Food chains and trophic levels are considered integral components of the biological cycle. It involves many elements. In more detail, we consider the trophic levels of the ecosystem.


The food chain is the transfer of energy, which is contained in plant foods, through a series of organisms due to their eating each other. Only plants form an organic matter from inorganic matter. The trophic level is a complex of organisms. Between them there is interaction in the process of transfer of nutrients and energy from the source. Trophic chains (trophic level) presuppose a certain position of organisms at a certain stage (link) during this movement. Marine and terrestrial biological structures have many differences. One of the main ones can be called that in the first the food chains are longer than in the second.

The first trophic level is represented by autotrophs. They are also called producers. The second trophic level consists of the initial consumers. At the next stage there are consumers who consume herbivorous organisms. These consumers are called secondary. To them, for example, are primary carnivores, carnivores. Also in the third trophic level are the third-order consuments. They consume, in turn, weaker predators. As a rule, there are a limited number of trophic levels - 4 or 5. Rarely more than six. This food chain is usually closed by decomposers or destructors. They are bacteria, microorganisms that decompose organic remains.

Consumables: general information

They are not just "eaters", which contain a food chain. They satisfy their needs through a system of reverse (positive) communication. Consumers influence the trophic levels of the ecosystem that are higher. So, for example, the consumption of vegetation in African savannahs by large herds of antelopes together with fires in the dry period contributes to an increase in the rate of return to the soil of nutrients. Subsequently, during the rainy season, the restoration of herbaceous plantations and their products is increasing.Oduda's example is quite interesting. He describes the impact of consumer goods on producers in the marine ecosystem. Crabs, consuming detritus and algae, "take care" of their herbs in several ways. They tear the ground, thus increasing the circulation of water near the roots and introducing oxygen and necessary elements into the anaerobic coastal zone. In the process of continuous processing of bottom sediments, rich in organic matter, crabs improve the conditions for the development and growth of benthic algae. One trophic level is composed of organisms that receive energy through the same number of steps.

The food consumed at each trophic level is not completely assimilated. This is due to significant losses in the stages of metabolic processes. In this regard, the production of organisms entering the next trophic level is less than in the previous one. Inside the biological system, organic compounds containing energy are formed by autotrophic organisms. These substances are a source of energy and the necessary components for heterotrophs. The following is an easy example: an animal uses plants. In turn, the beast can be eaten by another larger representative of the fauna. This can be the transfer of energy through several organisms. The next uses the previous one, which supplies energy and nutrients. It is this sequence that forms the food chain, in which the trophic level acts as a link.

Producers of the 1st order

The original trophic level contains autotrophic organisms. They are mainly referred to as green plantations. Some prokaryotes, in particular blue-green algae, as well as a few species of bacteria, also have the ability to photosynthesize. However, their contribution to the trophic level is insignificant.Thanks to the activity of photosynthesis, solar energy is converted into chemical energy. It lies in organic molecules, from which, in turn, the tissues are built. A relatively small contribution to the production of organic matter is made by chemosynthetic bacteria. They extract energy from inorganic compounds. Algae are the main producers in aquatic ecosystems. They are often represented by small unicellular organisms that form phytoplankton in the surface layers of lakes and oceans. Most of the primary products on land are supplied by more highly organized forms. They refer to gymnosperms and angiosperms. Due to them, meadows and forests are formed.

Consumers of the 1st order

They consume primary producers. They are presented as herbivores. Typical representatives on land are reptiles, insects, mammals and birds. The most important groups include rodents and ungulates. Among the latter, we can identify pasture animals: sheep, horses, cattle. In aquatic ecosystems (marine and fresh) small crustaceans and mollusks act as herbivorous forms. Most of them - copepods and branching crayfish, bivalve mollusks, crab larvae and others - feed by filtration of primary producers from the water column. Many of them, together with protozoa, form the basis of zooplankton, which consumes phytoplankton. The primary consumers are also plant parasites (fungi, animals, crops).

Consumers 2, 3 orders of magnitude

Secondary consumers consume herbivores. This means that they already fall into the category of carnivores. To the same group include the tertiary consumer, eating, in turn, secondary. Both these and other consumers can be predators and hunters, be parasites or eat carrion, seize and kill the victim.If there is parasitism, then tertiary consumer, as a rule, are smaller than secondary ones. Their food chains are specific in some parameters. In typical predator systems, carnivorous representatives become larger at each successive stage.

Food chains can be of two kinds. In particular, detrital and pastoral structures are distinguished. The above are examples of the latter. In them on the first level there are green plants, on the second - pasture animals, on the third - predators. However, in the bodies of dead plants and animals, energy and "building material" are still contained, along with intravital excreta (urine and feces). All these organic materials are decomposed by the activity of microorganisms - bacteria and fungi. They live on organic remains like saprophytes.Organisms of this type are called decomposers. They are allocated digestive enzymes to waste life or to dead bodies, and then absorbed digestion products. Decomposition can occur at different rates. Consumption of organic compounds of feces, urine, animal corpses is carried out within a few weeks. In this case, fallen branches or trees can decompose for years.


An important role in the process of decay of wood belongs to fungi. They are a cellulase enzyme. It softens on wood, which makes it possible to penetrate and absorb material to small animals. Fragments of decomposed material are called detritus. They are fed by many small living organisms (detritophages) and accelerate the process of destruction.Since the decomposition involves two types of organisms (fungi and bacteria, as well as animals), they are often combined under the same name - "decomposers". But in fact this term is applicable only to saprophytes. Detritophages, in turn, can be absorbed by larger organisms. In this case, a chain of another type is formed - starting with detritus. To the detritophages of the coastal and forest communities include the moquard, the earthworm, the larva of the fall flies, the crimson, the holothurian, the polychaete.

Food Network

In systems schemes, each organism can be represented as consuming others belonging to a particular type. But the existing food links in the biological structure have a much more complex structure. This is due to the fact that the animal can consume organisms of various types. In this case, they can belong to one food chain or belong to different. This is particularly evident among predators at high levels of the biological cycle. There are animals that consume other representatives of fauna and plants at the same time. Such individuals belong to the category of omnivores. In particular, such is the person. In the existing biological system, the interlacing of food chains is quite common. As a result, a new multicomponent structure is formed-the network. In the scheme, only some of all possible connections can be reflected. As a rule, it contains only one or two predators belonging to the upper trophic levels. In the flow of energy and the cycle within a typical structure, there can be two ways of exchange. On the one hand, the interaction is between predators, on the other hand between the decomposers and the detritus. The latter can consume dead animals. At the same time, living decomposers and detritus can act as food for predators.