Aspects of evolutionary parasitology.

Parasitic animals make up one fifth to one fourth of all known animal species. There are many correct definitions of the parasitism, but the determinations as a qualitatively specific form of existence of organisms are logically well-grounded only within the concepts of symbiosis. The parasitism opposes with the predatoriness which cannot be ascribed to symbiotic types of vital activity. The problems of the population and niche are discussed in the present paper. An analysis is given of the parasitological niche the parameters of which coincide with the phenomena characteristic for the specificity. A somewhat changed definition of parasitism is proposed. The applicability of some biological concepts (theory of r and K selection, theory of granular environment) to parasitic organisms is considered.