Lichens are common on tree trunks and rocks throughout Canada. These composite organisms involve the symbiosis of a fungus and either a green alga or a cyanobacterium. In this symbiosis, each species is dependent upon the other. The term used to describe this type of relationship is

Question

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Obligate symbiosis refers to a relationship where both organisms involved are so interdependent that each cannot survive without the other, which accurately describes the relationship between the fungus and the alga or cyanobacterium in lichens.

Lichens Are Common on Tree Trunks and Rocks Throughout Canada