Prion - A causative agent of infectious disease that is composed primarily of protein.⏎
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.⏎
Parasitism - A close relationship between two organisms in which one organism, the parasite, benefits at the expense of the host organism.⏎
Pandemic - An increase in the occurrence of a particular disease over a very large region, such as a continent or the entire globe, that is greater than what is expected over a given period of time.⏎
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.⏎