Large power chain. Lesson topic "food chain"
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 are ultimately returned 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. A 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. The first trophic level is occupied by autotrophs, or the 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 are cladocera and copepods, crab larvae, barnacles and bivalves(for example, mussels and oysters) - feed by filtering the smallest primary producers from the water. Together with protozoa, many of them form the bulk of the zooplankton that feed on phytoplankton. Life in oceans and lakes depends almost entirely on plankton, since almost everything begins with it food chains.
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 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 weeks, while fallen trees and 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 food 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 a fresh water body 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 effect 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 plants die, their substance is completely used by 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 poorly 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.
Nadezhda Lichman
NOD “Food chains in the forest” (preparatory group)
Target. Give children an idea of the relationships that exist in nature and food chains.
Tasks.
Expand children’s knowledge about the relationship between plants and animals, their food dependence on each other;
Develop the ability to create food chains and justify them;
Develop children’s speech by answering the teacher’s questions; enrich the vocabulary with new words: relationship in nature, link, chain, food chain.
Develop children's attention and logical thinking.
To promote interest in nature and curiosity.
Methods and techniques:
Visual;
Verbal;
Practical;
Problem-search.
Forms of work: conversation, task, explanation, didactic game.
Educational areas of development: cognitive development, speech development, social communicative development.
Material: toy bibabo grandmother, toy owl, illustrations of plants and animals (clover, mouse, owl, grass, hare, wolf, cards of plants and animals (leaf, caterpillar, bird, spikelets, mouse, fox, clock, balloon, meadow layout, emblems green and red according to the number of children.
Reflection.
Children sit on chairs in a semicircle. There's a knock on the door. Grandma (bibabo doll) comes to visit.
Hello guys! I came to visit you. I want to tell you a story that happened in our village. We live near the forest. Residents of our village graze cows in the meadow, which is located between the village and the forest. Our cows ate clover and gave a lot of milk. At the edge of the forest, in the hollow of an old large tree, there lived an owl who slept during the day and at night flew to hunt and hooted loudly. The owl's cry disturbed the villagers' sleep, and they drove it away. The owl was offended and flew away. And suddenly, after a while, the cows began to lose weight and give very little milk, since there was little clover, but a lot of mice appeared. We cannot understand why this happened. Help us get everything back!
Goal setting.
Guys, do you think we can help grandma and the villagers? (Children's answers)
How can we help the villagers? (Children's answers)
Joint activity of children and teacher.
Why did it happen that cows began to produce little milk?
(There is not enough clover.) The teacher puts a picture of clover on the table.
Why is there less clover?
(The mice gnawed.) The teacher posts a picture of a mouse.
Why are there so many mice? (The owl flew away.)
Who hunted mice?
(There is no one to hunt, the owl has flown away.) A picture of an owl is posted.
Guys, we have a chain: clover - mouse - owl.
Do you know what other chains there are?
The teacher shows a decoration, a chain, a door chain, a picture of a dog on a chain.
What is a chain? What does it consist of? (Children's answers)
From the links.
If one link of the chain breaks, what happens to the chain?
(The chain will break and collapse.)
Right. Let's look at our chain: clover - mouse - owl. This chain is called a food chain. Why do you think? Clover is food for a mouse, a mouse is food for an owl. That's why the chain is called the food chain. Clover, mouse, owl are links in this chain. Think about it: is it possible to remove a link from our food chain?
No, the chain will break.
Let's remove clover from our chain. What will happen to the mice?
They will have nothing to eat.
What if mice disappear?
What if an owl flies away?
What mistake did the villagers make?
They destroyed the food chain.
Right. What conclusion can we draw?
It turns out that in nature all plants and animals are interconnected. They cannot do without each other. What needs to be done to get cows to produce a lot of milk again?
Bring back the owl, restore the food chain. The children call the owl, the owl returns to the hollow of the big old tree.
So we helped the grandmother and all the villagers and brought everything back.
And now you and grandma and I will play the didactic game “Who Eats Who?”, practice and train grandma in drawing up food chains.
But first, let's remember who lives in the forest?
Animals, insects, birds.
What are the names of animals and birds that eat plants?
Herbivores.
What are the names of animals and birds that eat other animals?
What are the names of animals and birds that eat plants and other animals?
Omnivores.
Here are pictures of animals and birds. Circles of different colors are glued to the pictures depicting animals and birds. Predatory animals and birds are marked with a red circle.
Herbivores and birds are marked with a green circle.
Omnivores - with a blue circle.
On the children's tables are sets of pictures of birds, animals, insects and cards with a yellow circle.
Listen to the rules of the game. Each player has his own field, the presenter shows a picture and names the animal, you must make the correct food chain, who eats whom:
1 cell is plants, a card with a yellow circle;
2nd cell - these are animals that feed on plants (herbivores - with a green circle, omnivores - with a blue circle);
3rd cell - these are animals that feed on animals (predators - with a red circle; omnivores - blue). Cards with a dash close your chain.
The one who correctly assembles the chain wins; it can be long or short.
Independent activity of children.
Plants – mouse – owl.
Birch - hare - fox.
Pine seeds – squirrel – marten – hawk.
Grass – elk – bear.
Grass – hare – marten – eagle owl.
Nuts - chipmunk - lynx.
Acorns – boar – bear.
Cereal grain – mouse vole – ferret – owl.
Grass – grasshopper – frog – snake – falcon.
Nuts – squirrel – marten.
Reflection.
Did you like our communication with you?
What did you like?
What new have you learned?
Who remembers what a food chain is?
Is it important to preserve it?
In nature, everything is interconnected, and it is very important that this relationship is maintained. All forest inhabitants are important and valuable members of the forest brotherhood. It is very important that people do not interfere with nature, do not litter the environment and treat animals and flora with care.
Literature:
The main educational program of preschool education From birth to school, edited by N. E. Veraksa, T. S. Komarova, M. A. Vasilyeva. Mosaic – Synthesis. Moscow, 2015.
Kolomina N.V. Education of the fundamentals of ecological culture in kindergarten. M: Sphere shopping center, 2003.
Nikolaeva S. N. Methods of environmental education of preschool children. M, 1999.
Nikolaeva S.N. Let's get to know nature - get ready for school. M.: Education, 2009.
Salimova M.I. Ecology classes. Minsk: Amalfeya, 2004.
There are many holidays in the country,
But Women's Day is given to Spring,
After all, only women can
Create a spring holiday with affection.
I sincerely congratulate everyone
Happy International Women's Day !
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Image library:
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 eat, breathe, excrete products, and reproduce. After death, their bodies decompose into simple substances and return to the external environment.
The transfer of chemical elements from living organisms to the environment and back 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 circulation 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. The basic rule of the ecological pyramid is 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.
In ecosystems, producers, consumers and decomposers are united by complex processes of transfer of substances and energy, which is contained in food created mainly by plants.
The transfer of potential food energy created by plants through a number of organisms by eating some species by others is called a trophic (food) chain, and each link is called a trophic level.
All organisms that use the same type of food belong to the same trophic level.
In Fig.4. a diagram of the trophic chain is presented.
Fig.4. Food chain diagram.
Fig.4. Food chain diagram.
First trophic level form producers (green plants) that accumulate solar energy and create organic substances through the process of photosynthesis.
In this case, more than half of the energy stored in organic substances is consumed in the life processes of plants, turning into heat and dissipating in space, and the rest enters the food chain and can be used by heterotrophic organisms of subsequent trophic levels during nutrition.
Second trophic level form consumers of the 1st order - these are herbivorous organisms (phytophages) that feed on producers.
First-order consumers spend most of the energy contained in food to support their life processes, and the rest of the energy is used to build their own body, thereby transforming plant tissue into animal tissue.
Thus , 1st order consumers carry out the first, fundamental stage in the transformation of organic matter synthesized by producers.
Primary consumers can serve as a source of nutrition for 2nd order consumers.
Third trophic level form consumers of the 2nd order - these are carnivorous organisms (zoophages) that feed exclusively on herbivorous organisms (phytophages).
Second-order consumers carry out the second stage of transformation of organic matter in food chains.
However, the chemical substances from which the tissues of animal organisms are built are quite homogeneous and therefore the transformation of organic matter during the transition from the second trophic level of consumers to the third is not as fundamental as during the transition from the first trophic level to the second, where plant tissues are transformed into animals.
Secondary consumers can serve as a source of nutrition for third-order consumers.
Fourth trophic level form consumers of the 3rd order - these are carnivores that feed only on carnivorous organisms.
Last level of the food chain occupied by decomposers (destructors and detritivores).
Reducers-destructors (bacteria, fungi, protozoa) in the process of their life activity decompose organic remains of all trophic levels of producers and consumers into mineral substances, which are returned to the producers.
All links of the food chain are interconnected and interdependent.
Between them, from the first to the last link, the transfer of substances and energy takes place. However, it should be noted that when energy is transferred from one trophic level to another, it is lost. As a result, the power chain cannot be long and most often consists of 4-6 links.
However, such food chains in their pure form are usually not found in nature, since each organism has several food sources, i.e. uses several types of food, and is itself used as a food product by numerous other organisms from the same food chain or even from different food chains.
For example:
Omnivorous organisms consume both producers and consumers as food, i.e. are simultaneously consumers of the first, second, and sometimes third order;
a mosquito that feeds on the blood of humans and predatory animals is at a very high trophic level. But the swamp sundew plant feeds on mosquitoes, which is thus both a producer and a consumer of a high order.
Therefore, almost any organism that is part of one trophic chain can simultaneously be part of other trophic chains.
Thus, trophic chains can branch and intertwine many times, forming complex food webs or trophic (food) webs , in which the multiplicity and diversity of food connections acts as an important mechanism for maintaining the integrity and functional stability of ecosystems.
In Fig.5. shows a simplified diagram of a power network for a terrestrial ecosystem.
Human intervention in natural communities of organisms through the intentional or unintentional elimination of a species often has unpredictable negative consequences and leads to disruption of the stability of ecosystems.
Fig.5. Scheme of the trophic network.
There are two main types of trophic chains:
pasture chains (grazing chains or consumption chains);
detrital chains (decomposition chains).
Pasture chains (grazing chains or consumption chains) are processes of synthesis and transformation of organic substances in trophic chains.
Pasture chains begin with producers. Living plants are eaten by phytophages (consumers of the first order), and the phytophages themselves are food for carnivores (consumers of the second order), which can be eaten by consumers of the third order, etc.
Examples of grazing chains for terrestrial ecosystems:
3 links: aspen → hare → fox; plant → sheep → human.
4 links: plants → grasshoppers → lizards → hawk;
nectar of plant flower → fly → insectivorous bird →
bird of prey.
5 links: plants → grasshoppers → frogs → snakes → eagle.
Examples of grazing chains for aquatic ecosystems:→
3 links: phytoplankton → zooplankton → fish;
5 links: phytoplankton → zooplankton → fish → predatory fish →
birds of prey.
Detrital chains (decomposition chains) are processes of step-by-step destruction and mineralization of organic substances in trophic chains.
Detrital chains begin with the gradual destruction of dead organic matter by detritivores, which successively replace each other in accordance with a specific type of nutrition.
At the last stages of destruction processes, reducers-destructors function, mineralizing the remains of organic compounds into simple inorganic substances, which are again used by producers.
For example, when decomposing dead wood, they successively replace each other: beetles → woodpeckers → ants and termites → destructive fungi.
Detrital chains are most common in forests, where most (about 90%) of the annual increase in plant biomass is not consumed directly by herbivores, but dies and enters these chains in the form of leaf litter, then undergoing decomposition and mineralization.
In aquatic ecosystems, most of the matter and energy is included in grazing chains, and in terrestrial ecosystems, detrital chains are most important.
Thus, at the level of consumers, the flow of organic matter is divided into different groups of consumers:
living organic matter follows grazing chains;
dead organic matter goes along detrital chains.
The energy of the Sun plays a huge role in the reproduction of life. The amount of this energy is very large (approximately 55 kcal per 1 cm 2 per year). Of this amount, producers - green plants - record no more than 1-2% of energy as a result of photosynthesis, and deserts and the ocean - hundredths of a percent.
The number of links in the food chain may vary, but usually there are 3-4 (less often 5). The fact is that so little energy reaches the final link of the food chain that it will not be enough if the number of organisms increases.
Rice. 1. Food chains in a terrestrial ecosystem
A set of organisms united by one type of nutrition and occupying a certain position in the food chain is called trophic level. Organisms that receive their energy from the Sun through the same number of steps belong to the same trophic level.
The simplest food chain (or food chain) may consist of phytoplankton, followed by larger herbivorous planktonic crustaceans (zooplankton), and ending with a whale (or small predators) that filter these crustaceans from the water.
Nature is complex. All its elements, living and nonliving, are one whole, a complex of interacting and interconnected phenomena and creatures adapted to each other. These are links of one chain. And if you remove at least one such link from the overall chain, the results may be unexpected.
Breaking food chains can have a particularly negative impact on forests—whether they are temperate forest biocenoses or tropical forest biocenoses that are rich in species diversity. Many species of trees, shrubs, or herbaceous plants rely on a specific pollinator—bees, wasps, butterflies, or hummingbirds—that live within the plant species' range. As soon as the last flowering tree or herbaceous plant dies, the pollinator will be forced to leave this habitat. As a result, phytophages (herbivores) feeding on these plants or tree fruits will die. The predators that hunted phytophages will be left without food, and then the changes will successively affect the remaining links of the food chain. As a result, they will affect humans, since they have their own specific place in the food chain.
Food chains can be divided into two main types: grazing and detritus. Food prices that begin with autotrophic photosynthetic organisms are called pasture, or chains of eating. At the top of the pasture chain there are green plants. At the second level of the pasture chain there are usually phytophages, i.e. animals that eat plants. An example of a grassland food chain is the relationships between organisms in a floodplain meadow. Such a chain begins with a meadow flowering plant. The next link is a butterfly that feeds on the nectar of a flower. Then comes the inhabitant of wet habitats - the frog. Its protective coloration allows it to ambush prey, but does not save it from another predator - the common snake. The heron, having caught the snake, closes the food chain in the floodplain meadow.
If a food chain begins with dead plant remains, carcasses and animal excrement - detritus, it is called detrital, or chain of decomposition. The term "detritus" means a product of decay. It is borrowed from geology, where detritus refers to the products of rock destruction. In ecology, detritus is organic matter involved in the process of decomposition. Such chains are typical for communities at the bottom of deep lakes and oceans, where many organisms feed on the settling of detritus formed by dead organisms from the upper illuminated layers of the reservoir.
In forest biocenoses, the detrital chain begins with the decomposition of dead organic matter by saprophagous animals. The most active participation in the decomposition of organic matter here is taken by soil invertebrate animals (arthropods, worms) and microorganisms. There are also large saprophages - insects that prepare a substrate for organisms that carry out mineralization processes (for bacteria and fungi).
Unlike the pasture chain, the size of organisms when moving along the detritus chain does not increase, but, on the contrary, decreases. So, on the second level there may be gravedigging insects. But the most typical representatives of the detrital chain are fungi and microorganisms that feed on dead matter and complete the process of decomposition of bioorganics to the state of simple mineral and organic substances, which are then consumed in dissolved form by the roots of green plants at the top of the pasture chain, thereby starting a new circle of movement of matter.
Some ecosystems are dominated by pastures, while others are dominated by detritus chains. For example, a forest is considered an ecosystem dominated by detritus chains. In the ecosystem of a rotting stump, there is no grazing chain at all. At the same time, for example, in sea surface ecosystems, almost all producers represented by phytoplankton are consumed by animals, and their corpses sink to the bottom, i.e. leave the published ecosystem. Such ecosystems are dominated by grazing or grazing food chains.
General rule concerning any food chain, states: at each trophic level of a community, most of the energy absorbed from food is spent on maintaining life, is dissipated and can no longer be used by other organisms. Thus, the food consumed at each trophic level is not completely assimilated. A significant part of it is spent on metabolism. As we move to each subsequent link in the food chain, the total amount of usable energy transferred to the next higher trophic level decreases.
