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Credit: Donald Danforth plant science center in St. Louis; Don Hamerman; Courtesy of Zhonghua Zhang of the Chinese Academy of Agricultural Sciences in Beijing

Centromeres (pink dots) sit at chromosome centers (human shown). The centromere on horse chromosome 11 evolved relatively recently.
Credit: Institute for Genome Sciences and Policy/Duke Univ.

View larger version | Greenhouse gas emissions for developed nations shrunk overall by about 4 percent from 1990 to 2007, though much of the loss came through economic changes and not targeted action. Emissions below do not include those from deforestation.
Credit: UN FCCC

Scientists and policy makers will meet in Copenhagen this month to take steps toward an international agreement on curbing climate change.
Credit: Randall Fung/Corbis

In a new study of visual abilities, researchers asked volunteers to identify the biggest orange circle. Here, each orange circle on the right is 2 percent larger than the one on the left. Misleading images usually fooled adults but not children, while helpful images greatly aided adults but not kids.
Credit: M. Doherty

The pepper mild mottle virus attacks pepper plants (above, infected plant) is widespread in human waste, suggesting it could be a good way to track human-polluted waters.
Credit: Pamela Roberts/University of Florida

This week's word search.
Credit: J. Raloff

Bars indicate the net change in seagrass-dominated area by decade at sites that grew (green) and the net change at sites that shrank (red). Numerals indicate the number of sites in each category. Some sites (not shown) neither gained nor lost much during a decade.
Credit: Adapted from Waycott et al./PNAS 2009

In Bangladesh, bamboo shields keep delicious palm sap from being tainted by fruit bats that can spread the rare but lethal Nipah virus.
Credit: M. Salah Uddin Khan

No one has run 100 meters faster than sprinter Usain Bolt, pictured on the track in Berlin in August 2009. But even he has not yet reached the predicted maximum velocity for the human body.
Credit: Hannibal/EPA/Corbis

Peter Weyand has studied whether sprinter Oscar Pistorius' artificial limbs confer a biomechanical advantage.
Credit: Rice University

Dark patches in the water indicate seagrasses thriving around Garden Key, home to the brick ruins of 19th century Fort Jefferson, in the Dry Tortugas.
Credit: Michael O'Leary/US Imaging Inc

Plucked near the Tortugas Ecological Reserve, this wisp of the seagrass Halophila decipiens comes from a vast meadow that grows each year from seed in spring and hurriedly blooms, producing a crop of seed before dying off as light dims in the ocean depths each autumn.
Credit: S. Milius

Seagrass meadows provide food and shelter for myriad residents including the bay scallop, the charismatic West Indian manatee, the seahorse and the green turtle.
Credit: Clockwise from top left:Kimberly Petersen Manzo, www.seagrassli.org; Robert Stewart/Animals Animals; Chris Pickerell, www.seagrassli.org; Rich Carey/Istockphoto

Seagrasses, such as the Zostera shown at top, can grow in dense clumps. The close-up image at bottom left shows two tiny female flowers opening, with a male flower releasing white pollen in between the other two. At bottom right, filaments of pollen in Zostera marina float around fine metal forceps.
Credit: Top photo: Chris Pickerell, www.seagrassli.org; Bottom photos: J. Ackerman