This is a collection of lists of organisms by their population. While most of the numbers are estimates, they have been made by the experts in their fields. Species population is a science falling under the purview of population ecology and biogeography. Individuals are counted by census, as carried out for the piping plover;[3][4] using the transect method, as done for the mountain plover;[5] and beginning in 2012 by satellite, with the emperor penguin being first subject counted in this manner.[6]
More than 99 percent of all species, amounting to over five billion species,[7] that ever lived on Earth are estimated to be extinct.[8][9] Estimates on the number of Earth's current species range from 10 million to 14 million,[10] of which about 1.2 million have been documented and over 86 percent have not yet been described.[11] According to another study, the number of described species has been estimated at 1,899,587.[12] 2000–2009 saw approximately 17,000 species described per year.[12] The total number of undescribed organisms is unknown, but marine microbial species alone could number 20,000,000.[12] For this reason, the number of quantified species will always lag behind the number of described species, and species contained in these lists tend to be on the K side of the r/K selection continuum. More recently, in May 2016, scientists reported that 1 trillion species are estimated to be on Earth currently with only one-thousandth of one percent described.[13] The total number of related DNA base pairs on Earth is estimated at 5.0 x 1037 and weighs 50 billion tonnes.[14] In comparison, the total mass of the biosphere has been estimated to be as much as 4 TtC (trillion [million million] tonnes of carbon).[15] In July 2016, scientists reported identifying a set of 355 genes from the Last universal common ancestor (LUCA) of all organisms living on Earth.[16]
The domain of eukaryotes represent a small minority of the number of organisms;[17] however, due to their generally much larger size, their collective global biomass is estimated to be about equal to that of prokaryotes.[17] Prokaryotes number about 4–6 × 1030 cells and 350–550 Pg of C.[18]
It is estimated that the most numerous bacteria are of a species of the Pelagibacterales (or SAR11) clade, perhaps Pelagibacter ubique, and the most numerous viruses are bacteriophages infecting these species.[19] It is estimated that the oceans contain about 2.4 × 1028 (24 octillion) SAR11 cells.[20] The Deep Carbon Observatory has been exploring living forms in the interior of the Earth. "Life in deep Earth totals 15 to 23 billion tons of carbon".[21]
Recent figures indicate that there are more than 1.4 billion insects for each human on the planet,[27] or roughly 1019 (10 quintillion) individual living insects on the earth at any given time.[28] An article in The New York Times claimed that the world holds 300 pounds of insects for every pound of humans.[28] Ants have colonised almost every landmass on Earth. Their population is estimated as between 1016–1017 (10-100 quadrillion).[29] With an estimated 20 quadrillion ants their biomass comes to 12 megatons of dry carbon, which is more than all wild birds and non-human mammals combined.[30][31][32]
According to NASA in 2005, there were over 400 billion trees on our globe.[33] However, more recently, in 2015, using better methods, the global tree count has been estimated at 3 trillion.[34] Other studies show that the Amazonian forest alone yields approximately 430 billion trees.[35] Extrapolations from data compiled over a period of 10 years suggest that greater Amazonia, which includes the Amazon Basin and the Guiana Shield, harbors around 390 billion individual trees.[36]
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