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 Population ecology is a sub-field of ecology that deals with the dynamics of species populations and how these populations interact with the environment (biophysical), environment, such as birth rate, birth and death rates, and by immigration an ...

and

biogeography Biogeography is the study of the species distribution, distribution of species and ecosystems in geography, geographic space and through evolutionary history of life, geological time. Organisms and biological community (ecology), communities o ...

. Individuals are counted by census, as carried out for the

piping plover The piping plover (''Charadrius melodus'') is a small sand-colored, Passerellidae, sparrow-sized wader, shorebird that nests and feeds along coastal sand and gravel beaches in North America. The adult has yellow-orange-red legs, a black band acro ...

; using the transect method, as done for the mountain plover; and beginning in 2012 by satellite, with the

emperor penguin The emperor penguin (''Aptenodytes forsteri'') is the tallest and heaviest of all living penguin species and is Endemism in birds, endemic to Antarctica. The male and female are similar in plumage and size, reaching in length and weighing fr ...

being first subject counted in this manner.

Number of species

More than 99 percent of all species, amounting to over five billion species, that ever lived on Earth are estimated to be

extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...

. Estimates on the number of Earth's current

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

range from 10 million to 14 million, of which about 1.2 million have been documented and over 86 percent have not yet been described. According to another study, the number of described species has been estimated at 1,899,587. 2000–2009 saw approximately 17,000 species described per year. The total number of undescribed organisms is unknown, but marine microbial species alone could number 20,000,000. 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 ''Trillion'' is a number with two distinct definitions: *1,000,000,000,000, i.e. one million 1,000,000, million, or (ten to the twelfth Exponentiation, power), as defined on the long and short scales, short scale. This is now the meaning in bot ...

species are estimated to be on Earth currently with only one-thousandth of one percent described. The total number of related

DNA Deoxyribonucleic acid (; DNA) is a polymer composed of two polynucleotide chains that coil around each other to form a double helix. The polymer carries genetic instructions for the development, functioning, growth and reproduction of al ...

base pair A base pair (bp) is a fundamental unit of double-stranded nucleic acids consisting of two nucleobases bound to each other by hydrogen bonds. They form the building blocks of the DNA double helix and contribute to the folded structure of both DNA ...

s on Earth is estimated at 5.0 x 10³⁷ and weighs 50 billion

tonne The tonne ( or ; symbol: t) is a unit of mass equal to 1,000 kilograms. It is a non-SI unit accepted for use with SI. It is also referred to as a metric ton in the United States to distinguish it from the non-metric units of the s ...

s. In comparison, the total

mass Mass is an Intrinsic and extrinsic properties, intrinsic property of a physical body, body. It was traditionally believed to be related to the physical quantity, quantity of matter in a body, until the discovery of the atom and particle physi ...

of the

biosphere The biosphere (), also called the ecosphere (), is the worldwide sum of all ecosystems. It can also be termed the zone of life on the Earth. The biosphere (which is technically a spherical shell) is virtually a closed system with regard to mat ...

has been estimated to be as much as 4 TtC (trillion illion milliontonnes of

carbon Carbon () is a chemical element; it has chemical symbol, symbol C and atomic number 6. It is nonmetallic and tetravalence, tetravalent—meaning that its atoms are able to form up to four covalent bonds due to its valence shell exhibiting 4 ...

). In July 2016, scientists reported identifying a set of 355

gene In biology, the word gene has two meanings. The Mendelian gene is a basic unit of heredity. The molecular gene is a sequence of nucleotides in DNA that is transcribed to produce a functional RNA. There are two types of molecular genes: protei ...

s from the

Last universal common ancestor The last universal common ancestor (LUCA) is the hypothesized common ancestral cell from which the three domains of life, the Bacteria, the Archaea, and the Eukarya originated. The cell had a lipid bilayer; it possessed the genetic code a ...

(LUCA) of all

organism An organism is any life, living thing that functions as an individual. Such a definition raises more problems than it solves, not least because the concept of an individual is also difficult. Many criteria, few of them widely accepted, have be ...

s living on Earth.

By domain

The domain of

eukaryotes The eukaryotes ( ) constitute the domain of Eukaryota or Eukarya, organisms whose cells have a membrane-bound nucleus. All animals, plants, fungi, seaweeds, and many unicellular organisms are eukaryotes. They constitute a major group of ...

represent a small minority of the number of organisms; however, due to their generally much larger size, their collective global

biomass Biomass is a term used in several contexts: in the context of ecology it means living organisms, and in the context of bioenergy it means matter from recently living (but now dead) organisms. In the latter context, there are variations in how ...

is estimated to be about equal to that of

prokaryotes A prokaryote (; less commonly spelled procaryote) is a single-celled organism whose cell lacks a nucleus and other membrane-bound organelles. The word ''prokaryote'' comes from the Ancient Greek (), meaning 'before', and (), meaning 'nut' ...

. Prokaryotes number about 4–6 × 10³⁰ cells and 350–550 Pg of C.

Microbes

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

bacteriophage A bacteriophage (), also known informally as a phage (), is a virus that infects and replicates within bacteria. The term is derived . Bacteriophages are composed of proteins that Capsid, encapsulate a DNA or RNA genome, and may have structu ...

s infecting these species. It is estimated that the oceans contain about 2.4 × 10²⁸ (24 octillion) SAR11 cells. 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".

Animalia

Vertebrates

Mammals (Mammalia)

* Mammals by population ** Artiodactyla ** Carnivora ** Cetacea ** Chiroptera ** Perissodactyla ** Primates ** Proboscidea ** Marsupialia

Birds (Aves)

* Birds by population ** Anseriformes ** Apodiformes ** Caprimulgiformes ** Charadriiformes ** Ciconiiformes ** Columbiformes ** Coraciiformes ** Cuculiformes ** Falconiformes ** Galliformes *** The domesticated chicken (Gallus gallus domesticus), a Galliform, has an estimated population of 23.7 billion, which is higher than any other bird. ** Gaviiformes ** Gruiformes ** Passeriformes ** Pelecaniformes ** Phoenicopteriformes ** Piciformes ** Podicipediformes ** Procellariiformes ** Psittaciformes ** Sphenisciformes ** Strigiformes ** Struthioniformes ** Tinamiformes ** Trogoniformes

Reptiles (Reptilia)

Hexapoda

Insects (Insecta)

Recent figures indicate that there are more than 1.4 billion insects for each human on the planet, or roughly 10¹⁹ (10 quintillion) individual living insects on the earth at any given time. An article in ''

The New York Times ''The New York Times'' (''NYT'') is an American daily newspaper based in New York City. ''The New York Times'' covers domestic, national, and international news, and publishes opinion pieces, investigative reports, and reviews. As one of ...

'' claimed that the world holds 300 pounds of insects for every pound of humans. Ants have colonised almost every landmass on Earth. Their population is estimated as between 10¹⁶–10¹⁷ (10-100 quadrillion). 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.

Plantae

Trees

According to

NASA The National Aeronautics and Space Administration (NASA ) is an independent agencies of the United States government, independent agency of the federal government of the United States, US federal government responsible for the United States ...

in 2005, there were over 400 billion trees on our globe. However, more recently, in 2015, using better methods, the global tree count has been estimated at 3 trillion. Other studies show that the Amazonian forest alone yields approximately 430 billion trees. 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.

References

{{DEFAULTSORT:Organisms by population Biology-related lists Lists of biota