In the process of everyday life, not every person notices his interaction with various natural complexes. Hurrying to work, hardly anyone, except perhaps a professional ecologist or biologist, will pay special attention to the fact that he crossed the square or park. Well passed and passed, so what? But this is already a biocenosis. Each of us will be able to recall examples of such an involuntary, but constant interaction with ecosystems, if we only think about it. We will try to consider in more detail the question of what are biocenoses, what they are and what they depend on.
What is a biocenosis?
Most likely, few people remember that he studied biocenoses at school. Grade 7, when this topic is being studied in biology, is far in the past, and completely different events are recalled. Recall what is a biocenosis. This word is formed by the merger of two Latin words: "bios" - life and "cenosis" - common. This term refers to the totality of microorganisms, fungi, plants and animals living in the same territory, interconnected and interacting with each other.
Any biological community includes the following components of a biocenosis:
- microorganisms (microbiocenosis);
- vegetation (phytocenosis);
- animals (zoocenosis).
Each of these components plays an important role and can be represented by individuals of different species. However, it should be noted that phytocenosis is a leading component that determines microbiocenosis and zoocenosis.
When did this concept appear?
The concept of "biocenosis" was proposed by the German hydrobiologist Möbius at the end of the 19th century, when he studied the habitats of oysters in the North Sea. During the study, he found that these animals can live only in strictly defined conditions, characterized by depth, flow rate, salinity and water temperature. In addition, Mobius noted that along with oysters in the same territory strictly defined species of marine plants and animals live. Based on the data obtained, in 1937, the scientist introduced the concept we are considering to designate the association of groups of living organisms living and coexisting in the same territory, due to the historical development of species and long-term natural selection. The modern concept of "biocenosis" is interpreted by biology and ecology somewhat differently.
Classification
Today, there are several signs according to which biocenosis can be classified. Size classification examples:
- macrobiocenosis (sea, mountain ranges, oceans);
- mesobiocenosis (swamp, forest, field);
- microbiocenosis (flower, old stump, leaf).
Biocenoses can also be classified according to habitat. The following three types are recognized as the main ones:
- nautical;
- freshwater;
- ground.
Each of them can be divided into subordinate, smaller and local groups. So, marine biocenoses can be subdivided into benthic, pelagic, shelf and others. Freshwater biological communities are river, swamp and lake. Terrestrial biocenoses include coastal and inland, mountain and lowland subtypes.
The simplest classification of biological communities is their division into natural and artificial biocenoses. Among the first, primary ones are formed, formed without human influence, as well as secondary ones, which underwent a change due to the influence of natural elements or the activities of human civilization. Let us consider in more detail their features.
Natural biological communities
Natural biocenoses are associations of living things created by nature itself. Such communities are natural systems that form, develop and function according to their own special laws. The German ecologist V. Tischler identified the following features characterizing such formations:
1. There are communities of prefabricated elements, which can act as representatives of individual species, and entire complexes.
2. Parts of the community may be interchangeable. So, one species can be supplanted and completely replaced by another, having similar requirements for the conditions of existence, without negative consequences for the entire system.
3. Due to the fact that in the biocenosis the interests of different species are opposite, the whole supraorganic system is founded and exists due to the balancing of forces directed opposite.
4. Each natural community is built on the quantitative regulation of one species by others.
5. The dimensions of any supraorganism systems depend on external factors.
Artificial Biological Systems
Artificial biocenoses are created, maintained and managed by humans. Professor B. G. Johannsen introduced the concept of anthropocenosis into ecology, that is, a natural system artificially created by people, for example, a public garden, a terrarium or an aquarium. Among the artificial biocenoses are distinguished agrobiocenoses (agrocenoses) - communities created by humans to produce any products. These include:
- reservoirs;
- channels
- ponds;
- drained swamps;
- pastures;
- fields for growing various crops;
- shelterbelts;
- Artificially renewed afforestation.
The characteristic features of agrocenoses are:
Such artificial systems are ecologically rather unstable, and without human participation, agrocenoses of vegetable and grain crops will last about a year, agrobiocenoses of perennial herbs will last about three years. The most stable biocenoses are artificial fruit crops, since without human exposure they can exist for several decades.
- agrophytocenosis as the basis of life;
- lack of system self-regulation;
- low species diversity;
- dominance of domestic animals or cultivated plants;
- receiving additional support from a person (weed and pest control, fertilizing, etc.);
- the impossibility of a long existence without human participation.
However, it should be noted that even the poorest agrocenoses in species diversity have dozens of organisms belonging to different ecological and systematic groups. Any field sown by a person with fodder or agricultural crops is a biocenosis populated by various living organisms. Examples are the field of rye or wheat, where, in addition to the main crop, weeds also “live”; and various insects (both pests and their antagonists); and many microorganisms and invertebrates.
Structural units of biosystems
As already mentioned, natural and artificial biocenoses consist of several stable structural components, such as phytocenosis, zoocenosis and microbiocenosis. The leading one is phytocenosis, which is a sustainable community of plants. Due to its fixity and immobility, it is he who serves as a relatively constant basis for the structure of the biological system. Microorganisms, unlike plants, are not attached to any part of the surface and can be carried by wind or water over fairly large distances. The interconnection of the components of the biocenosis is manifested in the dependence of animals on plants, since only representatives of the flora can convert inorganic substances into organic ones.
A large role in the life of any biocenosis is played by a variety of microorganisms that contribute to the conversion of dead organic matter into minerals.
The structure of biological systems
Each biocenosis is characterized by a certain structure:
- Spatial, vertical or horizontal, formed as a result of space exploration of the biological community and resulting from competing relationships for energy sources.
- Species, determined by the composition, wealth and diversity of the elements of the biosystem, as well as the ratio of the number of all populations included in it. The types of biocenosis that have the largest quantitative representation are called dominants.
- Trophic or food, which is determined by the food chains between organisms.
All the various structural aspects of biocenoses are closely interconnected. As a rule, the more complex the spatial structure is, the richer and more diverse its species representation is. Over time, the structure of the biocenosis varies insignificantly. Such a state of relative stability arising in the process of interaction of constituent elements is called homeostasis.
Let us consider in more detail the main structures characterizing the biocenosis.
Spatial structure
Biocenosis has its own structure in space, which can be both vertical and horizontal.
The vertical structure is formed as a result of the distribution of different species of plants and animals at different altitudinal levels of the biosystem, which leads to the formation of a tier. Such a structure is largely determined by the layering of the plant community, namely, the horizons of the location of the most productive parts of plants, such as the root system and photosynthetic foliage. Phytocenosis is characterized by both aboveground and underground tiers. The first is manifested in the possibility of joint growth of many plant species with different needs in sunlight. This is most pronounced in the forests of the temperate climatic zone, where there are arboreal and shrubbery upper tiers, shrubs and grasses are located somewhat lower, and just above the surface of the earth there is a subsoil tier, usually consisting of mosses or lichens.
Underground layering in biological systems allows the phytocenosis to make the most use of soil moisture, due to the different depths of the plant root system. The steppe regions are characterized by a three-level arrangement: the root-root systems lie most deeply, then the roots of various cereal crops go, and very close to the surface are tubers, bulbs and root systems of annual plants.
The horizontal structure of the biocenosis is reflected in the synusia - parts of the phytocenosis, consisting of plants of one or more closely related species, ecologically or spatially separated from each other. They can be temporary or permanent, epiphytic, longline or intrasoil.
The species structure of biological communities
A distinctive feature of any biocenosis is its species structure. The complexity and diversity of the species composition is largely determined by the habitat and the degree of complexity of the conditions in which the biocenosis exists. Examples of poor species diversity are highlands, tundra, desert. A rich ecosystem of species - coral reefs and rainforests.
The biological species, prevailing in number, are the species core and are called dominants. So, in a birch forest it will be birch, on a wheat field - wheat. In any biocenosis, there are species that exist only thanks to dominants, these are the so-called pre-dominants, for example, roe deer in the forest undergrowth or squirrel in the pine-spruce forest.
In addition, biological communities have edificators, that is, animal or plant species that create the necessary conditions for life for other creatures. So, for example, in the steppe biocenoses the most powerful edificator is feather grass.
In order to assess the role of a particular species in the structure of a biological community, indicators based on quantitative accounting are used, such as its abundance, frequency of occurrence, Shannon's diversity index, and species saturation.