Whales are a group of mammals that live in oceans. They include some of the largest animals on Earth. The blue whale is the biggest animal that has ever existed. Whales can be found in every ocean ...

About 250 million years ago, at the end of the Permian period, something killed some 90 percent of the planet's species. Less than 5 percent of the animal ... for the largest of the many mass ...

Earth's largest mass extinction ... them "a better sense of why some animal groups made it through while others perished," ...