Nature is home to many animals and plants. But very few things are exact 1 . For example, the Siberian Husky and the Toy Poodle are 2 dogs. But they are so 3 each other that they are in different species. So far, humans have found 1.5 million species. 4 , UN scientists think that there are about 13 million species on the Earth. Many 5 unknown species are probably in rainforests or deep in the sea.