Estimated total number of species of organisms

Range 3e6-5e6 Species
Organism Biosphere
Reference May RM. How Many Species Are There on Earth? Science. 1988 Sep 16 241(4872):1441-1449PubMed ID17790039
Method The total number of species actually named and recorded is around 1.5 million, and two-thirds of these are found in temperate regions. Most of these are insects. But most insects that have actually been named and taxonomically classified are from temperate zones. Thus, if the ratio of numbers of tropical to temperate species is the same for insects as for mammals and birds, we may expect there to be something like two yet-unnamed species of tropical insects for every one named temperate species. Hence the overall crude estimate of a total of roughly three times the number currently classified, or around 3 million to 5 million.
Comments This estimate is open to several questions. For one thing, the total includes relatively few species of bacterial, protozoan, and helminth parasites, largely because such parasites are usually studied in connection with economically important animal hosts. But it could be that essentially every animal species is host to at least one specialized such parasitic species (47), which would immediately double the estimated total. For another thing, the Acarina (mites), both tropical and temperate, are even less well studied than tropical insects it was largely tropical insects that carried the estimate from the known 1.5 million to 3 million to 5 million, and mites could carry it significantly higher. See Wartt et al. 2010 PMID 20847295: "There are estimated to be 48–58,000 vertebrate species and about two million invertebrates". For 10^7 different species of organisms on Earth see Encyclopedia of Molecular Cell Biology and Molecular Medicine, Werner Arber, Genetic Variation and Molecular Darwinism p.21 right column 3rd paragraph
Entered by Uri M
ID 103931