Long food chain. Food chains and trophic levels

Cycle of substances in nature and food chains

All living organisms are active participants in the cycle of substances on the planet. Using oxygen, carbon dioxide, water, mineral salts and other substances, living organisms feed, breathe, excrete products, and reproduce. After death, their bodies decompose into simple substances and return to the external environment.

Transfer chemical elements from living organisms to environment and back again does not stop for a second. Thus, plants (autotrophic organisms) take carbon dioxide, water and mineral salts from the external environment. In doing so, they create organic matter and release oxygen. Animals (heterotrophic organisms), on the contrary, inhale the oxygen released by plants, and by eating plants, they assimilate organic substances and release carbon dioxide and food debris. Fungi and bacteria eat the remains of living organisms and convert organic substances into minerals, which accumulate in soil and water. And minerals are again absorbed by plants. This is how nature maintains a constant and endless cycle of substances and maintains the continuity of life.

The cycle of substances and all the transformations associated with it require a constant flow of energy. The source of such energy is the Sun.

On earth, plants absorb carbon from the atmosphere through photosynthesis. Animals eat plants, passing carbon up the food chain, which we'll talk about later. When plants and animals die, they transfer carbon back to the earth.

At the surface of the ocean, carbon dioxide from the atmosphere dissolves into the water. Phytoplankton absorb it for photosynthesis. Animals that eat plankton exhale carbon into the atmosphere and thereby transmit it further along the food chain. After phytoplankton die, they can be recycled in surface waters or settle to the ocean floor. Over millions of years, this process has transformed the ocean floor into the planet's rich carbon reservoir. Cold currents transport carbon to the surface. When water is heated, it is released as a gas and enters the atmosphere, continuing the cycle.

Water constantly circulates between the seas, the atmosphere and the land. Under the rays of the sun it evaporates and rises into the air. There, droplets of water collect into clouds and clouds. They fall to the ground as rain, snow or hail, which turns back into water. Water is absorbed into the ground and returned to the seas, rivers and lakes. And everything starts all over again. This is how the water cycle occurs in nature.

Most of the water is evaporated by the oceans. The water in it is salty, and the water that evaporates from its surface is fresh. Thus, the ocean is the world’s “factory” of fresh water, without which life on Earth is impossible.

THREE STATES OF MATTER. There are three states of matter: solid, liquid and gaseous. They depend on temperature and pressure. IN everyday life we can observe water in all three of these states. Moisture evaporates and goes from a liquid state to a gaseous state, that is, water vapor. It condenses and turns into liquid. At sub-zero temperatures Water freezes and turns into a solid state - ice.

The cycle of complex substances in living nature includes food chains. This is a linear closed sequence in which each living creature feeds on someone or something and itself serves as food for another organism. Within the grassland food chain, organic matter is created by autotrophic organisms such as plants. Plants are eaten by animals, which in turn are eaten by other animals. Decomposer fungi decompose organic remains and serve as the beginning of the detrital trophic chain.

Each link in the food chain is called a trophic level (from the Greek word “trophos” - “nutrition”).
1. Producers, or producers, produce organic substances from inorganic ones. Producers include plants and some bacteria.
2. Consumers, or consumers, consume ready-made organic substances. First-order consumers feed on producers. 2nd order consumers feed on 1st order consumers. Consumers of the 3rd order feed on consumers of the 2nd order, etc.
3. Reducers, or destroyers, destroy, that is, mineralize organic substances to inorganic ones. Decomposers include bacteria and fungi.

DETRITAL FOOD CHAINS. There are two main types of food chains - grazing (grazing chains) and detrital (decomposition chains). The basis of the pasture food chain is made up of autotrophic organisms that are eaten by animals. And in detrital trophic chains, most of the plants are not consumed by herbivores, but die and then decompose by saprotrophic organisms (for example, earthworms) and are mineralized. Thus, detrital trophic chains start from detritus, and then go to detritivores and their consumers - predators. On land, these are the chains that predominate.

WHAT IS AN ECOLOGICAL PYRAMID? An ecological pyramid is a graphical representation of the relationships between different trophic levels of a food chain. The food chain cannot contain more than 5-6 links, because when moving to each next link, 90% of the energy is lost. Basic Rule ecological pyramid based on 10%. So, for example, to form 1 kg of mass, a dolphin needs to eat about 10 kg of fish, and they, in turn, need 100 kg of food - aquatic vertebrates, which need to eat 1000 kg of algae and bacteria to form such mass. If these quantities are depicted on an appropriate scale in the order of their dependence, then a kind of pyramid is actually formed.

FOOD NETWORKS. Often the interactions between living organisms in nature are more complex and visually resemble a network. Organisms, especially carnivores, can feed on a wide variety of creatures from different food chains. Thus, food chains intertwine to form food webs.

Introduction

1. Food chains and trophic levels

2. Food webs

3. Freshwater food connections

4. Forest food connections

5. Energy losses in power circuits

6. Ecological pyramids

6.1 Pyramids of numbers

6.2 Biomass pyramids

Conclusion

References

Introduction

Organisms in nature are connected by a commonality of energy and nutrients. The entire ecosystem can be likened to a single mechanism that consumes energy and nutrients to do work. Nutrients initially originate from the abiotic component of the system, to which they ultimately return either as waste products or after the death and destruction of organisms.

Within an ecosystem, energy-containing organic substances are created by autotrophic organisms and serve as food (a source of matter and energy) for heterotrophs. Typical example: An animal eats plants. This animal, in turn, can be eaten by another animal, and in this way energy can be transferred through a number of organisms - each subsequent one feeds on the previous one, supplying it with raw materials and energy. This sequence is called a food chain, and each link is called a trophic level.

The purpose of the essay is to characterize food connections in nature.

1. Food chains and trophic levels

Biogeocenoses are very complex. They always have many parallel and complexly intertwined power circuits, and total number species are often measured in hundreds and even thousands. Almost always different types They feed on several different objects and themselves serve as food for several members of the ecosystem. The result is a complex network of food connections.

Each link in the food chain is called a trophic level. First trophic level are occupied by autotrophs, or so-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.

The primary producers are autotrophic organisms, mainly green plants. Some prokaryotes, namely blue-green algae and a few species of bacteria, also photosynthesize, but their contribution is relatively small. Photosynthetics convert solar energy(light energy) into chemical energy contained in the organic molecules from which tissues are built. Chemosynthetic bacteria, which extract energy from inorganic compounds, also make a small contribution to the production of organic matter.

In aquatic ecosystems, the main producers are algae - often small single-celled organisms that make up the phytoplankton of the surface layers of oceans and lakes. On land, most of the primary production is supplied by more highly organized forms related to gymnosperms and angiosperms. They form forests and meadows.

Primary consumers feed on primary producers, i.e. they are herbivores. On land, typical herbivores include many insects, reptiles, birds and mammals. Most important groups herbivorous mammals are rodents and ungulates. The latter include grazing animals such as horses, sheep, and cattle, which are adapted to running on their toes.

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

Plant material (e.g. nectar) → fly → spider →

→ shrew → owl

Juice rose bush→ aphid → ladybug→ spider → insectivorous bird → bird of prey

There are two main types of food chains – grazing and detrital. Above were examples of pasture chains in which the first trophic level is occupied by green plants, the second by pasture animals and the third by predators. The bodies of dead plants and animals still contain energy and " building material”, as well as intravital excretions, such as urine and feces. These organic materials are decomposed by microorganisms, namely fungi and bacteria, living as saprophytes on organic residues. Such organisms are called decomposers. They release digestive enzymes onto dead bodies or waste products and absorb the products of their digestion. The rate of decomposition may vary. Organic matter urine, feces and animal carcasses are consumed within a few weeks, while fallen trees and the branches can take many years to decompose. A very significant role in the decomposition of wood (and other plant debris) is played by fungi, which secrete the enzyme cellulose, which softens the wood, and this allows small animals to penetrate and absorb the softened material.

Pieces of partially decomposed material are called detritus, and many small animals (detritivores) feed on them, speeding up the decomposition process. Since both true decomposers (fungi and bacteria) and detritivores (animals) are involved in this process, both are sometimes called decomposers, although in reality this term refers only to saprophytic organisms.

Larger organisms can, in turn, feed on detritivores, and then a different type of food chain is created - a chain, a chain starting with detritus:

Detritus → detritivore → predator

Detritivores of forest and coastal communities include earthworm, woodlice, carrion fly larva (forest), polychaete, scarlet fly, holothurian (coastal zone).

Here are two typical detrital food chains in our forests:

Leaf litter → Earthworm → Blackbird → Sparrowhawk

Dead animal → Carrion fly larvae → Grass frog → Common grass snake

Some typical detritivores are earthworms, woodlice, bipeds and smaller ones (<0,5 мм) животные, такие, как клещи, ногохвостки, нематоды и черви-энхитреиды.

2. Food webs

In food chain diagrams, each organism is represented as feeding on other organisms of one type. However, actual food relationships in an ecosystem are much more complex, since an animal may feed on different types of organisms from the same food chain or even from different food chains. This is especially true for predators of the upper trophic levels. Some animals eat both other animals and plants; they are called omnivores (this is the case, in particular, with humans). In reality, food chains are intertwined in such a way that a food (trophic) web is formed. A food web diagram can only show a few of the many possible connections, and it usually includes only one or two predators from each of the upper trophic levels. Such diagrams illustrate nutritional relationships between organisms in an ecosystem and provide the basis for quantitative studies of ecological pyramids and ecosystem productivity.

3. Freshwater food connections

The food chains of fresh water bodies consist of several successive links. For example, protozoa, which are eaten by small crustaceans, feed on plant debris and the bacteria that develop on them. The crustaceans, in turn, serve as food for fish, and the latter can be eaten by predatory fish. Almost all species do not feed on one type of food, but use different food objects. Food chains are intricately intertwined. An important general conclusion follows from this: if any member of the biogeocenosis falls out, then the system is not disrupted, since other food sources are used. The greater the species diversity, the more stable the system.

The primary source of energy in aquatic biogeocenosis, as in most ecological systems, is sunlight, thanks to which plants synthesize organic matter. Obviously, the biomass of all animals existing in a reservoir completely depends on the biological productivity of plants.

Often the reason for the low productivity of natural reservoirs is a lack of minerals (especially nitrogen and phosphorus) necessary for the growth of autotrophic plants, or unfavorable acidity of the water. The application of mineral fertilizers, and in the case of an acidic environment, liming of reservoirs, contributes to the proliferation of plant plankton, which feeds animals that serve as food for fish. In this way, the productivity of fishery ponds is increased.

4. Forest food connections

The richness and diversity of plants, which produce enormous amounts of organic matter that can be used as food, cause the development in oak forests of numerous consumers from the animal world, from protozoa to higher vertebrates - birds and mammals.

Food chains in the forest are intertwined into a very complex food web, so the loss of one species of animal usually does not significantly disrupt the entire system. The importance of different groups of animals in biogeocenosis is not the same. The disappearance, for example, in most of our oak forests of all large herbivorous ungulates: bison, deer, roe deer, elk - would have little impact on the overall ecosystem, since their numbers, and therefore biomass, have never been large and did not play a significant role in the general cycle of substances . But if herbivorous insects disappeared, the consequences would be very serious, since insects perform the important function of pollinators in biogeocenosis, participate in the destruction of litter and serve as the basis for the existence of many subsequent links in food chains.

Of great importance in the life of the forest are the processes of decomposition and mineralization of the mass of dying leaves, wood, animal remains and products of their vital activity. Of the total annual increase in biomass of above-ground parts of plants, about 3-4 tons per 1 hectare naturally dies and falls, forming the so-called forest litter. A significant mass also consists of dead underground parts of plants. With litter, most of the minerals and nitrogen consumed by plants return to the soil.

Animal remains are very quickly destroyed by carrion beetles, leather beetles, carrion fly larvae and other insects, as well as putrefactive bacteria. Fiber and other durable substances, which make up a significant part of plant litter, are more difficult to decompose. But they also serve as food for a number of organisms, such as fungi and bacteria, which have special enzymes that break down fiber and other substances into easily digestible sugars.

As soon as the plants die, their substance is completely used by the destroyers. A significant part of the biomass is made up of earthworms, which do a tremendous job of decomposing and moving organic matter in the soil. The total number of insects, oribatid mites, worms and other invertebrates reaches many tens and even hundreds of millions per hectare. The role of bacteria and lower, saprophytic fungi is especially important in the decomposition of litter.

5. Energy losses in power circuits

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.

6. Ecological pyramids

6.1 Pyramids of numbers

To study the relationships between organisms in an ecosystem and to graphically represent these relationships, it is more convenient to use ecological pyramids rather than food web diagrams. In this case, the number of different organisms in a given territory is first counted, grouping them by trophic levels. After such calculations, it becomes obvious that the number of animals progressively decreases during the transition from the second trophic level to subsequent ones. The number of plants at the first trophic level also often exceeds the number of animals that make up the second level. This can be depicted as a pyramid of numbers.

For convenience, the number of organisms at a given trophic level can be represented as a rectangle, the length (or area) of which is proportional to the number of organisms living in a given area (or in a given volume, if it is an aquatic ecosystem). The figure shows a population pyramid reflecting the real situation in nature. Predators located at the highest trophic level are called final predators.

When sampling - in other words, at a given point in time - the so-called standing biomass, or standing yield, is always determined. It is important to understand that this value does not contain any information about the rate of biomass production (productivity) or its consumption; otherwise errors may occur for two reasons:

1. If the rate of biomass consumption (loss due to consumption) approximately corresponds to the rate of its formation, then the standing crop does not necessarily indicate productivity, i.e. about the amount of energy and matter moving from one trophic level to another over a given period of time, for example, a year. For example, a fertile, intensively used pasture may have lower standing grass yields and higher productivity than a less fertile but little used pasture.

2. Small-sized producers, such as algae, are characterized by a high renewal rate, i.e. high growth and reproduction rates, balanced by their intensive consumption as food by other organisms and natural death. Thus, although standing biomass may be small compared to large producers (such as trees), productivity may not be less because trees accumulate biomass over a long period of time. In other words, phytoplankton with the same productivity as a tree will have much less biomass, although it could support the same mass of animals. In general, populations of large and long-lived plants and animals have a lower renewal rate compared to small and short-lived ones and accumulate matter and energy over a longer period of time. Zooplankton have greater biomass than the phytoplankton on which they feed. This is typical for planktonic communities of lakes and seas at certain times of the year; the biomass of phytoplankton exceeds the biomass of zooplankton during the spring “blooming”, but in other periods the opposite relationship is possible. Such apparent anomalies can be avoided by using energy pyramids.

Conclusion

Completing the work on the abstract, we can draw the following conclusions. A functional system that includes a community of living beings and their habitat is called an ecological system (or ecosystem). In such a system, connections between its components arise primarily on a food basis. A food chain indicates the path of movement of organic matter, as well as the energy and inorganic nutrients it contains.

In ecological systems, in the process of evolution, chains of interconnected species have developed that successively extract materials and energy from the original food substance. This sequence is called a food chain, and each link is called a trophic level. The first trophic level is occupied by autotrophic organisms, or so-called primary producers. Organisms of the second trophic level are called primary consumers, the third - secondary consumers, etc. The last level is usually occupied by decomposers or detritivores.

Food connections in an ecosystem are not straightforward, since the components of the ecosystem are in complex interactions with each other.

References

1. Amos W.H. The living world of rivers. - L.: Gidrometeoizdat, 1986. - 240 p.

2. Biological encyclopedic dictionary. - M.: Soviet Encyclopedia, 1986. - 832 p.

3. Ricklefs R. Fundamentals of General Ecology. - M.: Mir, 1979. - 424 p.

4. Spurr S.G., Barnes B.V. Forest ecology. - M.: Timber Industry, 1984. - 480 p.

5. Stadnitsky G.V., Rodionov A.I. Ecology. - M.: Higher School, 1988. - 272 p.

6. Yablokov A.V. Population biology. - M.: Higher School, 1987. -304 p.

Target: expand knowledge about biotic environmental factors.

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

Work 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 begins 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 from the sun's rays falling on the tops of trees or on the surface of a pond is captured by green plants - be they huge trees or tiny algae - and 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. The producers, in turn, provide 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 food energy from its source - plants - through a number of organisms, which occurs by eating some organisms by others, energy is dissipated, 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 of 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 there are always green plants at the beginning of the food chain, and predators 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-spiked fish - 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 dung. 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.

All these diverse connections provide the possibility of the existence of species in the biocenosis, keep them close to each other, turning them into stable self-regulating communities.

A connection between two links is established if one group of organisms acts as food for another group. The first link in 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.

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 (chains of decomposition), 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 that inhabit our planet do not exist on their own; they depend on the environment and experience its influence. 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 cycle 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 mass; 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.

REFERENCES

Akimova T.A., Khaskin V.V. Ecology. Study guide. – M.: DONITI, 2005.

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

In living nature there are practically no living organisms that do not eat other creatures or are not food for someone. Thus, many insects feed on plants. The insects themselves are prey for larger creatures. Certain organisms are the links from which the food chain is formed. Examples of such “dependence” can be found everywhere. Moreover, in any such structure there is a first initial level. As a rule, these are green plants. What are some examples of food? What organisms can be links? How does the interaction between them occur? More on this later in the article.

General information

The food chain, examples of which will be given below, is a certain set of microorganisms, fungi, plants, animals. Each link is at its own level. This “dependence” is built on the principle “food - consumer”. At the top of many food chains is man. The higher the population density in a particular country, the fewer links will be contained in the natural sequence, since people are forced in such conditions to eat plants more often.

Number of levels

How does interaction occur within ecological pyramids?

How does the food chain work? The examples given above show that each subsequent link should be at a higher level of development than the previous one. As already mentioned, relationships in any ecological pyramid are built on the “food-consumer” principle. Due to the consumption of some organisms by others, energy is transferred from lower to higher levels. The result occurs in nature.

Food chain. Examples

Conventionally, several types of ecological pyramids can be distinguished. There is, in particular, a grazing food chain. Examples that can be seen in nature are sequences where the transfer of energy occurs from lower (protozoan) organisms to higher (predator) organisms. Such pyramids, in particular, include the following sequences: “caterpillars-mice-vipers-hedgehogs-foxes”, “rodents-predators”. The other, detrital food chain, examples of which will be given below, is a sequence in which the biomass is not consumed by predators, but a process of decay with the participation of microorganisms takes place. It is believed that this ecological pyramid begins with plants. This is, in particular, what the forest food chain looks like. Examples include the following: “fallen leaves—rotting with the participation of microorganisms,” “dead (carnivorous)—predators—centipedes—bacteria.”

Producers and consumers

In a large body of water (ocean, sea), planktonic organisms are food for Cladocera (animal filter feeders). They, in turn, are prey for predatory mosquito larvae. A certain type of fish feeds on these organisms. They are eaten by larger predatory individuals. This ecological pyramid is an example of a sea food chain. All organisms acting as links are at different trophic levels. At the first stage there are producers, at the next - consumers of the first order (consumers). The third trophic level includes 2nd order consumers (primary carnivores). They, in turn, serve as food for secondary predators - third-order consumers, and so on. As a rule, ecological pyramids of land include three to five links.

open water

Beyond the shelf sea, in the place where the slope of the continent breaks off more or less abruptly towards the deep-sea plain, the open sea begins. This area has predominantly blue and clear water. This is due to the absence of inorganic suspended compounds and a smaller volume of microscopic planktonic plants and animals (phyto- and zooplankton). In some areas, the surface of the water has a particularly bright blue color. For example, in such cases they talk about so-called ocean deserts. In these zones, even at a depth of thousands of meters, sensitive equipment can detect traces of light (in the blue-green spectrum). The open sea is characterized by the complete absence of various larvae of benthic organisms (echinoderms, mollusks, crustaceans) in the composition of zooplankton, the number of which sharply decreases with distance from the coast. Both in shallow water and in wide open spaces, sunlight is the only source of energy. As a result of photosynthesis, phytoplankton uses chlorophyll to form organic compounds from carbon dioxide and water. This is how the so-called primary products are formed.

Links in the sea food chain

Organic compounds synthesized by algae are transferred indirectly or directly to all organisms. The second link in the food chain in the sea is animal filter feeders. The organisms that make up phytoplankton are microscopically small in size (0.002-1mm). They often form colonies, but their size does not exceed five millimeters. The third link is carnivores. They are filter feeders. There are quite a lot of such organisms in the shelf, as well as in the open seas. These, in particular, include siphonophores, ctenophores, jellyfish, copepods, chaetognaths, and carinarids. Among fish, herring should be classified as filter feeders. Their main food is the large aggregations that form in northern waters. The fourth link is considered to be large predatory fish. Some species are of commercial importance. The final link should also include cephalopods, toothed whales and seabirds.

Nutrient transfer

The transfer of organic compounds within food chains is accompanied by significant energy losses. This is mainly due to the fact that most of it is spent on metabolic processes. About 10% of the energy is converted into body matter by the organism. Therefore, for example, the anchovy, which feeds on planktonic algae and is part of an exceptionally short food chain, can develop in such huge quantities as it does in the Peruvian Current. The transfer of food into the twilight and deep zones from the light zone is due to active vertical migrations of zooplankton and certain fish species. Animals moving up and down end up at different depths at different times of the day.

Conclusion

It should be said that linear food chains are quite rare. Most often, ecological pyramids include populations belonging to several levels at once. The same species can eat both plants and animals; carnivores can feed on both first- and second-order consumers; Many animals consume living and dead organisms. Due to the complexity of linkages, the loss of a species often has virtually no effect on the state of the ecosystem. Those organisms that took the missing link for food may well find another source of food, and other organisms begin to consume the food of the missing link. This way the community as a whole maintains balance. A more sustainable ecological system will be one in which there are more complex food chains, consisting of a large number of links, including many different species.