Three of Becca Francis' horses contracted EHV-1 at a horse event in Utah; one had to be euthanized. Kirk Siegler/KUNC hide caption

itoggle caption Kirk Siegler/KUNC

CT scans of fossil Hadrocodium skulls allowed scientists to reconstruct its brain. The olfactory bulbs, located at the front of the brain, grew steadily larger as millions of years passed. Matt Colbert/University of Texas at Austin hide caption

itoggle caption Matt Colbert/University of Texas at Austin

"Can something be called chicken or pork if it was born in a flask and produced in a vat?" asks Michael Spector. "Questions like that have rarely been asked and have never been answered." iStockphoto.com hide caption

itoggle caption iStockphoto.com

Several Asian clams are seen in this 1994 photo, after they were taken from San Francisco Bay. The Asian clam is one of hundreds of aquatic alien species that thrive in the Bay Area. Andrew N. Cohen/San Francisco Estuary Institute via AP hide caption

itoggle caption Andrew N. Cohen/San Francisco Estuary Institute via AP

Intern Lynn Brown feeds a robin at the Alabama Wildlife Center south of Birmingham. Andrew Yeager/NPR hide caption

itoggle caption Andrew Yeager/NPR