Symbiosis is a close relationship between two organisms in which one organism lives near, on, or even inside another organism and in which at least one organism benefits. Commensalism results in benefit to one organism. The other organism is neither helped nor harmed.
Mutualism is a relationship that is helpful to both organisms.
These relationships are often necessary for the survival of both organisms. Parasitism is a relationship in which one organism benefits and the other organism is harmed. Mutualism Relationship Rhinoceros and Red-Billed Oxpecker. A red-billed oxpecker sits on the nose of a white rhinoceros as it grazes, eating parasites and warning the rhino of imminent danger. Parasitism Relationship Flea in Dog's Fur.