September 18, 2019

The ecosystem and biogeocenosis

By Jessica Cantrell


Community (biocenosis) (Greek: bios – life, koinos – general) – a stable population of plants, animals, fungi and microorganisms historically established and adapted to live together in a homogeneous area or territory.

The adaptability of community members to live together is expressed in a certain similarity that is required for the most important environmental conditions (lighting, the nature of the soil and air humidity, thermal conditions, etc.) and in regular relationships with each other. The connection between organisms is necessary for the implementation of their nutrition, reproduction, resettlement, protection, etc.

The scale of biocenotic groupings of organisms is different: from communities in a tree trunk, a burrow or a swamp (called microcommunities) to a site’s population of oak, pine or fir forests, meadows, lakes or ponds.

There is no fundamental discordance between communities of different scales, as small communities are an integral part of larger ones, which are characterized by an increase in the complexity and proportion of indirect connections between species.


The components of biocenosis are

  • Phytocenosis (a stable plant community)
  • Zoocenosis (a collection of interrelated animal species)
  • Mycocenosis (fungal community)
  • Microbiocenosis (community of microorganisms)


Communities of organisms are closely connected not only to each other, but also to the inorganic environment. Plants can only exist in the presence of light, carbon dioxide, water, mineral salts. Animals and other heterotrophic organisms (fungi, most bacteria) live on autotrophs, but need inorganic compounds such as oxygen and water.

In any biotope, the reserves of inorganic compounds necessary to maintain the vital activity of the organisms that inhabit it are relatively small and constantly diminishing; therefore, their renewal is necessary. From the environment, living organisms absorb nutrients and energy and return them (e.g. by respiration, excretion, decomposition of plant and animal waste). Thanks to these metabolic processes, biocenosis and the surrounding inorganic environment (ecotope) are a complex system called ecosystem or biogeocenosis.

Therefore, biogeocenosis is a homogeneous area on the earth’s surface with a certain composition of living organisms (biocenosis) and certain environmental conditions (biotope), which are combined through the exchange of substances and energy into a single natural complex. In many countries of the world, these natural complexes are called ecological systems (ecosystems).

The concept of ecosystem has no range or dimension, therefore, it applies to simple (anthill, rotten stump) as well as artificial (aquarium, reservoir, park) and natural complexes of organisms with their habitat.


The formation of the community is carried out due to the interspecific relationships that determine its structure, that is, the order of the conformation and functioning of the ecosystem.


The species structure of a community is understood as the diversity of species in the community and the proportion of the quantity of biomass of all the populations included in it.

Organisms of different species have different demands on the environment, therefore, under various environmental conditions, a composition of different species is formed. If the biological characteristics of one species differ sharply from others, then this species, due to competition, leaves the community and enters another corresponding biogeocenosis. In other words, in each community there is a natural selection of the organisms best adapted to the given environmental conditions.


In deserts of polar ice and tundra, with extreme heat shortages, in hot deserts without water, heavily polluted by sewage, community water bodies are extremely poor in species, as only a few can adapt to such adverse conditions. In the same biotopes where environmental conditions are close to optimal, in contrast, extremely species-rich communities emerge (the total number of species of living organisms in such ecosystems varies from hundreds to thousands). Examples include rain forests, complex oak forests and floodplains.

Species that are prevalent in the community in number of individuals or occupy a large area are called dominant. For example, forests, spruce dominate among trees, acidic grass, moss in the grass cover, field mice among rodents, etc. However, not all dominant species affect the community equally. Among them are the species that form the environment, which play a dominant role in determining the composition, structure and properties of the ecosystem by creating an environment for the whole community.


This community structure is mainly determined by the addition of phytocenosis. As a general rule, phytocenoses are divided into structural elements that are fairly well defined in space (vertically and horizontally) and sometimes in time. These elements include levels and microgroups. The former characterize the vertical; the latter the horizontal dissection of phytocenoses.

The main factor that determines the vertical distribution of plants is the amount of light that determines the temperature and humidity conditions at different levels above the soil surface.

Plants on the upper levels are more photophilic than those on the lower levels, and are better adapted to fluctuations in temperature and humidity; the lower levels are made up of plants that are less demanding on light; the grass cover of the forest as a result of the death of leaves, stems and roots is involved in the process of soil formation and therefore affects the plants on the upper level.