical-geographical region and the biosphere are carried out through changes in the gas composition of the atmosphere and the chemical composition of water bodies.

Finally, all ecosystems of the globe are connected through the atmosphere and the World Ocean, into which the waste products of organisms enter, and form a single whole - biosphere.

The ecosystem includes:

1) living organisms (their totality can be called a biocenosis or biota of an ecosystem);

2) non-living (abiotic) factors - atmosphere, water, nutrients, light;

3) dead organic matter - detritus.

Of particular importance for identifying ecosystems are trophic , i.e. food relationships between organisms that regulate the entire energy of biotic communities and the entire ecosystem as a whole.

First of all, all organisms are divided into two large groups - autotrophs and heterotrophs.

Autotrophic organisms use inorganic sources for their existence, thereby creating organic matter from inorganic matter. Such organisms include photosynthetic green plants of land and aquatic environments, blue-green algae, some bacteria due to chemosynthesis, etc.

Since organisms are quite diverse in types and forms of nutrition, they enter into complex trophic interactions with each other, thereby performing the most important ecological functions in biotic communities. Some of them produce products, others consume them, and others convert them into inorganic form. They are called accordingly: producers, consumers and decomposers.

Producers- producers of products that all other organisms then feed on - these are terrestrial green plants, microscopic sea and freshwater algae, producing organic substances from inorganic compounds.

Consumers are consumers of organic substances. Among them there are animals that eat only plant foods - herbivores(cow) or eating only the meat of other animals – carnivores(predators), as well as those who use both – “ omnivores"(man, bear).

Reducers (destructors)– reducing agents. They return substances from dead organisms back to inanimate nature, decomposing organic matter into simple inorganic compounds and elements (for example, CO 2, NO 2 and H 2 O). By returning biogenic elements to the soil or aquatic environment, they thereby complete the biochemical cycle. This is done mainly by bacteria, most other microorganisms and fungi. Functionally, decomposers are the same consumers, which is why they are often called micro-consumers.

A.G. Bannikov (1977) believes that insects also play an important role in the processes of decomposition of dead organic matter and in soil-forming processes.

Microorganisms, bacteria and other more complex forms, depending on their habitat, are divided into aerobic, i.e. living in the presence of oxygen, and anaerobic– living in an oxygen-free environment.

All living organisms are divided into two groups according to their feeding method:

autotrophs(from Greek autos– himself and tropho- nutrition);

heterotrophs(from Greek heteros- another).

Autotrophs use inorganic carbon ( inorganic energy sources) and synthesize organic substances from inorganic ones; these are the producers of the ecosystem. According to the source (used) energy, they, in turn, are also divided into two groups:

Photoautotrophs– solar energy is used to synthesize organic substances. These are green plants that have chlorophyll (and other pigments) and absorb sunlight. The process by which its absorption occurs is called photosynthesis.

(Chlorophyll is a green pigment that causes plant chloroplasts to turn green. With its participation, the process of photosynthesis is carried out.

Choroplasts are green plastids that are found in the cells of plants and some bacteria. With their help, photosynthesis occurs.)

Chemoautotrophs– chemical energy is used to synthesize organic substances. These are sulfur bacteria and iron bacteria that obtain energy from the oxidation of sulfur and iron compounds (chemosynthesis). Chemoautotrophs play a significant role only in groundwater ecosystems. Their role in terrestrial ecosystems is relatively small.

Heterotrophs They use carbon from organic substances that are synthesized by producers, and together with these substances they obtain energy. Heterotrophs are consumers(from lat. consumo– consume), consuming organic matter, and decomposers, decomposing it into simple compounds.

Phytophagous(herbivores). These include animals that feed on living plants. Among the phytophages there are small animals, such as aphids or grasshoppers, and giants, such as the elephant. Almost all farm animals are phytophages: cows, horses, sheep, rabbits. There are phytophages among aquatic organisms, for example, the grass carp fish, which eats 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.

Zoophagi(predators, carnivores). Zoophages are 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. There are predator plants (sundew, bladderwort) that use insects as food.

Symbiotrophs. These are bacteria and fungi that feed on plant root secretions. Symbiotrophs are very important for the life of the ecosystem. Fungal threads entangling plant roots help absorb water and minerals. Symbiotrophic bacteria absorb nitrogen gas from the atmosphere and bind it into compounds available to plants (ammonia, nitrates). This nitrogen is called biological (as opposed to nitrogen from mineral fertilizers).

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

Detritivores are organisms that feed on dead organic matter. These are centipedes, earthworms, dung beetles, crayfish, crabs, jackals and many others.

Some organisms use both plants and animals and even detritus for food, and are classified as euryphages (omnivores) - bear, fox, pig, rat, chicken, crow, cockroaches. Man is also a euryphage.

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

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

In Fig. shows the structure of an ecosystem, the basis of which is plants - photoautotrophs, and the table shows examples of representatives of different trophic groups for some ecosystems.

Rice. Ecosystem structure

Organic substances created by autotrophs serve as food and a source of energy for heterotrophs: phytophagous consumers eat plants, first-order predators eat phytophages, second-order predators eat first-order predators, etc. This sequence of organisms is called food chain, its links are located at different trophic levels (representing different trophic groups).

The trophic level is the location of each link in the food chain. The first trophic level is producers, all the rest are consumers. The second trophic level is herbivorous consumers; the third is carnivorous consumers, feeding on herbivorous forms; the fourth are consumers who consume other carnivores, etc. therefore, consumers can be divided into levels: consumers of the first, second, third, etc. orders (Fig.).

Rice. Food relationships of organisms in biogeocenosis

Only consumers specializing in a certain type of food are clearly divided into levels. However, there are species that eat meat and plant foods (humans, bears, etc.) that can be included in food chains at any level.

In Fig. Five examples of food chains are given.

Rice. Some food chains in ecosystems

The first two food chains represent natural ecosystems - terrestrial and aquatic. In the terrestrial ecosystem, predators such as foxes, wolves, and eagles that feed on mice or gophers complete the chain. In an aquatic ecosystem, solar energy, absorbed mainly by algae, passes to small consumers - daphnia crustaceans, then to small fish (roach) and, finally, to large predators - pike, catfish, pike perch. In agricultural ecosystems, the food chain can be complete when raising farm animals (third example), or shortened when plants are grown that are directly used by humans for food (fourth example).

The given examples simplify the actual picture, since the same plant can be eaten by different herbivores, and they, in turn, become victims of different predators. A plant leaf can be eaten by a caterpillar or slug, the caterpillar can become a victim of a beetle or an insectivorous bird, which can also peck the beetle itself. A beetle can also become a victim of a spider. Therefore, in real nature, it is not food chains that form, but food webs.

During the transition of energy from one trophic level to another (from plants to phytophages, from phytophages to first-order predators, from first-order predators to second-order predators) approximately 90% of the energy is lost through excrement and respiration. In addition, phytophages eat only about 10% of plant biomass, the rest replenishes the supply of detritus and is then destroyed by decomposers. Therefore, secondary biological products are 20–50 times less than primary ones.

Rice. Main types of ecosystems

Organic molecules, synthesized by autotrophs, serve as a source of nutrition (matter and energy) for heterotrophic animals. These animals, in turn, are eaten by other animals and in this way energy is transferred through a series of organisms, where each subsequent one feeds on the previous one. This sequence is called a food chain, and each link in the chain corresponds to a specific trophic level (from the Greek troph - food). The first trophic level is always composed of autotrophs, called producers (from the Latin producere - to produce). The second level is herbivores (phytophages), which are called consumers (from the Latin consumo - “I devour”) of the first order; third level (for example, predators) - consumers of the second order, etc.

Usually in an ecosystem sometimes 4-5 trophic levels and rarely more than 6. This is partly due to the fact that at each level some of the matter and energy is lost (incomplete consumption of food, breathing of consumers, “natural” death of organisms, etc.); such losses are reflected in the figure and are discussed in more detail in the corresponding article. However, recent research suggests that the length of food chains is also limited by other factors. Perhaps a significant role is played by the availability of preferred food and territorial behavior, which reduces the density of settlement of organisms, and, therefore, the number of consumers of higher orders in a particular habitat. According to existing estimates, in some ecosystems up to 80% of primary production is not consumed by phytophages. Dead plant material becomes prey for organisms that feed on detritus (detritivores) or reducers (destructors). In this case, we talk about detrital food chains. Detrital food chains predominate, for example, in tropical rainforests.

Producers

Almost all producers- photoautotrophs, i.e. green plants, algae and some prokaryotes, such as cyanobacteria (formerly called blue-green algae). The role of chemoautotrophs on the biosphere scale is negligible. Microscopic algae and cyanobacteria that make up phytoplankton are the main producers of aquatic ecosystems. On the contrary, the first trophic level of terrestrial ecosystems is dominated by large plants, for example, trees in forests, grasses in savannas, steppes, fields, etc.

Flow of energy and cycling of substances in a typical food chain. Please note that a two-way exchange is possible between predators and detritivores, as well as decomposers: detritivores feed on dead predators, and predators in some cases eat living detritivores and decomposers. Phytophages are consumers of the first order; carnivores are consumers of the second, third, etc. orders.

Consumers of the first order

On land, the main phytophages- insects, reptiles, birds and mammals. In fresh and sea water, these are usually small crustaceans (daphnia, sea acorns, crab larvae, etc.) and bivalves; most of them are filter feeders, filtering out producers, as described in the corresponding article. Together with protozoa, many of them are part of zooplankton - a collection of microscopic drifting heterotrophs that feed on phytoplankton. The life of oceans and lakes depends almost entirely on planktonic organisms, which virtually form the beginning of all food chains in these ecosystems.

Consumers of the second, third and subsequent orders

Second-order consumers They eat phytophages, i.e. they are carnivorous organisms. Third-order consumers and higher-order consumers are also carnivores. These consumers can be divided into several ecological groups:

Here are two examples based on photosynthesis food chain:

Plant (leaves) -> Slug -» Frog -» Snake -* -» Ermine

Plant (phloem sap) -» Aphid -> Ladybug -> -» Spider -^ Starling -> Hawk

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The meaning of the word consumers

Encyclopedic Dictionary, 1998

consumers

CONSUMERS (from Latin consumo - I consume) organisms that are consumers of organic matter in the food chain, all heterotrophic organisms. Consumers of the first order are herbivorous animals, Consumers of the second, third, etc. orders of predators. Wed. Producers.

Consumers

(from Latin Consume ≈ consume), organisms that are consumers of organic matter in the food chain, i.e. all heterotrophic organisms. See Power Circuits.

Wikipedia

Consumers

four orders of consumers.

Consumers of the first order, feed directly on biomass producers.

A single organism can be a consumer of different orders in different trophic chains, for example, an owl eating a mouse is simultaneously a consumer of the second and third order, and a mouse is a consumer of the first and second, since the mouse feeds on both plants and herbivorous insects.

Any consumer is heterotroph, since it is not able to synthesize organic substances from inorganic ones. The term “consumer of order” allows us to more accurately indicate the place of an organism in the food chain. Decomposers (for example, fungi, decay bacteria) are also heterotrophs; they are distinguished from consumers by their ability to completely decompose organic matter (

PRIMARY CONSUMER - an organism, for example a rabbit or deer, that feeds mainly or exclusively on green plants, their fruits or seeds.[...]

These are primary consumers that feed on algae, bacteria and detritus. They reproduce sexually (although crustaceans and rotifers can reproduce in other ways) and therefore reproduce more slowly than phytoplankton. The feeding process of zooplankton occurs through filtration and grazing of phytoplankton; in mesotrophic water bodies, consumption can be comparable to the rate of primary production. Most are 0.5-1mm long, but some may be less than 0.1mm. Zooplankton includes both plant and predatory organisms. In lakes they migrate during daylight hours to deeper waters; the almost transparent outer shell protects them from death (eaten by fish). [...]

Against the background of primary zoning, based mainly on physical factors, secondary zoning is clearly visible - both vertical and horizontal; this secondary zonation is evident in the distribution of communities. The communities of each primary zone, with the exception of the euphotic one, are divided into two fairly clear vertical components - benthic, or bottom (benthos), and pelagic. In the sea, as in large lakes, plant producers are represented by microscopic phytoplankton, although large multicellular algae (macrophytes) can be significant in some coastal areas. Primary consumers, therefore, primarily include zooplankton. Medium-sized animals feed on either plankton or detritus formed from plankton, while large animals are mainly predators. There are only a small number of large animals that, like large land animals such as deer, cows and horses, feed exclusively on plant foods.[...]

Primary macroconsumers, or plant-telivores (see Fig. 2.3, IIA and IIB), feed directly on living plants or their parts. There are two types of primary macroconsumers in the pond: zooplankton (animal plankton) and benthos (bottom forms), corresponding to two types of producers. In a grassland ecosystem, herbivores are also divided into two size groups: small - herbivorous insects and other invertebrates, and large - herbivorous rodents and ungulate mammals. Another important type of consumers is represented by detritivores (IIIA and IIIB), which exist due to the “rain” of organic detritus falling from the upper autotrophic layers. Together with herbivores, detritivores serve as food for carnivores. Many, and perhaps even all, detritivores obtain most of their food by digesting microorganisms that colonize detritus particles. [...]

P - producers C, - primary consumers. D. Soil arthropods - according to Engeliann (1968).[...]

Then the primary consumers are connected - herbivorous animals (T) and, finally, carnivorous consumers (X). All of them occupy a certain place in the hierarchy of participants in the biotic cycle and perform their functions of transforming the branches of energy flow that they receive and transferring biomass. But everyone is united, their substances are depersonalized and the general circle is closed by a system of single-cell destructors. They return to the abiotic environment of the biosphere all the elements necessary for new and new turns of the cycle.[...]

The second group is represented by consumers, i.e. consumers (from Latin consumo - to consume) - heterotrophic organisms, mainly animals, eating other organisms. There are primary consumers (animals that eat green plants, herbivores), and secondary consumers (predators, carnivores that eat herbivores). A secondary consumer can serve as a source of food for another predator - a third-order consumer, etc.[...]

A person, eating cow meat, is a secondary consumer at the third trophic level, and eating plants, he is a primary consumer at the second trophic level. Each person requires about 1 million kcal of energy received through food per year for the physiological functioning of the body. Humanity produces about 810 5 kcal (with a population of over 6 billion people), but this energy is distributed extremely unevenly. For example, in the city energy consumption per person reaches 80 million kcal per year, i.e. For all types of activities (transport, household, industry), a person spends 80 times more energy than is necessary for his body.[...]

All producers belong to the first trophic level, all primary consumers, regardless of whether they feed on living or dead producers, belong to the second trophic level, respectively, consumers of the 2nd order belong to the third, etc. As a rule, the number of trophic levels does not exceeds three or four. B. Nebel (1993) confirms this conclusion with the following: the total mass of organisms (their biomass) at each trophic level can be calculated by collecting (or capturing) and then weighing the corresponding samples of plants and animals. Thus, it was established that at each trophic level the biomass is 90-99% less than at the previous one. From this it is not difficult to imagine that the existence of a large number of trophic levels is impossible due to the fact that biomass will very quickly approach zero. Graphically this is represented in the form of a biomass pyramid (Fig. 47).[...]

The amount of detritus produced also increases. Corresponding changes also occur in trophic networks. Detritus becomes the main source of nutrients.[...]

3.15

In the case of pasture forest food chains, when trees are producers and insects are primary consumers, the level of primary consumers is numerically richer in individuals of the producer level. Thus, pyramids of numbers can be reversed. For example in Fig. Figure 9.7 shows pyramids of numbers for ecosystems of the steppe and forests of the temperate zone.[...]

A fish pond is a good example of how secondary production depends on 1) the length of the food chain, 2) primary productivity, and 3) the nature and amount of external energy introduced into the pond system. As shown in table. 3.11, large lakes and seas produce 1 m2 less fish than small productive fertilized ponds with intensive farming, and the point is not only that in large reservoirs primary productivity is lower and food chains are longer, but also that in these In large bodies of water, a person collects only part of the population of consumers, namely the part that is beneficial to him. In addition, the production yield is several times higher when breeding herbivorous species (for example, carp) than when breeding predatory species (perch, etc.); the latter, of course, need a longer food chain. High product yields indicated in table. 3.11. Therefore, when calculating production per unit area in such cases, it would be necessary to include the area of ​​​​the land from which additional food comes. Many people incorrectly assess the high productivity of reservoirs in Eastern countries by comparing it with the productivity of fish ponds in the United States, which usually does not receive additional food. Naturally, the method of conducting pond farming depends on the population density in the area.[...]

It is argued that in the upper reaches of rivers, communities are shaded by tree canopy and receive little light. Consumers depend mainly on leaf litter and other allochthonous organic matter. The fauna of the river is represented mainly by primary consumers, classified as mechanical destroyers.[...]

Despite the diversity of food chains, they have common patterns: from green plants to primary consumers, from them to secondary consumers, etc., then to detritivores. Detritivores always come in last place; they close the food chain.[...]

Lakes contain fish that can consume large quantities of phytoplankton. They are classified as primary consumers, since they feed on ready-made organic matter and cannot create food on their own. Other animals, mainly insect larvae, but also some fish, feed on zooplankton; they are secondary consumers. Fish use various inhabitants of the reservoir as food (Fig. 2.22).[...]

The biotic communities of each of these zones, except for the euphotic, are divided into benthic and pelagic. In them, the primary consumers include zooplankton; insects in the sea are ecologically replaced by crustaceans. The overwhelming majority of large animals are predators. The sea is characterized by a very important group of animals called sessile (attached). They are not found in freshwater systems. Many of them resemble plants and hence their names, for example, crinoids. Mutualism and commensalism are widely developed here. All benthic animals in their life cycle pass through the pelagic stage in the form of larvae.[...]

Each link in the food chain is called a trophic level. The first trophic level is occupied by autotrophs, otherwise called primary producers. Organisms of the second trophic level are called primary consumers, the third - secondary consumers, etc. There are usually four or five trophic levels and rarely more than six (Fig. 5.1).[...]

A deer that eats buds and young bark from trees will already be the first consumer of these substances and the energy contained in them, or the primary consumer. Moving from tree to tree, he loses energy, but at the same time receives much more than he expends. A large predator, for example a wolf, is a secondary consumer, since by eating a deer, it receives energy, so to speak, second-hand.[...]

[ ...]

HERBIVORE - an organism, such as a rabbit or deer, that feeds primarily on green plants or their fruits and seeds.[...]

TROPHIC LEVEL - the stage of movement of solar energy (as part of food) through the ecosystem. Green plants are on the first trophic level, primary consumers are on the second, secondary consumers are on the third, etc. [...]

The location of each link in the food chain is a trophic level. The first trophic level, as noted earlier, is occupied by autotrophs, or so-called primary producers. Organisms of the second trophic. level are called primary consumers, the third - secondary consumers, etc.[...]

The metabolism of the system is carried out due to solar energy, and the intensity of metabolism and the relative stability of the pond system depend on the intensity of the supply of substances with precipitation and runoff from the drainage basin.[...]

Complex forms of interdependence between plants and animals were also formed on the basis of direct trophic connections. The balance of plant biomass removed by phytophages, which determines the stable relationship between the populations of producers and primary consumers, is largely determined by the adaptations of plants to limit their consumption by animals. Such adaptations often include the formation of hard bark, various kinds of thorns, prickles, etc. Without ensuring complete inaccessibility for phytophages (they develop adaptations of the opposite nature), these formations still reduce the range of possible consumers, and accordingly increase the likelihood of sufficient for effective reproduction of the number and density of populations of the species.[...]

First, multicellular plants (P) develop - higher producers. Together with unicellular organisms, they create organic matter through the process of photosynthesis, using the energy of solar radiation. Subsequently, primary consumers are involved - herbivorous animals (T), and then carnivorous consumers. We examined the biotic cycle of land. This fully applies to the biotic cycle of aquatic ecosystems, for example, the ocean (Fig. 12.17).[...]

At the ecosystem “step” there is a shift in the relationship between the links of the ecological (in this case, energy) pyramid. For example, the overall energy balance of two similar (say, meadow) ecosystems, in one of which the dominant primary consumers are large ungulates, and in the other small invertebrate phytophages (after large herbivorous mammals, most of the rodents and even a significant proportion of arthropods) may be similar.[...]

Thanks to a certain sequence of nutritional relationships, individual trophic levels of transfer of substances and energy in the ecosystem associated with the nutrition of a certain group of organisms are distinguished. Thus, the first trophic level in all ecosystems is formed by producers - plants; the second - primary consumers - phytophages, the third - secondary consumers - zoophages, etc. As already noted, many animals feed not at one, but at several trophic levels (an example is the diet of the gray rat, brown bear and human).[...]

Analysis of trophic relationships between fish larvae and food invertebrates allows one to imagine the complexity of these relationships. Fish larvae at different stages of development consume food items of different energy significance and thereby determine their distribution among trophic levels from consumers of the second to consumers of the fourth and fifth orders, and at the same stage of development they can simultaneously occupy different trophic levels. Pike perch larvae, for example, move through all links of the trophic chain from primary consumers to n-order predators, occupying two, sometimes three, trophic levels at once. The transition of larvae at one or another stage of development to feeding on organisms of lower energy levels, reducing the length of the food chain, can be considered as an adaptation leading to a balanced supply of energy through food during the period of their larval development. This is especially important in years when the food supply in the reservoir is unfavorable. Of the three trophic complexes of larvae in reservoirs - coastal-phytophilic, coastal-pelagic and pelagic) - the most significant with a large number of species is coastal-phytophilic. The larvae of this complex live in protected shallow waters, forming common schools, and do not travel long distances throughout the entire larval development period, since different depths, islands, flooded shrubs, and different densities of coastal aquatic vegetation create conditions for the ecological isolation of individual areas of the littoral zone. Larvae of perch and pike perch also come here from open coastal areas, which, starting from stages D1 and Dg, form significant accumulations at night. Based on this, the protected coastal area should be considered not only a breeding ground for phytophilic fish, but also a feeding area for the larvae of the main commercial species, requiring special treatment and protection.[...]

In the case of acidification of a watercourse, the changes occurring in its ecosystem largely have a different direction. Although the biodiversity of the ecosystem is decreasing, the overall structure of the river continuum is maintained. At the same time, the processes of destruction of organic matter by bacteria are suppressed and the biomass of primary consumers is significantly reduced, which often leads to an increase in biomass and a complication of the spatial structure of periphyton. The role of secondary consumers, among which predatory larvae of aquatic insects dominate, is sharply increasing. Many of them have a long life cycle and can be classified as r-strategists. In general, acidification leads to the predominance of pasture food chains, a decrease in the rate of destruction of organic matter and an increase in the P/R and K2 ratio of the ecosystem and, therefore, causes a shift in the functioning of the ecological system of the watercourse to an equilibrium state.[...]

The distance of an organism in a food chain from its producers is called its food or trophic level. Organisms that receive energy from the Sun through the same number of steps in the food chain are considered to belong to the same trophic level. So. green plants occupy the first trophic level (level of producers), herbivores occupy the second (level of primary consumers), primary predators eating herbivores occupy the third (level of secondary consumers), and secondary predators occupy the fourth (level of tertiary consumers). An organism of a given species can occupy one or more trophic levels, depending on what energy sources it uses.[...]

There are calculations showing that 1 hectare of some forest receives an average of 2.1 109 kJ of solar energy annually. However, if we burn all the plant matter stored over the year, the result will be only 1.1 106 kJ, which is less than 0.5% of the energy received. This means that the actual productivity of photosynthetics (green plants), or primary productivity, does not exceed 0.5%. Secondary productivity is extremely low: during the transfer from each previous link of the trophic chain to the next, 90-99% of energy is lost. If, for example, on 1 m2 of soil surface, plants create an amount of substance equivalent to approximately 84 kJ per day, then the production of primary consumers will be 8.4 kJ, and that of secondary consumers will not exceed 0.8 kJ. There are specific calculations that to produce 1 kg of beef, for example, you need 70-90 kg of fresh grass.[...]

Secondary production is defined as the rate of formation of new biomass by heterotrophic organisms. Unlike plants, bacteria, fungi and animals are not able to synthesize the complex, energy-rich compounds they need from simple molecules. They grow and obtain energy by consuming plant matter either directly or indirectly by eating other heterotrophs. Plants, the primary producers, constitute the first trophic level in the community. The second contains primary consumers; on the third - secondary consumers (predators), etc. [...]

The concept of energy flow not only allows ecosystems to be compared among themselves, but also provides a means for assessing the relative roles of populations within them. In table Figure 14 shows estimates of density, biomass and energy flow rate for 6 populations that differ in the size of individuals and habitat. The numbers in this series vary by 17 orders of magnitude (1017 times), biomass by about 5 orders of magnitude (10° times), and energy flow by only about 5 times. This comparative uniformity of energy flows indicates that all 6 populations belong to the same trophic level in their communities (primary consumers), although this cannot be assumed either by numbers or biomass. It is possible to formulate a certain “ecological rule”: data on numbers lead to an exaggeration of the importance of small organisms, and data on biomass lead to an exaggeration of the role of large organisms; Consequently, these criteria are unsuitable for comparing the functional role of populations that differ greatly in the ratio of metabolic intensity to the size of individuals, although, as a rule, biomass is still a more reliable criterion than abundance. At the same time, energy flow (i.e. P-Y) serves as a more suitable indicator for comparing any component with another and all components of the ecosystem with each other. [...]

In Fig. Figure 4.11 presents a graphical model of the “lower” part of the water cycle, showing how biotic communities adapt to changing conditions in the so-called river continuum (gradient from small to large rivers; see Wannoe et al., 1980). In the upper reaches, rivers are small and often completely shaded, so that the aquatic community receives little light. Consumers depend mainly on leaf and other organic detritus brought from the drainage basin. The detritus is dominated by large organic particles, such as leaf fragments, and the fauna is represented mainly by aquatic insects and other primary consumers, which ecologists who study river ecosystems classify as mechanical destroyers. The upper reaches ecosystem is heterotrophic; the P/I ratio is much less than one.[...]

Fallout from atomic explosions differs from radioactive waste in that the radioactive isotopes generated by the explosion combine with iron, silicon, dust and anything else that happens to be nearby, resulting in relatively insoluble particles. The sizes of these particles, which often resemble tiny marble balls of different colors under a microscope, vary from several hundred microns to almost colloidal sizes. The smallest of them stick tightly to plant leaves, causing radioactive damage to leaf tissue; If such leaves are eaten by any herbivorous animal, the radioactive particles dissolve in its digestive juices. Thus, this type of sediment can directly enter the food chain at the trophic level of herbivores, or primary consumers.[...]

The transfer of food energy from its source - plants - through a number of organisms, occurring by eating some organisms by others, is called a food chain. With each successive transfer, most (80-90%) of the potential energy is lost, turning into heat. This limits the possible number of steps, or “links,” in the chain, usually to four or five. The shorter the food chain (or the closer the organism is to the beginning of it), the greater the amount of energy available. Food chains can be divided into two main types: grazing chains, which start with a green plant and go further to grazing, herbivorous (that is, organisms that eat green plants) and carnivores (organisms that eat animals), and detrital chains , which start from dead organic matter, go to microorganisms that feed on it, and then detritivores and their predators. Food chains are not isolated from one another, but are closely intertwined. Their network is often called a food web. In a complex natural community, organisms that obtain their food from plants through the same number of stages are considered to belong to the same trophic level. Thus, green plants occupy the first trophic level (the level of producers), herbivores occupy the second (the level of primary consumers), predators that eat herbivores occupy the third (the level of secondary consumers), and secondary predators occupy the fourth level (the level of tertiary consumers). It must be emphasized that this trophic classification divides into groups not the species themselves, but their types of life activity; a population of one species can occupy one or more trophic levels, depending on what energy sources it uses. The flow of energy through a trophic level is equal to the total assimilation (L) at that level, and the total assimilation in turn is equal to biomass production (P) plus respiration (/?).