Reservoir - An organism in which a parasite that is pathogenic for some other organism lives and reproduces without harming its host.⏎
Plasmid - A ring of DNA usually found in bacteria that is separate from and can replicate independently from DNA in a chromosome and can provide bacteria with some advantages, such as antibiotic resistance.⏎
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. ⏎
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.⏎