Exoskeleton - An external skeleton that protects and supports an organism, in contrast to an internal endoskeleton.⏎
Disease - Any abnormal condition that affects all or part of an organism, resulting in symptoms such as pain or loss of function.⏎
Gene - The physical and functional unit of heredity made up of DNA. Every individual has two copies of each gene, one inherited from the mother and the other from the father.⏎
Fertilized Egg - Sometimes referred to as a zygote, this is the resulting initial cell formed when a sperm cell unites with an egg cell.⏎
Contagion - A general term for any disease-causing infectious agent spread by direct or indirect contact.⏎