All substances on the planet are in the process of circulation. Solar energy causes two cycles of substances on Earth: large (geological, biosphere) And small (biological).
The large cycle of substances in the biosphere is characterized by two important points: it occurs throughout the entire geological development of the Earth and is a modern planetary process that takes a leading part in the further development of the biosphere.
The geological cycle is associated with the formation and destruction of rocks and the subsequent movement of destruction products - clastic material and chemical elements. The thermal properties of the surface of land and water played and continue to play a significant role in these processes: absorption and reflection of solar rays, thermal conductivity and heat capacity. The unstable hydrothermal regime of the Earth's surface, together with the planetary atmospheric circulation system, determined the geological circulation of substances, which at the initial stage of the Earth's development, along with endogenous processes, was associated with the formation of continents, oceans and modern geospheres. With the formation of the biosphere, the waste products of organisms were included in the large cycle. The geological cycle supplies living organisms with nutrients and largely determines the conditions of their existence.
Main chemical elements lithosphere: oxygen, silicon, aluminum, iron, magnesium, sodium, potassium and others - participate in a large cycle, passing from the deep parts of the upper mantle to the surface of the lithosphere. Igneous rock formed by crystallization
magma, arriving on the surface of the lithosphere from the depths of the Earth, undergoes decomposition and weathering in the biosphere. Weathering products enter a mobile state, are carried by water and wind to low areas of the relief, enter rivers, the ocean and form thick layers of sedimentary rocks, which over time, plunging to depth in areas with increased temperature and pressure, undergo metamorphosis, i.e. "remelted". During this melting, a new metamorphic rock appears, entering the upper horizons of the earth's crust and again entering the cycle of substances (Fig. 32).
Rice. 32. Geological (large) cycle of substances
Easily mobile substances - gases and natural waters that make up the atmosphere and hydrosphere of the planet - undergo the most intense and rapid circulation. The lithosphere material cycles much more slowly. In general, each cycle of any chemical element is part of the general large cycle of substances on Earth, and they are all closely interconnected. The living matter of the biosphere in this cycle performs a tremendous job of redistributing chemical elements that continuously circulate in the biosphere, passing from the external environment into organisms and again into the external environment.
Small, or biological, cycle of substances- This
circulation of substances between plants, animals, fungi, microorganisms and soil. The essence of the biological cycle lies in the occurrence of two opposite but interconnected processes - the creation of organic substances and their destruction. The initial stage of the emergence of organic substances is due to photosynthesis of green plants, i.e., the formation of living matter from carbon dioxide, water and simple mineral compounds using solar energy. Plants (producers) extract molecules of sulfur, phosphorus, calcium, potassium, magnesium, manganese, silicon, aluminum, zinc, copper and other elements from the soil in solution. Herbivorous animals (consumers of the first order) absorb compounds of these elements in the form of food of plant origin. Predators (II-order consumers) feed on herbivores, consuming food of a more complex composition, including proteins, fats, amino acids and other substances. In the process of destruction of organic substances of dead plants and animal remains by microorganisms (decomposers), simple mineral compounds enter the soil and aquatic environment, available for assimilation by plants, and the next round of the biological cycle begins (Fig. 33).
Cycle and biogeochemical cycles of substances
Explain the meaning of the geological cycle using the example of the water cycle.
How does the biological cycle occur?
What is the law of biogenic migration of atoms V.I. Vernadsky?
What are reserve and exchange funds of the natural cycle? What is the difference between them?
Earth as a living superorganism
*In order for the biosphere to exist and develop, there must be a constant cycle of biologically important substances on Earth, i.e., after use, they must again transform into a form that is assimilated by other organisms. This transition of biologically important substances can only be carried out with a certain expenditure of energy, the source of which is the Sun.
Scientist V. R. Williams believes that solar energy provides two cycles of substances on Earth - geological , or large, gyre and biological , small, cycle.
Geological k The circulation is most clearly manifested in the water cycle. The Earth receives 5.24-1024 J of radiated energy annually from the Sun. About half of it is spent on water evaporation. At the same time, more water evaporates from the ocean than returns with precipitation. On land, on the contrary, more precipitation falls than water evaporates. Its excess flows into rivers and lakes, and from there again into the ocean (while transferring a certain amount of mineral compounds). This causes a large cycle in the biosphere, based on the fact that the total evaporation of water from the Earth is compensated by precipitation.
**With the advent of living matter on the basis of the geological cycle, the organic cycle arose in properties, biological (small) cycle.
The water cycle as an example of a geological cycle
(according to H. Penman)
As living matter develops, more and more elements are constantly extracted from the geological cycle and enter a new, biological cycle. In contrast to the simple transfer of minerals in the large cycle, both in the form of solutions and in the form of mechanical precipitation, in the small cycle the most important aspects are the synthesis and destruction of organic compounds. In contrast to the geological cycle, the biological cycle has negligible energy. As is known, only 0.1-0.2% of all solar energy arriving on Earth is spent on the creation of organic matter (up to 50% for the geological cycle). Despite this, the energy involved in the biological cycle does a lot of work to create primary products.
Biological cycle
With the appearance of living matter on Earth, chemical elements continuously circulate in the biosphere, moving from the external environment
into organisms and again into the external environment. Such circulation of substances along more or less closed paths is called biogeochemical cycle.
The main biogeochemical cycles are the cycles of oxygen, carbon, water, nitrogen, phosphorus, sulfur and other nutrients.
*** Biogenic migration of matter - one of the forms of general migration of elements in nature. Biogenic geochemical migration should be understood as the migration of organic and inert matter involved in the growth and development of living organisms and produced by the latter as a result of complex biochemical and biogeochemical processes. IN AND. Vernadsky formulated law of biogenic migration of atoms in the following form:
The migration of chemical elements in the biosphere occurs either with the direct participation of living matter (biogenic migration), or it occurs in an environment whose geochemical features (O2, CO2, H2, etc.) are determined by living matter (that which currently inhabits the biosphere , and that which has acted on Earth throughout geological history).
Man affects primarily the biosphere and its living population, therefore he thereby changes the conditions of biogenic migration of atoms, creating the preconditions for profound chemical changes. Thus, the process can become self-developing, independent of human desire, and on a global scale practically uncontrollable.
From the point of view of the planetary cycle of matter, the most important are the soil-landscape, hydrosphere and deep (intraterrestrial) cycles. In the first of them, chemical elements are extracted from rocks, water, air, organic matter decomposes, and various organic and organomineral compounds are absorbed and synthesized. In the hydrosphere cycle, the main role is played by the composition of water and the biological activity of living organisms. The bioproduction of the substance here is carried out with the dominant participation of phyto and zooplankton. In the deep cycle of biogenic migration, the most important role is played by the activity of anaerobic microorganisms.
****The processes occurring in various shells of the Earth are in a state of dynamic equilibrium, and a change in the course of any of them entails endless chains of sometimes irreversible phenomena. In each natural cycle it is advisable to distinguish two parts, or two “funds”:
reserve fund- a large mass of slowly moving substances, mainly of inorganic nature;
mobile, or exchange fund- smaller, but more active, characterized by rapid exchange between organisms and the environment.
The exchange fund is formed by substances that are returned to the cycle either due to primary excretion (from the Latin excretum - excreted) by animals, or during the decomposition of detritus by microorganisms.
If we keep in mind the biosphere as a whole, then biogeochemical cycles can be divided into two main types:
circulation of gaseous substances with a reserve fund in the atmosphere or hydrosphere;
sedimentary cycle with a reserve fund in the earth's crust.
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The biological cycle is associated with metabolism (metabolism) and the formation, as well as the decomposition of water in living matter, during its life activity.
Any biological cycle is characterized by the repeated inclusion of atoms of chemical elements in the bodies of living organisms and their release into the environment, from where they are again captured by plants and drawn into the cycle. The small biological cycle is characterized by capacity - the number of chemical elements simultaneously present in living matter in a given ecosystem, and speed - the amount of living matter formed and decomposed per unit time.
The biological cycle of land and the hydrosphere combines the cycles of individual landscapes through water flow and atmospheric movements. The role of circulation of water and atmosphere is especially important in uniting all continents and oceans into a single circulation of the biosphere.
The biological cycle of substances has a creative function, the creation of organic matter and the enrichment of soil with nutrients. Life in any plant communities depends on it: gardens, meadows, fields, forests. In recent years, the need has arisen to create high-intensity types of circulation in closed systems that could ensure life activity on long interplanetary travel.
The intensity of the biological cycle is primarily determined by the ambient temperature and the amount of water. For example, the biological cycle is more intense in tropical rainforests than in the tundra.
The speed of biological cycles on land is years and tens of years, in aquatic ecosystems - several days or weeks.
The biological cycle in the forest is characterized by a long-term exclusion of nitrogen and ash elements contained in the long-term biomass of trees and shrubs, transformation of litter on the soil surface with the formation of forest litter and various water-soluble organic and mineral products of its decomposition.
The speed of biological cycles and the total amount of matter involved in these cycles are determined by the scale and environmental conditions in ecosystems. Ecosystems are characterized by various environmental conditions, which refer to environmental environmental factors that directly or indirectly affect living organisms. These factors can be abiotic and biotic.
Part of the biological cycle, consisting of cycles of carbon, water, nitrogen, phosphorus, sulfur and other nutrients, is called the biogeochemical cycle.
Nitrogen has a special place in the biological cycle of substances. When organic matter decomposes, nitrogen escapes into the atmosphere either in the form of gaseous compounds or in a free state. The return of nitrogen to the soil, from where plants take it, is carried out in a complex way, as a result of a process that involves special bacteria and some other organisms that bind atmospheric nitrogen gas into compounds available for consumption by plants.
V. A. Kovda’s concept of biological cycle includes the sum of cyclic processes of metabolism and energy between the environment and the totality of plant and animal organisms. If you follow the chain of successive transformations and migration of individual elements involved in the exchange between the habitat, in particular soil, and biota, you can discover, for example, using an isotope label, that the complete transformation-migration cycle of an element in all soils and at all stages of its functioning includes both biological and abiotic processes of transformation and movement of matter. For example, during the period between the return of an element to the soil surface with forest litter and its subsequent absorption by plant roots, it can migrate along the soil profile. At the same time, the intensity and direction of this process will be determined not only by the biota, but also by climatic factors, water-physical, sorption and other soil properties.
Being included in the biological cycle, they enter the human body through plant and animal food and, accumulating in it, cause radioactive radiation.
On the contrary, the biological cycle of matter takes place within the boundaries of the inhabited biosphere and embodies the unique properties of the living matter of the planet. Being part of a large, small cycle is carried out at the level of biogeocenosis, it consists in the fact that soil nutrients, water, carbon are accumulated in the substance of plants, spent on building the body and life processes of both themselves and organisms - consumers. The products of decomposition of organic matter by soil microflora and mesofauna (bacteria, fungi, mollusks, worms, insects, protozoa, etc.) are again decomposed into mineral components, again accessible to plants and therefore again involved by them in the flow of matter.
12.1. The concept of biological circulation
The biological cycle is a cycle of chemical elements and substances that arose simultaneously with the appearance of life on Earth, carried out by the vital activity of organisms. It plays a special role in the biosphere. On this occasion, N.V. Timofeev-Resovsky wrote: “There is a huge, eternal, constantly working biological cycle in the biosphere, a number of substances, a number of forms of energy constantly circulate in this large cycle of the biosphere” (M. M. Kamshilov, 1974; V. A. Vronsky, 1997). The laws of the biological cycle solve the problem of the long-term existence and development of life. On a body of finite volume, such as the Earth, the reserves of available mineral elements necessary to carry out the function of life cannot be infinite. If they were only consumed, life would sooner or later have to end. “The only way to give a limited quantity the property of infinity,” writes W. R. Williams, “is to make it rotate along a closed curve.” Life used exactly this method. “Green plants create organic matter, non-green plants destroy it. From mineral compounds obtained from the breakdown of organic matter, new green plants build new organic matter, and so on endlessly.” Taking this into account, each type of organism represents a link in the biological cycle. Using the bodies or decay products of some organisms as means of subsistence, he must give into the environment something that others can use. The role of microorganisms is especially important. Mineralizing the organic remains of animals and plants, microorganisms transform them into a “single currency” - mineral salts and simple organic compounds such as biogenic stimulants, which are again used by green plants in the synthesis of new organic matter. One of the main paradoxes of life is that its continuity is ensured by processes of decay and destruction. Complex organic compounds are destroyed, energy is released, and the supply of information characteristic of complexly organized living bodies is lost. As a result of the activity of destructors, mainly microorganisms, any form of life will inevitably be included in the biological cycle. Therefore, with their help, natural self-regulation of the biosphere is carried out. Two properties allow microorganisms to play such an important role: the ability to adapt relatively quickly to different conditions and the ability to use a wide variety of substrates as a source of carbon and energy. Higher organisms do not have such abilities. Therefore, they can exist only as a kind of superstructure on a solid foundation of microorganisms. The biological cycle, based on the interaction of synthesis and destruction of organic matter, is one of the most significant forms of organization of life on a planetary scale. Only he ensures the continuity of life and its progressive development.
Individuals and species of organisms of different systematic groups act as links in the biological cycle, interacting with each other directly and indirectly through numerous and multilateral direct and feedback connections. The biological cycle of the planet also appears to be a complex system of private cycles - ecological systems interconnected by various forms of interaction.
The biological cycle occurs mainly through trophic (food) chains (Figure 12.1).
Given the important role of plants and animals in it, the flow of nutrients such as nitrogen, phosphorus, sulfur through populations of microorganisms in the cycle is approximately an order of magnitude higher than through populations of plants and animals. An important indicator of the intensity of the biological cycle is the rate of circulation of chemical elements. As an indicator of this intensity, one can use the rate of accumulation and decomposition of dead organic matter resulting from the annual fall of leaves and the death of organisms.
The ratio, for example, of the mass of litter to that part of the litter that forms the litter serves as an indicator of the rate of decomposition of litter and the release of chemical elements. The higher this index, the lower the intensity of the biological cycle in a given ecosystem. The highest index value (more than 50) is characterized by swampy forests and tundra. In dark coniferous forests the index is 10–17, in broad-leaved forests – 3–4, in steppes – 1.0–1.5, in savannas – no more than 0.2. In tropical rainforests, plant residues practically do not accumulate (index no more than 0.1). Therefore, here the biological cycle is most intense.
I had occasion to read literature that described a “fashionable trend” in the science of the 16th–17th centuries - the creation of a perpetual motion machine. This dream remained unrealizable, but the idea, in my opinion, was copied from nature. The cycle of living and nonliving things occurs constantly. Someone will say that in billions of years the Earth will disappear, but I would object, because a new one will form from the remains of our galaxy. Our Universe is a perpetual motion machine.
What is the essence of the biological cycle of substances
There are two types of cycles continuously occurring on Earth: biotic and abiotic.
Substances themselves are not living and take part equally in both cycles, but as soon as they find themselves inside a living organism, it can be considered a participant in the biological cycle.
Elements involved in the biological cycle:
- minerals;
- gases;
- water.
The range of substances is very wide. Conventionally, they can be divided into those that are vital for organisms (water, oxygen, nitrogen, carbon dioxide) and those that cause harm to living things.
The process of circulation of substances
Regardless of its harmfulness or usefulness, any substance once enters the body and one day leaves it.
In the case of water, circulation occurs constantly. For example, the human body excretes about 6 liters per day, but we do not lose weight due to constant replenishment of water reserves. Having evaporated from the body, water molecules rush to the clouds, fall out as rain, enter the water supply and end up back in the body.
By a similar principle, minerals and gases pass through any living organism.
Air circulation occurs most intensely: per day a person inhales 13 thousand liters of air containing 20% oxygen, which is converted into carbon dioxide upon exhalation. However, thanks to plants, there is no excess carbon dioxide in nature; they use it during photosynthesis.
Some substances accumulate in the body and are not eliminated until death; they usually cause damage to the living organism. Examples of such substances include carcinogens that are inhaled by smokers.
