Make a large food chain in biology. Abstract: Food chains in nature

Food chain structure

A food chain is a connected linear structure of links, each of which is connected with neighboring links by the “food-consumer” relationship. Groups of organisms, for example, specific biological species, act as links in the chain. 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.

Trophic network

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.

Trophic level

A trophic level is a set of organisms that, depending on their method of nutrition and type of food, constitute a certain link in the food chain.

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 a trophic level.

Types of food chains

There are 2 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 (consumers) (for example, zooplankton feeding on phytoplankton), then 1st order predators (for example, fish consuming zooplankton), 2nd order predators order (for example, pike feeding on other fish). The trophic chains are especially long in the ocean, where many species (for example, tuna) occupy the place of fourth-order consumers.

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

Terrestrial detrital food chains are more energy intensive, since most of the organic mass created by autotrophic organisms remains unclaimed and dies off, forming detritus. On a planetary scale, grazing chains account for about 10% of the energy and substances stored by autotrophs, while 90% is included in the cycle through decomposition chains.

Literature

Trophic chain / Biological encyclopedic dictionary / chapter. ed. M. S. Gilyarov. - M.: Soviet Encyclopedia, 1986. - P. 648-649.

Wikimedia Foundation.

2010.

See what “Food chain” is in other dictionaries: - (food chain, trophic chain), relationships between organisms in which groups of individuals (bacteria, fungi, plants, animals) are connected to each other by relationships: food consumer. The food chain usually includes from 2 to 5 links: photos and... ...

Modern encyclopedia - (food chain, trophic chain), a series of organisms (plants, animals, microorganisms), in which each previous link serves as food for the next. Connected to each other by relationships: food consumer. The food chain usually includes from 2 to 5... ...

Big Encyclopedic Dictionary Scientific and technical encyclopedic dictionary

See Trophic chain. Ecological encyclopedic dictionary. Chisinau: Main editorial office of the Moldavian Soviet Encyclopedia. I.I. Dedu. 1989 ... Ecological dictionary

food chain- — EN food chain A sequence of organisms on successive trophic levels within a community, through which energy is transferred by feeding; energy enters the food chain during fixation… Technical Translator's Guide

- (food chain, trophic chain), a series of organisms (plants, animals, microorganisms), in which each previous link serves as food for the next. Connected to each other by relationships: food consumer. The food chain usually includes from 2 to... ... encyclopedic Dictionary

food chain- mitybos grandinė statusas T sritis ekologija ir aplinkotyra apibrėžtis Augalų, gyvūnų ir mikroorganizmų mitybos ryšiai, dėl kurių pirminė augalų energija maisto pavidalu perduodama vartotojams ir skaidytojams. Vienam organizmui pasimaitinus kitu… Ekologijos terminų aiškinamasis žodynas

- (food chain, trophic chain), a number of organisms (plants, animals, microorganisms), in which each previous link serves as food for the next one. Connected to each other by relationships: food consumer. P. c. usually includes from 2 to 5 links: photo and... ... Natural science. encyclopedic Dictionary

- (trophic chain, food chain), the relationship of organisms through food-consumer relationships (some serve as food for others). In this case, a transformation of matter and energy occurs from producers (primary producers) through consumers... ... Biological encyclopedic dictionary

See Power Circuit... Large medical dictionary

Books

The omnivore's dilemma. A shocking study of the modern diet, Pollan Michael. Have you ever thought about how food gets to our table? Did you buy your groceries at the supermarket or farmers market? Or maybe you grew your own tomatoes or brought a goose with...

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

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

There are various connections between the components of an ecosystem, and first of all they are connected together by the flow of energy and the circulation of matter. The channels through which energy flows through a community are called food circuits. The energy 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 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 just one food source, but several). The greater the species diversity in a biocenosis, the more stable it is. So, in the plant-hare-fox food chain there are only three links. But the fox eats not only hares, but also mice and birds. The general pattern is that green plants are always at the beginning of the food chain, and predators are at the end. With each link in the chain, organisms become larger, they reproduce more slowly, and their number decreases. Species occupying the position of lower links, although provided with food, are themselves intensively consumed (mice, for example, are exterminated by foxes, wolves, owls). Selection goes in the direction of increasing fertility. Such organisms turn into a food source for higher animals without any prospects for progressive evolution.

In any geological epoch, organisms that were at the highest level in food relationships evolved at the highest speed, for example, in the Devonian - lobe-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 manure. A particularly important role in creating or changing the environment for other organisms belongs to plants. In thickets of plants, be it a forest or a meadow, the temperature fluctuates less than in open spaces, and the humidity is higher.
Often one species participates in the spread of another. Animals carry seeds, spores, pollen, and other smaller animals. Plant seeds can be captured by animals upon accidental contact, especially if the seeds or infructescences have special hooks (string, burdock). When eating fruits and berries that cannot be digested, the seeds are released along with the droppings. Mammals, birds and insects carry numerous mites on their bodies.

All these diverse connections provide the possibility of the existence of species in a 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.

All species that form the food chain exist on organic matter created by green plants. In this case, there is an important pattern associated with the efficiency of use and conversion of energy in the nutrition process. Its essence is as follows.

In total, only about 1% of the radiant energy of the Sun falling on a plant is converted into potential energy of chemical bonds of synthesized organic substances and can be further used by heterotrophic organisms for nutrition. When an animal eats a plant, most of the energy contained in the food is spent on various vital processes, turning into heat and dissipating. Only 5-20% of food energy passes into the newly built substance of the animal’s body. If a predator eats a herbivore, then again most of the energy contained in the food is lost. Due to such large losses of useful energy, food chains cannot be very long: they usually consist of no more than 3-5 links (food levels).

The amount of plant matter that serves as the basis of the food chain is always several times greater than the total mass of herbivorous animals, and the mass of each of the subsequent links in the food chain also decreases. This very important pattern is called the rule of the ecological pyramid.

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

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

2. LEVELS AND STRUCTURAL ELEMENTS OF THE FOOD CHAIN

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

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

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

3. TYPES OF TROPHIC CHAINS

There are several classifications of trophic chains.

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

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

herbivores;

predators - carnivores;

omnivores, including humans.

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

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

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

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

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

CONCLUSION

All living organisms inhabiting our planet do not exist on their own; they depend on 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.

BIBLIOGRAPHY

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

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

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 food chains, about reproduction and stages of development, adaptability 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 sense 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 of sunlight, plants convert carbon dioxide, water and salts into sugar and starch. Their peculiarity is that they prepare their food themselves.)

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 suggest you act as environmental scientists and engage in search activities. 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 (extra - 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 conduct 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's 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. The hare can also be eaten by other animals. 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 Around You” (the picture shows a garden plot. Make several possible food chains).

Back forward

Attention! Slide previews are for informational purposes only and may not represent all of the presentation's features. If you are interested in this work, please download the full version.

The purpose of the lesson: To form knowledge about the constituent components of a biological community, about the features of the trophic structure of the community, about food connections that reflect the path of substance circulation, to form the concepts of food chain, food web.

During the classes

1. Organizational moment.

2. Checking and updating knowledge on the topic “Composition and structure of the community.”

On the board: Our world is not an accident, not chaos - there is a system in everything.

Question. What system in living nature is this statement talking about?

Working with terms.

Exercise. Fill in the missing words.

A community of organisms of different species closely interconnected is called …………. . It consists of: plants, animals, …………. , …………. . A set of living organisms and components of inanimate nature, united by the exchange of substances and energy on a homogeneous area of the earth’s surface is called …………….. or …………….

Exercise. Select four components of the ecosystem: bacteria, animals, consumers, fungi, abiotic component, climate, decomposers, plants, producers, water.

Question. How are living organisms connected to each other in an ecosystem?

3. Studying new material. Explain using presentation.

4. Consolidation of new material.

Task No. 1. Slide No. 20.

Identify and label: producers, consumers and decomposers. Compare power circuits and establish similarities between them. (at the beginning of each chain there is plant food, then there is a herbivore, and at the end there is a predatory animal). Name the way plants and animals feed. (plants are autotrophs, i.e. they produce organic matter themselves, animals – heterotrophs – consume finished organic matter).

Conclusion: a food chain is a series of organisms sequentially feeding on each other. Food chains begin with autotrophs - green plants.

Task No. 2. Compare two food chains, identify similarities and differences.

Clover - rabbit - wolf
Plant litter - earthworm - blackbird - hawk - sparrowhawk (The first food chain begins with producers - living plants, the second with plant residues - dead organic matter).

In nature, there are two main types of food chains: pasture (grazing chains), which begin with producers, detrital (decomposition chains), which begin with plant and animal residues, animal excrement.

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

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

Task No. 3. Make a food chain, including the following organisms: caterpillar, cuckoo, tree with leaves, buzzard, soil bacteria. Indicate producers, consumers, decomposers. (tree with leaves - caterpillar - cuckoo - buzzard - soil bacteria). Determine how many trophic levels this food chain contains (this chain consists of five links, therefore there are five trophic levels). Determine which organisms are located at each trophic level. Draw a conclusion.

The first trophic level is green plants (producers),
Second trophic level – herbivores (consumers of the 1st order)
Third trophic level – small predators (2nd order consumers)
Fourth trophic level – large predators (3rd order consumers)
Fifth trophic level - organisms that consume dead organic matter - soil bacteria, fungi (decomposers)

In nature, each organism uses not one food source, but several, but in biogeocenoses food chains intertwine and form food web. For any community, you can draw up a diagram of all the food relationships of organisms, and this diagram will have the form of a network (we consider an example of a food network in Fig. 62 in the biology textbook by A.A. Kamensky and others)

5. Implementation of acquired knowledge.

Practical work in groups.

Task No. 1. Solving environmental situations

1. In one of the Canadian reserves, all wolves were destroyed in order to increase the herd of deer. Was it possible to achieve the goal in this way? Explain your answer.

2. Hares live in a certain territory. Of these, there are 100 small hares weighing 2 kg, and 20 of their parents weighing 5 kg. The weight of 1 fox is 10 kg. Find the number of foxes in this forest. How many plants must grow in the forest for hares to grow up?

3. A reservoir with rich vegetation is home to 2000 water rats, each rat consumes 80g of plants per day. How many beavers can this pond feed if a beaver consumes an average of 200 g of plant food per day?

4. Present the disordered facts in a logically correct sequence (in the form of numbers).

1. Nile perch began to eat a lot of herbivorous fish.

2. Having multiplied greatly, the plants began to rot, poisoning the water.

3. Smoking Nile perch required a lot of wood.

4. In 1960, British colonists released Nile perch into the waters of Lake Victoria, which quickly multiplied and grew, reaching a weight of 40 kg and a length of 1.5 m.

5. Forests on the shores of the lake were intensively cut down - so water erosion of the soil began.

6. Dead zones with poisoned water appeared in the lake.

7. The number of herbivorous fish decreased, and the lake began to be overgrown with aquatic plants.

8. Soil erosion has led to a decrease in the fertility of fields.

9. Poor soils did not produce crops, and the peasants went bankrupt .

6. Self-test of acquired knowledge in the form of a test.

1. Producers of organic substances in the ecosystem

A) producers

B) consumers

B) decomposers

D) predators

2. To which group do microorganisms living in the soil belong?

A) producers

B) consumers of the first order

B) consumers of the second order

D) decomposers

3. Name the animal that should be included in the food chain: grass -> ... -> wolf

B) hawk

4. Identify the correct food chain

A) hedgehog -> plant -> grasshopper -> frog

B) grasshopper -> plant -> hedgehog -> frog

B) plant -> grasshopper -> frog -> hedgehog

D) hedgehog -> frog -> grasshopper -> plant

5. In a coniferous forest ecosystem, 2nd order consumers include

A) common spruce

B) forest mice

B) taiga ticks

D) soil bacteria

6. Plants produce organic substances from inorganic substances, therefore they play a role in food chains

A) final link

B) initial level

B) consumer organisms

D) destructive organisms

7. Bacteria and fungi play the role of:

A) producers of organic substances

B) consumers of organic substances

B) destroyers of organic substances

D) destroyers of inorganic substances

8. Identify the correct food chain

A) hawk -> tit -> insect larvae -> pine

B) pine -> tit -> insect larvae -> hawk

B) pine -> insect larvae -> tit -> hawk

D) insect larvae -> pine -> tit -> hawk

9. Determine which animal should be included in the food chain: cereals -> ? -> already -> kite

A) frog

D) lark

10. Identify the correct food chain

A) seagull -> perch -> fish fry -> algae

B) algae -> seagull -> perch -> fish fry

C) fish fry -> algae -> perch -> seagull

D) algae -> fish fry -> perch -> seagull

11. Continue the food chain: wheat -> mouse -> ...

B) gopher

B) fox

D) triton

7. General conclusions of the lesson.

Answer the questions:

How are organisms interconnected in biogeocenosis (food connections)
What is a food chain (a series of organisms sequentially feeding on each other)
What types of food chains are there (pastoral and detrital chains)
What is the name of the link in the food chain (trophic level)
What is a food web (intertwined food 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 detrital. 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 sedimentation 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 the 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.