Parasitism- a symbiotic relationship where only the symbiont benefits, and the host is harmed.
Ex: liver tapeworm cysts are common parasites involved in a symbiosis with moose, caribou, and wolves.
Mutualism- a symbiotic relationship where the host, and the symbiont are both benefitted, and no one is harmed.
Ex: Lichen are the symbionts in a symbiotic relationship with fungus. The alga is photosynthetic in nature and reduces Co2 into sugars that feed the fungus. The fungus helps provides protection to the alga by retaining water and helping it obtain minerals from substrate.
Commensalism- a symbiotic relationship where the symbiont is benefitted, and the host is neither harmed, or benefitted.
Ex: An Arctic fox follow around a caribou when the caribou is hunting. The Arctic fox then digs further into where the caribou was last digging, and gets its food in the form of mammals. The Arctic fox is benefited and the caribou is neither harmed, nor benefited.