Studying the biotic structures of various ecosystems, scientists noticed that all the organisms in them are arranged in food chains. And there are many such chains in each such ecosystem. According to them, a substance that is a source of energy, as well as building material, moves from one organism to another. That is, one organism eats another, and a third in turn eats it. Here is a simple example of such a chain: grass - cow - man.
And all these chains are rarely isolated from each other - they are all combined into one food network. The relationships on this network are quite complex. For example, herbivores feed on plants of several species. And predators are also not very picky in choosing meat for their diet. But, despite the fact that there are many such food networks and they are all quite diverse - they can be entered into one scheme. But this scheme looks like this: green plants - primary consumers - secondary consumers - tertiary consumers - reproducers. Moreover, reproducers always stand at the end of the food chain, and there may be several consumers in it. All these links are called trophic levels.
That is, from a scientific point of view, the trophic level is the entire set of organisms that occupy a certain place in the food web. And in an ordinary ecosystem, no more than 3-4 such levels can be counted. The first trophic level is, of course, plants. All food chains begin with them . The second trophic level is occupied by phytophages, that is, herbivorous. These are first-order consumers and eat only flora.
The third trophic level is occupied by second-order consumers. They are predators that feed only on herbivores. Also here can be euriphages, that is, omnivores. They can equally eat both plant and animal food. These include pigs, foxes, rats, cockroaches, and the like. Man, in essence, is also a euryphage. Also at this level can be third-level consumers - such predators that feed only on carnivores.
And the last trophic level is usually occupied by reducers, that is, heterotrophic organisms. They destroy, mineralize and degrade ecosystem waste. After their “work” simple mineral compounds are obtained. And reducers, in turn, are divided into two classes. These are detritophages - animals that directly feed on organic debris and dead organisms. These include vultures, vultures, jackals, hyenas, earthworms and other scavengers.
Reducers also include destructors. They already decompose dead "organic" into inorganic compounds. Simply put, they support decay and decay processes. These include bacteria and fungi. And all these trophic chains are arranged in such a way that producers, consumers and reducers closely interact through them. They maintain the integrity and structure of biocenoses, while coordinating the flow of matter and energy. This contributes to environmental regulation.
Graphically, such a trophic structure of an ecological system can be depicted as a pyramid of energy flows. Its basis is producers or the 1st trophic level. And all subsequent levels are the floors and the top of this pyramid. And through each of these levels there is a flow of energy. In this case, the energy leaving one level is the input energy for the next. And the main reason for such a small number of trophic levels in each ecosystem is that a significant part of the energy is lost during these transitions. Here the 10% rule applies, and according to it only such an amount of useful energy is transferred to the next level. And 10% is the maximum figure. In some ecosystems, this efficiency is only one percent.