The three types of symbiosis are mutualism, parasitism and commensalism. Symbiosis is the close relationship between two or more different species.
Mutualism is when two organisms work together with each organism benefiting from the relationship. An example of this kind of relationship is that of the rhino and the oxpecker bird. The oxpecker lands on the rhino and eats parasites from the rhino's skin; the rhino receives pest control and the oxpecker gets an easy meal.
Parasitism is a relationship in which one species, usually a parasite, feeds on the other species. This typically causes harm to the species being fed upon. An example of parasitism is a tapeworm living on the inside of its host, stealing vital nutrients. The relationship between ticks and mammals is also an example of parasitism.
Commensalism is the relationship between two species in which one species gets food or shelter from the other species without harming its host, but the host doesn't benefit from the relationship. An example of commensalism is when one animal feeds off the pieces of food left over by another animal, usually after a hunt.
Symbiotic relationships are a vital part of life in every ecosystem. This balance is sometimes irrevocably affected when one species becomes extinct.