Numbers of Species
![Biodiversity_Numbers of Species](https://www.drze.de/media/bp/module/globalnumbersofspecies.gif/@@images/image/preview)
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Fig. 2: Global numbers of species in different groups of organisms – comparison between known species and species probably existing on Earth (based on the Millennium Ecosystem Assessment).
Millennium Ecosystem Assessment (2005): Ecosystems and Human Well-Being: Synthesis Report. Washington DC: Island Press. Online Version (Englisch)