TROPHIC RELATIONSHIPS: CONCEPT AND EXAMPLES - BIOLOGY - 2025

The trophic relationships are those that link two or more organisms where one acts as a predator or entity other feeds, and other functions as food or entity which feed. This includes the transfer of energy from one place in the ecosystem to another.

It is a general rule that plants, algae and any organism that synthesizes its own food (autotrophic organisms) represent the basis for any trophic relationship in nature, since they are in charge of transforming the energy of the environment into organic molecules that can be used by other organisms in the ecosystem.

Image by Olya Adamovich on www.pixabay.com

There is a great diversity of ecological relationships that link different species, but any type of trophic relationship, in one way or another, involves some autotrophic organism.

Trophic relationships can be observed in all ecosystems, even those with the most extreme conditions. Thus, scientists always try to know all the trophic relationships of an ecosystem, since this allows them to understand and represent its functioning and the flow of nutrients in it.

To properly understand a trophic relationship, many hours of observation and study of the behavior of the species in the ecosystem where they live are required, which imposes some restrictions for the study of these relationships between species.

Trophic relationship concept

Every form of life on the planet survives because it can obtain and use energy from a source external to itself. This energy allows it to develop, grow, reproduce and carry out all the biological processes that characterize it.

However, in nature there are many different strategies and ways of life. For example, plants and algae get their energy from sunlight; herbivores feed on plants and carnivores feed on herbivorous animals, for example.

The concept of "trophic relationships" must, therefore, include many different evolutionary strategies, since the transfer of energy from one individual to another can occur through a great diversity of processes.

Trophic relationships can range from the mutual cooperation of the species, to the benefit of one species and the death of the other. In some strategies, both linked species transfer energy to each other, in a kind of feedback.

Thus, the concept of trophic relationships can be found in the literature from many different approaches. However, all agree that trophic relationships are the "transfer of energy from one individual to another. "

Examples of trophic relationships

In ecological studies, interspecific relationships are defined first and then trophic relationships based on these interactions. Some examples of the most studied and observed strategies within trophic relationships are:

Competition

Competition is perhaps the interspecific interaction, and in turn the trophic relationship, mostly observed in nature, since this controls the energy that an animal can obtain that feeds on an animal or the surrounding environment, in the case of animals. autotrophic organisms.

- Plants in cloud forest forests compete for spaces where they can capture the most sunlight.

Image by SplitShire on www.pixabay.com

- In the sea we observe how predators of different species compete to catch the largest number of fish in a school of a given species.

In all these cases there is a transfer of energy, since the one who "wins" the competition recovers the forces used for this purpose, while the one who "loses" ends up with their energy reserves diminished and, sometimes, even the loser dies..

Parasitism

From an anthropocentric point of view, parasitism is, perhaps, one of the worst trophic relationships in nature. This consists of one of the individuals obtaining their food from another, without the other obtaining any benefit.

Furthermore, the individual that is parasitized is harmed due to the energy that the parasitic individual takes away from him.

Graphic scheme of a Taenia saginata (Source: Servier Medical Art / CC BY (https://creativecommons.org/licenses/by/2.0) via Wikimedia Commons)

A classic example of parasitism as a trophic relationship is represented in the various parasites that affect humans: T. cruzi, T. saginata, P. falciparum, among others.

All these parasites use the human body as an ecosystem to live, lodging, feeding and even reproducing within it; being able to do so from the energy they obtain from the environment they parasitize.

On the other hand, these parasites decrease the energy of the bodies they infect, causing great deterioration and a decrease in the normal physiological activity of the hosts.

Mutualism

Mutualism is a trophic relationship in which both individuals depend on each other for energy. This type of relationship is very common in nature and they are very successful interactions, especially in extreme environments.

An example of this type of interaction that is found in almost any ecosystem on the planet (except Antarctica) corresponds to lichens, which are made up of a species of fungus and a species of algae.

Photograph of a lichen (Image by Hans Braxmeier at www.pixabay.com)

The alga provides part of its photoassimilates to the fungus, while the fungus provides the alga with a suitable substrate on which to live (with enough water and light, etc.).

Predation

This interaction, seen from the trophic point of view, consists in the benefit of one of the individuals that participates and in the death of the other. The individual defined as a "predator" obtains energy from the death of the other, called "prey".

Image by Andrea Bohl on www.pixabay.com

Classic examples of this trophic relationship are lions (Panthera leo) hunting antelope (Hippotragus niger) on the African plains. The lions stalk the antelope herd to capture and eat some of the individuals in it.

The lions that are predators obtain assimilable energy by devouring their prey, this being the antelope.

Amensalism

Amensalism is an interspecific interaction that is very difficult to identify in ecosystems.

However, it is a trophic relationship easy to describe, since one individual does not perceive any effect of the interaction (does not obtain energy) and the other is harmed from the interaction, that is, loses energy.

From the trophic point of view there is a transfer of energy from a species to the ecosystem, since the energy is not obtained by any of the individuals that participate. In other words, one of the species causes the other to lose energy, but does not gain it for itself.

Image by Karsten Paulick on www.pixabay.com

An amensal trophic relationship can be observed when dogs eat grass to "purge" themselves. These cause a negative effect on the plant because they take away the light absorption surface and cause wounds in its tissues, while the dog does not gain a single gram of energy by feeding on the plant.

This relationship can be seen from the trophic point of view in that there is a transfer of energy from the plant to the environment due to the relationship that occurs between the two individuals: the dog and the plant.

Commensalism

Remora under a shark

Commensalism is defined as an interspecific ecological interaction between two organisms in which one of them benefits, while the other obtains neither benefits nor losses. In literature it is represented as a "+/-" interaction.

A commensal trophic relationship can be seen in the remora (Remora remora) that accompany the sharks at all times. They feed on the pieces of meat that are released around the shark when it feeds on its prey.

Commensalism is a trophic relationship that is difficult to identify in ecosystems, since in many cases it is temporary, that is, it occurs only during a defined period of time and only rarely is this interaction permanent or maintained for a long time..

References

1. Bradstreet, MS, & Cross, WE (1982). Trophic relationships at high Arctic ice edges. Arctic, 1-12.
2. Bunwong, K. (2011). Numerical Simulation on Ecological Interactions in Time and Space. Numerical Analysis: Theory and Application, 121.
3. Clarke, GL (1955). Elements of ecology (Vol. 79, No. 3, p. 227). LWW.
4. Glavič, P., & Lukman, R. (2007). Review of sustainability terms and their definitions. Journal of cleaner production, 15 (18), 1875-1885.
5. Lindeman, RL (1942). The trophic-dynamic aspect of ecology. Ecology, 23 (4), 399-417.
6. Robert, S. (2015). Elements of Ecology. Pearson Education India.