Have you heard about mutualism , but don’t know what it means? So, follow this article to understand a little more about this type of relationship of living beings, how it works and some examples.
First, it is important to know that the living beings that make up the ecosystem are constantly influenced by their environment, but also act on it. The organisms of a community interact, exerting reciprocal influences that are reflected in the populations involved.
These interactions can occur between individuals from the same population (intraspecific), such as colonies and societies, or between individuals from populations of different species (interspecific), such as mutualism and commensalism , for example.
When analyzed in isolation, these interactions can turn out to be harmonic or disharmonious. Harmonic or positive interactions are those in which there is no harm to any of the populations in the interaction. In disharmonious or negative interactions, at least one of the populations suffers some kind of disadvantage.
However, considering the total of interactions in a community, it appears that even disharmonious ones can have positive indirect effects, as they are important for the balance of the populations that interact.
Index
- Mutualism
- Interspecific interactions
- Protocooperation x mutualism
- Commensalism and tenancy
- Symbiosis or mutualism?
Mutualism
It is a type of harmonic interspecific relationship in which participants benefit and maintain a relationship of dependence. Sometimes, this relationship is extremely intimate, as with lichens. They represent an association of fungi and algae that are functionally dependent and morphologically integrated.
Lichens are classified into species, although in reality each species of lichen is formed by two different species of organisms (algae or cyanobacteria and fungus).
Cows have a mutual relationship with bacteria present in the digestive tract (Photo: depositphotos)
Some herbivorous mammals , especially ruminants, harbor bacteria in their digestive tract that produce cellulase, an enzyme that digests cellulose, transforming it into usable carbohydrates: the bacteria use one part and the animal uses another. This is yet another example of mutualism.
Another case is that of protozoa that also produce cells and live in the termite digestive tube, receiving food already particulate ingested by these insects. This allows termites to take advantage of the nutrients from the digestion of wood. These protozoa depend on this association, as they only survive in the body of termites.
Other examples of mutualism are mycorrhizae , associations between fungi and plant roots, and bacterioryras , associations between nitrogen-fixing bacteria and plant roots.
In mycorrhizae, fungi contribute to the absorption of mineral nutrients from the soil, benefiting plants, while they provide organic nutrients to fungi . In bacterioristries, bacteria fix the nitrogen in the air that is between the soil particles and pass to the plant, which provides protection and energy to the bacteria.
Interspecific interactions
Interspecific interactions can be: h harmonics, such as mutualism, proto-cooperation, tenancy and commensalism; or d esarmônicas, such as the amensalismo (or antibiosis), predation or parasitism and interspecies competition.
In interspecific ecological interactions, signs are usually used to represent the effect of this relationship on the populations involved. The + sign is used when the population grows; the sign – when the population decreases; and signal 0 , when there is no growth or reduction in the population. So we have:
- (- -): competition
- (+ +): mutualism, when the two populations have favorable interaction and are completely dependent on each other
- (+ +): proto-cooperation, when both populations interact favorably, but not mandatory
- (+ 0): commensalism
- (- 0): Amensalism
- (+ -): predation, including herbivory
- (+ -): parasitism.
Protocooperation x mutualism
In proto-cooperation, although participants benefit, they can live independently, without the need to unite. In mutualism, union is mandatory , and individuals are interdependent.
One of the most well-known examples of protocooperation is the association between the sea anemone and the paguran , a crustacean similar to the crab, also known as the hermit or hermit.
The pagoda has a soft abdomen and usually occupies the interior of abandoned shells of gastropods. Usually one or more sea anemones are placed on the shell. From this union, mutual benefit arises: the anemone has stinging cells, which scare away predators, and the pagan, when moving, allows the anemone to better explore the space in search of food.
A very common example of protocooperation can be seen in Brazilian pastures: birds that land on oxen and cows to feed on ticks. Birds find food, and oxen get rid of ticks that parasitize them (ectoparasites).
Another example of protocooperation is the case of insects and pollinating birds . They obtain nectar from plants that serve as food, while transporting pollen from one flower to another, involuntarily contributing to the pollination of plants.
Commensalism and tenancy
In these two types of association, only one of the participants benefits , without, however, causing damage to the other. In commensalism, the association occurs in terms of obtaining food. In commensalism, the benefited species receives the name of commensal and feeds on the remains left by the host species.
An example of commensalism is the association of the shark with the pilot fish . Pilot fish (called commensals) live around the shark, feeding on the remains of food that escape the mouth of this predator.
In tenants, the association often occurs for protection, shelter or physical support. An example of tenancy involves the fieráster , a small fish that lives as a tenant inside the body of the sea cucumber to feed and then comes back.
In this case of tenancy, the fish finds protection in the body of the cucumber, which, in turn, does not receive benefits or suffer disadvantages. Among the vegetables we have the epiphytes (orchids and bromeliads), which are fixed on the trees without however causing any harm to them.
Symbiosis or mutualism?
The term symbiosis, coined in 1879 by biologist De Bary, has been misused as a synonym for mutualism. Symbiosis originally refers to any stable association between individuals of different species, whether positive or negative.
Thus, we could consider three well-defined types of symbiosis : parasitism, commensalism and mutualism.
Currently, however, the use of the term symbiosis has been expanded, applying to any type of interspecific relationship. The classification of ecological interactions can vary widely. In some, commensalism includes tenancy, which is no longer one of the categories.
With mutualism and protocooperation something similar happens: mutualism can include protocooperation, which is no longer a valid category. In addition, there are cases where the boundaries between one category and the other are not very clear, and there are types of interactions that do not fit well in any category.
