One example of parasitism is when a tick draws blood from a deer to survive. Parasitism represents a relationship between two species in which one of the animals (or plants) obtains a benefit at the expense of another.
Some species involved in parasitism, or parasites, can be classified as ectoparasites. These are parasites that live on the surface of a host, like a tick on a deer. Other parasites are called endoparasites. These are parasites that inhabit space within the body of its host, and some of these parasites inhabit individual cells with a host's body. An example of an endoparasite is a heartworm.