Species such as the dusky seaside sparrow, the passenger pigeon, and the woolly mammoth are extinct. Populations of other species have declined to the point where they are designated as threatened or endangered. Identify one threatened or endangered species and explain why its population has declined. Describe three characteristics of organisms that would make them particularly vulnerable to extinction. Present three arguments in favor of the maintenance of biodiversity. Name and describe one United States federal law or one international treaty that is intended to prevent the extinction of species.