An endangered species is a group of organisms that are at risk of becoming extinct. 40% of all organisms are considered to be endangered. Many countries have created preserves where endangered animals live, and many have also created laws to protect them. However, only a few groups make it to the endangered species list and receive legal protection.
World Conservation Union categories of endangered species include:
Extinct: the last remaining member of the species has died, or is presumed to have died. Examples: Passenger Pigeon, Thylacine (Tasmanian Tiger), Dodo (Bird)
Extinct in the wild: animals in captivity survive, but there is no free-living, natural population. Examples: Alagoas Currassow (pheasant-like bird)
Critically endangered: faces an extremely high risk of extinction in the immediate future. Examples: Javan Rhino, Arakan Forest Turtle, Ivory-billed Woodpecker
Endangered: faces a very high risk of extinction in the near future. Examples: African Wild Dog, Cheetah, Blue Whale, Snow Leopard
Vulnerable: faces a high risk of extinction. Examples: Lion, Wolverine, Gaur (large, dark-coated ox)
Least Concern: no immediate threat. Examples: Nootka Cypress (tree), Brown Rat