Populations in nature do not live in isolation. They interact with populations of other species, forming together with them integral systems of an even higher supraspecific level of organization – biotic communities, ecosystems.
A community (biocenosis) is a set of plant and animal species that coexist for a long time in a certain space and represent a certain ecological unity.
These formations develop according to their own laws. One of the main tasks of ecology is to identify these laws; find out how the sustainable existence and development of communities is maintained, what effect changes in various environmental factors have on them.
The fact that communities are not random formations is evidenced by the fact that similar communities appear in areas similar in geographic location and natural conditions.
Example: the lakes of the middle zone are characterized by a great similarity of fauna and flora. In the composition of the fish population, you can easily find such well-known species as roach, perch, pike, ruff, etc.
A careful study reveals not only the similarity of species in biocenoses, but also the similarity of the connections between them. These connections are extremely varied. The species included in the community supply each other with everything necessary for life – food, shelter, conditions for reproduction. The interrelationships of living organisms make it possible to use up natural resources more fully. They limit the increase in the number of individuals of certain species, that is, they perform a regulatory function and ensure the stability of ecosystems.
The natural living space occupied by a community is called a biotope (or ecotope).
Biotope and biocenosis form a biogeocenosis, in which stable interactions between elements of animate and inanimate nature are maintained for a long time.
A biogeocenosis is a historically formed set of living organisms (biocenosis) and an abiotic environment together with the area of the earth’s surface (biotope) occupied by them.
The boundary of the biogeocenosis is usually determined by the plant community (phytocenosis).
Plant communities usually do not have sharp boundaries and gradually transform into each other when natural conditions change.
The transition zones between communities are called ecotones.
Example: on the border of forests and tundra in the north of our country, there is a transition zone – forest tundra. Here woodlands, shrubs, sphagnum bogs and meadows alternate. On the border of the forest and the steppe, the forest-steppe zone extends. The more humid areas of this zone are occupied by forest, while dry areas are occupied by the steppe.
From site to site, not only the composition of vegetation changes, but also the animal world, the features of the material-energy exchange between organisms and their physical environment.
An ecosystem (from the Greek oikos – “dwelling” and systema – “union”) is any community of living organisms together with their physical environment, united by the metabolism and energy into a single complex.
Consideration of the ecosystem is important in those cases when it comes to the flows of matter and energy circulating between living and inanimate components of nature, the dynamics of elements that support the existence of life, and the evolution of communities. Neither an individual organism, nor a population, nor a community as a whole can be studied in isolation from the environment. An ecosystem is essentially what we call nature.
Example: the ecosystem of a lake, which includes all living organisms, as well as their habitat, which includes water, features of the bottom and soil, air in contact with water, solar radiation, etc.
Ecosystem and biogeocoenosis are close concepts, but if the term “ecosystem” is suitable for denoting systems of any rank, then “biogeocenosis” is a territorial concept, referring to such land areas that are occupied by plant communities – phytocenoses.
Not every ecosystem is a biogeocenosis, but every biogeocenosis is an ecosystem.
Ecosystem is a very broad concept and is applicable to both natural (for example, tundra, ocean) and artificial complexes (for example, an aquarium).
The scale of ecosystems can vary.
Example: a tree bud, a puddle, a crumbling stump with its inhabitants.
- Mesoecosystem = biogeocenosis.
Example: spruce, oak, birch, meadow.
- Macroecosystem is a biome, or natural area.
Example: desert, tundra, ocean.
All ecosystems of our planet are interconnected and constitute a single large ecosystem – the biosphere. It covers part of the atmosphere, part of the lithosphere and the entire hydrosphere. The integral doctrine of the biosphere was created by the outstanding Russian scientist V. I. Vernadsky (1863–1945).