In a food chain, living things and the environment continually transfer and exchange energy and matter. The main energy source of ecosystems, solar energy is captured by the producers (plants) and, through photosynthesis, is transformed into chemical energy. According to the law of thermodynamics, "Energy can not be created or destroyed but transformed", that is, photosynthesis uses about 1 to 2% of the luminous energy that reaches an ecosystem, enough to provide tons of energy. organic matter per year.


The organic compounds obtained as a product of photosynthesis are used by the plant as energy for its metabolism and eliminated as carbon dioxide and water. Some of the organic matter and energy is retained in the plant, as in the stem, leaves, among others and serve as food for the primary consumers and the other part goes out as heat. Consumers, feeding on autotrophic beings, eliminate part of the energy in the faeces and urine and another is oxidized in the respiration for the energy production of the living being. The matter that circulates from the producers to the consumers, returns to the ecosystem being available to the producers in the inorganic form by the action of the decomposers. As the energy used is not reused by living beings, with only 10% of energy from one trophic level passing to the next, it is said that the energy flow in an ecosystem is unidirectional.

In an ecosystem, at a given time and given area, the organic matter produced by the plants is called gross primary productivity (PPP) and, when we discount the consumed part of the respiration (R), we have the net primary productivity (NPP), represented by the following equation: PPB - R = PPL. In stable ecosystems, PPB equals PPL.

Secondary productivity refers to the amount of organic matter, gross or net, accumulated by consumers. In some regions, productivity is high, for example in coastal regions and estuaries. Some methodologies can increase the productivity of an ecosystem such as the use of fertilizers and pesticides, although such substances pollute the environment and create an ecological imbalance.