Biologists have identified approximately 1.4 million named species, with estimates suggesting the total number of species could range from 2 million to as high as 100 million. The United Nations Environment Programme estimates around 1.75 million species, while other studies cite figures of 1.5 million and 1.7 million. A significant challenge in determining the total number of species is the lack of comprehensive information, particularly regarding bacteria, with estimates indicating that 99% remain unidentified. The discussion highlights the variability in species estimates and the ongoing debate within the scientific community.