Almost all living organisms are exploited by parasites of one type or another. But what are parasites? How many different types are there? And what exactly is parasitism? In this undergraduate textbook parasitism is described as an ecological relationship. Ecology implies the study of the interaction between organisms and their environments and the fact that parasites' hosts are alive makes this concept even more exciting, combining traditionally disparate disciplines such as immunology and physiology with ecology and epidemiology! All the major groups of animal parasites are described, who they are and how they live. Also examined are their biogeography, evolution, and the way they influence the populations of their hosts and the immunological, pathological and biochemical implications of parasites. Written in an accessible style, the subject matter is brought to life with numerous illustrations and textboxes containing anecdotal, interesting and supplementary material. Essential for all undergraduate students studying parasitology, Parasitism: The Ecology and Diversity of Animal Parasites will also be useful reading for graduates and researchers in zoology and ecology.