An endangered species is a population of an organism which is at risk of becoming extinct because it's either few in numbers, or threatened by changing environmental or predation parameters. An endangered species is usually a taxonomic species, but may be another evolutionary significant unit. The World Conservation Union (IUCN) has calculated the percentage of endangered species as 40 percent of all organisms based on the sample of species that have been evaluated through 2006. (Note: the IUCN… (More on Endangered)