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Erwin's Calculations[Hammond 1992] and [Hawksworth & Kalin-Arroyo 1995] have listed the number of species that have been formally described for major taxa, and also the numbers estimated to occur.
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Described and Estimated SpeciesThis figure, from [Hawksworth & Kalin-Arroyo 1995] , shows the number of species that have been formally described, and the number that are estimated to occur, for major taxa How many species have been formally identified and described, according to [Hawksworth & Kalin-Arroyo 1995] ?
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The proportion of described species on the Earth
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Speciation and Extinction
Speciation gives rise to new species. Extinction removes some of these species. These are both dynamic processes and their overall balance will effect levels of global biodiversity, as measured by species numbers. Extinction is a natural
process, so why should there be such concern over the current rates
at which species are being threatened with extinction or
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