In ecosystems, there is a continuous exchange of energy and matter between living and inanimate nature. Energy and matter are constantly needed by living organisms, and they draw them from the surrounding inanimate nature.
Substances and energy in communities are transmitted through food chains. The amounts of matter and energy passing through living organisms are extremely large.
Example: a field mouse is capable of eating tens of kilograms of grain in its life; plant growth is accompanied by huge water consumption, etc.
Energy cannot be transmitted in a vicious circle.
It is available to living organisms in the form of solar radiation, which can be associated in the process of photosynthesis. Then spent in the form of chemical energy, it is lost, turning into heat.
Elements necessary for life and dissolved salts are conventionally called nutrients, or biogenic (life-giving) elements.
Example: biogenic elements include elements that make up the chemical basis of tissues of living organisms (macronutrients): carbon, hydrogen, oxygen, nitrogen, phosphorus, potassium, calcium, magnesium, sulfur. This group also includes elements whose content in living organisms is small (trace elements): iron, manganese, copper, zinc, boron, sodium, molybdenum, chlorine, vanadium and cobalt.
It is quite clear that if living organisms irretrievably borrowed all the necessary nutrients from inanimate nature, without returning anything back, the reserves of these substances on Earth would dry up and life would cease. This does not happen, because nutrients are constantly returned to the environment as a result of the vital activity of the organisms themselves.
Nutrients can be transferred in closed cycles, repeatedly circulating between organisms and the environment. This phenomenon is called the circulation of substances.
This issue will be considered in more detail in the section on the biosphere.
Different types of organisms in a community turn out to be closely related to each other, interdependent on each other. Thanks to these links, organic substances synthesized by producers with the absorption of solar energy are transferred to consumers and undergo chemical transformations.
Most of the produced substance is spent on supporting the vital processes of organisms of different trophic levels, a certain amount is spent on building the bodies of consumers. As a result, all organic substances are decomposed by decomposers and returned to the environment in the form of mineral substances, which can again be used by producer plants. Thus, a stable circulation of substances arises, in which living organisms play a decisive role.
The reserves of nutrients are not constant. The preservation of their atoms in living organisms reduces the amount of these elements in the non-living part of the ecosystem. And if plants and other organisms did not ultimately decompose, the supply of nutrients could be depleted, and life on Earth would be impossible. Therefore, the activity of heterotrophs and, especially, reducers involved in decomposition chains is of such great importance. As a result of the activity of these organisms, the cycle of biogenic elements is preserved and life on Earth can continue.