A plume of steam billows from the coal-fired Merrimack Station in Bow, N.H. in January 2015. Jim Cole/AP hide caption

itoggle caption Jim Cole/AP

A Maasai boy and his dog, near the skeleton of an elephant killed by poachers outside of Arusha, Tanzania, in 2013. Jason Straziuso/AP hide caption

itoggle caption Jason Straziuso/AP

This clay facial reconstruction of Kennewick Man, who died about 8,500 years ago in what's now southeast Washington, was based on forensic scientists' study of the morphological features of his skull. Brittney Tatchell/Smithsonian Institution hide caption

itoggle caption Brittney Tatchell/Smithsonian Institution

Chris Tremblay, a member of the Passive Acoustics group at NOAA's Northeast Fisheries Science Center, deploys an underwater recording device along the Eastern Seaboard to listen for the mating sounds of Atlantic cod. Courtesy of Chris Tremblay hide caption

itoggle caption Courtesy of Chris Tremblay

Plankton collected in the Pacific Ocean with a 0.1mm mesh net. Seen here is a mix of multicellular organisms — small zooplanktonic animals, larvae and single protists (diatoms, dinoflagellates, radiolarians) — the nearly invisible universe at the bottom of the marine food chain. Christian Sardet/CNRS/Tara Expeditions hide caption

itoggle caption Christian Sardet/CNRS/Tara Expeditions

A 2008 view of the leading edge of the Larsen B ice shelf, extending into the northwest part of the Weddell Sea. Huge, floating ice shelves that line the Antarctic coast help hold back sheets of ice that cover land. Mariano Caravaca /Reuters/Landov hide caption

itoggle caption Mariano Caravaca /Reuters/Landov

Staghorn coral planted by scientists in the Florida Keys. Researchers hope to give the same sort of boost to the world's shrinking population of pillar coral, now that they can raise the creatures in a laboratory. Joe Berg/Way Down Video/Mote hide caption

itoggle caption Joe Berg/Way Down Video/Mote

Reconstruction of the giant filter feeder, scooping up a plankton cloud. Aegirocassis benmoulae was one of the biggest arthropods that ever lived. Family members include today's insects, spiders and lobsters. Marianne Collins/ArtofFact hide caption

itoggle caption Marianne Collins/ArtofFact

With the help of researcher Sabudo Boraru (right), anthropologist Chris Campisano, of Arizona State University, takes samples from the fossil-filled Ledi-Geraru project area in Ethiopia. The jawbone was found nearby. Courtesy of J Ramón Arrowsmith hide caption

itoggle caption Courtesy of J Ramón Arrowsmith

Fernandina's Flicker (Colaptes fernandinae), a woodpecker found only in Cuba. Pete Oxford/Minden Pictures/Corbis hide caption

itoggle caption Pete Oxford/Minden Pictures/Corbis

Crew members pull an oyster dredge in Tangier Sound of the Chesapeake Bay near Deal Island, Md., in 2013. A study found that the Chesapeake Bay shellfishery is a "hot zone" for ocean acidification. Patrick Semansky/AP hide caption

itoggle caption Patrick Semansky/AP