Eight million, seven hundred and four thousand eukaryote species share this planet, give or take 1.3 million. Eukaryotes have cells with nuclei and other membrane bound structures, which means bacteria and other simple organisms were excluded from the count.
But it looks like a lot of species neglected to fill out their census cards. Eighty-six percent of all land-dwelling species and 91 percent in the water have yet to be discovered and cataloged by science, according to an estimate published in PLoS Biology by the Census of Marine Life scientists.
To complete their count of life on Earth, the scientists didn't go from door to door, or crevice to cave as the case may be. They used a statistical technique to extrapolate from patterns in branches of the taxonomic classification system started 253 years ago by Carl Linnaeus.
There are 1.2 million species officially registered in the Catalogue of Life and the World Register of Marine Species. The researchers discovered numerical relationships between the higher levels of taxonomic division, like order and phylum, and the number of species. Using these patterns they were able to make a more realistic estimate of species numbers that previous guesses, which ranged from 3 to 100 million.
"We discovered that, using numbers from the higher taxonomic groups, we can predict the number of species,” said Sina Adl, one of the co-authors of the study. “The approach accurately predicted the number of species in several well-studied groups such as mammals, fishes and birds, providing confidence in the method."
Census Results for the Five Kingdoms of Eukaryotes (approximate)
- ANIMALS - 7.77 million species (of which 953,434 have been described and cataloged)
- PLANTS - 298,000 species (of which 215,644 have been described and cataloged)
- FUNGI - 611,000 species (of which 43,271 have been described and cataloged)
- PROTOZOA - 36,400 species (single-cell organisms with animal-like behavior, such as movement, of which 8,118 have been described and cataloged)
- CHROMISTS - 27,500 species (including, brown algae, diatoms, water molds, of which 13,033 have been described and cataloged)
Many of the researchers involved in the census look forward to the discovery of the millions of species yet to be described, but they fear that many species may disappear before they are even discovered.
"We have only begun to uncover the tremendous variety of life around us," says co-author Alastair Simpson. "The richest environments for prospecting new species are thought to be coral reefs, seafloor mud and moist tropical soils. But smaller life forms are not well known anywhere. Some unknown species are living in our own backyards -- literally."
"The question of how many species exist has intrigued scientists for centuries and the answer, coupled with research by others into species' distribution and abundance, is particularly important now because a host of human activities and influences are accelerating the rate of extinctions,” said lead author Camilo Mora of University of Hawaii and Dalhousie University in Halifax, Canada.
“Many species may vanish before we even know of their existence, of their unique niche and function in ecosystems, and of their potential contribution to improved human well-being,” said Mora.
"Awaiting our discovery are a half million fungi and moulds whose relatives gave humanity bread and cheese," says Jesse Ausubel, Vice-President of the Alfred P. Sloan Foundation and co-founder of the Census of Marine Life.
Another author, Boris Worm, noted that the International Union for the Conservation of Nature has assessed only 59,508 species, of which 19,625 are classified as threatened. That means less than 1% of life on Earth is being watched for threats of extinction.
Read more at Discovery News
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