Population

{{Short description|All the organisms of a given species that live in a specified region}}
{{Other uses}}
{{pp-move-indef}}
{{Use dmy dates|date=November 2019}}

'''Population''' is the term typically used to refer to the number of people in a single area. Governments conduct a [[census]] to quantify the size of a resident population within a given jurisdiction. The term is also applied to non-human [[Animal|animals]], [[Microorganism|microorganisms]], and [[Plant|plants]], and has specific uses within such fields as [[ecology]] and [[genetics]].

== Etymology ==
The word population is derived from the [[Late Latin]] ''populationem'' (a people, a multitude), which itself is derived from the [[Latin]] word ''populus'' (a people).<ref>{{Cite web |title=population {{!}} Etymology, origin and meaning of population by etymonline |url=https://www.etymonline.com/word/population |access-date=2023-06-08 |website=etymonline.com |language=en}}</ref>

== Use of the term ==
=== Social sciences ===
{{For|the statistics of populations|Demography}}
[[File:Population density key.png|thumb|upright=0.9|Population key|alt=population]]

In [[sociology]] and [[population geography]], population refers to a group of [[human]] beings with some predefined criterion in common, such as location, [[Race (human categorization)|race]], [[ethnicity]], [[nationality]], or [[religion]].{{citation needed|date=May 2023}}

=== Ecology ===
{{main|Population ecology}}
In [[ecology]], a population is a group of [[organism]]s of the same [[species]] who inhabit the same particular [[geographical area]] and are capable of [[Sexual reproduction|interbreeding]].<ref>{{cite web |title=Population |url=http://www.biology-online.org/dictionary/Population|publisher=Biology Online |access-date=5 December 2012}}</ref><ref>{{cite web |title=Definition of population (biology) |url=http://oxforddictionaries.com/definition/english/population?q=population |archive-url=https://web.archive.org/web/20130510042807/http://oxforddictionaries.com/definition/english/population?q=population |url-status=dead |archive-date=10 May 2013 |work=Oxford Dictionaries |publisher=Oxford University Press |access-date=5 December 2012 |quote=a community of animals, plants, or humans among whose members interbreeding occurs}}</ref> The area of a [[sex]]ual population is the area where [[interbreeding|inter-breeding]] is possible between any pair within the area and more probable than [[Crossbreed|cross-breeding]] with individuals from other areas.<ref>{{cite book | last=Hartl | first=Daniel | title=Principles of Population Genetics | publisher=[[Sinauer Associates]] | year=2007 | isbn=978-0-87893-308-2 | page=45}}</ref>

In ecology, the population of a certain species in a certain area can be estimated using the [[Lincoln index]] to calculate the total population of an area based on the number of individuals observed.

==== Dynamics ====
{{excerpt|Population dynamics}}

=== Genetics ===
{{main|Population genetics}}

In genetics, a ''population'' is often defined as a set of organisms in which any pair of members can [[Breeding in the wild|breed]] together. They can thus routinely exchange gametes in order to have usually fertile progeny, and such a [[Sexual reproduction|breeding]] group is also known therefore as a gamodeme. This also implies that all members belong to the same species.<ref>{{cite book | last=Hartl | first=Daniel | title=Principles of Population Genetics | publisher=[[Sinauer Associates]] | year=2007 | isbn=978-0-87893-308-2 | page=95}}</ref>
If the gamodeme is very large (theoretically, approaching infinity), and all gene alleles are uniformly distributed by the gametes within it, the gamodeme is said to be panmictic. Under this state, [[allele]] ([[gamete]]) frequencies can be converted to genotype ([[zygote]]) frequencies by expanding an appropriate [[quadratic equation]], as shown by Sir [[Ronald Fisher]] in his establishment of quantitative genetics.<ref>{{cite book | last=Fisher | first=R. A. | title=The Genetical Theory of Natural Selection | publisher=[[Oxford University Press]] (OUP) | year=1999 | isbn=978-0-19-850440-5}}</ref>

This seldom occurs in nature: localization of gamete exchange – through dispersal limitations, preferential mating, cataclysm, or other cause – may lead to small actual gamodemes which exchange gametes reasonably uniformly within themselves but are virtually separated from their neighboring gamodemes. However, there may be low frequencies of exchange with these neighbors. This may be viewed as the breaking up of a large sexual population (panmictic) into smaller overlapping sexual populations. This failure of [[panmixia]] leads to two important changes in overall population structure: (1) the component gamodemes vary (through gamete sampling) in their allele frequencies when compared with each other and with the theoretical panmictic original (this is known as dispersion, and its details can be estimated using expansion of an appropriate [[binomial equation]]); and (2) the level of homozygosity rises in the entire collection of gamodemes. The overall rise in homozygosity is quantified by the inbreeding coefficient (f or φ). All homozygotes are increased in frequency – both the deleterious and the desirable. The mean phenotype of the gamodemes collection is lower than that of the panmictic original – which is known as inbreeding depression. It is most important to note, however, that some dispersion lines will be superior to the panmictic original, while some will be about the same, and some will be inferior. The probabilities of each can be estimated from those binomial equations. In [[plant breeding|plant]] and [[animal breeding]], procedures have been developed which deliberately utilize the effects of dispersion (such as line breeding, pure-line breeding, backcrossing). It can be shown that dispersion-assisted selection leads to the greatest genetic advance (ΔG=change in the phenotypic mean), and is much more powerful than selection acting without attendant dispersion. This is so for both allogamous (random fertilization)<ref>{{cite journal | last=Gordon  | first=Ian L. | title=Quantitative genetics of allogamous F2 : an origin of randomly fertilized populations | journal=[[Heredity (journal)|Heredity]]| year=2000  | volume=85  | pages=43–52  | doi=10.1046/j.1365-2540.2000.00716.x  | pmid=10971690| doi-access=free  }}</ref> and autogamous (self-fertilization) gamodemes.<ref>{{cite journal | last=Gordon  | first=Ian L. | title=Quantitative genetics of autogamous F2 | journal=[[Hereditas]] | year=2001 | volume=134 | pages=255–262 | doi=10.1111/j.1601-5223.2001.00255.x | pmid=11833289 | issue=3| doi-access=free }}</ref>

== World human population ==
{{Main|World population|Demographics of the world}}

According to the [https://www.worldometers.info/world-population/ UN] the world's population surpassed 8 billion on 15 November 2022,<ref>{{Cite web |title=Population Clock |url=https://www.worldometers.info/world-population/ |access-date=15 November 2022 |website=www.worldometers.info |url-status=live |archive-url=https://archive.today/20221115125002/https://www.worldometers.info/world-population/ |archive-date=15 November 2022}}</ref> a gain of 1 billion since 12 March 2012. According to a separate estimate by the United Nations, Earth's population exceeded seven billion in October 2011. According to [[United Nations Population Fund|UNFPA]], growth to such an extent offers unprecedented challenges and opportunities to all of humanity.<ref>[http://www.unfpa.org/public/home/news/pid/8328Countdown to a World of Seven Billion People] {{webarchive|url=https://web.archive.org/web/20120113192804/http://www.unfpa.org/public/home/news/pid/8328Countdown |date=13 January 2012 }} [[UNFPA]] 12 September 2011</ref>

According to papers published by the United States Census Bureau, the world population hit 6.5 billion on 24 February 2006. The [[United Nations Population Fund]] designated 12 October 1999 as the approximate day on which world population reached 6 billion. This was about 12 years after the world population reached 5 billion in 1987, and six years after the world population reached 5.5 billion in 1993. The population of countries such as [[Nigeria]] is not even known to the nearest million,<ref>{{cite web |url=http://www.mongabay.com/igapo/2005_world_city_populations/Nigeria.html | title=Cities in Nigeria: 2005 Population Estimates&nbsp;– MongaBay.com |access-date=1 July 2008}}</ref> so there is a considerable margin of error in such estimates.<ref>{{cite news |url=http://news.bbc.co.uk/2/hi/africa/country_profiles/1064557.stm |title=Country Profile: Nigeria |access-date=1 July 2008 | work=BBC News | date=24 December 2009}}</ref>

Researcher Carl Haub calculated that a total of over 100 billion people have probably been born in the last 2000 years.<ref>Haub, C. 1995/2004. "How Many People Have Ever Lived on Earth?" Population Today, {{cite web |url=http://www.prb.org/Articles/2002/HowManyPeopleHaveEverLivedonEarth.aspx |title=How Many People Have Ever Lived on Earth? - Population Reference Bureau |access-date=29 April 2013 |url-status=dead |archive-url=https://web.archive.org/web/20130424014209/http://www.prb.org/Articles/2002/HowManyPeopleHaveEverLivedonEarth.aspx |archive-date=24 April 2013  }}</ref>

=== Predicted growth and decline ===
{{Main|Population growth}}
[[File:World population growth - time between each billion-person growth.svg|thumb|upright=1.8|The years taken for every billion people to be added to the world's population, and the years that population was reached (with future estimates).]]

[[Population growth]] increased significantly as the [[Industrial Revolution]] gathered pace from 1700 onwards.<ref name="historic population graphs">As graphically illustrated by [[:File:Poulation-since-10000BC.jpg|population since 10,000BC]] and [[:File:Poulation-since-1000AD.jpg|population since 1000AD]]</ref> The last 50 years have seen a yet more rapid increase in the [[Population growth#Population growth rate|rate]] of population growth<ref name=" historic population graphs " /> due to [[History of medicine#Contemporary medicine|medical advances]] and substantial increases in agricultural productivity, particularly beginning in the 1960s,<ref>{{Cite news |url=http://news.bbc.co.uk/1/hi/world/south_asia/4994590.stm |work=BBC News |title=The end of India's green revolution? |date=29 May 2006 |access-date=29 November 2009 }}</ref> made by the [[Green Revolution]].<ref>[http://www.foodfirst.org/media/opeds/2000/4-greenrev.html Food First/Institute for Food and Development Policy] {{webarchive|url=https://web.archive.org/web/20090714215036/http://www.foodfirst.org/media/opeds/2000/4-greenrev.html |date=14 July 2009 }}</ref> In 2017 the [[United Nations Population Division]] projected that the world's population will reach about 9.8 billion in 2050 and 11.2 billion in 2100.<ref>{{Cite web|url=https://population.un.org/wpp/Publications/Files/WPP2017_KeyFindings.pdf|title=UN Population Prospects 2017}}</ref>

[[File:PRB 2017 Data Sheet Largest Populations.jpg|thumb|left|upright=0.9|PRB 2017 Data Sheet Largest Populations]]

In the future, the world's population is expected to peak,<ref>[http://www.statista.com/statistics/1717/forecast-about-the-development-of-the-world-population/ World Population Development Statistics: Forecast], United Nations, 2011.</ref> after which it will decline due to economic reasons, health concerns, land exhaustion and environmental hazards. According to one report, it is very likely that the world's population will stop growing before the end of the 21st century. Further, there is some likelihood that population will actually decline before 2100.<ref>{{cite journal |title= The End of World Population Growth | volume=412|issue= 6846 |doi=10.1038/35087589 |pmid= 11484054 |journal=Nature |pages=543–545|year= 2001 |last1= Lutz |first1= Wolfgang |last2= Sanderson |first2= Warren |last3= Scherbov |first3= Sergei | bibcode=2001Natur.412..543L| s2cid=4425080| url=http://pure.iiasa.ac.at/id/eprint/6524/1/RR-01-12.pdf}}</ref><ref>{{cite journal | last1 = Ojovan | first1 = M.I. | last2 = Loshchinin | first2 = M.B. | year = 2015 | title = Heuristic Paradoxes of S.P. Kapitza Theoretical Demography | journal = European Researcher | volume = 92 | issue = 3| pages = 237–248 | doi=10.13187/er.2015.92.237| doi-access = free }}</ref> Population has already declined in the last decade or two in Eastern Europe, the Baltics and in the Commonwealth of Independent States.<ref>{{Cite web|url=http://gsociology.icaap.org/report/demsum.html|title=world demographic trends|website=gsociology.icaap.org|access-date=18 July 2019}}</ref>

The population pattern of less-developed regions of the world in recent years has been marked by gradually declining birth rates. These followed an earlier sharp reduction in death rates.<ref name="users.rcn.com">{{cite web |url=http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/P/Populations.html |title=Human Population Growth |access-date=7 April 2009 |url-status=dead |archive-url=https://web.archive.org/web/20090330191122/http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/P/Populations.html |archive-date=30 March 2009  }}</ref> This transition from high birth and death rates to low birth and death rates is often referred to as the [[demographic transition]].<ref name="users.rcn.com" />

=== Population planning ===
{{Main|Human population planning}}

Human population planning is the practice of altering the rate of growth of a human population. Historically, human population control has been implemented with the goal of limiting the rate of population growth. In the period from the 1950s to the 1980s, concerns about global population growth and its effects on poverty, [[environmental degradation]], and political stability led to efforts to reduce population growth rates. While population control can involve measures that improve people's lives by giving them greater control of their reproduction, a few programs, most notably the Chinese government's one-child per family policy, have resorted to coercive measures.

In the 1970s, tension grew between population control advocates and women's health activists who advanced women's [[reproductive rights]] as part of a [[human rights]]-based approach.<ref>{{cite book |title=Reproductive Rights in a Global Context |last= Knudsen |first=Lara |year=2006 |publisher= Vanderbilt University Press |isbn=978-0-8265-1528-5 |pages=[https://archive.org/details/reproductiverigh0000knud/page/2 2] |url=https://archive.org/details/reproductiverigh0000knud |url-access=registration |quote=reproductive rights. }}</ref> Growing opposition to the narrow population control focus led to a significant change in population control policies in the early 1980s.<ref>{{cite book |title=Reproductive Rights in a Global Context |last= Knudsen |first=Lara |year=2006 |publisher= Vanderbilt University Press |isbn=978-0-8265-1528-5 |pages=[https://archive.org/details/reproductiverigh0000knud/page/4 4]–5 |url=https://archive.org/details/reproductiverigh0000knud |url-access=registration |quote=reproductive rights. }}</ref>

== See also ==
* [[Community (ecology)]]
* [[Human overpopulation]]
* [[List of countries by population]]
* [[Lists of organisms by population]]
* [[Population ethics]]
*[[Population geography]]

== References ==
{{Reflist|2}}

==Further reading==
*Hopfenberg, Russell. "[https://ia802907.us.archive.org/4/items/3anexpansionofthedemographictransitionmodel/3%20An%20expansion%20of%20the%20demographic%20transition%20model.pdf An expansion of the demographic transition model: the dynamic link between agricultural productivity and population.]" Biodiversity 15.4 (2014): 246–254.

== External links ==
* [https://www.un.org/esa/population/unpop.htm United Nations Population Division]
* [http://www.cicred.org/Eng/Publications/IndexPublications.htm CICRED homepage] a platform for interaction between research centres and international organizations, such as the United Nations Population Division, [[UNFPA]], [[WHO]] and [[FAO]].
* [http://www.prb.org/ Population Reference Bureau] analyzes demographic data and research providing objective, accurate, and up-to-date population information in accessible formats.
* {{cite EB9 |wstitle = Population |volume= XIX  |last= Hooper |first= Wynnard  |author-link= | pages=513-517 |short=1 }}
* [https://web.archive.org/web/20080205020959/http://www.census.gov/ipc/www/popclockworld.html Current World Population]
* [https://web.archive.org/web/20070301130913/http://www.necsp.org/ NECSP HomePage]
* [http://www.overpopulation.info/ Overpopulation] {{Webarchive|url=https://web.archive.org/web/20081123064142/http://www.overpopulation.info/ |date=23 November 2008 }}
* [https://web.archive.org/web/20100929072740/http://www.populationworld.com/ Population World: Population of World]. Retrieved 13 February 2004.
* [https://web.archive.org/web/20070927092719/http://www.sieds.it/index_en.htm SIEDS, Italian Society of Economics Demography and Statistics]
* {{oweb|http://www.unece.org/pau}} of the United Nations Economic Commission for Europe
* [http://www.counttheworld.com/?counter=pop_world World Population Counter, and separate regions.]
* [http://www.worldpopclock.com/ WorldPopClock.com]. {{In lang|fr}}
* [http://www.populationsdumonde.com/ Populations du monde]. {{In lang|fr}}
* [http://stats.oecd.org/wbos/Index.aspx?QueryId=254 OECD population data]{{Dead link|date=February 2022 |bot=InternetArchiveBot |fix-attempted=yes }}
* [http://gsociology.icaap.org/  Understanding the World Today] Reports about world and regional population trends
* {{cite encyclopedia |last1=Lee |first1=Ronald Demos |editor=David R. Henderson |editor-link=David R. Henderson |encyclopedia=[[Concise Encyclopedia of Economics]] |title=Population |url=http://www.econlib.org/library/Enc/Population.html |year=2008 |edition= 2nd |publisher=[[Library of Economics and Liberty]] |location=Indianapolis |isbn=978-0-86597-665-8 |oclc=237794267}}

{{Population}}
{{Population country lists}}
{{biological organisation}}
{{Sustainability}}
{{Ethnicity}}
{{Evolution}}
{{Evolutionary psychology}}
{{Authority control}}

[[Category:Population| ]]
[[Category:Demography]]
[[Category:Lists by population|Countries]]
[[Category:Population ecology]]
[[Category:Population models]]