What is Food Chain?

Food chain is the unidirectional sequence of matter and energy exchanged between living beings through food. In this way, living organisms depend on each other to survive in different ecosystems.

The energy and nutrients used by all beings, through the food chain, is lost at the time of each transfer, in the form of heat that is not reusable.

Meaning of the Food Chain

Elements of the Food Chain: Trophic Levels

The food chain is composed of three main groups of living beings: producers, consumers and decomposers.

Each represents a trophic level of the energy flow transmitted through the power supply. The first trophic level is formed by the producers and the last are the decomposers.


This is the first trophic level of the food chain. Producers are those who produce their own food (autotrophs), either through photosynthesis or chemosynthesis.

Plants and plankton are the main examples of producing organisms, because they use nutrients from the soil and sunlight to obtain energy in a self-sufficient way.

Producing organisms will always be the basis of the food chain and beings with the greatest amount of energy.


It is all living things that need to feed on each other to get energy and nutrients (heterotrophs).
Within the consumer group there are different classifications:

  • Primary Consumers:are all organisms that feed directly from the Producers. In this case, they are usually herbivorous or omnivorous animals, because they consume plants. Examples: rabbit and cow.
  • Secondary consumers: they are the living beings that feed on the primary consumers. They are carnivorous or omnivorous. Example: human being and cat.
  • Tertiary consumers: these are the organisms that consume the secondary ones. They may also be carnivorous or omnivorous. Example: lion and shark.

Trophic levels can continue in succession, but as energy is lost with each new transmission, there are not many stages of consumption in a food chain.


Finally, in the last trophic phase of the food chain, are the decomposers. These are beings that decompose dead organic matter, remove the nutrients they need to survive, and give back to the environment what is needed to restart the cycle.

Even though they belong to the last trophic level of the food chain, decomposers are present on all other levels. For example, when an animal that is a primary consumer dies, the decomposing organisms act in the decomposition of the organic matter of this. The same thing happens if a secondary or tertiary dies.

Bacteria and fungi are some examples of decomposing organisms present in most ecosystems.

Examples of Food Chain

Food chains are represented according to the ecosystem. In this case, the main types are:

Aquatic Food Chain

In aquatic ecosystems the main producers are phylloplankton, which are a set of unicellular and microscopic algae that make photosynthesis.

As primary consumers are zooplankton (protozoa, worms, crustaceans, etc.), organisms that feed on phylloplankton or some types of bacteria.

Zooplankton, in turn, serves as food for fish, and so on.

Terrestrial Food Chain

In the terrestrial food chain we have the plants as producers that, in turn, serve as food for the primary consumers (herbivores or omnivores), represented by the locust.

The decomposers (fungi and bacteria) appear at the end of the cycle, but can act at any trophic level, from the decomposition of dead organic matter. This is a fundamental activity to ensure the balance of the ecosystem and the life cycle.

Human Food Chain

The human being is omnivorous, that is, it feeds on both plants and meats. In this case, it can be classified as a primary, secondary or tertiary consumer, according to the food it consumes.

For example, man is a secondary consumer when he eats beef, since this animal, when alive, fed on grass, that is, acted as a primary consumer.

Food Chain and Food Web

The difference between the two lies in the fact that the food chain is a linear and unidirectional sequence that indicates which living being serves as food for another.

Already the food web is the set of several food chains, presenting in a more complex way the reality of the feeding relations existing in the ecosystems.

The food web is represented graphically with a large number of living beings, revealing a set of food chains with arrows that indicate who consumes whom. The arrows on this set of food chains make it look like a spider’s web, and so the designation “food web” emerged.

Thus, in the food web we see that the same organism can be present in different trophic levels, as a primary consumer, as well as secondary or tertiary. In this way, it is possible to follow all the different paths that energy can pass through the ecosystem.

Crisis in the Food Chain

The imbalance of the ecosystem is one of the main environmental problems of the present time. With the extinction of some animal and plant species, more and more problems are occurring in food chains and as a consequence, damages to the ecosystem.

Predatory hunting of animals, pollution of water, air and contamination of rivers are the factors that directly influence the food chain.