Extinction and Endangered Species - What Are Endangered Species?

A species is described as extinct when no living members remain. Scientists know from their study of fossils that dinosaurs, mammoths, saber-toothed cats, and countless other animal and plant species that once lived on Earth no longer exist. These species have "died out," or gone extinct. Once a species is extinct, there is no way to bring it back.

The U.S. Fish and Wildlife Service, an agency of the federal government, defines endangered species as those that are at risk of extinction through all or a significant portion of their natural habitats. Threatened species are defined as those likely to become endangered in the foreseeable future. The Fish and Wildlife Service maintains a list of species that are endangered or threatened in the U.S. and abroad. Both endangered and threatened species are protected by laws aimed to save them from extinction. In many cases, recovery plans for endangered species have also been developed and implemented. These include measures designed to protect endangered and threatened species and to help their populations grow. Nevertheless, scientists estimate that hundreds, or even thousands, of species are lost each year.