Message on the topic of natural natural communities. Natural community: concept and types. Ties in the natural community

>>Natural communities

§ 89. Natural communities

The relationship of organisms.

As you know, various types of plants are not distributed evenly, but depending on local conditions, forming natural groupings, or vegetative communities.

Finally, the natural community also includes various organisms that feed on waste: dead plants or their parts (branches, leaves), as well as the corpses of dead animals or their excrement. They may be some animals - gravedigger beetles, earthworms. But the main role in the process of decomposition of organic matter is played by mold fungi and bacteria. It is they who bring the decomposition of organic substances to mineral substances, which can again be used by plants. In general, in natural communities there is a cycle of substances.

In addition to food links, there are others in natural communities.

So, plants in any place create a special climate, a microclimate. Various factors of inanimate nature - temperature, humidity, illumination, movement of air or water - under the canopy of plants will differ markedly from those common to the area. Changes in these factors under the canopy of plants will always be less dramatic than in open areas. So, in the forest during the day it is always cooler, more humid and shady, and at night, on the contrary, it is warmer than in the open air. Even in a meadow covered only with grass, the temperature and humidity on the surface of the soil will be different than on bare soil.

Finally, only the presence of vegetation cover protects the soil from erosion - spraying and erosion.

Naturally, the microclimate also affects the species composition and life activity of animals inhabiting a given community. Each animal species chooses for its habitat places not only with the availability of the necessary food, but also with the most suitable temperature, illumination, conditions for burrows and nests.

But animals in natural communities also influence plants.

First of all, many flowering plants are pollinated by insects, sometimes even by certain species, and in the absence of them they cannot reproduce. Further, seed dispersal in some plants is also produced by animals. Finally, the burrowing activity of various animals, primarily earthworms, contributes to the loosening of the soil, water and air penetrate it more easily and deeper, and the processes of decomposition of organic residues take place faster.

1. What is called a natural community?
2. What connections, besides food, exist in natural communities?

3. How is the circulation of substances carried out in natural communities?

4. What effect do animals have on plants?
5. What is the importance of microorganisms in the natural community?
6. Why can lichens, fungi and various arthropods be seen on old trees?

Biology: Animals: Proc. for 7 cells. avg. school / B. E. Bykhovsky, E. V. Kozlova, A. S. Monchadsky and others; Under. ed. M. A. Kozlova. - 23rd ed. - M.: Education, 2003. - 256 p.: ill.

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A natural community is a group of living organisms, together with an abiotic environment, located in a certain area. Its structure includes several components that interact with each other, as a result, the circulation of substances and energy occurs in nature.

The ecosystem includes a phytocenosis, which, like the natural community of animals, plays one of the main roles in the biogeocenosis.

What is a natural community

All living organisms in nature are interconnected, they do not live separately, but constantly interact with each other, forming communities. These complexes of living organisms include both plants, bacteria, fungi, and animals.

All emerging natural communities are not accidental, their emergence and development is due to the interaction of factors of inanimate nature - the abiotic environment. Thus, each community is characteristic of a particular environment.

It should be noted that communities of organisms are not permanent, they can move from one to another - it depends on external and internal factors. The transition process can take hundreds or thousands of years. A striking example of such a transition is the overgrowth of a lake. Over time, the reservoir accumulates organic matter, becomes shallow, some plants are replaced by others, and in the end the lake becomes a swamp. But the process does not stop there - the swamp can overgrow, gradually turning into a forest. The natural community of the field can also turn into a forest.

Kinds

Natural communities come in different sizes. The largest are communities of continents, oceans, islands. Smaller - communities of the desert, taiga, tundra. The smallest communities are meadows, fields, forests and others.

One can also distinguish between natural and artificial natural communities. Natural ones arise for natural reasons - a change in the species composition of organisms, climate change. Such natural communities are very stable, and the transition from one to another can take quite a long time. Examples are forest, steppe, swamp, etc.

Artificial natural communities arise as a result of human impact on nature. They are unstable and can exist only if a person constantly affects the environment: flying, planting, watering. Only then does the given natural community remain unchanged. A field, a garden, a square, a park are all examples of artificial groups.

Ties in the natural community

Each natural community has various connections, the most important of which is food. This is the main form of interaction between living organisms.

The very first and main link is plants, as they use solar energy for their development. Plants can, by processing carbon dioxide and minerals, create organic matter.

Representatives of the flora, in turn, feed on various microorganisms, herbivores.

Predators feed on microorganisms and invertebrates, they can also eat other animals.

Thus, a food chain arises: plants - herbivores - predatory animals. This is a primitive chain, in nature everything is much more complicated: usually some animals feed on others, predators can eat invertebrates and some plants, etc.

The structure of the natural community

In total there are four main links that continuously interact with each other.

1. Solar energy and inorganic substances of the environment.
2. Autotrophic living organisms or plants. This includes a large number of living organisms, they consume only solar energy and inorganic substances.
3. Heterotrophic living organisms - animals and fungi. These organisms consume both energy and autotrophic organisms.
4. Heterotrophic living organisms - worms, bacteria and fungi. This group recycles dead organic matter. Thanks to them, salts, minerals, water and gas are formed - everything that is necessary for living beings from the second group.

All these links interact with each other, as a result of this, a cycle of energy and substances exists in nature.

The peculiarity of the natural community

The originality almost completely depends on the species composition of organisms living in a given territory.

The name of the biocenosis is given by the predominant species. For example, if an oak occupies a dominant place in a natural community, then we will call it an oak forest, if spruce and pine forests grow in equal numbers, then this is a coniferous or spruce-pine forest. The same applies to fields and meadows, which can be sedge, wheat and others.

A person should always remember that the natural community, or biogeocenosis, is an integral living organism, and if one component is violated or changed, the entire system will change. Therefore, destroying one species of plants or animals or introducing an alien species into the territory of the community, it is possible to disrupt all internal processes, which will adversely affect the entire community.

Man constantly influences the world around him, natural communities change. So, for example, deforestation leads to desertification of land, the construction of dams - to swamping of nearby territories.

Natural community - a set of plants, animals, microorganisms adapted to the conditions of life in a certain area, affecting each other and the environment. It carries out and maintains the circulation of substances.

Natural communities of different scales can be distinguished, for example, continents, oceans, forests, meadows, taiga, steppes, deserts, ponds, and lakes. Smaller natural communities are part of larger ones. Man creates artificial communities, such as fields, gardens, aquariums, spaceships.

Each natural community is characterized by a variety of relationships - food, habitat, etc.

The main form of links between organisms in a natural community is food links. Plants are the initial, main link in any natural community, which creates a reserve of energy in it. Only plants, using solar energy, can create organic substances from the minerals and carbon dioxide in the soil or water. Plants are eaten by herbivorous invertebrates and vertebrates. They, in turn, feed on carnivorous animals - predators. So in natural communities, food ties arise, a food chain: plants - herbivores - carnivores (predators - approx. site). Sometimes this chain becomes more complicated: others can feed on the first predators, and third ones, in turn, can feed on them. For example, caterpillars eat plants, and caterpillars are eaten by predatory insects, which, in turn, serve as food for insectivorous birds, and birds of prey eat them.

Finally, the natural community also includes various organisms that feed on waste: dead plants or their parts (branches, leaves), as well as the corpses of dead animals or their excrement. They may be some animals - gravedigger beetles, earthworms. But the main role in the process of decomposition of organic matter is played by mold fungi and bacteria. It is they who bring the decomposition of organic substances to mineral substances, which can again be used by plants. In general, in natural communities there is a cycle of substances.

The change of natural communities can take place 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 a major role in these processes. An example of a community change under the influence of the vital activity of organisms is the process of overgrowing of water bodies. Most of the lakes are gradually shallowing and decreasing in size. At the bottom of the reservoir, over time, the remains of aquatic and coastal plants and animals accumulate, as well as soil particles washed off the slopes. Gradually, a thick layer of silt forms at the bottom. As the lake becomes shallow, its shores become overgrown with reeds and reeds, then with sedges. Organic residues accumulate even faster, forming 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 is formed on the site of the lake - a swamp. But the change of communities does not stop there. Shrubs and trees unpretentious to the soil may appear in the swamp, and eventually the swamp may be replaced by a forest.

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

Change of communities under the influence of human activities. 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 sewage, fertilizers from the fields, household waste enter the reservoirs, then the oxygen dissolved in the water is spent on their oxidation. As a result, species diversity decreases, various aquatic plants (floating salvinia, highlander amphibian) are replaced by duckweed, blue-green algae, and "water bloom" occurs. Valuable commercial fish are being replaced by low-value ones, mollusks and many insect species are disappearing. A rich aquatic ecosystem turns into an ecosystem of a decaying reservoir.

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

If the species and trophic structures are so simplified that the process of self-healing can no longer occur, then a person is again forced to intervene in this natural community, but now with good goals: grasses are sown on 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 in case of partial violations. Therefore, the impact 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 has been greatly influenced by abrupt climate changes, fluctuations in solar activity, mountain-building processes, and volcanic eruptions. These factors are called abiotic - factors of inanimate nature. They violate the stability of the habitat of living organisms.

Unfortunately, the ability of natural communities to self-heal is not unlimited: if external impact exceeds a certain limit, the ecosystem will collapse, and the territory where it was located will itself become a source of ecological imbalance. Even if the restoration of the ecosystem is possible, it will cost much more than timely measures to preserve it.

The ability of natural communities to self-regulate is achieved due to the natural diversity of living beings that have adapted to each other as a result of long-term co-evolution. With a decrease in the number of one of the species, its partially vacated ecological niche is temporarily occupied by an ecologically close species of the same community, preventing the development of certain destabilizing processes.

The situation is quite different if any species has fallen out of the community. In this case, the system of "mutual hedging" of ecologically close species is violated, and part of the resources they consume is not used, that is, an ecological imbalance arises. With further impoverishment of the natural species composition of the community, conditions are created for excessive accumulation of organic matter, outbreaks of insect numbers, introduction of alien species, etc.
Usually, the so-called rare species are the first to fall out of the natural community, since their rarity is due to the fact that they are the most demanding in terms of habitat conditions and are sensitive to their change. In a stable community, rare species should be among all groups of living organisms. Therefore, the presence of various rare species serves as an indicator of the conservation of natural biodiversity in general and, thus, the ecological usefulness of the natural community.

As you know, the biotic cycle of substances is provided by species occupying different trophic levels:

Producers that produce organic matter from inorganic are, first of all, green plants;
first-order consumers consuming phytomass are herbivores, both vertebrates and invertebrates;
consumers of the second and higher orders that feed on other consumers, for example, predatory insects and spiders, predatory fish, amphibians and reptiles, insectivorous and predatory birds and mammals;
decomposers that decompose dead organic matter - this process is provided, first of all, by a variety of microorganisms, fungi, as well as earthworms and some other soil invertebrates.

The study of full-fledged natural communities shows that rare species are present in them at all trophic levels. The most indicative is the presence in the community of viable populations of consumers of higher orders: they are at the top of the trophic pyramid and, thus, their state to the greatest extent depends on the state of the trophic pyramid as a whole.

An important characteristic of any species is the size of the territory, the minimum necessary for the existence of its viable population. For conservation purposes, several size classes of territories necessary for the existence of a viable population of the species can be distinguished.

In the size range from a separate plant association to biogeocenosis inclusive, it is advisable to distinguish areas of the following size classes:

1 - microbiotopes, separate areas of plant associations, necessary, for example, for fungi, many plants and invertebrates;
2 - a combination of certain microbiotopes and plant associations, necessary, for example, for some plants, for amphibians, reptiles, dragonflies, many butterflies;
3 - biogeocenosis as a whole, necessary for small birds and mammals, the largest and most mobile insects, and from plants - for forest-forming tree species.

For the existence of populations of medium and large birds and mammals, territories are usually required that significantly exceed the area occupied by one biogeocenosis. For such territories, we distinguish the following size classes:

4 - a group of similar biocenoses or their combinations;
5 - natural massifs, consisting of various biotopes;
6 - natural massifs and their complexes of the regional level.

Under the conditions of transformation of natural territories, the most vulnerable species are those that need territories of higher (IV-VI) size classes, especially since most of these species belong to consumers of higher orders.

Thus, the presence of all trophic levels serves as an indicator of the qualitative usefulness of an ecosystem, and within each trophic level there are species whose populations occupy significantly different ecological niches and territories of different size classes.

The condition for the preservation of the environment-forming functions of natural communities is inter-ecosystem connections that make it possible to naturally restore disturbed areas due to the migration of living organisms from neighboring areas that are better preserved. Then they insure each other in the same way as populations of similar species within the same community. Being functionally interconnected within the region, natural communities form a natural framework on which regional ecological stability rests. Therefore, the preservation of a system of interconnected natural communities capable of self-healing is the only real way to maintain the human habitat.