Exoskeleton - An external skeleton that protects and supports an organism, in contrast to an internal endoskeleton.⏎
Contagion - A general term for any disease-causing infectious agent spread by direct or indirect contact.⏎
Encephalitis - Inflammation of the brain, often caused by a virus.⏎
Evolution - The change in heritable traits in a population of organisms over successive generations.⏎
Egg Cell - The female gamete, or sex cell, which carries the hereditary material of the female parent and unites with the male sperm cell during sexual reproduction.⏎