How many species of animals are there?
Scientists have described about 1.5 to 2 million animal species, but estimates suggest there may be around 7 to 8 million in total, most of them insects and other invertebrates not yet discovered.
A widely cited 2011 study estimated that Earth has about 8.7 million species of eukaryotes, organisms with complex cells, including about 7.8 million animals. Most have never been named by scientists. Each year, researchers describe around 15,000 to 20,000 new species, mostly insects.
Insects are by far the most diverse group, with about one million described species, including roughly 400,000 beetles. Vertebrates, animals with backbones, make up only a small fraction: about 6,500 mammals, around 11,000 birds, about 12,000 reptiles, around 8,000 amphibians and more than 35,000 fish.
Why counts are uncertain
Many species live in hard-to-reach places such as deep oceans, rainforest canopies and soil. Others are tiny or look almost identical to known species. Some scientists think the true number of species, including bacteria, could be far higher.
Did You Know?
Many species are going extinct before they are even discovered, mainly because of habitat loss.