Concept  of  Biodiversity
Levels  of  Biodiversity
Studying  Biodiversity
Threats  to  Biodiversity
Resources

 

   


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.

  • Which of theabove taxa has the most number of species?

  • Why are do some taxa contain many more species than others do?
       
   

Described and Estimated Species

This 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] ?

  • less than half a million described species ;
  • 1.5 - 2 million described species ;
  • 5 - 10 million described species ;
  • around 20 million described species ;
  • 30 million or more described species ?
  • What figure do you think scientists place on the total estimated number of species on Earth?
       
   

The proportion of described species on the Earth

  • What proportion of the estimated 13.6 million species has actually been described?

  • Where might the "missing" section of biodiversity be found?
       
   


Speciation and Extinction

  • Are global biodiversity levels constant?

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 lost?

  • Are speciation and extinction rates constant over long time scales?