Tai Shan on his first birthday. The panda was conceived in 2005 through artificial insemination in a procedure performed by National Zoo scientists and veterinarians.
Ann Batdorf/Smithsonian Institution via AP
An artist's rendition of two Sinosauropteryx dinosaurs, showing their short, bristle-like feathers along the midline of the head, neck, back and around the tail, forming irregular stripes.
Chuang Zhao and Lida Xing
The ring-tailed lemur is one of many pint-sized creatures on the island of Madagascar. Scientists have long noted that despite the great diversity of fauna on the island, there are few large beasts, like the lions and elephants found on mainland Africa.
Researchers dyed sperm from each deer mouse a different color; in this case, red represents one male and green another. The sperm joined together with their own kind, as seen here, allowing them to swim faster than those that did not cluster together.
Sudan, one of four endangered northern white rhinoceroses shipped to Kenya from a zoo in the Czech Republic, explores his new pen at the Ol Pejeta reserve near the town of Nanyuki in central Kenya.
Tony Karumba/AFP/Getty Images