Biodiversity for development CD-Rom

The term ‘biodiversity’ – short for ‘biological diversity’ – refers to the totality and variety of life on earth.

Biodiversity exists at three levels: ecosystems, species, and genes.

An ecosystem is an array of living organisms and the physical and chemical environment with which they interact. There are many types of ecosystems, ranging from the very large (forests, oceans, etc.) to the relatively small (a single pond can comprise an ecosystem by itself). The functioning of a given ecosystem is driven by its constituent organisms and is best understood as a cyclical flow of energy and materials. Depending on its characteristics (area, latitude, diversity of terrain, etc.) an ecosystem may contain many millions of different species or merely a handful.

The species is the yardstick by which the variety of life has traditionally been measured. To date, roughly 1.7 million species of plants, animals and microorganisms have been discovered and formally described. This roster of known species represents only a fraction of the total number. The gaps in our knowledge are easily seen. For example, the catalogue of named species is artificially ‘biased’ towards terrestrial organisms: only around 275,000 marine species have been identified, compared with some 1.5 million terrestrial species. In reality, coral reef ecosystems alone are probably home to at least 1 million species, and as many as 10 million more may lurk in the deep ocean basins (only one-tenth of which have been systematically mapped). It is reasonably certain, then, that the greater part of species diversity remains to be discovered. Estimates of the true number of species on earth range from as ‘few’ as 5 million to as many as 100 million.


Around 1.7 million species have been formally described

This spectacular variety of life is the result of billions of years of evolution: the cumulative, non-random selection of random genetic mutations. At the genetic level, biodiversity can be seen within as well as between species – in the differences between populations and even individuals of the same species. The almost limitless variability of genes is thus the fundamental basis of biodiversity.



Online resources:

Global biodiversity information facility

Species 2000
A multi-year programme with the aim to enumerate all known species of plants, animals, fungi and microbes on earth in order to provide a baseline dataset for studies of global biodiversity

All Species Foundation
A non-profit organization dedicated to the complete inventory of all species of life on Earth within the next 25 years

WWF Global 200 Ecoregions