Symbiosis 

Symbiotic relationships between organisms have been an evolutionary process that is an essential part of life itself.The classic example is lichens, symbiosis between green algae and cyanobacteria.However, as this field has been exploring interesting findings they have been made which show that such interactions are present in almost all living beings in the biosphere.Although symbiotic relationships are not limited to microorganisms, such as the case of the remora and shark, microorganisms and their interactions with other living things have a big impact on issues such as health and agriculture, which are of relevance to humans.The importance of knowing and understanding these phenomena has led to a boom in the study of symbiotic relationships that microorganisms have the other species on the planet.

By definition, a symbiotic relationship is the joint interaction with two different organisms, being a close association process, the product of an evolutionary history entwined.

Generally symbiotic associations are classified according to the effects of the interaction on the organisms involved.These consequences can be where one of the bodies is benefited, causing damage to the other (parasitism), or simply taking advantage of the conditions without having a negative effect or a benefit on the other (commensal).

There is also the case where both agencies receive a benefit, these relationships are called mutualism.

Mutualism

Mutualism is a biological interaction between individuals of different species, where both benefit and improve their biological aptitude. Similar actions that occur between members of the same species are called cooperation.

Mutualisms can be:
- Temporary or optional (not required): both species derive benefits from each other, yet they can survive separately.

- Permanent or forced (dependency): in this case one party (or both) is strictly dependent on the other. In this type of interaction, the organism or organisms can not survive without the presence of his symbiont partner.

Because of the focus has been the study of symbiotic relationships, mutualism has not received as much attention as other interactions (eg parasitism).

However, this trend has changed, and is now known that mutualism is of great importance for life on Earth. Mutualism is a phenomenon so present that from humans to bacteria bind in mutualistic networks with other agencies receiving benefits from these associations.

Examples include the mutuality of zompopas and fungal garden.

This interaction is described in more detail in other sections, ants cultivate the fungus, which is the source of their livelihood. The process involves culturing the fungus ants feed it with leaf pieces that they collect. Also insect fungus care giving preventive maintenance that prevents the proliferation of parasites on it. This is an interesting case of how two very different beings have come to be complemented by an evolutionary process as a whole.

Parasitism

Parasitism is a biological interaction between organisms of different species, in which one of the organisms (parasite) benefits from the close relationship with another (the host). Parasites can be classified according to where they live with respect to the host. Those who live inside living within the host are called endoparasites, while living outside are called ectoparasites. Parasitism is a process by which a species expands its survivability using other species to cover some of their basic and vital needs. This does not necessarily refer to nutritional issues, and can cover functions as advantages for breeding or rearing the offspring of parasitic species. To further clarify this can be shown examples, such as the leech, which feeds on the blood of the host. In this case parasitism it exemplified with nutritional benefits. On the other hand the cuckoo makes a type of parasitism where it displaces the eggs of other birds nest and place yours for the host bird's breed. In the case of leaf-cutting ants, there parasitism by a Escovopsis fungus, which destroys the symbiont fungus ants in the fungal gardens to feed.

Exploited species usually do not make a profit for services rendered to the parasite. In fact, in most cases they are impaired by this interaction. As a result of constant exposure to the interaction of the parasite, the host decrease in viability, and even may die. Parasites are organisms often highly specialized.

These have dedicated their existence to adapt to the lifestyle that defines them and the host. At other times the parasitic relationship is short, and therefore the level of specialization is lower. Similarly, the host-parasite interaction leads to biological processes in which the former seeks to evade the barriers developed by the host.

Reference

De Bary, H.A. Die Erscheinung der Symbiose (Karl J. Trubner, Strasburg, 1879) citado en inglés en Relman, D.A. "Till death do us part": coming to terms with symbiotic relationships. Nature Reviews Microbiology 6, 721-724 (2008)