Louis E. Pratt, master ivory cutter for Pratt, Read & Co., shows off eight ivory tusks, April 1, 1955. Courtesy of Deep River Historical Society hide caption

itoggle caption Courtesy of Deep River Historical Society

A bed of eel grass (Zostera marina) flutters in the current along the California coast. David Wrobel/Visuals Unlimite/Corbis hide caption

itoggle caption David Wrobel/Visuals Unlimite/Corbis

Our popular image of Homo erectus as the proto-guy who whose human-like traits all emerged at once needs overhauling, some anthropologists say. Sylvain Entressangle/Science Source hide caption

itoggle caption Sylvain Entressangle/Science Source

Being a bit coldblooded has its charms, scientists say. A mammal the size of a T. rex, for example, would have to eat constantly to feed its supercharged metabolism — and would probably starve. Publiphoto/Science Source hide caption

itoggle caption Publiphoto/Science Source

Clint Muhlfeld, an aquatic ecologist with the USGS, holds a native Westslope cutthroat trout in Glacier National Park. Noah Clayton/USGS hide caption

itoggle caption Noah Clayton/USGS

Kalron and his team have set up video cameras that transmit real-time images of the bai via satellite. Courtesy of Maisha Consulting hide caption

itoggle caption Courtesy of Maisha Consulting

A female forest elephant charges, in Dzanga-Sangha Special Reserve in the Central African Republic. Michael K. Nichols/National Geographic/Getty Images hide caption

itoggle caption Michael K. Nichols/National Geographic/Getty Images

Pat Leiggi (right) of the Museum of the Rockies prepares to move a leg bone of the T. rex at the Smithsonian's Natural History Museum in Washington, D.C., on Tuesday. Maggie Starbard/NPR hide caption

itoggle caption Maggie Starbard/NPR

Magellanic penguins strut their stuff on the rocky shoreline of Argentina's Punta Tombo, home to the largest colony of the birds in the world. Craig Lovell/Corbis hide caption

itoggle caption Craig Lovell/Corbis