Food chains and trophic levels are considered integral components of the biological cycle. It involves many elements. Next, we take a closer look at the trophic levels of the ecosystem.


The food chain is the movement of energy, which is enclosed in plant food, through a number of organisms as a result of eating each other. Only plants form organic matter from inorganic matter. The trophic level is a complex of organisms. Interaction between them occurs in the process of transfer of nutrients and energy from the source. Trophic chains (trophic level) suggest a certain position of organisms at one or another stage (link) during this movement. Marine and terrestrial biological structures have many differences. One of the main ones is that in the first 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 is made up of initial consults. At the next stage are consumers who consume herbivorous organisms. These consumers are called secondary. These include, for example, primary predators, carnivores. Also in the 3rd trophic level includes consumers of the 3rd order. They, in turn, consume weaker predators. As a rule, there is 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 residues.

Consuments: general information

They are not just "eaters", which contains the food chain. The satisfaction of their needs by them is carried out through a system of feedback (positive) communication. The consumers have an impact on the trophic levels of the ecosystem that are higher. So, for example, the consumption of vegetation in African savannas by large herds of antelope, along with fires in the dry season, increases the rate of return of nutrients to the soil. Subsequently, during the rainy season, the restoration of grassy plantations and their products is enhanced.An interesting example of Odum. He describes the impact of consumer products on producers in the marine ecosystem. Crabs consuming detritus and algae “look after” their herbs in several ways. They tear up the soil, thus enhancing the circulation of water around the roots and introducing oxygen and the necessary elements into the anaerobic coastal zone. In the process of continuous processing of bottom sludge rich in organic matter, crabs contribute to the improvement of conditions for the development and growth of benthic algae. One trophic level consists of organisms that receive energy through the same number of stages.

Food consumed at every trophic level is not fully assimilated. This is due to its significant losses at the stages of metabolic processes. In this regard, the production of organisms in 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 necessary components for heterotrophs. The following example is simple: an animal consumes plants. In turn, the beast can be eaten by another larger representative of the fauna. This is how energy can be transferred through several organisms. The next one 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 1 order

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

Consumers 1 order

They consume primary producers. They are presented as herbivores. Reptiles, insects, mammals and birds are considered typical representatives on land. The most important groups include rodents and ungulates. Among the latter can be distinguished pasture animals: sheep, horses, cattle. In aquatic ecosystems (marine and fresh), small crustaceans and mollusks act as herbivorous forms. Most of them — copepods and branched crayfish, bivalves, crab larvae, and others — feed by filtering the primary producers from the water column. Many of them, together with protozoa, form the basis of zooplankton, which consumes phytoplankton. Vegetable parasites (fungi, animals, cultures) also belong to the primary consuments.

Consumers 2, 3 orders

Secondary consumers consume herbivores. This means that they are already in the category of carnivores. This group also includes tertiary consumers who eat, in turn, secondary ones. Both those and other consumers can be predators and hunt, be parasites or eat carrion, seize and kill the prey.If parasitism takes place, then tertiary consumers, as a rule, are smaller than the secondary ones. Their food chains are specific in some respects. In typical predator systems, carnivorous representatives become larger at each next stage.

Food chains can be of two types. In particular, they emit detrital and pasture structures. The above are examples of the latter. They contain green plants on the first level, grazing animals on the second, and predators on the third. However, the bodies of dead plants and animals still contain energy and “building material”, along with in vivo secretions (urine and faeces). All these organic materials are decomposed due to the activity of microorganisms - bacteria and fungi. They live on organic remains like saprophytes.Organisms of this type are called decomposers. They allocate digestive enzymes to waste or dead bodies, and then absorbed by the products of digestion. Decomposition can occur at different rates. The consumption of organic compounds of faeces, urine, animal corpses is carried out within a few weeks. In this case, fallen branches or trees can decompose over the years.


A significant role in the process of decay of wood belongs to mushrooms. They release the cellulase enzyme. It has a softening effect on wood, which makes it possible for small animals to penetrate and absorb material. Fragments of decomposed material are called detritus. They feed on many small living organisms (detritus) 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 one name - “decomposers”. But in reality, this term applies only to saprophytes. Detritophages, in turn, can be absorbed by larger organisms. In this case, a chain of a different type is formed - starting with detritus. The detritophages of the coastal and forest communities include woodlice, earthworm, the larva of the fly fly, purple bug, holoturia, polychaete.

Food Network

In systems schemes, each organism can be represented as consuming others belonging to a particular type. But existing in the biological structure of food communication have a much more complex structure. This is due to the fact that the animal can consume organisms of various types. However, they may belong to the same food chain or relate to different. This is especially clearly seen among predators that are at high levels of the biological cycle. There are animals that consume other representatives of the fauna and plants at the same time. Such individuals are omnivorous. In particular, this is the man. In the existing biological system, the intertwining of food chains is quite common. As a result, a new multicomponent structure is formed - a network. Only some of all possible links can be reflected in the diagram. As a rule, it contains only one or two predators belonging to the upper trophic levels. In the flow of energy and circulation within the framework of a typical structure, there can be two ways of exchange. On the one hand, the interaction is between predators, on the other - between decomcendents and detriadites. The latter can consume dead animals. At the same time, live decomposers and detritopids can act as food for predators.