Symbiosis

symbiosis-close relationship between organisms of a different species

species-organisms of a similar type that can reproduce with one another in nature and whose offspring are capable of reproduction too

benefit-to gain an advantage, be helped

mutualism-helps both species

commensalism-helps one species while other is not helped or harmed

parasitism- helps one species and harms the other

parasite-organism that benefits 

host-organism that is harmed

Symbiosis is a close relationship between organisms of two different species.

Mutualism is a symbiotic relationship where the organisms from both species benefit.  For example, clownfish help sea anemone catch prey, and in return, the sea anemone do not sting the clownfish and instead protect  them from predators.

Commensalism is a type of symbiotic relationship where one species benefits and the other species is not helped or harmed.  An example of this is a bird living in a nest in a tree.  The bird benefits by having a home that is difficult for predators to reach.  The tree is not affected by the bird nest at all. 

Parasitism is a symbiotic relationship that helps one species and harms the other.  An example of this is a tick feeding on a rabbit.  The tick gets food, but the rabbit suffers from blood loss, sickness, and possible infection.  

A parasite benefits by living on or in an organism of a different species.  It gets food, a home, and help with reproduction.

A host is the organism that is harmed by the parasite living on it or in it.  Some hosts die because of the parasitic relationship.  For example, Toxoplasma gondii parasites change a rat's fear of cats to attraction.  Infected rats seek out cats and are eaten.   The adult parasites live in and feed on rats but can only reproduce in the stomach of the cat.