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'''''Biodiversity''''' | '''''Biodiversity''''' | ||
'''''Species''''' | '''''All Species Day''''' | ||
Definition: A species is a group of organisms capable of interbreeding and producing fertile offspring of both genders, and separated from other such groups with which interbreeding does not characteristically occur: however, for asexual organisms, a distinct species may be considered a collection of organisms which have very similar DNA or physical characteristics. Certain species are further subdivided into subspecies. | Definition: A species is a group of organisms capable of interbreeding and producing fertile offspring of both genders, and separated from other such groups with which interbreeding does not characteristically occur: however, for asexual organisms, a distinct species may be considered a collection of organisms which have very similar DNA or physical characteristics. Certain species are further subdivided into subspecies. |
Revision as of 15:26, 9 April 2015
- Encyclopedia of Earth
http://www.eoearth.org/view/article/156210/
Biodiversity
All Species Day
Definition: A species is a group of organisms capable of interbreeding and producing fertile offspring of both genders, and separated from other such groups with which interbreeding does not characteristically occur: however, for asexual organisms, a distinct species may be considered a collection of organisms which have very similar DNA or physical characteristics. Certain species are further subdivided into subspecies.
History of the concept
The early Greeks and Romans had a well established set of taxonomic names for species of animals and plants, based upon the macroscopically observable characteristics of organisms, with Aristotle being the chief architect of this codification; even earlier, the Egyptians and Cretans developed basic symbols and names for species important in farming and culture. It was not until the year 1686 when English naturalist John Ray introduced the concept that species were distinguished by inevitably producing the same species, though considerable morphological variation was observed within a species.[1] Carl Linnaeus (1707–1778) formalized the taxonomic rank of species, and developed the two part naming system of binomial nomenclature that survives to current times, with genus and species names in Latin form.
Estimation of species numbers
Since most of the planet's species are deemed to be undiscovered, it is exceedingly difficult even to estimate the total number of species on Earth. An 2011 innovative study estimated the total number of species to be about 8.7 million, with around 86 percent of which are presently undiscovered.[2] The following represents a rough approximation of the number of species by taxonomic group, with ranges given for varying estimates of the species total numbers:
Total species: 7,000,000 to 100,000,000 (the lower number reflecting described species and the higher based upon estimates of Earth's species):
Bacteria: 5,000,000 to 10,000,000[3]
Archaea: 20,000 (based upon only marine species) [4]
Eukarya: 1,660,000
Of the described eukarya species 1,600,000 based on described species, including:
297,326 plants, including:
15,000 mosses
12,000 ferns
1,025 fern allies
980 gymnosperms
258,650 angiosperms
199,350 dicotyledons
59,300 monocotyledons
9,671 red and green algae
2,849 brown algae
100,000 fungi (of an estimated total 1,500,000 other non-animals) including:
25,000 lichens,
16,000 mushrooms
30,000 red, brown and blue-green molds
17,000 conidial fungi
1,260,000 animals, including:
1,203,375 invertebrates:
950,000 insects
81,000 mollusks
50,000 crustaceans
2175 corals
130,200 others
59,811 vertebrates:
29,300 fish
6199 amphibians
8240 reptiles
9956 birds
5416 mammals
Endangered species...
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