Mutualism is a type of symbiosis. In this case both organisms gain fitness from the interaction. The most obvious example is the flower-pollinator relationship; trading nectar for fertility. There are other forms, some more obscure than others. read more
Protocooperation is a form of mutualism, but the cooperating species do not depend on each other for survival. An example of protocooperation happens between soil bacteria or fungi, and the plants that occur growing in the soil. read more