<< Chapter < Page | Chapter >> Page > |
It is also useful to define ecosystem diversity , meaning the number of different ecosystems on the planet or in a given geographic area ( [link] ). Whole ecosystems can disappear even if some of the species might survive by adapting to other ecosystems. The loss of an ecosystem means the loss of interactions between species, the loss of unique features of coadaptation, and the loss of biological productivity that an ecosystem is able to create. An example of a largely extinct ecosystem in North America is the prairie ecosystem. Prairies once spanned central North America from the boreal forest in northern Canada down into Mexico. They are now all but gone, replaced by crop fields, pasture lands, and suburban sprawl. Many of the species survive, but the hugely productive ecosystem that was responsible for creating the most productive agricultural soils is now gone. As a consequence, soils are disappearing or must be maintained at greater expense.
Despite considerable effort, knowledge of the species that inhabit the planet is limited. A recent estimate suggests that the eukaryote species for which science has names, about 1.5 million species, account for less than 20 percent of the total number of eukaryote species present on the planet (8.7 million species, by one estimate). Estimates of numbers of prokaryotic species are largely guesses, but biologists agree that science has only begun to catalog their diversity. Even with what is known, there is no central repository of names or samples of the described species; therefore, there is no way to be sure that the 1.5 million descriptions is an accurate number. It is a best guess based on the opinions of experts in different taxonomic groups. Given that Earth is losing species at an accelerating pace, science is very much in the place it was with the Lake Victoria cichlids: knowing little about what is being lost. [link] presents recent estimates of biodiversity in different groups.
Estimates of the Numbers of Described and Predicted Species by Taxonomic Group | ||||||
---|---|---|---|---|---|---|
Mora et al. 2011 Mora Camilo et al., “How Many Species Are There on Earth and in the Ocean?” PLoS Biology (2011), doi:10.1371/journal.pbio.1001127. | Chapman 2009 Arthur D. Chapman, Numbers of Living Species in Australia and the World , 2nd ed. (Canberra, AU: Australian Biological Resources Study, 2009). http://www.environment.gov.au/biodiversity/abrs/publications/other/species-numbers/2009/pubs/nlsaw-2nd-complete.pdf. | Groombridge&Jenkins 2002 Brian Groombridge and Martin D. Jenkins. World Atlas of Biodiversity: Earth’s Living Resources in the 21 st Century . Berkeley: University of California Press, 2002. | ||||
Described | Predicted | Described | Predicted | Described | Predicted | |
Animalia | 1,124,516 | 9,920,000 | 1,424,153 | 6,836,330 | 1,225,500 | 10,820,000 |
Chromista | 17,892 | 34,900 | 25,044 | 200,500 | — | — |
Fungi | 44,368 | 616,320 | 98,998 | 1,500,000 | 72,000 | 1,500,000 |
Plantae | 224,244 | 314,600 | 310,129 | 390,800 | 270,000 | 320,000 |
Protozoa | 16,236 | 72,800 | 28,871 | 1,000,000 | 80,000 | 600,000 |
Prokaryotes | — | — | 10,307 | 1,000,000 | 10,175 | — |
Total | 1,438,769 | 10,960,000 | 1,897,502 | 10,897,630 | 1,657,675 | 13,240,000 |
Notification Switch
Would you like to follow the 'Bi 101 for lbcc ilearn campus' conversation and receive update notifications?