Male and female tungara frogs. Among these frogs, the guy with the best call usually wins the gal — except when you throw a third-choice loser into the mix. Alexander T. Baugh/Encyclopedia of Life hide caption

itoggle caption Alexander T. Baugh/Encyclopedia of Life

Margaret Sanger appears before a Senate committee for federal birth-control legislation in Washington, D.C., on March 1, 1934, arguing that federal courts be given the right to discuss contraceptive methods with their patients. Anonymous/AP hide caption

itoggle caption Anonymous/AP

President George W. Bush (center) surveys the devastation in New Orleans with (from left to right) Vice Adm. Thad Allen, Louisiana Gov. Kathleen Blanco, Mayor Ray Nagin and Lt. Gen. Russel Honore on Sept. 12, 2005, two weeks after Hurricane Katrina slammed into the Gulf Coast. Jim Watson/AFP/Getty Images hide caption

itoggle caption Jim Watson/AFP/Getty Images

All the talk about immigration in the U.S. presidential campaign has renewed focus on the linguistic question of how to refer to people from Latin America. Here, the flags of Latin American and Caribbean states fly at a regional summit in San Jose, Costa Rica, in January. Arnoldo Robert/LatinContent/Getty Images hide caption

itoggle caption Arnoldo Robert/LatinContent/Getty Images