Doctors at a hospital in Aleppo, Syria, treat a boy injured in what the government said was a chemical weapons attack on March 19. Syria's government and rebels accused each other of firing a rocket loaded with chemical agents outside of Aleppo. George Ourfalian/Reuters/Landov hide caption

itoggle caption George Ourfalian/Reuters/Landov

The research of British naturalist Alfred Russel Wallace (1823-1913) played a pivotal role in developing the theory of natural selection. But over time, Charles Darwin became almost universally thought of as the father of evolution. Hulton-Deutsch Collection/Corbis hide caption

itoggle caption Hulton-Deutsch Collection/Corbis

Beekeepers demonstrate at the EU headquarters in Brussels Monday, as lawmakers vote on whether to ban pesticides blamed for killing bees. Georges Gobet/AFP/Getty Images hide caption

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Eduardo Somarriba is a researcher at the Center for Tropical Agricultural Research and Education in Turrialba, Costa Rica. Dan Charles/NPR hide caption

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Researchers are using small remote-controlled planes to survey the populations of the greater sage grouse. Stephen J. Krasemann/Science Source hide caption

itoggle caption Stephen J. Krasemann/Science Source

An oil sheen appears along the shore of the Kalamazoo River in August 2012. In July 2010, more than 800,000 gallons of tar sands oil entered Talmadge Creek and flowed into the Kalamazoo River, a Lake Michigan tributary. Heavy rains caused the river to overtop existing dams and carried oil 30 miles downstream. John W. Poole/NPR hide caption

itoggle caption John W. Poole/NPR

By this time last year, 26 percent of the country's corn crop was already planted. A wet, cold spring means that only 4 percent is in the ground right now. Seth Perlman/AP hide caption

itoggle caption Seth Perlman/AP

Luis Fernando Vasquez has been a coffee farmer in the central valley of Costa Rica his entire life. Dan Charles/NPR hide caption

itoggle caption Dan Charles/NPR