What are food webs and examples

The trophic relationships are those established between individuals and species around food, or rather around obtaining organic material for energy purposes, functional and structural. As a note, it is important not to confuse food with nutrition, since nutrition includes, in addition to obtaining organic matter, aspects related to water balance and respiration.

Those organisms that present a similar diet are grouped into levels. In most ecosystems we find the following trophic levels :

• Producers: transform inorganic matter into organic matter. In general, species capable of photosynthesis. Producers are the only “autotrophic” organisms, or that are capable of generating their own organic matter. The rest of organisms, which need an external contribution of organic matter, are the “heterotrophs”.
• Primary consumers: they feed on primary producers. They are called herbivores.
• Secondary consumers: they feed on secondary consumers. They are the carnivores.
• Tertiary consumers: they feed on secondary consumers. They are known as super predators.
• Decomposers: they close the cycle by transforming organic matter into inorganic matter that can be used by the producing organisms. In this other AgroCorrn article you can learn more about What are decomposing living beings with examples .

Now then, we see that a cycle of matter takes place , with various chemical transformations and ecological relationships involved. All organisms have some kind of relationship with organisms located at these levels. In fact, most organisms have not one, but several relationships with other species. The “food webs” or sets of trophic relationships between the organisms of an ecosystem are then formed. An illustrative graphic representation is usually made with the different organisms and arrows that indicate the transfer relationships of matter.

Networks include a multitude of “food chains”, or a chain in which organisms serve as a supply of matter for another, and so on. An example of a food chain would be: Wheat => Field mouse => Bird of prey => Decomposing bacteria. They are more or less useful simplifications of food webs , although they are not a good representation of what happens in nature.

Food webs are usually very complex, since most organisms establish a large number of relationships. For example, a producer plant organism can be consumed by several herbivores, and omnivorous organisms can have relationships that span more than two trophic levels. More complete decomposers , such as small insects or bacteria, can also feed from a wide variety of sources.

Trophic networks are of great importance within ecosystems, since they are one of the main factors for the regulation of populations, or regulation of the number of individuals of each species that belong to the ecosystem.

The number of relationships that an organization establishes within its network establishes its importance within it. The greater the number of relationships, the greater the importance, since they influence the regulation of a greater number of populations. That is why conservation efforts often focus on large superpredators , such as wolves ( Canis lupus ) or brown bears ( Ursus arctos ), since these are usually one of the organisms that have the most influence on this regulation.

As a reflection, it should be noted that the whole world behaves like a large solar battery. Although there are autotrophic bacteria that do not depend on sunlight, their contribution to the whole of the terrestrial biomass is not very significant. Thus, plant organisms are the “batteries” that transform the energy that comes to us from the sun into chemical energy contained in the bonds of organic matter.

Let’s see some interesting examples of food webs :

Terrestrial food web

An example of a food web that occurs on the earth’s surface is that established in agroecological systems, very complete systems in which a clear anthropic influence is seen, which has modified the previously existing trophic relationships.

Aquatic or marine food web

Marine food webs are highly dependent on how deep they are. Near the surface we find photosynthetic algae, which are the basis of the chain of small invertebrates. However, at high depths the light is not able to penetrate the ecosystem. In the deeper areas, a large part of the organisms are decomposers, which feed on “what falls from above.”

Although the total relationships are cyclical, the same biomass does not accumulate at all levels. In fact, each level that is promoted reduces the amount of biomass that is in that level. Thus, we can find an ecological pyramid in which the autotrophic producing organisms are the base.

It is important to note that the passage of biomass from one trophic level to another is a very inefficient process. In fact, it is estimated that about 90% of the accumulated energy is lost in the bonds of organic matter from one level to another. Therefore, based on this, it could be said that reducing our meat consumption is not only better from an ethical point of view, but also from an energy point of view.

In this other AgroCorrn post we will discover more about what are ecological pyramids and their types .

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