Determine the correct sequence of the animal food chain. Abstract: Food chains in nature

Question 28. Food chain. Types of food chains.

FOOD CHAIN(trophic chain, food chain), the interconnection of organisms through food-consumer relationships (some serve as food for others). In this case, a transformation of matter and energy occurs from producers(primary producers) through consumers(consumers) to decomposers(converters of dead organic matter into inorganic substances assimilated by producers). There are 2 types of food chains - pasture and detritus. The pasture chain begins with green plants, goes to grazing herbivorous animals (consumers of the 1st order) and then to the predators that prey on these animals (depending on the place in the chain - consumers of the 2nd and subsequent orders). The detrital chain begins with detritus (a product of the breakdown of organic matter), goes to microorganisms that feed on it, and then to detritivores (animals and microorganisms involved in the process of decomposition of dying organic matter).

An example of a pasture chain is its multi-channel model in the African savanna. Primary producers are grass and trees, 1st order consumers are herbivorous insects and herbivores (ungulates, elephants, rhinoceroses, etc.), 2nd order are predatory insects, 3rd order are carnivorous reptiles (snakes, etc.), 4th – predatory mammals and birds of prey. In turn, detritivores (scarab beetles, hyenas, jackals, vultures, etc.) at each stage of the grazing chain destroy the carcasses of dead animals and the food remains of predators. The number of individuals included in the food chain in each of its links consistently decreases (the rule of the ecological pyramid), i.e., the number of victims each time significantly exceeds the number of their consumers. Food chains are not isolated from one another, but are intertwined with each other to form food webs.

Question 29. What are ecological pyramids used for? Name them.

Ecological pyramid- graphic images of the relationship between producers and consumers of all levels (herbivores, predators, species that feed on other predators) in the ecosystem.

The American zoologist Charles Elton suggested schematically depicting these relationships in 1927.

In a schematic representation, each level is shown as a rectangle, the length or area of ​​which corresponds to the numerical values ​​of a link in the food chain (Elton’s pyramid), their mass or energy. Rectangles arranged in a certain sequence create pyramids of various shapes.

The base of the pyramid is the first trophic level - the level of producers; subsequent floors of the pyramid are formed by the next levels of the food chain - consumers of various orders. The height of all blocks in the pyramid is the same, and the length is proportional to the number, biomass or energy at the corresponding level.

Ecological pyramids are distinguished depending on the indicators on the basis of which the pyramid is built. At the same time, the basic rule has been established for all pyramids, according to which in any ecosystem there are more plants than animals, herbivores than carnivores, insects than birds.

Based on the rule of the ecological pyramid, it is possible to determine or calculate the quantitative ratios of different species of plants and animals in natural and artificially created ecological systems. For example, 1 kg of mass of a sea animal (seal, dolphin) requires 10 kg of eaten fish, and these 10 kg already need 100 kg of their food - aquatic invertebrates, which, in turn, need to eat 1000 kg of algae and bacteria to form such a mass. IN in this case the ecological pyramid will be sustainable.

However, as you know, there are exceptions to every rule, which will be considered in each type of ecological pyramid.

The first ecological schemes in the form of pyramids were built in the twenties of the 20th century. Charles Elton. They were based on field observations of a number of animals of different size classes. Elton did not include primary producers and did not make any distinction between detritivores and decomposers. However, he noted that predators are usually larger than their prey, and realized that this ratio is extremely specific only to certain size classes of animals. In the forties, the American ecologist Raymond Lindeman applied Elton's idea to trophic levels, abstracting from the specific organisms that comprise them. However, while it is easy to distribute animals into size classes, it is much more difficult to determine which trophic level they belong to. In any case, this can only be done in a very simplified and generalized manner. Nutritional relationships and the efficiency of energy transfer in the biotic component of an ecosystem are traditionally depicted in the form of stepped pyramids. This provides a clear basis for comparing: 1) different ecosystems; 2) seasonal states of the same ecosystem; 3) different phases of ecosystem change. There are three types of pyramids: 1) pyramids of numbers, based on counting organisms at each trophic level; 2) biomass pyramids, which use the total mass (usually dry) of organisms at each trophic level; 3) energy pyramids, taking into account the energy intensity of organisms at each trophic level.

Types of ecological pyramids

pyramids of numbers- at each level the number of individual organisms is plotted

The pyramid of numbers displays a clear pattern discovered by Elton: the number of individuals making up a sequential series of links from producers to consumers is steadily decreasing (Fig. 3).

For example, to feed one wolf, he needs at least several hares for him to hunt; To feed these hares, you need a fairly large variety of plants. In this case, the pyramid will look like a triangle with a wide base tapering upward.

However, this form of a pyramid of numbers is not typical for all ecosystems. Sometimes they can be reversed, or upside down. This applies to forest food chains, where trees serve as producers and insects serve as primary consumers. 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), therefore the pyramids of numbers are the least informative and least indicative, i.e. the number of organisms of the same trophic level largely depends on their size.

biomass pyramids- characterizes the total dry or wet mass of organisms at a given trophic level, for example, in units of mass per unit area - g/m2, kg/ha, t/km2 or per volume - g/m3 (Fig. 4)

Usually 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 that of second-order consumers, etc.

In this case (if the organisms do not differ too much in size) the pyramid will also have the appearance of a triangle with a wide base tapering upward. However, there are significant exceptions to this rule. For example, in the seas, the biomass of herbivorous zooplankton is significantly (sometimes 2-3 times) greater than the biomass of phytoplankton, represented mainly by unicellular algae. This is explained by the fact that algae are very quickly eaten by zooplankton, but they are protected from being completely eaten away by the very high rate of division of their cells.

In general, terrestrial biogeocenoses, where producers are large and live relatively long, are characterized by relatively stable pyramids with a wide base. In aquatic ecosystems, where producers are small in size and have short life cycles, the pyramid of biomass can be inverted or inverted (with the tip pointing down). Thus, in lakes and seas, the mass of plants exceeds the mass of consumers only during the flowering period (spring), and during the rest of the year the opposite situation can occur.

Pyramids of numbers and biomass reflect the statics of the system, that is, they characterize the number or biomass of organisms in a certain period of time. They do not provide complete information about the trophic structure of an ecosystem, although they allow solving a number of practical problems, especially related to maintaining the sustainability of ecosystems.

The pyramid of numbers allows, for example, to calculate the permissible amount of fish catch or shooting of animals during the hunting season without consequences for their normal reproduction.

energy pyramids- shows the amount of energy flow or productivity at successive levels (Fig. 5).

In contrast to the pyramids of numbers and biomass, which reflect the statics of the system (the number of organisms at a given moment), the pyramid of energy, reflecting the picture of the speed of passage of food mass (amount of energy) through each trophic level of the food chain, gives the most complete picture of the functional organization of communities.

The shape of this pyramid is not affected by changes in the size and metabolic rate of individuals, and if all energy sources are taken into account, the pyramid will always have a typical appearance with a wide base and a tapering apex. When constructing a pyramid of energy, a rectangle is often added to its base to show the influx of solar energy.

In 1942, the American ecologist R. Lindeman formulated the law of the energy pyramid (the law of 10 percent), according to which, on average, about 10% of the energy received at 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, movement, etc. As a result of metabolic processes, organisms lose about 90% of all energy in each link of the food chain, which is spent on maintaining their vital functions.

If a hare ate 10 kg of plant matter, then its own weight may increase by 1 kg. A fox or wolf, eating 1 kg of hare meat, increases its mass by only 100 g. In woody plants, this proportion is much lower due to the fact that wood is poorly absorbed by organisms. For grasses and seaweeds, this value is much greater, since they do not have difficult-to-digest tissues. However, the general pattern of the process of energy transfer remains: much less energy passes through the upper trophic levels than through the lower ones.

Target: expand knowledge about biotic environmental factors.

Equipment: herbarium plants, stuffed chordates (fish, amphibians, reptiles, birds, mammals), collections of insects, wet preparations of animals, illustrations of various plants and animals.

Progress:

1. Use the equipment and make two power circuits. Remember that the chain always starts with a producer and ends with a reducer.

________________ →________________→_______________→_____________

2. Remember your observations in nature and make two food chains. Label producers, consumers (1st and 2nd orders), decomposers.

________________ →________________→_______________→_____________

_______________ →________________→_______________→_____________

What is a food chain and what underlies it? What determines the stability of a biocenosis? State your conclusion.

Conclusion: ______________________________________________________________________________________________________________________________________________________________________________________________________________________________

3. Name the organisms that should be in the missing place in the following food chains

1. From the proposed list of living organisms, create a trophic network:

2. grass, berry bush, fly, tit, frog, grass snake, hare, wolf, rotting bacteria, mosquito, grasshopper. Indicate the amount of energy that moves from one level to another.

3. Knowing the rule for the transfer of energy from one trophic level to another (about 10%), build a pyramid of biomass for the third food chain (task 1). Plant biomass is 40 tons.

4. Conclusion: what do the rules of ecological pyramids reflect?

1. Wheat → mouse → snake → saprophytic bacteria

Algae → fish → seagull → bacteria

2. Grass (producer) – grasshopper (first order consumer) – birds (second order consumer) – bacteria.

Grass (producers) - elk (consumer of the first order) - wolf (consumer of the second order) - bacteria.

Conclusion: A food chain is a series of organisms that feed on each other in sequence. Food chains begin with autotrophs - green plants.

3. flower nectar → fly → spider → tit → hawk

wood → bark beetle → woodpecker

grass → grasshopper → frog → grass snake → snake eagle

leaves → mouse → cuckoo

seeds → sparrow → viper → stork

4. From the proposed list of living organisms, create a trophic network:

grass→grasshopper→frog→grass→rotting bacteria

bush→hare→wolf→fly→decay bacteria

These are chains, the network consists of the interaction of chains, but they cannot be indicated in text, well, something like this, the main thing is that the chain always begins with producers (plants), and always ends with decomposers.

The amount of energy always passes according to the rules of 10%; only 10% of the total energy passes to each next level.

Trophic (food) chain is a sequence of species of organisms that reflects the movement in the ecosystem of organic substances and the biochemical energy contained in them in the process of feeding organisms. The term comes from the Greek trophe - nutrition, food.

Conclusion: Consequently, the first food chain is pasture, because begins with producers, the second is detrital, because starts with dead organic matter.

All components of food chains are distributed into trophic levels. The trophic level is a link in the food chain.

Spike, plants of the grass family, monocots.

Target: expand knowledge about biotic environmental factors.

Equipment: herbarium plants, stuffed chordates (fish, amphibians, reptiles, birds, mammals), collections of insects, wet preparations of animals, illustrations of various plants and animals.

Progress:

1. Use the equipment and make two power circuits. Remember that the chain always starts with a producer and ends with a reducer.

Plants → insects→lizard → bacteria

Plants → grasshopper→ frog → bacteria

Remember your observations in nature and make two food chains. Label producers, consumers (1st and 2nd orders), decomposers.

Violet → Springtails→predatory mites→predatory centipedes→ bacteria

Producer - consumer1 - consumer2 - consumer2 - decomposer

Cabbage→ slug→ frog →bacteria

Producer – consumer1 - consumer2 - decomposer

What is a food chain and what underlies it? What determines the stability of a biocenosis? State your conclusion.

Conclusion:

Food (trophic) chain- a series of species of plants, animals, fungi and microorganisms that are connected to each other by the relationship: food - consumer (a sequence of organisms in which a gradual transfer of matter and energy occurs from source to consumer). Organisms of the next 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, a large part (up to 80-90%) of the potential energy is lost, 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. The stability of a biocenosis is determined by the diversity of its species composition. Producers- organisms capable of synthesizing organic substances from inorganic ones, that is, all autotrophs. Consumers- heterotrophs, organisms that consume ready-made organic substances created by autotrophs (producers). Unlike decomposers

3. Name the organisms that should be in the missing place in the following food chains.

1) Spider, fox

2) tree-eater-caterpillar, snake-hawk

3) caterpillar

4. From the proposed list of living organisms, create a trophic network:

grass, berry bush, fly, tit, frog, snake, hare, wolf, rotting bacteria, mosquito, grasshopper. Indicate the amount of energy that moves from one level to another.

1. Grass (100%) - grasshopper (10%) - frog (1%) - snake (0.1%) - rotting bacteria (0.01%).

2. Shrub (100%) - hare (10%) - wolf (1%) - rotting bacteria (0.1%).

3. Grass (100%) - fly (10%) - tit (1%) - wolf (0.1%) - rotting bacteria (0.01%).

4. Grass (100%) - mosquito (10%) - frog (1%) - snake (0.1%) - rotting bacteria (0.01%).

5. Knowing the rule for the transfer of energy from one trophic level to another (about 10%), build a pyramid of biomass for the third food chain (task 1). Plant biomass is 40 tons.

Grass (40 tons) -- grasshopper (4 tons) -- sparrow (0.4 tons) -- fox (0.04).

6. Conclusion: what do the rules of ecological pyramids reflect?

The rule of ecological pyramids very conditionally conveys the pattern of energy transfer from one level of nutrition to the next in the food chain. These graphic models were first developed by Charles Elton in 1927. According to this pattern, the total mass of plants should be an order of magnitude greater than that of herbivorous animals, and the total mass of herbivorous animals should be an order of magnitude greater than that of first-level predators, etc. to the very end of the food chain.

Laboratory work No. 1

Topic: Studying the structure of plant and animal cells under a microscope

Goal of the work: get acquainted with the structural features of plant and animal cells, show the fundamental unity of their structure.

Equipment: microscope , onion scale skin , epithelial cells from the human oral cavity, teaspoon, cover glass and slide glass, blue ink, iodine, notebook, pen, pencil, ruler

Progress:

1. Separate a piece of the skin covering it from the scales of the bulb and place it on a glass slide.

2. Apply a drop of a weak aqueous solution of iodine to the preparation. Cover the preparation with a coverslip.

3. Use a teaspoon to remove some mucus from the inside of your cheek.

4. Place the mucus on a slide and tint with blue ink diluted in water. Cover the preparation with a coverslip.

5. Examine both preparations under a microscope.

6. Enter the comparison results in tables 1 and 2.

7. Draw a conclusion about the work done.

Option #1.

Table No. 1 “Similarities and differences between plant and animal cells.”

Option number 2.

Table No. 2 “Comparative characteristics of plant and animal cells.”

containing genetic information (DNA molecules), performing the main functions: storage, transmission and implementation of hereditary information, ensuring protein synthesis.

Conclusion: _All plants and animals are made up of cells. A cell is an elementary unit of structure and vital activity of all living organisms. A plant cell has a thick cellulose membrane, vacuole and plastids; animals, unlike plants, have a thin glycogen membrane (carries out pinocytosis, endocytosis, exocytosis, phagocytosis), and there are no vacuoles (except in protozoa).

Laboratory work No. 2

Target: expand knowledge about biotic environmental factors.

Equipment: herbarium plants, stuffed chordates (fish, amphibians, reptiles, birds, mammals), collections of insects, wet preparations of animals, illustrations of various plants and animals.

Progress:

1. Use the equipment and make two power circuits. Remember that the chain always starts with a producer and ends with a reducer.

Plants → insects→lizard → bacteria

Plants → grasshopper→ frog → bacteria

Remember your observations in nature and make two food chains. Label producers, consumers (1st and 2nd orders), decomposers.

Violet → Springtails→predatory mites→predatory centipedes→ bacteria

Producer - consumer1 - consumer2 - consumer2 - decomposer

Cabbage→ slug→ frog →bacteria

Producer – consumer1 - consumer2 - decomposer

What is a food chain and what underlies it? What determines the stability of a biocenosis? State your conclusion.

Conclusion:

Food (trophic) chain- a series of species of plants, animals, fungi and microorganisms that are connected to each other by the relationship: food - consumer (a sequence of organisms in which a gradual transfer of matter and energy occurs from source to consumer). Organisms of the next 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, a large part (up to 80-90%) of the potential energy is lost, 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. The stability of a biocenosis is determined by the diversity of its species composition. Producers- organisms capable of synthesizing organic substances from inorganic ones, that is, all autotrophs. Consumers- heterotrophs, organisms that consume ready-made organic substances created by autotrophs (producers). Unlike decomposers

Consumers are not able to decompose organic substances into inorganic ones. Decomposers- microorganisms (bacteria and fungi) that destroy dead remains of living beings, turning them into inorganic and simple organic compounds.

3. Name the organisms that should be in the missing place in the following food chains.

1) Spider, fox

2) tree-eater-caterpillar, snake-hawk

3) caterpillar

4. From the proposed list of living organisms, create a trophic network:

grass, berry bush, fly, tit, frog, snake, hare, wolf, rotting bacteria, mosquito, grasshopper. Indicate the amount of energy that moves from one level to another.

1. Grass (100%) - grasshopper (10%) - frog (1%) - snake (0.1%) - rotting bacteria (0.01%).

2. Shrub (100%) - hare (10%) - wolf (1%) - rotting bacteria (0.1%).

3. Grass (100%) - fly (10%) - tit (1%) - wolf (0.1%) - rotting bacteria (0.01%).

4. Grass (100%) - mosquito (10%) - frog (1%) - snake (0.1%) - rotting bacteria (0.01%).

5. Knowing the rule for the transfer of energy from one trophic level to another (about 10%), build a pyramid of biomass for the third food chain (task 1). Plant biomass is 40 tons.

Grass (40 tons) -- grasshopper (4 tons) -- sparrow (0.4 tons) -- fox (0.04).

6. Conclusion: what do the rules of ecological pyramids reflect?

The rule of ecological pyramids very conditionally conveys the pattern of energy transfer from one level of nutrition to the next in the food chain. These graphic models were first developed by Charles Elton in 1927. According to this pattern, the total mass of plants should be an order of magnitude greater than that of herbivorous animals, and the total mass of herbivorous animals should be an order of magnitude greater than that of first-level predators, etc. to the very end of the food chain.

Laboratory work No. 1

The food chain is the sequential transformation of elements of inorganic nature (biogenic, etc.) with the help of plants and light into organic substances (primary production), and the latter - by animal organisms at subsequent trophic (food) links (steps) into their biomass.

The food chain starts with solar energy, and each link in the chain represents a change in energy. All food chains in a community form trophic relationships.

There are various connections between the components of an ecosystem, and first of all they are connected together by the flow of energy and the circulation of matter. The channels through which energy flows through a community are called food circuits. The energy of the sun's ray falling on the tops of trees or on the surface of a pond is captured by green plants - be it huge trees or tiny algae - and is used by them in the process of photosynthesis. This energy goes into the growth, development and reproduction of plants. Plants, as producers of organic matter, are called producers. Producers, in turn, serve as a source of energy for those who eat the plants and, ultimately, for the entire community.

The first consumers of organic matter are herbivorous animals - consumers of the first order. Predators that eat herbivorous prey act as second-order consumers. When moving from one link to another, energy is inevitably lost, so there are rarely more than 5-6 participants in a food chain. Decomposers complete the cycle - bacteria and fungi decompose animal corpses and plant remains, converting organic matter into minerals, which are again absorbed by producers.

The food chain includes all plants and animals, as well as the chemical elements contained in water necessary for photosynthesis. A food chain is a coherent linear structure of links, each of which is connected to neighboring links by “food-consumer” relationships. Groups of organisms, for example, specific biological species, act as links in the chain. In water, the food chain begins with the smallest plant organisms—algae—that live in the euphotic zone and use solar energy to synthesize organic substances from inorganic chemical nutrients and carbon dioxide dissolved in water. In the process of transferring the energy of food from its source - plants - through a number of organisms, which occurs by eating some organisms by others, there is a dissipation of energy, part of which turns into heat. With each successive transition from one trophic link (stage) to another, up to 80-90% of potential energy is lost. This limits the possible number of steps, or links in the chain, to usually four or five. The shorter the food chain, the more available energy is stored.

On average, 1 thousand kg of plants produces 100 kg of the body of herbivores. Predators that eat herbivores can build 10 kg of their biomass from this amount, and secondary predators only 1 kg. For example, a person eats a big fish. Its food consists of small fish that consume zooplankton, which lives off phytoplankton that capture solar energy.

Thus, to build 1 kg of a human body, 10 thousand kg of phytoplankton are required. Consequently, the mass of each subsequent link in the chain progressively decreases. This pattern is called the rule of the ecological pyramid. There is a pyramid of numbers, reflecting the number of individuals at each stage of the food chain, a pyramid of biomass - the amount of organic matter synthesized at each level, and a pyramid of energy - the amount of energy in food. They all have the same focus, differing in the absolute value of the digital values. In real conditions, power chains may have a different number of links. In addition, power circuits can intersect to form power networks. Almost all species of animals, with the exception of very specialized ones in terms of nutrition, use not one food source, but several). The greater the species diversity in a biocenosis, the more stable it is. So, in the plant-hare-fox food chain there are only three links. But the fox eats not only hares, but also mice and birds. The general pattern is that green plants are always at the beginning of the food chain, and predators are at the end. With each link in the chain, organisms become larger, they reproduce more slowly, and their number decreases. Species occupying the position of lower links, although provided with food, are themselves intensively consumed (mice, for example, are exterminated by foxes, wolves, owls). Selection goes in the direction of increasing fertility. Such organisms turn into a food source for higher animals without any prospects for progressive evolution.

In any geological epoch, organisms that were at the highest level in food relationships evolved at the highest speed, for example, in the Devonian, lobe-formed fish were piscivorous predators; in the Carboniferous period - predatory stegocephalians. In Permian - reptiles that hunted stegocephalians. Throughout the Mesozoic era, mammals were exterminated by predatory reptiles and only as a result of the extinction of the latter at the end of the Mesozoic did they occupy a dominant position, giving rise to a large number of forms.

Food relationships are the most important, but not the only type of relationships between species in a biocenosis. One species can influence another in different ways. Organisms can settle on the surface or inside the body of individuals of another species, can form a habitat for one or several species, and influence air movement, temperature, and illumination of the surrounding space. Examples of connections affecting species habitats are numerous. Sea acorns are marine crustaceans that lead a sessile lifestyle and often settle on the skin of whales. The larvae of many flies live in cow manure. A particularly important role in creating or changing the environment for other organisms belongs to plants. In thickets of plants, be it a forest or a meadow, the temperature fluctuates less than in open spaces, and the humidity is higher.
Often one species participates in the spread of another. Animals carry seeds, spores, pollen, and other smaller animals. Plant seeds can be captured by animals upon accidental contact, especially if the seeds or infructescences have special hooks (string, burdock). When eating fruits and berries that cannot be digested, the seeds are released along with the droppings. Mammals, birds and insects carry numerous mites on their bodies.

A connection between two links is established if one group of organisms acts as food for another group. The first link of the chain has no predecessor, that is, organisms from this group do not use other organisms as food, being producers. Most often, plants, mushrooms, and algae are found in this place. Organisms in the last link in the chain do not act as food for other organisms.

Each organism has a certain amount of energy, that is, we can say that each link in the chain has its own potential energy. During the feeding process, the potential energy of food is transferred to its consumer.

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.

In total, only about 1% of the radiant energy of the Sun falling on a plant is converted into potential energy of chemical bonds of synthesized organic substances and can be further used by heterotrophic organisms for nutrition. When an animal eats a plant, most of the energy contained in the 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. If a predator eats a herbivore, then again most of the energy contained in the food is lost. Due to such large losses of useful energy, food chains cannot be very long: they usually consist of no more than 3-5 links (food levels).

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 the rule of the ecological pyramid.

When transferring potential energy from link to link, up to 80-90% is lost in the form of heat. This fact limits the length of the food chain, which in nature usually does not exceed 4-5 links. The longer the trophic chain, the lower the production of its last link in relation to the production of the initial one.

In Baikal, the food chain in the pelagic zone consists of five links: algae - epishura - macroectopus - fish - seal or predatory fish (lenok, taimen, adult omul, etc.). Man participates in this chain as the last link, but he can consume products from lower links, for example, fish or even invertebrates when using crustaceans, aquatic plants, etc. as food. Short trophic chains are less stable and subject to greater fluctuations than long ones and complex in structure.

2. LEVELS AND STRUCTURAL ELEMENTS OF THE FOOD CHAIN

Usually, for each link in the chain, you can specify not one, but several other links connected to it by the “food-consumer” relationship. So not only cows, but also other animals eat grass, and cows are food not only for humans. The establishment of such connections turns the food chain into a more complex structure - food web.

In some cases, in a trophic network, it is possible to group individual links into levels in such a way that links at one level act only as food for the next level. This grouping is called trophic levels.

The initial level (link) of any trophic (food) chain in a reservoir is plants (algae). Plants do not eat anyone (with the exception of a small number of species of insectivorous plants - sundew, butterwort, bladderwort, nepenthes and some others); on the contrary, they are the source of life for all animal organisms. Therefore, the first step in the chain of predators are herbivores (grazing) animals. Following them are small carnivores that feed on herbivores, then a link of larger predators. In the chain, each subsequent organism is larger than the previous one. Predator chains contribute to the stability of the food chain.

The food chain of saprophytes is the final link in the trophic chain. Saprophytes feed on dead organisms. Chemicals formed during the decomposition of dead organisms are again consumed by plants - the producing organisms from which all trophic chains begin.

3. TYPES OF TROPHIC CHAINS

There are several classifications of trophic chains.

According to the first classification, there are three trophic chains in Nature (trophic means determined by Nature for destruction).

The first trophic chain includes the following free-living organisms:

herbivores;


predators - carnivores;


omnivores, including humans.


The basic principle of the food chain: “Who eats whom?”


The second trophic chain unites living things that metabolize everything and everyone. This task is performed by decomposers. They reduce the complex substances of dead organisms to simple substances. The property of the biosphere is that all representatives of the biosphere are mortal. The biological task of decomposers is to decompose the dead.


According to the second classification, there are two main types of trophic chains - pasture and detrital.


In the pasture trophic chain (grazing chain), the basis is made up of autotrophic organisms, then there are herbivorous animals consuming them (for example, zooplankton feeding on phytoplankton), then predators (consumers) of the 1st order (for example, fish consuming zooplankton), predators of the 2nd order order (for example, pike perch feeding on other fish). The trophic chains are especially long in the ocean, where many species (for example, tuna) occupy the place of fourth-order consumers.


In detrital trophic chains (decomposition chains), most common in forests, most plant production is not consumed directly by herbivores, but dies, then undergoes decomposition by saprotrophic organisms and mineralization. Thus, detrital trophic chains start from detritus, go to microorganisms that feed on it, and then to detritivores and to their consumers - predators. In aquatic ecosystems (especially in eutrophic reservoirs and at great depths of the ocean), this means that part of the production of plants and animals also enters detrital trophic chains.


CONCLUSION


All living organisms inhabiting our planet do not exist on their own, they depend on environment and experience its effects. This is a precisely coordinated complex of many environmental factors, and the adaptation of living organisms to them determines the possibility of the existence of all kinds of forms of organisms and the most varied formation of their life.


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


All living beings are objects of food for others, i.e. interconnected by energy relationships. Food connections in communities, these are mechanisms for transferring energy from one organism to another. In every community trophic connections are intertwined in a complex net.


Organisms of any species are potential food for many other species


trophic networks in biocenoses are very complex, and it seems that the energy entering them can migrate for a long time from one organism to another. In fact, the path of each specific portion of energy accumulated by green plants is short; it can be transmitted through no more than 4-6 links in a series consisting of organisms sequentially feeding on each other. Such series, in which it is possible to trace the ways in which the initial dose of energy is spent, are called food chains. The location of each link in the food chain is called a trophic level. The first trophic level is always producers, creators of organic matter; plant consumers belong to the second trophic level; carnivores, living off herbivorous forms - to the third; consuming other carnivores - to the fourth, etc. Thus, consumers of the first, second and third orders are distinguished, occupying different levels in the food chain. Naturally, the food specialization of consumers plays a major role in this. Species with a wide range of nutrition are included in food chains at different trophic levels.


BIBLIOGRAPHY

1. Akimova T.A., Khaskin V.V. Ecology. Tutorial. – M.: DONITI, 2005.
   

   Moiseev A.N. Ecology in the modern world // Energy. 2003. No. 4.