Estimates of the total number of species range from 7 to 100 million, with a probably good estimate being around 13 to 15 million species. Up to this day, only about 1.75 million living species have been identified and described scientifically. Many new species continue to be discovered each year, most of them invertebrates. During the nineties, the number of newly described species averaged 13.000 per year.

The table below shows approximate numbers of species in major groups (UNEP, Global Biodiversity Assessment, 1995):

Group	No. of described species	Estimated total no. of species
Viruses	4,000	400,000
Bacteria	4,000	1,000,000
Fungi	72,000	1,500,000
Protozoa	40,000	200,000
Algae	40,000	400,000
Plants	270,000	320,000Â
Nematodes	25,000	400,000
Crustaceans	40,000	150,000
Arachnids	75,000	750,000
Insects	950,000	8,000,000
Mollusks	70,000	200,000
Vertebrates	45,000	50,000
Others	115,000	250,000
Totals	1,750,000	13,620,000

The figures of the table were compiled more than 10 years ago already. If we consider the 1995 data, together with a rate of new species description of 13,000 species, we can estimate that there are now about 2.1 million of described species.