Parasites
Parasites are those living organisms, either plant or animal, which live in, on, or with some other living organism, known as the host, from which they obtain their food, shelter and other advantages. They are of two classes—ectoparasites and endoparasites—and may be either plant or animal organisms. An ectoparasite is one that lives upon the outside of another living organism known as the host. The endoparasite is one that lives within the body of the host.