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Population typically refers to the number of people in a single area, whether it be a
city A city is a human settlement of notable size.Goodall, B. (1987) ''The Penguin Dictionary of Human Geography''. London: Penguin.Kuper, A. and Kuper, J., eds (1996) ''The Social Science Encyclopedia''. 2nd edition. London: Routledge. It can be def ...
or
town A town is a human settlement. Towns are generally larger than villages and smaller than cities, though the criteria to distinguish between them vary considerably in different parts of the world. Origin and use The word "town" shares an o ...
, region,
country A country is a distinct part of the world, such as a state, nation, or other political entity. It may be a sovereign state or make up one part of a larger state. For example, the country of Japan is an independent, sovereign state, whi ...
,
continent A continent is any of several large landmasses. Generally identified by convention rather than any strict criteria, up to seven geographical regions are commonly regarded as continents. Ordered from largest in area to smallest, these seven ...
, or the
world In its most general sense, the term "world" refers to the totality of entities, to the whole of reality or to everything that is. The nature of the world has been conceptualized differently in different fields. Some conceptions see the worl ...
.
Government A government is the system or group of people governing an organized community, generally a state. In the case of its broad associative definition, government normally consists of legislature, executive, and judiciary. Government i ...
s typically quantify the size of the resident population within their jurisdiction using a
census A census is the procedure of systematically acquiring, recording and calculating information about the members of a given population. This term is used mostly in connection with national population and housing censuses; other common censuses inc ...
, a process of collecting, analysing, compiling, and publishing data regarding a population.


Perspectives of various disciplines


Social sciences

In
sociology Sociology is a social science that focuses on society, human social behavior, patterns of social relationships, social interaction, and aspects of culture associated with everyday life. It uses various methods of empirical investigation an ...
and
population geography Population geography relates spatial variations in the distribution, composition, migration, and growth of populations to the terrain. Population geography involves demography in a geographical perspective. It focuses on the characteristics of po ...
, population refers to a group of
human Humans (''Homo sapiens'') are the most abundant and widespread species of primate, characterized by bipedalism and exceptional cognitive skills due to a large and complex brain. This has enabled the development of advanced tools, cultu ...
beings with some predefined criterion in common, such as location, race,
ethnicity An ethnic group or an ethnicity is a grouping of people who identify with each other on the basis of shared attributes that distinguish them from other groups. Those attributes can include common sets of traditions, ancestry, language, history, ...
,
nationality Nationality is a legal identification of a person in international law, establishing the person as a subject, a ''national'', of a sovereign state. It affords the state jurisdiction over the person and affords the person the protection of t ...
, or
religion Religion is usually defined as a social- cultural system of designated behaviors and practices, morals, beliefs, worldviews, texts, sanctified places, prophecies, ethics, or organizations, that generally relates humanity to supernatur ...
.
Demography Demography () is the statistical study of populations, especially human beings. Demographic analysis examines and measures the dimensions and dynamics of populations; it can cover whole societies or groups defined by criteria such as ed ...
is a
social science Social science is one of the branches of science, devoted to the study of societies and the relationships among individuals within those societies. The term was formerly used to refer to the field of sociology, the original "science of s ...
which entails the statistical study of populations.


Ecology

In
ecology Ecology () is the study of the relationships between living organisms, including humans, and their physical environment. Ecology considers organisms at the individual, population, community, ecosystem, and biosphere level. Ecology overl ...
, a population is a group of
organism In biology, an organism () is any living system that functions as an individual entity. All organisms are composed of cells ( cell theory). Organisms are classified by taxonomy into groups such as multicellular animals, plants, and fu ...
s of the same
species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriat ...
who inhabit the same particular
geographical area The geographic coordinate system (GCS) is a spherical or ellipsoidal coordinate system for measuring and communicating positions directly on the Earth as latitude and longitude. It is the simplest, oldest and most widely used of the various ...
and are capable of
interbreeding In biology, a hybrid is the offspring resulting from combining the qualities of two organisms of different breeds, varieties, species or genera through sexual reproduction. Hybrids are not always intermediates between their parents (such as in ...
. The area of a sexual population is the area where inter-breeding is possible between any pair within the area and more probable than cross-breeding with individuals from other areas. In ecology, the population of a certain species in a certain area can be estimated using the
Lincoln index The Lincoln index is a statistical measure used in several fields to estimate the number of cases that have not yet been observed, based on two independent sets of observed cases. Described by Frederick Charles Lincoln in 1930, it is also sometimes ...
.


Genetics

''In genetics, a population is often defined as a set of organisms in which any pair of members can
breed A breed is a specific group of domestic animals having homogeneous appearance (phenotype), homogeneous behavior, and/or other characteristics that distinguish it from other organisms of the same species. In literature, there exist several slig ...
together. This means that they can regularly exchange gametes to produce normally-fertile offspring, and such a
breeding Breeding is sexual reproduction that produces offspring, usually animals or plants. It can only occur between a male and a female animal or plant. Breeding may refer to: * Animal husbandry, through selected specimens such as dogs, horses, and r ...
group is also known therefore as a gamodeme. This also implies that all members belong to the same species. 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 An allele (, ; ; modern formation from Greek ἄλλος ''állos'', "other") is a variation of the same sequence of nucleotides at the same place on a long DNA molecule, as described in leading textbooks on genetics and evolution. ::"The chrom ...
(
gamete A gamete (; , ultimately ) is a haploid cell that fuses with another haploid cell during fertilization in organisms that reproduce sexually. Gametes are an organism's reproductive cells, also referred to as sex cells. In species that produce ...
) frequencies can be converted to genotype (
zygote A zygote (, ) is a eukaryotic cell formed by a fertilization event between two gametes. The zygote's genome is a combination of the DNA in each gamete, and contains all of the genetic information of a new individual organism. In multicell ...
) frequencies by expanding an appropriate
quadratic equation In algebra, a quadratic equation () is any equation that can be rearranged in standard form as ax^2 + bx + c = 0\,, where represents an unknown value, and , , and represent known numbers, where . (If and then the equation is linear, not qu ...
, as shown by Sir Ronald Fisher in his establishment of quantitative genetics.'' ''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 Panmixia (or panmixis) means random mating. A panmictic population is one where all individuals are potential partners. This assumes that there are no mating restrictions, neither genetic nor behavioural, upon the population and that therefore all ...
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 In algebra, a binomial is a polynomial that is the sum of two terms, each of which is a monomial. It is the simplest kind of sparse polynomial after the monomials. Definition A binomial is a polynomial which is the sum of two monomials. A bino ...
); 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). Note that 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 Plants are predominantly photosynthetic eukaryotes of the kingdom Plantae. Historically, the plant kingdom encompassed all living things that were not animals, and included algae and fungi; however, all current definitions of Plantae excl ...
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) and autogamous (self-fertilization) gamodemes.''


World human population

According to th
UN
the world's population surpassed 8 billion on 15 November 2022 and that the 7 billion number was surpassed on 12 March 2012. According to a separate estimate by the United Nations, Earth's population exceeded seven billion in October 2011, a milestone that offers unprecedented challenges and opportunities to all of humanity, according to
UNFPA The United Nations Population Fund (UNFPA), formerly the United Nations Fund for Population Activities, is a UN agency aimed at improving reproductive and maternal health worldwide. Its work includes developing national healthcare strategies a ...
. 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 Nigeria ( ), , ig, Naìjíríyà, yo, Nàìjíríà, pcm, Naijá , ff, Naajeeriya, kcg, Naijeriya officially the Federal Republic of Nigeria, is a country in West Africa. It is situated between the Sahel to the north and the Gulf o ...
is not even known to the nearest million, so there is a considerable margin of error in such estimates. Researcher Carl Haub calculated that a total of over 100 billion people have probably been born in the last 2000 years.


Predicted growth and decline

Population growth Population growth is the increase in the number of people in a population or dispersed group. Actual global human population growth amounts to around 83 million annually, or 1.1% per year. The global population has grown from 1 billion in 1800 to ...
increased significantly as the
Industrial Revolution The Industrial Revolution was the transition to new manufacturing processes in Great Britain, continental Europe, and the United States, that occurred during the period from around 1760 to about 1820–1840. This transition included going f ...
gathered pace from 1700 onwards.As graphically illustrated by population since 10,000BC and population since 1000AD The last 50 years have seen a yet more rapid increase in the rate of population growth due to medical advances and substantial increases in agricultural productivity, particularly beginning in the 1960s, made by the Green Revolution. In 2017 the
United Nations Population Division The United Nations Department of Economic and Social Affairs (UN DESA) is part of the United Nations Secretariat and is responsible for the follow-up to major United Nations Summits and Conferences, as well as services to the United Nations Ec ...
projected that the world's population will reach about 9.8 billion in 2050 and 11.2 billion in 2100. In the future, the world's population is expected to peak, 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. Population has already declined in the last decade or two in Eastern Europe, the Baltics and in the Commonwealth of Independent States. 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. This transition from high birth and death rates to low birth and death rates is often referred to as the
demographic transition In demography, demographic transition is a phenomenon and theory which refers to the historical shift from high birth rates and high death rates in societies with minimal technology, education (especially of women) and economic development, to l ...
.


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 Environmental degradation is the deterioration of the environment through depletion of resources such as quality of air, water and soil; the destruction of ecosystems; habitat destruction; the extinction of wildlife; and pollution. It is defin ...
, 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 Reproductive rights are legal rights and freedoms relating to reproduction and reproductive health that vary amongst countries around the world. The World Health Organization defines reproductive rights as follows: Reproductive rights rest o ...
as part of a
human rights Human rights are moral principles or normsJames Nickel, with assistance from Thomas Pogge, M.B.E. Smith, and Leif Wenar, 13 December 2013, Stanford Encyclopedia of PhilosophyHuman Rights Retrieved 14 August 2014 for certain standards of hu ...
-based approach. Growing opposition to the narrow population control focus led to a significant change in population control policies in the early 1980s.


See also

* Community (ecology) *
Human overpopulation Humans (''Homo sapiens'') are the most abundant and widespread species of primate, characterized by bipedalism and exceptional cognitive skills due to a large and complex brain. This has enabled the development of advanced tools, cultu ...
*
List of countries by population This is a list of countries and dependencies by population. It includes sovereign states, inhabited dependent territories and, in some cases, constituent countries of sovereign states, with inclusion within the list being primarily based on the ...
* Lists of organisms by population * Population ethics *
Population geography Population geography relates spatial variations in the distribution, composition, migration, and growth of populations to the terrain. Population geography involves demography in a geographical perspective. It focuses on the characteristics of po ...


References


External links


United Nations Population Division


a platform for interaction between research centres and international organizations, such as the United Nations Population Division,
UNFPA The United Nations Population Fund (UNFPA), formerly the United Nations Fund for Population Activities, is a UN agency aimed at improving reproductive and maternal health worldwide. Its work includes developing national healthcare strategies a ...
, WHO and FAO.
Population Reference Bureau
analyzes demographic data and research providing objective, accurate, and up-to-date population information in accessible formats.


NECSP HomePage

Overpopulation

Population World: Population of World
Retrieved 13 February 2004.


United Nations Economic Commission for Europe – Official Web Site

World Population Counter, and separate regions.

WorldPopClock.com
(French)
Populations du monde
(French)
OECD population data

Understanding the World Today
Reports about world and regional population trends * {{Authority control Demography
Countries A country is a distinct part of the world, such as a state (polity), state, nation, or other polity, political entity. It may be a sovereign state or make up one part of a larger state. For example, the country of Japan is an independent, so ...
Population ecology Population models