Different species occupy different positions in the food chain, creating the trophic structure of communities. Consistently feeding on each other, living organisms form links in the food chain, called trophic levels.
Trophic level – a set of organisms that receive the energy of the Sun converted into food through the same number of intermediaries in the food chain.
The following trophic levels are distinguished in pasture food chains:
1st trophic level
The 1st trophic level is formed by producers – producers of biological substances – autotrophs.
Autotrophs are able to fix light energy and use simple inorganic substances in their diet.
As a rule, green plants are producers. Autotrophs are the most important part of any community, because almost all other organisms directly or indirectly depend on the supply of matter and energy stored by plants.
On land, autotrophs are usually large plants with roots; in reservoirs, producers are microscopic algae that live in the water column (phytoplankton).
All other organisms are heterotrophs that feed on ready-made organic matter.
Heterotrophs decompose, rearrange and assimilate complex organic substances created by primary producers.
All animals and many microorganisms are heterotrophs.
In turn, heterotrophic organisms are subdivided into consumers (consumers) and decomposers, or destructors (decomposers).
Consumers (consumers) are mainly animals that feed on other organisms (plant or animal) or comminuted organic matter.
2nd trophic level
The 2nd trophic level is formed by consumers of the 1st order, or primary consumers (herbivorous animals that feed on producers).
3rd trophic level
The 3rd trophic level is formed by consumers that eat herbivorous animals of the 1st order, they are called consumers of the 2nd order, or secondary consumers, or primary predators (carnivorous animals-predators).
4th trophic level
The 4th trophic level is formed by consumers of the III order, or tertiary consumers, or secondary predators (predators feeding on secondary consumers), etc.
Since many animals are omnivorous and feed on both plants and animals, they cannot be attributed to any one level. In these cases, it is believed that such organisms represent several trophic levels at once, and their participation in each of the levels is proportional to the composition of their diet.
At the end of the food chain are decomposers that convert dead organic matter into inorganic compounds.
Reducers are mainly represented by fungi and bacteria that decompose the complex constituent components of the dead cytoplasm, bringing them to simple organic compounds, which can then be used by producers.
Natural communities can radically differ in the composition of organisms, but they are similar in trophic structure: they contain the main ecological components – producers (autotrophs), consumers of various orders, and decomposers (heterotrophs).