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 same number steps.
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, be it forest biocenoses temperate zone or distinguished by rich species diversity biocenoses tropical forest. 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 its prey, but does not save it from another predator - the common grass 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 destruction rocks. 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. Pastures predominate in such ecosystems. food chains, or chains of eating.
General rule concerning any the food chain, states: at each trophic level of the 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. When moving to each subsequent link in the food chain total usable energy transferred to the next higher trophic level decreases.
Every living creature on our planet needs nutrition for normal development. Nutrition is the process of receiving energy and necessary chemical elements into a living organism. The source of food for some animals is other plants and animals. The process of transferring energy and nutrients from one living organism to another occurs by eating one by another. Some animals and plants serve as food for others. Thus, energy can be transferred through several links.
The set of all links in this process is called power circuit. An example of a food chain can be seen in the forest, when a bird eats a worm and then itself becomes food for a lynx.
All types of living organisms, depending on the place they occupy, are divided into three types:
- producers;
- consumers;
- decomposers.
Producers are living organisms that produce their own nutrients. For example, plants or algae. To produce organic substances, producers can use sunlight or simple inorganic compounds, such as carbon dioxide or hydrogen sulfide. Such organisms are also called autotrophic. Autotrophs are the first link of any food chain and form its basis, and the energy received by these organisms supports each subsequent link.
Consumers
Consumers are the next link. The role of consumers is played by heterotrophic organisms, that is, those that do not produce organic substances on their own, but use other organisms as food. Consumers can be divided into several levels. For example, the first level includes all herbivores, some types of microorganisms, as well as plankton. Rodents, hares, moose, wild boars, antelopes and even hippos - all belong to the first level.
The second level includes small predators, such as wild cats, minks, ferrets, plankton-eating fish, owls, and snakes. These animals serve as food for third-level consumers - larger predators. These are animals such as fox, lynx, lion, hawk, pike, etc. Such predators are also called apex predators. Top predators do not necessarily eat only those at the previous level. For example, a small fox can become prey for a hawk, and a lynx can hunt both rodents and owls.
Decomposers
These are organisms that process animal waste products and their dead flesh into inorganic compounds. These include some types of fungi, decay bacteria. The role of decomposers is to close the cycle of substances in nature. They return water and simple inorganic compounds to the soil and air, which producers use for their life activities. Decomposers process not only dead animals, but also, for example, fallen leaves that begin to rot in the forest or dry grass in the steppe.
Trophic networks
All food chains exist in constant relationship with each other. The collection of several food chains constitutes a trophic web. This is a kind of pyramid consisting of several levels. Each level is formed by certain links in the food chain. For example, in chains:
- fly - frog - heron;
- grasshopper - snake - falcon;
The fly and grasshopper will belong to the first trophic level, the snake and frog to the second, and the heron and falcon to the third.
Types of food chains: examples in nature
They are divided into pasture and detritus. Pastoral food chains distributed in steppes and the world's oceans. The beginning of these chains are producers. For example, grass or algae. Next come first-order consumers, for example, herbivores or baby fish and small crustaceans that feed on algae. Next in the chain are small predators, such as foxes, minks, ferrets, perches, and owls. Superpredators, such as lions, bears, and crocodiles, complete the chain. Superpredators are not prey for other animals, but after their death they serve as food material for decomposers. Decomposers participate in the process of decomposition of the remains of these animals.
Detrital food chains originate from rotting organic matter. For example, from decaying leaves and remaining grass or from fallen berries. Such chains are common in deciduous and mixed forests. Fallen rotting leaves - woodlice - raven. Here is an example of such a food chain. Most animals and microorganisms can simultaneously be links in both types of food chains. An example of this is the woodpecker feeding on bugs that decompose dead wood. These are representatives of the detritus food chain. And the woodpecker itself can become prey for a small predator, for example, a lynx. Lynx can also hunt rodents - representatives of the pasture food chain.
Any food chain cannot be very long. This is due to the fact that only 10% of the energy of the previous level is transferred to each subsequent level. Most of them consist of 3 to 6 links.
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 addiction from 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, green and red emblems 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. On the edge of the forest, in the hollow of an old big 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 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 didactic game“Who’s eating who?”, let’s 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 are pasted on pictures depicting animals and birds. different color. 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 environment and treated animals and flora with care.
Literature:
Main educational program 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 basics ecological culture V kindergarten. M: TC Sfera, 2003.
Nikolaeva S. N. Methodology environmental education preschoolers. 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 congratulate everyone with all my heart
Happy International Women's Day !
Publications on the topic:
"Children about safety." Basic rules of safe behavior for preschool children in verse“For children about safety” Basic rules safe behavior for children preschool age in verse. Purpose of the event: To educate.
Formation of understanding of synonymous meanings of words in children of senior preschool age in various types of activities The system is carried out in several stages. First, synonyms are entered into passive dictionary children. Familiarize children with words with similar meanings.
Consultation for parents “What toys do children of older preschool age need” Nowadays, the choice of toys for children is so diverse and interesting that for every parent interested in the development of their child.
Consultation for parents “Cartoons are not a toy for children” for children of older preschool age CONSULTATION FOR PARENTS “Cartoons are not a toy for children!” Many parents are concerned about the relationship between the child and the TV. What to watch?.
Short-term creative project “Children about the war” for children of senior preschool age. Project type: According to the dominant activity in the project: informational. According to the number of project participants: group (preparatory school children.
Summary of the lesson-conversation “About war for children” for senior preschool age Type of activity: Teacher’s story “About war for children.” View photo presentation. Educational area: Cognitive development. Target:.
Pedagogical project “For preschool children about the holiday of the Nativity of Christ” Pedagogical project “For preschool children about the holiday of the Nativity of Christ.”
Instilling in preschool children the basics of a healthy lifestyle in various activities Teaching is an amazing profession. Another advantage is that it gives an opportunity to look into the country of childhood, into the world of a child. And at least.
Development of value-semantic perception and understanding of works of art in preschool children Nowadays, the main goal of education is to prepare comprehensively and harmoniously developed personality child. Creativity is the way.
Fairy tale and games to help children understand the seasons TALE AND GAMES TO MAKE CHILDREN EASIER UNDERSTANDING OF THE SEASONS “Four Daughters of the Year.” A long time ago it was like this: today the sun is hot, flowers.
Image library:
Lesson topic:“Who eats what? Food chains".
Lesson type:learning new material.
Textbook: “The world around us, grade 3, part 1” (author A.A. Pleshakov)
Goals and objectives of the lesson
Target:generalize students' knowledge about the diversity of the animal world, about groups of animals by type of food, about chains nutrition, reproduction and stages of development, adaptation to protection from enemies and protection of animals.
Tasks:
1. Contribute to the enrichment and development of subjective ideas about the life of animals.
2. To promote the development of children’s ability to draw up, “read” diagrams, and model environmental connections.
3. Contribute to the development of skills and abilities of independent and group work.
4. Create conditions for the development of logical thinking;
5. Cultivate a sense of responsibility for all living things that surround us, a feeling of love for nature.
Lesson equipment
Computer.
Worksheets with tasks. Cards with puzzles.
Multimedia projector.
Textbook: Pleshakov A.A. The world around us. - M., Education, 2007.
Board
During the classes.
1 .Organizing time.
2. Statement of the topic of the lesson and statement of the problem.
(Appendix slide 1)
Guys, look carefully at the slide. Think about how these representatives of wildlife are connected to each other. Based on this slide, who will determine the topic of our lesson?
(We will talk about who eats what.)
Right! If you look closely at the slide, you will see that all the items are connected by arrows in a chain according to the method of nutrition. In ecology, such chains are called ecological chains, or food chains. Hence the topic of our lesson “Who eats what?” Food chains.”
3. Updating knowledge.
To trace different food chains and try to compose them ourselves, we need to remember who eats what. Let's start with plants. What is special about their diet? Tell us based on the table.
(Appendix slide 3)
(Plants receive carbon dioxide from the air. They absorb water and salts dissolved in it through their roots from the soil. Under the influence sunlight Plants convert carbon dioxide, water and salts into sugar and starch. Their specialty is that they cook their own food.)
Now let’s remember what groups animals are divided into based on their feeding method and how they differ from each other.
(Herbivorous animals eat plant foods. Insectivores eat insects. Carnivorous animals feed on the flesh of other animals, therefore they are also called carnivores. Omnivores eat plant and animal foods.)
(Appendix slide 4)
4. Discovery of new knowledge .
Food chains are the nutritional connections of all living things. There are a lot of food chains in nature. In the forest they are alone, completely different in the meadow and in the pond, others in the field and in the garden. I invite you to act as environmental scientists and engage in search activity. All groups will go to different places. Here are the routes of environmental scientists.
(Appendix slide 5)
Where you will have to work will be decided by drawing lots.
I invite one person from each group, and they pull out a card with the name of the place. The same guys receive sheets with arrows and 4 cards with pictures of plants and animals.
Now listen to the task. Each group, using cards, must create a food chain. The cards are attached to the sheet with arrows using paper clips. Immediately agree who will present your circuit to the class. Consider whether you will need all the cards.
At the signal, the guys begin to work in groups. Those who finished early are offered riddles.
(Appendix slide 6)
All finished chains are hung on a board.
A pine tree grows in the forest. A bark beetle lives under the bark of a pine tree and feeds on it. In turn, the bark beetle is food for woodpeckers. We had an extra picture - a goat. This is a domestic animal and is not included in this food chain.
Let's check the guys' work.
(Appendix slide 7)
Other groups explain their chains in the same way.
2) Field: rye – mouse – snake (extra – fish).
(Appendix slide 8)
3) Vegetable garden: cabbage - slugs - toad (extra one - bear).
(Appendix slide 9)
4) Garden: apple tree – apple aphid – ladybug(the extra one is the fox).
(Appendix slide 10)
5) Reservoir: algae - crucian carp - pike (extra - hare).
(Appendix slide 11)
All the chains are on our board. Let's see what parts they consist of. What is on each table? What comes first? On the second ? On the third ?
(Plant. Herbivorous animal. Carnivorous, insectivorous or omnivorous animal.)
5. Primary consolidation of knowledge.
1. Work according to the textbook. pp. 96-97.
Now, guys, let's get acquainted with the textbook article and test ourselves. Children open the textbook p. 96–97 and silently read the article “Food Chains”.
– What power circuits are given in the textbook?
Aspen - hare - wolf.
Oaks – wood mice – owls.
In what order are the links in the food chain located?
I link – plants;
II link – herbivorous animals;
III link – other animals.
(Appendix slide 12)
2) Repetition of the rules of behavior in the forest.
Here we are in the forest. Listen to the sounds of the forest, look at the diversity of its inhabitants. Do you know how to behave in the forest?
1. Do not break branches of trees and bushes.
2.Do not pick or trample flowers and medicinal plants.
3.Do not catch butterflies, dragonflies and other insects.
4.Do not destroy frogs and toads.
5.Do not touch bird nests.
6.Do not bring animals home from the forest.
Slide 6 (appendix) opens with images of an owl, mice and acorns. Students create a food chain by moving pictures.
Who is bigger in this food chain?
The largest of all is the owl, and the mouse is larger than the acorn.
If we had a magic scale and we weighed all the owls, mice and acorns, it would turn out that acorns are heavier than mice, and mice are heavier than owls. Why do you think?
Because there are very, very many acorns in the forest, many mice, and few owls.
And this is no coincidence. After all, one owl needs a lot of mice for food, and one mouse needs a lot of acorns. It turns out to be an ecological pyramid.
Summary conclusion :
In nature, everything and everyone is connected to each other. Food webs intertwine to form a food web. Plants and animals form ecological pyramids. At the base are plants, and at the top are predatory animals.
6 .Introduction to the concept of “power network”
Food chains in nature are not as simple as in our example. Other animals can also eat the hare. Which? (fox, lynx, wolf)
A mouse can become prey for a fox, owl, lynx, wild boar, or hedgehog.
Many herbivorous animals serve as food for various predators.
Therefore, power chains are branched; they can intertwine with each other, forming a complex power network.
7. Problem situation .
Guys, what will happen if all the trees on which the hare eats disappear in the forest? (The hare will have nothing to eat)
- What if there are no hares? (There will be no food for both the fox and the wolf)
– What will happen to the chain? (It'll collapse)
What conclusion can be drawn? (If you destroy even one link in a chain, the whole chain will collapse.)
8.Make several possible power circuits
9. Summary of the lesson. Generalization on the topic.
Reflection.
“Finish the sentence.”
Animals and plants are related to each other in ……………………
At the heart of the power supply chain are ………………………………..
And they end the chain – ………………………………………..
In nature, food chains intertwine with each other, forming
…………………………………………
Homemadeexercise.
1. Prepare a message about one of Birch’s friends;
2. Complete tasks No. 4 from the manual “ The world"(The figure shows a section of the garden. Make several possible food chains).
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
Bibliography
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. 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 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 organic molecules, from which fabrics are constructed. 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, making up the phytoplankton of the surface layers of oceans and lakes. On the land most primary production supply 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. The most important groups of 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 cladocerans 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 all food chains begin with them.
Plant material (e.g. nectar) → fly → spider →
→ shrew → owl
Rosebush sap → aphid → ladybug → spider → insectivorous bird → bird of prey
There are two main types of food chains – grazing and detrital. Examples were given above pasture chains, in which the first trophic level is occupied by green plants, the second by grazing 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 secrete digestive enzymes into 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 of 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 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 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 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.
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