Biodiversity is a hallmark of life. Biologists have so far identified and named about 1.8 million species. This enormous diversity of life includes approximately 5,200 known species of prokaryotes, 100,000 fungi, 290,000 plants, 52,000 vertebrates, and 1,000,000 insects. Researchers identify thousands of additional species each year. Estimates of the total species count range from about 10 million to over 200 million. Whatever the actual number, the vast variety of life make biology's scope very wide.