Nearly all living organisms are exploited by some sort of parasite. But what are parasites? How many different types are there? 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, how they live, their biogeography, evolution, the influence they exert on their hosts' populations, their immunological, pathological, and biochemical implications. - Publisher.