Message about the community pond. Report: The natural community of a reservoir is a collection of various living organisms living together in any part of the reservoir

Rice. 2. Lake Arakul ()

Or artificial: pond, reservoir, canal (Fig. 4-6).

Rice. 5. Reservoir ()

Whatever the body of water, natural or artificial, it adorns our land and delights us with its beauty. We take water from fresh reservoirs, which we cannot do without either in everyday life or in production. We swim in bodies of water, sunbathe next to them, travel on ships on water, and transport goods. The importance of reservoirs in nature is great. Fresh water is the most important condition for human existence on Earth, and for animals that live in water, it is also the only home. Water contains everything necessary for life: light, heat, air and dissolved minerals.

What plants grow and what animals live in fresh water bodies? Finding yourself near a reservoir in the warm season, you could only observe those of its inhabitants who live on the surface. But life in a body of water is everywhere: near the shores, on the surface, in the water column, at the very bottom and at the bottom. On the banks of reservoirs you can see leaves and stems of reeds, reeds, cattails, and arrowheads. The shallow depth allows these plants to attach to the bottom of the reservoir. At a much greater depth, white water lily and yellow water lily grow (Fig. 7, 8). Their flowers and wide leaves float on the smooth surface of the water.

Rice. 7. White water lily ()

Rice. 8. Yellow egg capsule ()

How did these plants manage to adapt to life in highly moist soil, where there is almost no oxygen? If you examine a section of the stems of reeds, reeds, and cattails, you can see the air channels that run in the stems of these plants (Fig. 9, 10).

Rice. 9. Reed ()

There are air channels in both the leaves and roots of aquatic plants. In the white water lily and the yellow water lily, the petioles of the leaves and the peduncles on which the flowers sit are also pierced with air channels through which the oxygen necessary for breathing penetrates. By picking a flower, a person harms the entire plant. At the site of the rupture, water begins to penetrate into the plant, this leads to rotting of the underwater part and, ultimately, the death of the entire plant.

Duckweed grass in the form of small green plates also floats on the surface of the reservoir, but is not attached to the bottom by its roots, and in the water column there are tiny green algae, which can only be seen under a microscope. But their presence reveals the color of the water. When there are a lot of them in a reservoir, the color of the water turns green.

What role do plants play in the lives of numerous inhabitants of water bodies? Firstly, green plants, under the influence of sunlight, take carbon dioxide from the air and release oxygen into the water, which is necessary for the respiration of all animals. Secondly, birds, amphibians, insects and their larvae, and fish find shelter and food in the thickets of a reservoir. Animals are everywhere in reservoirs: on the surface and in the water column, on the shore, at the bottom, on aquatic plants. The main connections between animals and plants are food. Here water striders (Fig. 11) quickly run along the surface of the water and hunt mosquitoes and other small animals.

Rice. 11. Water strider ()

Their long legs are covered with fat underneath, which is why the water holds them. And snails live on aquatic plants: pond snail and coil (Fig. 12, 13).

Rice. 12. Prudovik ()

Without whom the river cannot live? Very small crustaceans of reservoirs, daphnia and cyclops, live and winter in water. Their value is slightly larger than the decimal point in the book (Fig. 14, 15).

The most remarkable thing about daphnia is its long mustache. They will wave their mustaches, lower them sharply, push off from the water and jump. The Cyclops has an unpaired frontal ocelli, from which it gets its name.

The river cannot live without crustaceans, since they purify the water from bacteria, green algae and tiny animals invisible to the eye; if not for the crustaceans, the river would quickly overflow with them. Daphnia and cyclops, like other inhabitants of the river, feed on these organisms, thereby purifying the water. They themselves serve as food for fish fry, mollusks, tadpoles, and insect larvae.

Is there really someone living in the river without a head? These are mollusks, toothless and pearl barley (Fig. 16).

Rice. 16 Clams ()

At first, the shell, consisting of two longitudinal plates, will lie motionless, then its doors will open slightly and a leg will stick out of it; neither the toothless nor the barley has a head. Toothless will extend his leg and stick it into the sand, the shell will move. The toothless one will move 2-3 centimeters, rest, and then hit the road again. This is how it travels along the bottom of the river. The toothless fish obtains food and air directly from the water. It opens the shell doors slightly and begins to draw in water, then throws it out. The water is full of tiny animals, they fall into the sink, and the toothless fish uses special devices to stop them. The toothless one breathes and eats, and at the same time purifies the water. And pearl barley also works. Each one purifies approximately 40-50 liters of water per day. Mollusks, insect larvae, and tadpoles are eaten by fish, storks, waders, and ducks. The swimming beetle preys on other insects, as well as worms, snails, and tadpoles. Frogs feed in the coastal parts of reservoirs, mainly on flying insects, and they themselves are food for newts and predatory fish, perch and pike. Herons, gulls, and kingfishers hunt for fish and newts.

The main food of cancer is plant-based. But he willingly eats animals, as well as the remains of dead animals. Therefore, crayfish are often called the orderlies of reservoirs (Fig. 17).

Crayfish change their shells throughout their lives. The sense organs of crayfish are perfectly developed, the eyes are pushed forward on thin stalks and consist of a huge number, 3000, of tiny eyes. A short pair of antennae are the organs of smell, and long ones are the organs of touch. If a predator grabs a crayfish by the claw, the crayfish breaks it off and hides in a hole. A lost claw will grow back. Crayfish are very sensitive to water pollution, so in places where they are found, they talk about the ecological cleanliness of water bodies.

Near the river you can see different dragonflies: the beauty, the arrow, the lute; they live near the river constantly (Fig. 18).

Rice. 18. Dragonfly ()

All dragonflies need water because that is the only place their larvae can live. The larvae are not similar to adult dragonflies, only their eyes are the same. Each eye consists of almost 30,000 tiny ocelli (Fig. 19).

Rice. 19. Dragonfly larva ()

Both eyes are convex, thanks to which the dragonfly can look in all directions at the same time (Fig. 20). All dragonflies are predators; they hunt in the air and grab insects in flight.

Rice. 20. Dragonfly eyes ()

The dragonfly larva, lying in wait for prey, throws forward its strongly elongated lower lip. Usually the lips are folded and cover the head like a mask. The larva sucks water into a large muscular sac inside the body and then forcefully throws it out. It turns out to be a water shot. After a year, and some after 3, the larvae emerge to the surface, the skin of the larva bursts, and a dragonfly emerges from it. It will sit for several hours, spread its wings and fly away.

Who lives in a drop of water? If you look through a microscope, a wonderful world of unusual creatures will open up. Here is an almost transparent lump that changes all the time - this is an amoeba (Fig. 21).

Other creatures resemble tiny shoes, which is what they are called. The body of the shoe is covered with cilia, each skillfully controls these cilia and swims quickly (Fig. 22).

Rice. 22. Shoe ()

Trumpeters are the most beautiful inhabitants of the drop, blue, green, similar to bindweed flowers (Fig. 23).

The trumpeters move slowly and only forward. If something scares them, they shrink and resemble balls. Amoebas, slippers and whelks are single-celled organisms that feed on bacteria.

Predators also live in a drop of water. This is didinium (Fig. 24).

Although he is smaller than a shoe, he not only boldly attacks her, but also swallows her whole, swelling up like a ball.

Plants, animals, and bacteria live together in a fresh body of water, all of them are well adapted to life in water and are interconnected by food chains. When plants and animals die, they accumulate at the bottom of reservoirs, are destroyed by bacteria and turn into salts, which dissolve in water and are used by other animals. A body of water is a natural community.

Today in the lesson you gained a new understanding of a freshwater body as a freshwater community and became acquainted with its inhabitants.

Bibliography

1. Vakhrushev A.A., Danilov D.D. The world around us 3. - M.: Ballas.
2. Dmitrieva N.Ya., Kazakov A.N. The world around us 3. - M.: Publishing House "Fedorov".
3. Pleshakov A.A. The world around us 3. - M.: Enlightenment.

1. Makuha.ru ().
2. Youtube.com().
3. Sbio.info().

Homework

1. What fresh water bodies do you know?
2. What animals can be found in bodies of water?
3. Why do they say that a body of water is a natural community?

The name of the natural community is forest.
The main element that forms the forest natural community is trees. Forests are different, depending on the tree species that predominate in them. For example, there are pine (pine forests) and spruce (spruce) forests, birch forests, oak forests where mainly oaks grow, etc. In addition to trees, many other plants live in the forest. Shrubs grow under the forest canopy: bird cherry, rose hips, honeysuckle, elderberry. There are also herbaceous plants in the forest - lily of the valley, lungwort, yarrow, strawberry, as well as various types of mosses and lichens.
The forests are home to a wide variety of animals: roe deer, elk, wild boars, wolves, foxes, hares, hedgehogs, mice. The forest also provides shelter to numerous birds. These are jays, cuckoos, owls, tits, woodpeckers, nightingales, thrushes, flycatchers and many other species. Numerous insects live in the forests - flies, mosquitoes, dragonflies, butterflies, bark beetles, and stag beetles. The forest floor is home to a huge number of bacteria, worms, and insects.
All forest inhabitants are interconnected by a complex network of food relationships. Plants, with the help of photosynthesis and soil minerals, produce food for herbivorous animals: moose, roe deer, hares, mice, birds, etc. Herbivorous animals are eaten by predators: foxes, wolves, weasels, birds of prey. Dead plants, dead animals and their metabolic products become food for a variety of soil organisms, which decompose the remains into simple components that are again absorbed by plants.
The forest is of great importance to humans. The forest is a source of game, wood, mushrooms and berries. Previously, people obtained their food in the forest through hunting. Now hunting has already lost its former meaning and people who truly love nature have abandoned this cruel activity.
The forest is a wonderful source of relaxation for soul and body. Admiring the beauty of the forest, inhaling its healing air, a person relaxes.
The forest has a water conservation role. In those places where forests are cut down, rivers become shallow, and small rivers disappear altogether.
Humans usually have a negative impact on the forest. For thousands of years, people have thoughtlessly cut down forests. Now on Earth there remains no more than a third of the forest wealth that the planet had before human development. As a result, many species of plants and animals become extinct and the ecological balance is disrupted. In addition, people pollute forests with various wastes, hunt animals, and pick beautiful forest flowers. Unextinguished fires cause forest fires.
Of course, forest restoration is also carried out, but this is a long-term task. because it takes a long time to grow a tree.
To protect forests, protected areas are created. In nature reserves and national parks, forest animals and plants are under state protection. Every person must treat the inhabitants of the forest with care, do not provoke fires, do not leave garbage, carefully and moderately collect mushrooms and berries, do not hunt, do not destroy bird nests, and do not cut down trees unnecessarily.

SURROUNDING WORLD, 4TH GRADE

Topic: NATURAL COMMUNITY OF FRESH RESERVOIR.

DIVERSITY OF RESERVOIR INHABITANTS.

Goals: - to continue the formation of ideas about natural communities using the example of a reservoir; introduce the diversity of its inhabitants, their connections and relationships, ensuring natural balance; show the adaptability of aquatic plants and animals to life in different places of the reservoir;

Develop observation and curiosity in children; ability to work with additional sources of information; the ability to draw conclusions and generalizations, development of speech, thinking, attention and logic; ability to work in a team;

To cultivate love for one’s native land and respect for nature.

Equipment: textbook, workbook, film fragment “The Life of a Freshwater Reservoir”, tape recording with the noise of a reservoir, a plane model of a reservoir, collections of the inhabitants of the reservoir, cards with group and individual tasks, entertaining material for the lesson.

DURING THE CLASSES:

ORG. MOMENT WEATHER FORECAST.

Hello guys. I am glad to welcome you to the natural history lesson and give the floor to the weather forecasters. Make a weather forecast for today, March 5th.

The weather is wonderful! We can continue our journey around our native land. But before we set off, let’s check our baggage – our baggage of knowledge on the topic “Meadow and Man”.

CHECKING YOUR HOMEWORK.

We do homework in groups. We sat down comfortably.

At the last lesson, you drew up a memo plan on the topic “Meadow and Man.” Each group checks the plan using a card, adds the missing point and prepares a story based on it.

There are performances in groups. Conclusions.

So that the river and streams do not become cloudy,

The animals would frolic and the birds would sing,

Greenery would save you from the sun in the heat,

It didn’t hurt for everyone to know the rules.

Formulate the rules of behavior in the meadow using the signs on the cards.

Finish the thought:

MEADOW IS...(natural community). Prove it.

I hang the cards on the board.

What other example of a natural community can you give?

So, your luggage is collected, checked, and you can hit the road.

I turn on the recording of the noise of the pond.

Here we are. Listen carefully and tell me where the path led us today.

Where did we end up?

TOPIC, LESSON OBJECTIVES.

Can you formulate the topic of the lesson? – “DIVERSITY OF RESERVOIR INHABITANTS.”

The path ran up to the ford,

I couldn't stop

Hastily ran into the water

And she dived in with what she was wearing.

And we remained standing on the shore of the reservoir. We stand and think: what new can we learn here?

Student answers.

Today in the lesson we will get acquainted with the diversity of the inhabitants of the reservoir, their connections and relationships, we will trace the adaptability of plants and animals to life in its various places, we will learn observation skills, draw conclusions and generalize, work in groups, and create our own model of the reservoir.

And at the end of the lesson we must answer the question: Is a body of water a natural community? I hang up the card and the “?”

And when can this knowledge be useful to us in life?

4. NEW MATERIAL.

In our region you can find a variety of bodies of water - rivers, streams, ponds. What bodies of water do you know?

I invite you to Ostrechina, about which our refugee poet said this:

Between the hills, calmly, decorously

Ostrechina waters flow.

The waves crash into the shores

And he laughs under the sun...

We are standing on the shore of a small pond where a wide variety of living creatures live.

RESERVOIR PLANTS.

Plants that have successfully adapted to the aquatic environment play a major role in the reservoir. Look...

Along the very shore. Mostly marsh-type plants grow near the water line. Here we will find sedge with narrow, hard leaves sticking up.

Plants have settled in shallow water off the coast, the lower part of which

immersed in water, and the upper one rises above it. Such, for example, is the arrowhead. (picture) Why do you think it got this name? – Its upper leaves look like arrows.

(picture) We all know and call a plant with leaves up to 3 meters long and dark velvet buds at the top of the stem….reed. But it's cattail. And the reed has a large, often bent panicle and looks like this. Remember. (rice)

But we found ourselves in an unusually charming, quiet place. We are surrounded by large white flowers, and a little further - yellow flowers. What kind of plant is this?

Let's listen to the message about the white water lily.

The student makes a message.

Among other plants, small plates are visible floating on the surface. Listen to a story about this interesting plant.

A student makes a report about duckweed.

And if we look deep into the water, we will see various green algae (picture)

The life of all these plants is closely connected with water. Guess what will happen to an aquatic plant if it is brought ashore.

There are so many plants in the reservoir, but what role do they play in the life of the reservoir?

(produce oxygen, serve as food and shelter for many animals)

ANIMALS OF THE RESERVOIR.

What else can’t we imagine a body of water without?

We will also meet animals everywhere in a reservoir: on the surface and in the water column, at the bottom and on aquatic plants.

Now we will dive into the water. After carefully watching the film fragment, say which of the animals can be found in the pond. We put on our fins and masks, filled our lungs with more air, and dived.

Additions to the text:

Water striders have legs covered in fat. They are predators and hunt small insects.

The swimming beetle is a beetle and its larvae that are predators. They eat everything they come across: mosquitoes, tadpoles, and even their own fellow creatures.

Silver spider - builds several airy houses: for hunting, dining, molting, wintering.

What animals did you meet from the film fragment?

Have you seen them in life?

A variety of fish feed on many of these insects. Let’s check how well you know the fish of the reservoir. I invite you to go fishing.

Physical education minute (turn on music)

We took fishing rods.

They planted a worm.

We are waiting for it to bite.

They sat down quietly, and the commanders chose a task for their group. Look carefully at the task, read the encrypted word and tell me what fish can be caught in our reservoirs. The commanders answer.

Among the caught fish there are peaceful ones - crucian carp and roach. They feed on plants and insect larvae. And there are also predators - pike, perch.

But what I found on the shore... These are mollusk shells. At the bottom of the reservoir we can see bivalves, the soft body of which is hidden in a shell of 2 halves, valves. And the herbivorous pond snails and spool snails live on aquatic plants. Their shells are twisted and have no valves.

What other inhabitants of the reservoir do you know?

In the pond you can find a green frog and its tadpoles and crayfish. Mammals include beavers, muskrats, and otters, and birds include ducks, herons, waders, and storks.

Are the inhabitants of the reservoir related to each other? We will answer this question by constructing power circuits.

POWER CIRCUITS are arranged in pairs. 1-2 answers are read out loud.

CYCLE OF SUBSTANCES.

When the plants and animals of a body of water die, their remains are affected by

microbes rot, are destroyed, turning into salts. And salts dissolved in water are used for nutrition by new plants and animals. This is how the cycle of substances occurs in a reservoir.

We got to know in detail the life of the inhabitants of the reservoir. To consolidate our knowledge, let’s complete an interesting task.

5. SECURING.

1) “Correct errors in the text.”

We work in groups. If it is difficult, you can use the text of the textbook (p. 143-146)

How many errors are there in the text?

How were they fixed?

2) Crossword puzzle, if the group quickly copes with No. 1.

6. SUMMARY.

Our acquaintance with the inhabitants of the reservoir is coming to an end. What do you want to say about the life of a reservoir? (what did you find out?)

Let's return to the question: Is a body of water a natural community? Prove it.

What will happen in a pond if you remove 1 of the plants or animals?

Do you have any wishes for other guys who are not yet familiar with the inhabitants of the reservoir?

What can you say to those who came to the shore of the reservoir?

Guys, try to evaluate our work. What are your impressions of traveling to the reservoir? What did you like? What else would you like to hear about the inhabitants of the reservoir?

7. EVALUATING CHILDREN’S WORK IN THE LESSON.

8. HOMEWORK.

1) Textbook – p.143-146, questions p.148 No. 1-3

Notebook - No. 98, 99

Messages about plants and animals of the reservoir.
A story about the inhabitants of the aquarium.
Interesting stuff.

Among the well-known natural communities, consider a pond. In it, as in any other natural community, plants, animals and microorganisms are distributed unevenly. Its most populated part is the coastal part (shallow water), where a variety of herbaceous plants grow, since living conditions are most favorable here: the water is better heated by the sun's rays, there is more oxygen, etc. Many animals live in this part of the pond, for example the gray heron. This bird usually stands for a long time in shallow water on long legs, patiently waiting for prey - frogs, aquatic insects, which it grabs with its long beak. Dragonflies fly over the coastal part of the pond - predators with large eyes, with which they detect small insects and grab them in flight. Dragonfly larvae are inactive; they live among aquatic plants and are also predators.

Figure: Natural communities - biocenosis of a reservoir

The population of the water column is diverse. This part of the pond is inhabited by various microorganisms: unicellular algae, protozoa. Small crustaceans (daphnia, cyclops) feed on these microorganisms, and they, in turn, feed on fish fry and amphibian larvae, such as tadpoles. The latter are food for many predatory fish (perch, pike, etc.).

At the bottom of a reservoir, life is poorer compared to its coastal part and the water column, since the sun's rays poorly penetrate here, the water is cool, and there is little oxygen in it. Single-celled plants and animals live in this part. Remember that an ordinary amoeba lives on the muddy bottom, and a white planaria lives under snags and stones; snails, for example the common pond snail, crawl along the stems of aquatic plants. It periodically rises to the surface of the pond to stock up on fresh air, and the pond snail feeds on aquatic plants. Aquatic beetles live at the bottom: swimming beetles, water lovers, etc. The first of them is a predator, it destroys insect larvae, worms, tadpoles, and fish fry. The water-loving beetle feeds on aquatic plants and does not refuse animal food.

The power chain here could be like this. Daphnia and mosquito larvae feed on single-celled algae. They serve as food for bedbugs and beetles, which are eaten by fish and frogs. They can also be grabbed by the same heron that feeds in shallow water.

Forest - natural community

We have all been to the forest more than once. Here at the edge of the forest a lizard darted and disappeared among the grass. Fresh piles of soil indicate that a mole lives in the soil here. The forest is twilight, not hot, and you can hardly feel the wind. Walking along the path, we come across the web of a cross spider. Here is a tall anthill with ants swarming on the surface. There are many flowering plants in the sunlit meadows. Bees and bumblebees collect nectar and pollen on them, flying from flower to flower. Taking a closer look, here and there on the leaves we will notice butterfly caterpillars, and among the clusters of aphids, ladybugs scurry about devouring them. A bird flew up, holding a caught grasshopper in its beak.

Thus, the differences between different natural communities are immediately noticeable. The heat, bright sun and wind on the shore of the pond are replaced by coolness, darkness and silence of the forest. And even without knowing the exact names of the plants and animals we see, we notice differences in their composition.

Impact of human activities on natural communities

In natural communities before the appearance of humans, the numbers of various organisms in individual years could vary greatly. But unless any disasters occurred (extensive fires, floods) or significant climate changes, the formed natural communities continued to exist for hundreds and thousands of years. However, with the advent of man on Earth, the situation changed. Human activity has become a factor influencing natural communities.

In primitive society, when people were few in number, they did not have a significant impact on nature. But the more people there were on Earth, and most importantly, the more often they resorted to collective action, the more their influence increased. The advent of agriculture had a particularly strong impact. Even when a virgin part of the steppe is plowed, the composition of plants and animals changes. And in order to obtain new plots of land suitable for cultivation, people began to cut down, burn and uproot the forest. Here the change of plants and animals became even more dramatic. But even if the forest is not completely cleared, ordinary logging in it greatly changes forest natural communities. In cleared areas, the composition of plants and animals is always different than under the forest canopy.

The use of various chemicals to control pests also has a strong impact on wildlife, since this kills not only pests, but also many other animals, often very useful and playing a large role in the community.

The construction of roads and industrial construction, and other structures also have an impact not only on the area directly occupied by them, but also on the surrounding area. For example, during the construction of hydraulic structures, primarily dams on rivers, the water regime and, accordingly, the natural aquatic communities completely change. Also, a strong impact is observed during reclamation - draining swamps and waterlogged soils: due to a decrease in groundwater levels, the composition of plants changes, and with it the composition of animals.

As a result of human activity, there are almost no untouched natural communities left on Earth. Currently, all countries are taking various measures aimed at preserving all the nature around us.

Protection of natural communities

The protection of natural communities is given great national importance. The country's fauna is considered state property, that is, the property of the entire people. The law requires reasonable and humane treatment of animals. It obliges all citizens in their personal life and in their professional activities to strictly comply with the requirements and rules that contribute to the conservation of natural complexes and individual species of animals.

To preserve natural communities, a wide network of reserves, sanctuaries and other protected areas has been created, in which human intervention in natural communities is completely or partially prohibited and where wild animals and plants are in the most favorable conditions.

Family competition “Water of Life” Theoretical round.

Completed by: Larina T.I.

Lazovsky Nature Reserve named after L.G. Kaplanova

Vladivostok

A natural community is a collection of plants, animals, microorganisms adapted to living conditions in a certain territory, influencing each other and the environment. In the natural community, the cycle of substances is carried out and maintained. The number of species in a community depends on climatic conditions and the type of plant community. By their origin, communities can be natural or can be created by man (artificial). Usually a natural community is called a biogeocenosis. The concept of biogeocenosis, introduced by V.N. Sukachev (1940), has become widespread mainly in Russian literature. Abroad, especially in English-speaking countries, the term “ecosystem” is more often used in a similar meaning, although the latter is more ambiguous and is also used in relation to artificial complexes of organisms and abiotic components (aquarium, spaceship) and to individual parts of biogeocenosis (for example, rotting stump in the forest with all the organisms inhabiting it). Ecosystems can have arbitrary boundaries (from a drop of water to the biosphere as a whole), while biogeocenosis always occupy a certain territory. Further in our work we will use both of these concepts as equivalent.

So, biogeocenosis is a stable community of plants, animals and microorganisms that are in constant interaction with the components of the atmosphere, hydrosphere and lithosphere. Solar energy, soil minerals and atmospheric gases, water enter this community, and heat, oxygen, carbon dioxide, and waste products of organisms are released from it. The main functions of biogeocenosis are the accumulation and redistribution of energy and the circulation of substances.

Biogeocenosis is an integral self-regulating and self-sustaining system. It includes the following mandatory components: inorganic (carbon, nitrogen, carbon dioxide, water, mineral salts) and organic substances (proteins, carbohydrates, lipids, etc.);

autotrophic organisms - producers of organic substances;

heterotrophic organisms - consumers of ready-made organic substances of plant origin - consumers (consumers of the first order) and animals (consumers of the second and subsequent orders).

Heterotrophic organisms include decomposers - decomposers, or destructors, which decompose the remains of dead plants and animals, turning them into simple mineral compounds.

When talking about biocenoses, we consider only interconnected living organisms living in a given area. Biocenoses are characterized by species diversity, i.e. the number of species of living organisms that form it;

population density, i.e. the number of individuals of a given species per unit area or per unit volume (for aquatic and soil organisms);

biomass - the total amount of animal organic matter expressed in units of mass. Biomass is formed as a result of the capture of solar energy. The efficiency with which plants assimilate solar energy varies in different biocenoses. The total production of photosynthesis is called primary production.

Plant biomass is used by first-order consumers - herbivores - as a source of energy and material for creating biomass; Moreover, it is used extremely selectively, which reduces the intensity of interspecific struggle for existence and contributes to the conservation of natural resources. Herbivorous animals, in turn, serve as a source of energy and material for second-order consumers - predators, etc.

The largest amount of biomass is formed in the tropics and in the temperate zone, very little in the tundra and ocean.

Organisms that are part of biogeocenoses are influenced by nonliving

nature - abiotic factors, as well as from living nature - biotic influences.

Biocenoses are integral, self-regulating biological systems, which include living organisms living in the same territory.

The energy from sunlight is assimilated by plants, which are subsequently used by animals as food.

Food connections.

Biogeocenoses are very complex. They always contain many parallel and complexly intertwined food chains, and the total number of species is often measured in hundreds and even thousands. Almost always, different species 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.

Development and change communities

Changes in natural communities can occur under the influence of biotic, abiotic factors and humans. The change of communities under the influence of the vital activity of organisms lasts hundreds and thousands of years. Plants play the main role in these processes. An example of a change in community under the influence of the vital activity of organisms is the process of overgrowing of water bodies. Most lakes gradually become shallow and decrease in size. Over time, the remains of aquatic and coastal plants and animals, as well as soil particles washed away from the slopes, accumulate at the bottom of the reservoir. Gradually, a thick layer of silt forms at the bottom. As the lake becomes shallower, its shores become overgrown with reeds and reeds, then with sedges. Organic residues accumulate even faster and form peaty deposits. Many plants and animals are replaced by species whose representatives are more adapted to life in new conditions. Over time, a different community forms in place of the lake - a swamp. But the change of communities does not stop there. Shrubs and trees that are unpretentious to the soil may appear in the swamp, and ultimately the swamp may be replaced by a forest.

Thus, a change in communities occurs because, as a result of changes in the species composition of communities of plants, animals, fungi, and microorganisms, the habitat gradually changes and conditions favorable for the habitat of other species are created.

Change of communities under the influence of human activity. If the change of communities under the influence of the life activity of the organisms themselves is a gradual and long process, covering a period of tens, hundreds and even thousands of years, then the change of communities caused by human activity occurs quickly, over several years.

So, if wastewater, fertilizers from fields, and household waste enter reservoirs, then the oxygen dissolved in the water is spent on their oxidation. As a result, species diversity decreases, various aquatic plants (floating salvinia, amphibian knotweed) are replaced by duckweed, algae are replaced by blue-green algae, and “water blooms” occur. Valuable commercial fish are being replaced by low-value ones, shellfish and many species of insects are disappearing. A rich aquatic ecosystem turns into an ecosystem of a decaying reservoir.

If the human impact that caused the change in communities ceases, then, as a rule, a natural process of self-healing begins. Plants continue to play a leading role in it. Thus, after the cessation of grazing, tall grasses appear on the pastures, typical forest plants appear in the forest, the lake is cleared of the dominance of unicellular algae and blue-greens, and fish, mollusks, and crustaceans reappear in it.

If the species and trophic structure are simplified so much that the process of self-healing can no longer occur, then man is again forced to intervene in this natural community, but now for good purposes: grass is sown in pastures, new trees are planted in the forest, water bodies are cleaned and juveniles are released there fish

The community is capable of self-healing only with partial violations. Therefore, the influence of human economic activity should not exceed the threshold after which self-regulation processes cannot be carried out.

Change of communities under the influence of abiotic factors. The development and change of communities was and is greatly influenced by sudden climate changes, fluctuations in solar activity, mountain-building processes, and volcanic eruptions. These factors are called abiotic - factors of inanimate nature. They disrupt the stability of the habitat of living organisms.

So, having considered the concept of the general concept of biogeocenosis (natural community) and the food connections existing within them, let us consider a fresh water body as a natural community, which exist in abundance on the territory of our region.

Any natural body of water, such as a lake or pond, with its plant and animal population is a separate biogeocenosis. This natural system, like other biogeocenoses, has the ability for self-regulation and continuous self-renewal. Plants and animals inhabiting a reservoir are distributed unevenly in it. Each species lives in the conditions to which it is adapted. The most diverse and favorable conditions for life are created in the coastal zone.

Here the water is warmer, as it is heated by the sun's rays. It is quite saturated with oxygen. The abundance of light penetrating to the bottom ensures the development of many higher plants. Small algae are also numerous. Most animals also live in the coastal zone. Some are adapted to life on aquatic plants, others actively swim in the water column (fish, predatory swimming beetles and water bugs). Many are found at the bottom (barley beetles, toothless beetles, larvae of some insects - caddis flies, dragonflies, mayflies, a number of worms, etc.). Even the surface film of water serves as a habitat for species specially adapted to it. In quiet pools you can see predatory water strider bugs running on the surface of the water and whirligig beetles swimming quickly in circles. The abundance of food and other favorable conditions attract fish to the coastal zone.

In the deep bottom areas of the reservoir, where sunlight poorly penetrates, life is poorer and more monotonous. Photosynthetic plants cannot exist here. Due to weak mixing, the lower layers of water remain cold. Here the water contains little oxygen.

Special conditions are also created in the thickness of the water in open areas of the reservoir. It is populated by a mass of tiny plant and animal organisms, which are concentrated in the upper, warmer and well-lit layers of water. Various microscopic algae develop here; Numerous protozoa - ciliates, as well as rotifers and crustaceans - feed on algae and bacteria. This entire complex of small organisms suspended in water is called plankton. Plankton plays a very important role in the cycle of substances and in the life of a reservoir.

2. Food connections and stability of the pond biogeocenosis.

Let's consider why the system of reservoir inhabitants exists and how it is maintained. Power supply chains consist of several consecutive 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.

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Note.

When compiling a list of references, I would like to note that it does not contain links to Internet resources. By this we do not pretend that we did not use its capabilities and that we wrote the work solely on the processing of printed material. No, it’s just that most of the articles and books listed in the references were actually found by us on the Internet, and when writing this work we simply used their electronic (often scanned) copies, which had all the details of a printed publication. In this regard, we most actively used the website of the World Wildlife Fund - WWW.WWF.RU.