The relationship between a human and Entamoeba histoytica is an example of parasitism (a form of symbiosis). The E. histolytica is a parasite that lives in a human’s gut. The human is harmed because E. histolytica causes dysentery, but the E. histoytica is benefited because it has a place to live and nutrients.

A lichen is an example of a symbiotic relationship (specifically commensalism) between two different species: an alga and a fungus. The alga and the fungus live in a close relationship together. They are both benefitted: The alga is protected and supported by the fungus, and the fungus gets its nutrients through the alga’s photosynthesis.

Mycorrhiza is another example of a symbiotic relationship (specifically, commensalism) between two species: a plant and a fungus. The fungus attaches itself to the roots of a plant and the two live in a close symbiotic relationship. They are both benefited: the fungus receives nutrients from the roots, and the plant receives minerals from the fungus.

I hope I helped! 🙂

Here is a rather exhaustive list: http://en.wikipedia.org/wiki/List_of_symbiotic_relationships