A species may live in association with another species. Such an arrangement is called symbiosis. Symbiosis in which both species benefit is called mutualism. If the symbiosis is beneficial to one species and neither beneficial nor harmful to the other, it is called commensalism. If one species benefits at the expense of the other, the relationship is called parasitism. A tick that attaches to the skin of a human or animal and feeds on its blood is an example of