Symbiosis: what it is, types and characteristics of this biological phenomenon

In the world, there are a total of 8 types of ecosystems or biomes that are home to the different species of living beings that inhabit today. To understand an ecosystem, it must be taken into account that it is made up of 2 large elements: the biotope and the biocenosis.

The biotope refers to an area with specific environmental conditions that provides a vital space for all flora and fauna. That is, the physical environment (rocks and sediment, among others), the availability of water, environmental parameters, geographical accidents and other non-living elements. On the other hand, the biocenosis corresponds to the set of populations of living beings that coexist in space and time. Thus, living matter is as essential in an ecosystem as the setting in which it develops.

If we look at the biocenosis, we can describe an infinite number of intra and interspecific interactions. You must bear in mind that 1,426,337 animal species have been described, so there is room for all kinds of interaction between them: predation, direct and indirect competition, parasitism, commensalism and symbiosis, among others. Today

we focus on this last type of biological interaction, symbiosis, because sometimes in the union of there is strength.

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What is symbiosis?

As with any scientific term, its etymological root will allow us to know its meaning. The word symbiosis comes from the Greek word σύν, syn (together) and βίωσις, biosis (to live). Thanks to this linguistic dissection, we can imagine where the shots will go from here.

The term symbiosis applies to the close and persistent relationship between organisms of different species, where the parties involved in this interaction are known as symbionts. In any case, it is necessary to make some acceptances before continuing to dissect symbiotic phenomena.

In its broadest and loosest sense, the term symbiosis is defined as any type of biological interaction between species, whether beneficial or detrimental to any of the parties. Thus, paradoxically, parasitism would be a type of negative symbiosis, since both elements are highly related to each other and coevolve together, even if one of them is severely impaired over time (the host). Also included in this definition is commensalism, an interaction where one party benefits and the other is indifferent.

At an informative level, symbiosis is usually associated indistinctly with mutualism. In this case, the relationship between the members must be positive for both, so parasitism and commensalism are left out. Finally, some authors use an even stricter meaning of the term, where the relationship is required to be essential for the life of both species. Although in mutualism both parties benefit, they can go on with their lives separately. In the most classical symbiosis, the components cannot survive without the action of the other.

Guys

Symbiosis can be classified into different types, but here we present the most important ones.

For example, If we look at the spatial relationship between both participants, there is a possible ectosymbiosis and an endosymbiosis. In ectosymbiosis, as its name indicates, one of the members lives on or around the body of the other. Perhaps crabs and anemones come to mind, for example, as these crustaceans live on them to protect themselves and, at the same time, prey on possible parasites that settle on the anemone.

On the other hand we have endosymbiosis, which cannot be seen externally but is equally (or more) important at an evolutionary level.. In this case, one of the individuals lives inside the other, so it must necessarily be smaller than the other (we generally talk about microorganisms). The intestinal microbiota and the human being are a clear example of this: many of our bacteria could not live outside our tract. gastrointestinal, and at the same time these help us digest substances, specialize the immune system and avoid infections, among others things.

Based on other parameters, symbioses can be optional or obligatory. These terms are fairly quickly explained: in the first case, both elements can live on their own. alone but benefit from the interaction, while in others one's life cannot be conceived without the other. A very curious case of facultative symbiosis is that of certain birds on the backs of large mammals: birds they deworm oxen and rhinos (among others), deworming them, but if there is no food, they look for it themselves same.

On the other hand, a clear example of obligate symbiosis are lichens, product of a close evolutionary union between a fungus and an alga or cyanobacteria. The alga is capable of photosynthesis, so it provides the fungus with organic matter without much difficulty. For its part, the hyphal structure of the fungal element captures water and mineral salts from the environment, thus defending the algae from drying out due to the dryness of the environment. In this case, neither of the 2 elements survive in the middle without the other.

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Degree of symbiosis in living beings

Another way of understanding symbiotic processes in living beings is by placing the level of interaction between participants on a numerical scale. Based on this parameter, we can create the following list or ranking:

1. Degree of least interaction

The members establish a behavioral relationship, that is, they live together, look for each other and have learned to interact in a positive way.

2. metabolic rate

This is the case of lichens. Generally, on these occasions the exudate or metabolic product of one of the members is the food of the other.

3. High degree of interaction

For example, the proteins of one of the members of the symbiosis is essential for the other. This it is the case of many vegetables.

4. Maximum degree of integration

It is produced a transfer of genetic material and the consequent fusion of the symbiotes, thus generating a new living being where there were 2 before.

Symbiosis or altruism?

It is very common for us to humanize the rest of living beings, since we believe that they are governed by the arbitrary moral and ethical codes that we have established. Nothing is further from reality. In nature, nothing is done randomly or out of disinterest, at least in the vast majority of animals.

Thus, a symbiosis can go astray throughout the evolutionary history of both species if it stops reporting benefits for either party. As soon as one of the species begins to "lose" in the relationship, the mechanism destabilizes and problems can arise., leading even to phenomena of parasitism. We give you an example.

A clear case that exemplifies what has been reported is that of the oxpecker, 2 species of birds belonging to the family Buphagidae. These cute little black birds perch on the backs of large mammals and symbiotically extract the insects and parasites that settle on their skin. So far, both participants clearly benefit, right?

What happens is that these birds love blood, and for this reason, they have a predilection for the swollen ticks present on the surface of the mammal. When there are not enough of them or the bird needs an extra caloric intake, it sometimes takes charge of keeping the wound open and sucking it directly from the host. Where before there was a symbiosis, a line has been crossed that leads to parasitism.

Summary

As we have been able to see, the term “symbiosis” presents more nuances than one might initially expect. In nature, not everything is black or white, as biological systems are influenced by the environment and can change at any time. When a species stops reporting benefits to another, in the best of cases one of the members separates, and in the most extreme, the dominant one subjugates the other and preys on it or parasitizes it.

The term "empathy" does not exist clearly in most members of the animal kingdom, and phenomena like these exemplify it perfectly. For living beings, the only thing that matters is the transmission of genes and the permanence of their species, at the cost and damage that may be necessary. Without a doubt, nature is as beautiful and fascinating as it is cruel.

Bibliographic references:

• Bleger, J. (2020). symbiosis.
• Canizares, P. J. g. (2015). Effective management of arbuscular mycorrhizal symbiosis via inoculation and mineral fertilization in grasses of the genus Brachiaria. University Press.
• Durán-Alvarado, F. J. (2003). Tufted magpie, Calocitta formosa (Aves: Corvidae), foraging on white-tailed deer Odocoileus virginianus (Mammalia: Cervidae). Brenesia., (59/60), 89-90.
• Hawksworth, D. L. (1989). Fungus-alga interactions in lichen and lichenoid symbioses. In Annals of the Botanical Garden of Madrid (Vol. 46, No. 1, p. 235-247). Royal Botanical Garden.
• Rivera, R., Ruiz, L., Fernández, F., Sánchez, C., Riera, M., Hernández, A.,... & Planas, R. (2006, March). Effective mycorrhizal symbiosis and the soil-plant-fertilizer system. In Congress Cuban Society of Soil Science (6: 2006 Mar 8–10: Havana). Memories. [CD–ROM] Havana City: Capitol Convention Center.