A natural community is a collection of plants, animals, microorganisms adapted to living conditions in a certain territory, influencing each other and the environment. The circulation of substances is carried out and maintained in it.
We can distinguish natural communities of different scales, 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, and spaceships.
Each natural community is characterized by various relationships - food, habitat, etc.
The main form of connections between organisms in a natural community is food connections. The initial, main link in any natural community, creating a supply of energy in it, are plants. Only plants, using solar energy, can create organic substances from minerals and carbon dioxide found in soil or water. Herbivorous invertebrates and vertebrates feed on plants. They, in turn, feed on carnivores - predators. This is how food connections, a food chain, arise in natural communities: plants - herbivores - carnivores (predators - website note). Sometimes this chain becomes more complicated: the first predators can feed on others, and they, in turn, feed on others. For example, caterpillars eat plants, and caterpillars are eaten by predatory insects, which, in turn, serve as food for insectivorous birds, which feed on birds of prey.
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 can be some animals - gravedigger beetles, earthworms. But the main role in the process of decomposition of organic matter is played by molds and bacteria. It is they who bring the decomposition of organic substances to mineral ones, which can again be used by plants. In total, the circulation of substances occurs in natural 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.
Unfortunately, the ability of natural communities to self-heal is not unlimited: if the 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 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 thanks to the natural diversity of living beings that have adapted to each other as a result of long-term joint evolution. When the number of one of the species decreases, 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 completely different if a species has dropped out of the community. In this case, the system of “mutual insurance” of ecologically similar species is disrupted, and part of the resources they consume is not used, that is, an ecological imbalance arises. As the natural species composition of the community further depletes, conditions are created for excessive accumulation of organic matter, outbreaks of insect numbers, the introduction of alien species, etc.
Usually, the so-called rare species are the first to drop out of the natural community, since their rarity is due to the fact that they are the most demanding of living conditions and sensitive to their changes. In a stable community, rare species should be present among all groups of living organisms. Therefore, the presence of various rare species serves as an indicator of the preservation of natural biodiversity as a whole and, thus, the ecological usefulness of the natural community.
As is known, the biotic cycle of substances is provided by species occupying different trophic levels:
Producers that produce organic matter from inorganic matter are, first of all, green plants;
First-order consumers who consume phytomass are herbivores, both vertebrates and invertebrates;
consumers of the second and higher orders, feeding on other consumers, for example, predatory insects and spiders, predatory fish, amphibians and reptiles, insectivores and birds of prey and mammals;
decomposers that decompose dead organic matter - this process is provided primarily 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 significant thing 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 condition is most dependent 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 a species can be distinguished.
In the size range from an individual plant association to the biogeocenosis inclusive, it is advisable to identify areas of the following size classes:
1 - microbiotopes, individual areas of plant associations, necessary, for example, for fungi, many plants and invertebrate animals;
2 - a combination of certain microbiotopes and plant associations, necessary, for example, for some plants, amphibians, reptiles, dragonflies, and many butterflies;
3 - biogeocenosis as a whole, necessary for small birds and mammals, the largest and most mobile insects, and among 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 at the regional level.
In the conditions of transformation of natural territories, the most vulnerable species are those that require territories of higher (IV-VI) size classes, especially since most of these species belong to consumers of higher orders.
Thus, an indicator of the qualitative usefulness of an ecosystem is the presence of all trophic levels, and within each trophic level there are species whose populations occupy significantly different ecological niches and territories of different size classes.
The condition for preserving the environment-forming functions of natural communities is inter-ecosystem connections that make possible the natural restoration of disturbed areas due to the migration of living organisms from neighboring areas that are better preserved. Then they protect 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 environmental stability rests. Therefore, preserving a system of interconnected natural communities capable of self-healing is the only real way to maintain the human habitat.
A natural community is a group of living organisms together with the abiotic environment located in a certain territory. Its structure includes several components that interact with each other, resulting in the circulation of substances and energy in nature.
The ecosystem includes a phytocenosis, which, like the natural community of animals, plays a major role 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 plants, bacteria, fungi, and animals.
All emerging natural communities are not accidental; their emergence and development are determined by the interaction of factors of inanimate nature - the abiotic environment. Thus, each community is characteristic of a specific environment.
It is worth noting that communities of organisms are not constant, they can move from one to another - this 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 overgrowing of a lake. Over time, the reservoir accumulates organic matter, becomes shallow, some plants are replaced by others, and eventually the lake becomes a swamp. But the process does not stop there - the swamp can become overgrown, 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, and islands. Smaller ones - desert, taiga, tundra communities. The smallest are communities of meadows, fields, forests and others.
You 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 include forest, steppe, swamp, etc.
Artificial natural communities arise as a result of human impact on nature. They are unstable and can only exist if a person constantly influences the environment: flying, planting, watering. Only then does the given natural community remain unchanged. A field, a vegetable garden, a square, a park - all these are examples of artificial groups.
Connections 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, since they use solar energy for their development. Plants can process carbon dioxide and minerals to create organic matter.
Representatives of the flora, in turn, feed on various microorganisms and herbivores.
Predators feed on microorganisms and invertebrates, and they can also eat other animals.
This creates a food chain: plants - herbivores - carnivores. 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.
Natural community structure
There are four main links in total that continuously interact with each other.
- Solar energy and inorganic substances of the environment.
- Autotrophic living organisms or plants. This includes a large number of living organisms; they consume only solar energy and inorganic substances.
- Heterotrophic living organisms - animals and fungi. These organisms consume both energy and autotrophic organisms.
- 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 which a cycle of energy and substances exists in nature.
The uniqueness of the natural community
The originality depends almost entirely on the species composition of organisms living in a given territory.
The name of the biocenosis is given according to the predominant species. For example, if oak occupies a dominant place in a natural community, then we will call it an oak forest; if spruce and pine trees 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 a natural community, or biogeocenosis, is an integral living organism, and if one component is disrupted or changed, the entire system will change. Therefore, by destroying one species of plants or animals or introducing an alien species into the territory of a community, all internal processes can be disrupted, which will adversely affect the entire community.
Man constantly influences the world around him, natural communities change. For example, deforestation leads to desertification of land, and the construction of dams leads to swamping of nearby areas.
>>Natural communities
§ 89. Natural communities
Interrelation of organisms.
As you know, different types of plants are not distributed evenly, but depending on local conditions, forming natural groups, or plant 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 molds and bacteria. It is they who bring the decomposition of organic substances to mineral ones, which can again be used by plants. In total, the circulation of substances occurs in natural communities.
In addition to food connections, there are others in natural communities.
Thus, plants in any place create a special climate, microclimate. Various factors of inanimate nature - temperature, humidity, light, air or water movement - under the plant canopy will differ markedly from the general ones for the area. Changes in these factors under a plant canopy will always be less dramatic than in open areas. So, in the forest during the day it is always cooler, humid and shady, and at night, on the contrary, it is warmer than in the open air. Even in a meadow covered only by grass, the temperature and humidity at the soil surface will be different than in bare soil.
Finally, only the presence of vegetation protects the soil from erosion - spraying and washout.
Naturally, the microclimate also affects the species composition and life activity of the animals inhabiting a given community. Each species of animal chooses for its habitat places not only with the presence of the necessary food, but also with the most suitable temperature, illumination, and conditions for constructing 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 their absence cannot reproduce. Further, the distribution of seeds in some plants is also carried out by animals. Finally, the digging activity of various animals, primarily earthworms, contributes to loosening the soil, water and air penetrate into it more easily and deeply, and the processes of decomposition of organic residues occur more quickly.
1. What is called a natural community?
2. What connections, besides food ones, 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 you see lichens, fungi and various arthropods on old trees?
Biology: Animals: Textbook. for 7th grade 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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