The relationships between living beings

The relationships between living beings

The ecosystems of the planet host hundreds of thousands of species that coexist in perfect harmony. This is possible thanks to the fact that relationships are formed between living beings of different species to reach the balance of all these animals in the same region.

The competition between species

Some of these relationships between living beings are negative for both participants. In this case, we say that when both species compete for the same resources this brings negative consequences for both.

In theory, between two species that compete one would achieve success over another, but thanks to the existence of ecological niches the relationships between living beings of a competitive nature do not prevent both from living together in the same habitat.

Eat or be eaten

Another form of relationship is predation and herbivorism: we talk about relationships between living beings that are negative for one of the participants and positive for another. For example, The lion that hunts a gazelle has much to gain, but the gazelle does not get any benefit.

In the case of herbivorism, at an ecological level the relationship is the same, although it happens that in many occasions the herbivorism does not lead to the death of the animal. Even, the consumption of plants can allow certain animals to act as natural dispersers.

The dreaded parasites

In this type of relationship a parasite takes advantage of a parasitized living being. We talk about relationships between living beings that, like predation, are negative for one participant and positive for another. However, in this case both beings live in close relationship or symbiosis.

On many occasions, parasites have complex cycles going through several hosts. Parasites cause negative effects by altering their density, survival or reproduction. Some parasites such as toxoplasma even change the behavior of their guests.

Another parasite that changes the behavior of its host is Leucochloridium, a worm that puts its larvae on the 'horns' of the snail, which move and attract attention to the birds, which are other guests of the worm.

These snails are nocturnal, so through mechanisms little studied at present, These snails begin to change their activity patterns and become more active during the day.


Some relationships between living beings are positive for both participants: we talk about mutualism, where Both species maintain a symbiotic relationship that benefits both animals.

For example, lichens are complex organisms where an algae receives sugars from a fungus and this allows algae to subsist in a protected habitat. Many lichen species could no longer live without this mutualism relationship. Another example of compulsory mutualism are termites and organisms that live in the digestive system, whose enzymes allow wood to be digested.

There are other examples of mutualism are the relationship between some African trees and ants: they sting and bother the great herbivores, who move away from the trees where they inhabit and consume their nectar.

Commensalism and amensalism

Commensalism is a relationship between living beings in which one of them benefits and the other does not have any effect. In the case of amensalism, we speak of a relationship in which, instead of benefiting, the other animal is harmed.

An example of commensalism are some seaweed that live in the shell of the loggerhead turtle and other sea turtles, although It is unknown if this relationship harms the turtles by decreasing their absorption of sunlight or by providing them camouflage. Another example of commensalism is the relationship of the cattle egret with the great herbivores.

An example of amensalismo are the giraffes trampling small grasses when trying to arrive at trees as the acacia, or the own shadow of this tree that harms these small plants.

Although this is a didactic way of seeing it, the relationships between living beings are very complex and often overlap each other. For example, although the giraffe eats the acacia and tramples the plants that surround it, it also fertilizes the soil, disperses its seeds and makes it produce more nectar.

This nectar is used by ants, so those trees that are protected from giraffes tend not to have these small insects. Interestingly, there are other ants that do not depend on nectar and that promote the infection of trees, so the absence of giraffes ends up harming them. This shows us how complex are the relationships between living beings in nature, and the danger that human beings modify these relationships.

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