Final answer:
Symbiosis refers to a close relationship between two different species, where at least one benefits. Types include mutualism (both benefit), commensalism (one benefits without affecting the other), and parasitism (one benefits at the other's expense).
Step-by-step explanation:
The term “symbiosis” describes a close relationship between two organisms of different species. In a symbiotic relationship, at least one of the organisms benefits, while the effects on the other organism can vary. These effects can be beneficial, harmful, or have no significant impact. There are three basic types of symbiosis - mutualism, commensalism, and parasitism.
In mutualism, both species benefit from their interaction. A classic example is the relationship between termites and the protozoa in their guts, which allows them to digest cellulose. Lichens, consisting of a partnership between fungi and photosynthetic algae or bacteria, is another example of mutualism.
Commensalism is a type of symbiosis where one species benefits and the other is neither helped nor harmed significantly. Finally, parasitism involves one organism benefiting at the expense of the other, often causing harm to the host.