Natural Selection - The process by which certain heritable traits that contribute to the survival and reproductive success of an organism become more widespread within a population over successive generations.⏎
Reservoir - An organism in which a parasite that is pathogenic for some other organism lives and reproduces without harming its host.⏎
Organism - A living being that can reproduce, grow, react to external stimuli, and maintain its internal equilibrium.⏎
Protozoa - A taxonomic group of single-celled microorganisms that live in almost every kind of habitat and include some pathogenic parasites of humans and other animals.⏎