No one knows exactly how many species live on earth.

Some species can live a few hours out of water.

More than 400 species live here so you won't want for action.

One is so very old that only a few species still live on earth.

This species may live to be about 11 years old.

But scientists have no idea how many species really live on earth.

These four species looked similar, but lived in different parts of the world.

Until that time, no one was sure if the species still lived.

The other four species can live on the sea ice.

More than 236 species of birds live in the park.