Symbiosis Symbiosis Symbiosis is a relationship in which two organisms live together and at least one of them benefits. The partner organisms are called the symbiont and the host .
Commensalism is a symbiotic relationship between two partners, the host and the symbiont.
One partner, the host, is not harmed. The other partner, the symbiont, benefits greatly. Mutualism is a symbiotic relationship in which both the symbiont and the host benefit. Parasitism is a symbiotic relationship in which the symbiont benefits at the expense of the host. In parasitism the host is harmed and the symbiont benefits.