Biosphere – the shell of the Earth, inhabited by living organisms, under their influence and occupied by the products of their vital activity; “film of life”; global ecosystem of the Earth.
The biosphere is the shell of the Earth inhabited by living organisms and transformed by them. The biosphere was formed 500 million years ago, when the first organisms began to emerge on our planet. It penetrates the entire hydrosphere, the upper part of the lithosphere and the lower part of the atmosphere, that is, it inhabits the ecosphere. The biosphere is the totality of all living organisms. It is home to over 3 million species of plants, animals, fungi and bacteria. Man is also a part of the biosphere, his activity surpasses many natural processes and, as V.I. Vernadsky: “Man becomes a mighty geological force.”
The term “biosphere” was introduced in biology by Jean-Baptiste Lamarck at the beginning of the 19th century. And in geology, the term was proposed by the Austrian geologist Eduard Suess in 1875.
A holistic doctrine of the biosphere was created by the biogeochemist and philosopher V.I. Vernadsky. For the first time, he assigned to living organisms the role of the main transforming force of the planet Earth, taking into account their activity not only at the present time, but also in the past. There is another, broader definition: the Biosphere is the area of distribution of life on the cosmic body. The existence of life on space objects other than the Earth is still unknown, it is believed that the biosphere can spread to them in more hidden areas, for example, in lithospheric cavities or in subglacial oceans. For example, the possibility of the existence of life in the ocean of Jupiter’s moon Europa is considered.
The boundaries of the biosphere
Upper boundary in the atmosphere: 15-20 km. It is determined by the ozone layer, which blocks short-wave UV radiation, which is harmful to living organisms. Lower boundary in the lithosphere: 3.5–7.5 km. It is determined by the temperature of the transition of water into steam and the temperature of protein denaturation, however, in general, the spread of living organisms is limited to a depth of several meters. The boundary between the atmosphere and the lithosphere in the hydrosphere: 10–11 kilometers. The boundary of the biosphere is determined by the bottom of the World Ocean, including bottom sediments.
The biosphere is made up of the following types of substances:
1. Living matter – the totality of the bodies of living organisms inhabiting the Earth is physico-chemically unified, regardless of their systematic affiliation. Living matter is distributed within the biosphere very unevenly.
There are five main functions of living matter:
1. Energy . It consists in the absorption of solar energy during photosynthesis, and chemical energy – through the decomposition of energy-saturated substances and the transfer of energy through the food chain of heterogeneous living matter.
2. Concentration . Selective accumulation during the life of certain types of matter. There are two types of concentrations of chemical elements by living matter: a) a massive increase in the concentrations of elements in a medium saturated with these elements, for example, sulfur and iron are abundant in living matter in areas of volcanism; b) a specific concentration of one or another element, regardless of the medium.
3. Destructive . It consists in the mineralization of non-biogenic organic matter, the decomposition of inanimate inorganic matter, and the involvement of the resulting substances in the biological cycle.
4. Environment-forming . Transformation of physical and chemical parameters of the medium (mainly due to non-biogenic matter).
5. Transport . The transfer of matter against gravity and in the horizontal direction.
2. Biogenic substance – a substance created and processed by living matter. Throughout organic evolution, living organisms have passed through their organs, tissues, cells, and blood a thousand times the entire atmosphere, the entire volume of the world ocean, and a huge mass of mineral substances. This geological role of living matter can be imagined by the deposits of coal, oil, carbonate rocks, etc.
3. Inert matter – products formed without the participation of living organisms.
4. Bioinert substance , which is created simultaneously by living organisms and inert processes, representing dynamically balanced systems of both. Such are soil, silt, weathering crust, etc. Organisms play a leading role in them.
5. Substance in radioactive decay.
6. Scattered atoms, continuously created from any kind of terrestrial matter under the influence of cosmic radiation.
7. Substance of cosmic origin.
The modern biosphere, along with living matter, includes the entire hydrosphere , the upper part of the lithosphere and the lower part of the atmosphere.
Hydrosphere. This geosphere is a collection of oceans, seas, lakes, rivers, groundwater and glaciers. It forms a discontinuous water shell of the Earth, occupying more than 70% of its surface. The mass of the hydrosphere is distributed extremely unevenly: 98.3% of it is the World Ocean , 1.6% is bound in continental ice, and only 0.1% is in the waters of the continents.
The World Ocean, which is the main part of the hydrosphere, serves as a habitat for a huge number of the most diverse representatives of the plant and animal world and the world of microorganisms. All marine organisms are divided into three large groups: plankton, nekton and benthos. Plankton is the largest group of organisms in terms of the number of species, including plants and animals that are not able to move independently, “floating” in the water column and moved by currents. Plankton are divided into phyto- and zooplankton. The main mass of phytoplankton is concentrated in the surface (50-80-meter) layer of ocean water, where there is enough sunlight for photosynthesis. Nekton includes animals that can move independently in water (fish, aquatic mammals, squids, etc.). Organisms attached to the bottom of water bodies, crawling along it and burrowing into it, are classified as benthos , which is divided into phytobenthos (various multicellular algae) and zoobenthos (sponges, worms, molluscs and other invertebrates).
The mass of living matter in the hydrosphere is distributed extremely unevenly. Phytoplankton has the highest biomass, the areas of concentration of which occupy about 10% of the area of the World Ocean, and are mainly located on the shelves. Since phytoplankton is the main or only source of food for most representatives of nekton and zoobenthos, the distribution of areas of their concentration is confined to the areas of phytoplankton.
Lithosphere. In the modern sense, the lithosphere is the upper solid shell of the Earth, the thickness of which varies between 50–200 km. The upper part of the lithosphere forms the earth’s crust , and the lower part forms the upper part of the Earth’s mantle. The earth’s crust, which, unlike the hydrosphere, is a continuous shell of the planet, consists of three layers: sedimentary, granite and basalt. The sedimentary layer is mainly composed of sedimentary rocks (clays, sandstones, limestones, dolomites, gypsums, etc.), formed on the surface of the Earth mainly as a result of the deposition of weathering products and the destruction of older rocks, chemical and the vital activity of organisms. The thickness of the sedimentary layer is extremely variable: in some places it is absent, in others it reaches a thickness of 20–25 km. The total volume of this layer is about 10% of the volume of the entire earth’s crust, and the main part of its constituent rocks falls on the continents and ocean shelves.
The lower boundary of the biosphere runs in the uppermost part of the earth’s crust. A distinct spread of life is observed here only to a depth of several tens of meters, however, with groundwater, microorganisms spread to depths of 2–3 km, although there are cases of detection of microorganisms in oil waters and oil produced by drilling wells from depths of more than 4 km.
From the point of view of the concentration of living matter in the biosphere, the soil layer is of particular interest, the thickness of which varies widely in various landscape and climatic zones (from a few centimeters to 1–1.5 m). Almost all land vegetation, and, consequently, its entire animal world, is associated with the soil as a necessary source of food. The most important property of the soil is its fertility, i.e. the ability to provide the necessary conditions for plant life. Of great importance in soil fertility is humus, which consists mainly of biochemical decomposition products of dead remains of organisms. The soil is a habitat for a huge number of microorganisms, algae, protozoa, insects, worms and other invertebrates and a large number of vertebrates.
Atmosphere. The third geosphere of the Earth, with which the biosphere is connected, is the atmosphere, which is the gaseous shell of the Earth, consisting of nitrogen (78.08% of volume), oxygen (20.95%), argon (0.93%) and carbon dioxide (0. 03%). The remaining gases account for about 0.01% of the total volume of the atmosphere. With distance from the Earth’s surface, the density of the atmosphere gradually decreases to a height of about 3 thousand km, where its density becomes equal to the density of interplanetary space. Usually the atmosphere is represented as a set of layers – the troposphere, stratosphere and ionosphere. Troposphere , containing about 80% of the mass of the entire atmosphere and almost all water vapor, extends to a height of approximately 9 km (at the poles) – 17 km (at the equator). In the lower part of the stratosphere , extending from the upper boundary of the troposphere to a height of about 50 km, is the ozone layer , which is characterized by an increased ozone content. The ozone concentration at the heights of the ozone layer of 15–26 km is more than 100 times higher than its concentration at the Earth’s surface.
As the upper boundary of the biosphere , the lower boundary of the ozone layer is taken, which almost completely absorbs ultraviolet rays that are harmful to all living things. This is why the ozone layer is often referred to as the “ozone shield” that protects life on Earth. Here it would be useful to note that the inclusion of the lower atmosphere in the biosphere is somewhat arbitrary, since the presence of organisms in it at significant heights above the earth’s surface in most cases can be temporary, and their true habitat is the hydrosphere, the upper part of the earth’s crust and a thin layer of surface atmosphere.