Normal extinction rate of various species as a result of changes in local environmental conditions.

Purpose is to protect and recover imperiled species and the ecosystems upon which they depend. It is administered by the U.S. Fish and Wildlife Service and the Commerce Department’s National Marine Fisheries Service (NMFS). 1973.

Breakup of a habitat into smaller pieces, usually as a result of human activities.

Species that migrate into an ecosystem or are deliberately or accidentally introduced into an ecosystem by humans and whose presence crowds out populations of native species, cause human health problems, and lead to economic losses.

Wild species that is still abundant in its natural range but it is likely to become endangered because of a decline in numbers.

Increase in concentration of DDT, PCBs, and other slowly degradable, fat-soluble chemicals in organisms at successively higher trophic levels of a food chain or web.

Act to prevent or reduce harm when preliminary evidence indicates acting is needed, even if some of the cause and effect relationships have not been fully established scientifically.

Complete disappearance of a species from the Earth. It happens when a species cannot adapt and successfully reproduce under new environmental conditions or when a species evolves into one or more new species.

International agreement between governments whose aim is to ensure that international trade in specimens of wild animals and plants does not threaten their survival. 1975.