In nature, all organisms, whether animals, plants or bacteria, create links and establish relationships that range from members of the same family to individuals of different species. We can observe relationships between a predator and its prey or interactions that are beyond our understanding with the naked eye.
Have you ever heard the word "symbiosis"? In this article on our site, we will see the definition of symbiosis and we will show curious examples. Keep reading!
What is symbiosis?
The word symbiosis in biology was coined by De Bary in 1879. He intended it to be a term that described the coexistence of two or more organismsthat are not closely related in phylogeny (relatedness between species). That is, they do not belong to the same species, without the implication of beneficial exchanges per se. Modern usage normally assumes that symbiosis means mutual dependency with a positive outcome for all involved.
The association between these individuals must be permanent, they can never be separated. The organisms involved in a symbiosis are called "symbionts" and can benefit from it, be harmed or have no effect at all from the association.
In these relationships, it is often the case that the organisms are unequal in size and are very far apart in the phylogenyFor example, relationships between different higher animals and microorganisms or between plants and microorganisms, where the microorganisms live inside the individual.
Definition of symbiosis according to the RAE
To show you in a summarized way what symbiosis is, we also provide you with the RAE definition [1]:
1. F. Biol. Association of animal or plant individuals of different species, especially if the symbionts take advantage of life in common.
Types of symbiosis
Before offering you some examples, it will be essential that you know the types of symbiosis that exist:
- Mutualism: in a mutualistic symbiosis, both parties benefit from the relationship However, the extent to which each symbiote benefits can vary and is generally difficult to measure. The benefit a symbiote receives from a mutualistic association must be considered depending on how much it costs you. There is probably no example of mutualism in which both partners benefit equally.
- Commensalism: This term was described three years before symbiosis. We call commensalism that relationship where one of the parties involved obtains benefits without harming or benefiting the other We use the term commensalism in its most extreme sense, where the benefit is only for one of the symbiotes and can be nutritional or protective.
- Parasitism: parasitism in a symbiotic relationship in which one of the symbionts benefits at the expense of another The first factor in parasitism in nutrition, although there may be others: the parasite obtains its food from the organism it parasitizes. This type of symbiosis affects the host in different ways. Some parasites are so pathogenic that they cause disease shortly after entering the host. In some associations, the symbionts have coevolved in such a way that the death of the host (the organism that has the parasite) is not caused, and the symbiotic relationship is much longer lasting.
Examples of symbiosis
Examples of mutualism:
- The symbiosis between algae and corals: Corals are animals that grow well in nutrient-poor environments thanks to their symbiotic relationship with the algae. They provide them with food and oxygen, while the corals give the algae waste substances such as nitrogen and nitrogen dioxide.
- The clown fish and the sea anemone: You have surely seen this example many times. The sea anemone (from the jellyfish family) has a stinging substance to paralyze its prey. The clown fish benefits from this relationship, since it obtains protection and also food, because daily it rids the anemone of small parasites and dirt, this being the benefit they obtain.
Examples of commensalism:
- Relationship between the silver fish and the ant: this insect lives with the ants, it waits for them to bring food and it eat. This relationship, contrary to what we might think, does not harm or benefit the ants, since the silverfish only eats a little of the food reserves.
- The tree house: One of the clearest examples of commensalism is the one in which an animal seeks refuge in the tree branches or trunks. The vegetable, generally, does not obtain any harm or benefit in this relationship.
Examples of parasitism:
- Fleas and the dog (example of parasitism): This is an example that we can easily observe in our daily lives. Fleas use the dog as a place to live and reproduce, in addition to feeding on his blood. The dog does not derive any benefit from this relationship, quite the opposite. In addition, fleas can transmit diseases to dogs.
- The cuckoo (example of parasitism): The cuckoo is a bird that parasitizes the nests of other species. When it comes to a nest with eggs, it dislodges them, lays its own, and leaves. When the birds that own the displaced eggs arrive, they don't realize it and breed the cuckoo's eggs.
Examples of symbiosis in humans:
- The guide bird of honey and the Maasai: There is a bird in Africa that guides the Maasai to the hives hidden in the trees. Humans scare away the bees and collect the honey, leaving the bird free to take honey without the threat of the bees.
- Our relationship with bacteria: Both inside the human intestines and on the skin, there are beneficial bacteria that protect us and they help us to be he althy, without them our existence would not be possible.
Endosymbiosis
We cannot finish this article without mentioning this very important fact, by which eukaryotic cells originated (animal and plant cells) and consequently, life as we know it.
The endosymbiotic theory, in a nutshell, explains that it was the union of two prokaryotic cells (bacteria, for example) that gave rise, on the one hand, to the chloroplasts (organelle responsible for photosynthesis in plant cells) and, on the other, to the mitochondria(organelles responsible for cellular respiration in both plant and animal cells).
The study of symbiosis has become a scientific discipline in its own right in recent years and it has been argued that symbiosis it is not an evolutionarily fixed relationship, but can manifest itself in many ways, such as commensalism or parasitism. A stable mutualism in which the contribution of each organization involved guarantees its own future.
