Megalodon was the largest shark and one of the largest fish on record. It went extinct about 2.6 million years ago.
Mustang horses roam freely across the western United States and are a symbol of pioneering spirit, but they aren't quite wild.
The ears are complex systems that not only provide the ability to hear, but also make it possible to maintain balance.
The term transgender describes people whose gender identity differs from the sex to which they were assigned at birth.
Most sexually active men and women will contract HPV at some point in their lives. So, yes, you should probably get the vaccine.
Throughout history, lions have been celebrated for their strength and beauty, and are the inspiration for many myths and stories worldwide.
Tigers are the biggest cats in the world, but their populations are struggling. With only 3,200 left in the wild, there are now more living in captivity than in the wild.
Penicillin is was once hailed as a "miracle drug." However, some bacteria have become resistant to penicillin, making those infections difficult or even impossible to treat.
Mumps is an unpleasant and highly contagious disease, but a simple two-dose vaccine is 88% effective against the infection.
With their big ears and long noses, the elephant is one of the most recognizable animals in the world.
Giant pandas, known for their distinctive markings and playful personalities, are considered China's national treasure.
Sloths spend most of their time sleeping and eating in the tropical rainforests of South and Central America.
Hippos are giant creatures that spend most of their lives in the water, but they don't actually swim. They can still kill you, though.
The small intestine is about as big around as a middle finger, but it is about 22 feet (6.7 meters) long.
Pink eye, or conjunctivitis, develops when the blood vessels in the eyeball get inflamed by a virus, bacteria, foreign object or allergic reaction.
Pigs are mammals with stocky bodies, flat snouts, small eyes and large ears. They are highly intelligent, social animals, and are found all over the world.
The flu (short for influenza) is a respiratory virus that affects the throat, nose, bronchi and, sometimes, the lungs.