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Circulation of substances and the stream of energy in ecosystem

In ecosystem organic substances are synthesized by autotrophic from inorganic substances. Then they are consumed by heterotrophic. Allocated during ability to live or after destruction of organisms (both autotrophic and heterotrophic) organic substances are exposed to a mineralization i.e. transformation into inorganic substances. These inorganic substances can be again used by autotrophic to synthesize organic substances. So, biological circulation of substances is carried out.

At the same time, energy cannot circulate within the limits of ecosystem. The stream of energy (transfer of energy), having in food, in the ecosystem is unidirectional carried out from autotrophic to heterotrophic.

· In picture the simplified scheme of energy stream at three trophic levels of the food chain is shown. Trophic levels are shown as tanks, which size corresponds to the energy having in their biomass (B), the size of channels connecting them is equal to size of streams of energy. The stream of solar energy (L} enters in an input in the system.

· At the first trophic level green plants absorb about 50 % of the solar energy (L_А.) | But, during photosynthesis, its some part will be transformed to energy of chemical bonds of organic substances. It is total primary production (P_G ). The most part of not assimilated energy disperses in an environment in the form of thermal energy. The part of the formed organic substances is oxidized, and liberated energy is consumed for maintenance of all metabolic processes. These are so-called expenses for breath (R). This energy, finally, also disperses in the form of heat. The remained part of new-formed organic substances makes up a gain of plants biomass (DB) and it is called as pure primary production (Р_N). Only 1 % of the energy absorbed by a plant is transformed into pure initial production. Thus, Р_N = P_G - R.

Only part of pure primary production reaches the second trophic level. Its some part (N_U) is not used by consumers of the first level. It can be collected or be exported for limits of system. That part which consumers assimilated (have consumed) (A), is partially spent for breath (Л), it is partially allocated with excrement (N_A), and the rest collects in the form of secondary production (P).

· Secondary production at each subsequent trophic level of consumers (_Р2, _Р3, etc.) composites about 10 % previous (though at a level of predators it can be above 20 %). As a result, the longer the food chain the less energy (collected in the organic substances) remains by its end. Therefore the number of trophic levels never meets too greater.