Some ranchers argue that they can raise organic beef using methods that many experts say are friendlier to the environment -- and healthier for beef eaters.

First recognized in the 1980s, mad cow disease -- or bovine spongiform encephalopathy (BSE) -- causes the brains of cattle to waste and become spongy and pockmarked.

The world's nearly 300 turtle species have a remarkable range of behaviors, from wood turtles that stomp the ground to attract worms, to sea turtles that travel thousands of miles to lay eggs.