Normally when people talk about symbiosis, they're talking about two different types of organisms cooperating to help each other survive. For example, clownfish hide from predators among the tentacles of sea anemones; in return, they feed the anemone with their own droppings. Yum yum. The anemone and the clownfish enjoy a symbiotic relationship. In biology however symbiosis has a broader definition than simple cooperation. It's classically defined as any long term living together of unlike organisms. Let me say that again symbiosis the long term living together of unlike organisms. Mutualistic symbiosis or mutualism is when both panners benefit from the relationship, like we saw in the clownfish and the anemone. When I say that both partners benefit from their relationship, what I mean is that both organisms experience a significant increase in evolutionary fitness. They both end up being better at surviving and reproducing. Parasitic symbiosis or parasitism is when one benefits while the other is harmed. Ticks, huh, are a good example of a parasite. They drink your blood and then sometimes repay you with Lyme disease. Total jerks. Commenced allistic symbiosis or commensalism is when one organism benefits, while the other is not dramatically helped or harmed.