Symbiosis
Interaction between 2 organisms living in the same ecosystem
Mutualism
Symbiosis that is beneficial to both organisms involved. An example of this is when a bird eats the leftover food from an alligator's teeth. The bird gets food and the alligator has its teeth cleaned.
Commensalism
Symbiosis that is beneficial to one organism while the other organism isn't affected. An example of this is when barnacles attach to whales. It gives them a source of food and a way of transportation.
Parasitism
Symbioses where one organism benefits and the other is harmed. An example of this is when a tick attaches to an animal and sucks its blood.