Biosphere, its structure and boundaries

The largest generalization in the complex of earth sciences (geology, geography, geochemistry, biology) was the doctrine of the biosphere, created by the Russian scientist V. I. Vernadsky. Having begun his scientific activity (as a geologist) with the study of sedimentary rocks of the earth's crust, V. I. Vernadsky revealed the enormous role of living organisms in the complex geochemical processes of our planet. In 1926, his book Biosphere was published. This work deeply analyzes the complex relationship between living organisms and the inanimate nature of the Earth. His work was somewhat ahead of its time. Only in the second half of the 20th century, against the backdrop of exacerbated environmental problems, did his theory of the biosphere become widespread.

An important element of V. I. Vernadsky's teaching about the biosphere is the idea of ​​the close dependence of the biosphere on human activity and its preservation as a result of a reasonable attitude of man to nature. The scientist wrote:

Humanity taken as a whole becomes a powerful geological force. Before him, before his thought and work is the question of the restructuring of the biosphere in the interests of free-thinking humanity as a whole. This new state of the biosphere, to which we are approaching without noticing it, is the noosphere. one

At present, the doctrine of the biosphere is the most important part of ecology, directly related to the problems of regulating the interaction between man and nature.

For the first time the term "biosphere" was used by J. B. Lamarck at the beginning of the 19th century. Later, it was mentioned in the work of the Austrian geologist E. Suess in 1875. However, this concept was not developed in detail by these scientists, but was used casually to designate the area of ​​life on Earth. Only in the works of V. I. Vernadsky it is analyzed in detail and carefully, and it is understood as the “shell of life” on our planet.

Biosphere call the totality of all living organisms of our planet and those areas of the geological shells of the Earth that are inhabited by living beings and have been exposed to their influence during geological history.

The boundaries of the biosphere. Living organisms are unevenly distributed in the geological shells of the Earth: lithosphere, hydrosphere and atmosphere(Fig. 1). Therefore, the biosphere now includes the upper part of the lithosphere, the entire hydrosphere and the lower part of the atmosphere.

Rice. one.The area of ​​distribution of organisms in the biosphere:1 - the level of the ozone layer, delaying hard ultraviolet radiation; 2 - snow border; 3 - soil; 4 - animals living in caves; 5 - bacteria in oil wells

The lithosphere is the outermost solid shell of the Earth. Its thickness varies between 50–200 km. The distribution of life in it is limited and sharply decreases with depth. The vast majority of species are concentrated in the upper layer, which is several tens of centimeters thick. Some species penetrate to a depth of several meters or tens of meters (burrowing animals - moles, worms; bacteria; plant roots). The greatest depth at which some types of bacteria have been found is 3–4 km (in groundwater and oil-bearing horizons). The spread of life into the depths of the lithosphere is hindered by various factors. Penetration of plants is impossible due to lack of light. For all forms of life, the density of the medium and temperature, which increase with depth, also serve as significant obstacles. On average, the temperature increase is about 3 ° C for every 100 m. That is why the three-kilometer depth is considered the lower limit of the distribution of life in the lithosphere (where the temperature reaches about +100 ° C).

Hydrosphere- the water shell of the Earth, is a collection of oceans, seas, lakes and rivers. Unlike the lithosphere and atmosphere, it is completely mastered by living organisms. Even at the bottom of the World Ocean, at depths of about 12 km, various types of living beings (animals, bacteria) were found. However, the majority of species inhabit the hydrosphere within 150–200 m from the surface. This is due to the fact that light penetrates to such a depth. And consequently, in the lower horizons, the existence of plants and many species that depend on plants for nutrition is impossible. The spread of organisms at great depths is ensured by the constant "rain" of excrement, the remains of dead organisms falling from the upper layers, as well as predation. Hydrobionts live in both fresh and salt water and are divided into 3 groups according to their habitat:

1) plankton - organisms living on the surface of water bodies and passively moving due to the movement of water;

2) nekton - actively moving in the water column;

3) benthos - organisms that live at the bottom of water bodies or burrow into silt.

Atmosphere- the gaseous shell of the Earth, which has a certain chemical composition: about 78% nitrogen, 21% oxygen, 1 - argon and 0.03% carbon dioxide. The biosphere includes only the lowest layers of the atmosphere. Life in them cannot exist without direct connection with the lithosphere and hydrosphere. Large woody plants reach several tens of meters in height, placing their crowns upwards. Flying animals rise hundreds of meters - insects, birds, bats. Some species of birds of prey rise 3-5 km above the Earth's surface, looking out for their prey. Finally, ascending air currents passively carry bacteria, plant spores, fungi, and seeds tens of kilometers upwards. However, all listed flying organisms or introduced bacteria are only temporarily in the atmosphere. There are no organisms permanently living in the air.

The upper boundary of the biosphere is considered to be the ozone layer, located at an altitude of 30 to 50 km above the Earth's surface. It protects all life on our planet from powerful ultraviolet solar radiation, largely absorbing these rays. Above the ozone layer, the existence of life is impossible.

Thus, the main part of the species of living organisms is concentrated on the boundaries of the atmosphere and lithosphere, atmosphere and hydrosphere, forming a relatively "thin film of life" on the surface of our planet.

Structure and functioning of the biosphere. Biosphere - it global ecological system, consisting of many ecosystems of a lower rank, biogeocenoses, the interaction of which with each other determines its integrity. Indeed, biogeocenoses do not exist in isolation - there are direct connections and relationships between them. For example, in aquatic biogeocenoses, mineral and organic substances are carried out from terrestrial ecosystems by wind, rain, and melt water. There may be a movement of organisms from one biogeocenosis to another (for example, seasonal animal migrations). And finally, everyone is united by the Earth's atmosphere, which serves as a common reservoir for living beings. It receives oxygen (released by plants during photosynthesis) and carbon dioxide (formed during the respiration of aerobic organisms). Plants of all ecosystems draw carbon dioxide from the atmosphere, which they need in the process of photosynthesis, and all breathing organisms receive oxygen.

The existence of the biosphere is based on the continuous circulation of substances, the energy basis of which is sunlight (Fig. 2).

Rice. 2.Scheme of biogeochemical cyclicity in the biosphere. On rightin the diagram, a section of soddy-podzolic soil under coniferous forest

The circulation of substances in nature between living and non-living matter is one of the most characteristic features of the biosphere. The biological cycle is the biogenic migration of atoms from the environment into organisms and from organisms into the environment. Biomass also performs other functions:

1) gas - constant gas exchange with the external environment due to the respiration of living organisms and plant photosynthesis;

2) concentration - constant biogenic migration of atoms into living organisms, and after their death - into inanimate nature;

3) redox - exchange of matter and energy with the external environment. During dissimilation, organic substances are oxidized; during assimilation, the energy of ATP is used;

4) biochemical - chemical transformations of substances that form the basis of the life of the organism.