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Population typically refers the number of people in a single area whether it be a city or town, region, country, or the world. Governments typically quantify the size of the resident population within their jurisdiction by a process called a
census A census is the procedure of systematically calculating, acquiring and recording information Information is processed, organised and structured data Data (; ) are individual facts, statistics, or items of information, often numeric. In ...

census
(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 Social science is the branch The branches and leaves of a tree. A branch ( or , ) or tree branch (sometimes referred to in botany Botany, also called , plant biology or phytology, is the scie ...
and
population geography 300px, Map of world population density in 1994 Population Geography relates spatial variations in the distribution, composition, migration, and growth of populations to the terrain. Population geography involves demography Demography (from ...
, population refers to a group of
human Humans (''Homo sapiens'') are the most abundant and widespread species In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes ...

human
s beings with some predefined criterion in common, such as location, race,
ethnicity An ethnic group or ethnicity is a grouping of people who identity (social science), identify with each other on the basis of shared attributes that distinguish them from other groups. Those attributes can include common sets of traditions, ancest ...

ethnicity
,
nationality Nationality is a of a person in , establishing the person as a subject, a ''national'', of a . It affords the state jurisdiction over the person and affords the person the protection of the state against other states. Article 15 of the stat ...
, or
religion Religion is a social Social organisms, including humans, live collectively in interacting populations. This interaction is considered social whether they are aware of it or not, and whether the exchange is voluntary/involuntary. Etymology ...

religion
.
Demography Demography (from prefix ''demo-'' from Ancient Greek Ancient Greek includes the forms of the used in and the from around 1500 BC to 300 BC. It is often roughly divided into the following periods: (), Dark Ages (), the period ...

Demography
is a
social science Social science is the branch A branch ( or , ) or tree branch (sometimes referred to in botany Botany, also called , plant biology or phytology, is the science of plant life and a branch of biology. A botanist, plant scientist o ...

social science
which entails the statistical study of populations.


Ecology

In
ecology Ecology (from el, οἶκος, "house" and el, -λογία, label=none, "study of") is the study of the relationships between living organisms, including humans, and their physical environment. Ecology considers organisms In biol ...
, a population is a group of
organism In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological me ...

organism
s of the same
species In biology, a species is the basic unit of biological classification, 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 individu ...

species
who inhabit the same particular
geographical area A geographic coordinate system (GCS) is a coordinate system associated with positions on Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. About 29% of Earth's surface is land c ...
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
sex Sex is either of two divisions, typically male Male (♂) is the sex of an organism that produces the gamete known as sperm. A male gamete can fuse with a larger female gamete, or ovum, in the process of fertilization. A male cannot sexual r ...
ual population is the area where
inter-breeding 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 b ...
is possible between any pair within the area and more probable than
cross-breeding A crossbreed is an organism with purebred Purebreds, also called purebreeds, are cultivated varieties or ''cultivars'' of an animal species In biology, a species is the basic unit of biological classification, classification and a taxonomic r ...

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 slight ...
together. This means that they can regularly exchange gametes to produce normally-fertile offspring, and such a
breeding Breeding is sexual reproduction Sexual reproduction is a type of reproduction Reproduction (or procreation or breeding) is the biological process by which new individual organism In biology, an organism (from Ancient Greek, Greek: ...
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 one of two, or more, forms of a given gene In biology, a gene (from ''genos'' "...Wilhelm Johannsen coined the word gene to describe the Mendelian_inheritance ...
(
gamete A gamete ( /ˈɡæmiːt/; from Ancient Greek Ancient Greek includes the forms of the Greek language Greek ( el, label=Modern Greek Modern Greek (, , or , ''Kiní Neoellinikí Glóssa''), generally referred to by speakers simply ...
) frequencies can be converted to genotype (
zygote A zygote (, ) is a eukaryotic Eukaryotes () are organism In biology, an organism () is any organic, life, living system that functions as an individual entity. All organisms are composed of cells (cell theory). Organisms are ...

zygote
) frequencies by expanding an appropriate
quadratic equation In algebra Algebra (from ar, الجبر, lit=reunion of broken parts, bonesetting, translit=al-jabr) is one of the areas of mathematics, broad areas of mathematics, together with number theory, geometry and mathematical analysis, analysis. ...

quadratic equation
, as shown by Sir
Ronald Fisher Sir Ronald Aylmer Fisher (17 February 1890 – 29 July 1962) was a British polymath A polymath ( el, πολυμαθής, , "having learned much"; la, homo universalis, "universal human") is an individual whose knowledge spans a subs ...
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 Behavior (American English Ameri ...
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 polynomial after the monomials. Definition A binomial is a polynomial which is the sum of two monomials. A binomial in a ...
); 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 Photosynthesis is a process used by plants and other organisms to Energy transformation, convert light energy into chemical energy that, through cellular respiration, can later be released to fuel ...
and
animal breeding Animal breeding is a branch of animal science Animal science (also bioscience) is described as "studying the biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Bioch ...
, 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 the
United States Census Bureau The United States Census Bureau (USCB), officially the Bureau of the Census, is a principal agency of the U.S. Federal Statistical System, responsible for producing data about the American American(s) may refer to: * American, something of, ...
the world's population was about 7.55 billion in 2019 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 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 ...
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 (), officially the Federal Republic of Nigeria, is a country in West Africa West Africa or Western Africa is the westernmost region of . The defines Western Africa as the 17 countries of , , , , , , , , , , , , , , , and as we ...

Nigeria
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 Population typically refers the number of people in a single area whether it be a city or town, region, country, or the world. Governments typically quantify the size ...
increased significantly as the
Industrial Revolution The Industrial Revolution was the transition to new manufacturing processes in Great Britain, continental Europe Continental Europe or mainland Europe is the contiguous continent A continent is any of several large landmasse ...
gathered pace from 1700 onwards.As graphically illustrated by
population since 10,000BC In biology, a population is a number of all the organisms of the same group or species who live in a particular geographical area and are capable of Sexual reproduction, interbreeding. The area of a sexual population is the area where interbree ...
and
population since 1000AD In biology, a population is a number of all the organisms of the same group or species who live in a particular geographical area and are capable of Sexual reproduction, interbreeding. The area of a sexual population is the area where interbree ...
The last 50 years have seen a yet more rapid increase in the rate of population growth due to
medical advances Medicine is the Art (skill), art, science, and Praxis (process) , practice of caring for a patient and managing the diagnosis, prognosis, Preventive medicine, prevention, therapy, treatment or Palliative care , palliation of their injury or dise ...
and substantial increases in agricultural productivity, particularly beginning in the 1960s, made by the
Green Revolution The Green Revolution, or the Third Agricultural Revolution, is the set of research technology transfer initiatives occurring between 1950 and the late 1960s, that increased agricultural production worldwide, beginning most markedly in the late ...

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 The United Nations Secretariat (french: link=no, Secrétariat des Nations unies) is one of the six major organs of the United N ...
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 Demography (from prefix ''demo-'' from Ancient Greek δῆμος (''dēmos'') meaning 'the people', and ''-graphy'' from γράφω (''graphō'') meaning 'writing, description or measurement') is the statistics, statistical s ...
.


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 Environment most often refers to: __NOTOC__ * Natural environment, all living and non-living things occurring naturally * Biophysical environment, the physical and biological facto ...
, 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 right Natural rights and legal rights are the two basic types of rights Rights are law, legal, social, or ethics, ethical principles of Liberty, freedom or entitlement; that is, rights are the fundamental norma ...
as part of a
human rights Human rights are moral A moral (from Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. ...
-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) In ecology, a community is a group or association Association may refer to: *Club (organization), an association of two or more people united by a common interest or goal *Trade association, an organization founded and funded by businesses tha ...
*
Human overpopulation Human overpopulation (or human population overshoot) is the concept of a human population becoming too large to be sustainability, sustained by its environment or resources in the long term. The idea is usually discussed in the context of world ...
*
List of countries by population This is a list of countries and dependencies by population. It includes sovereign state A sovereign state is a polity, political entity represented by one centralized government that has sovereignty over a geographic area. International law ...
* Lists of organisms by population *
Population ethics Population typically refers the number of people in a single area whether it be a city or town, region, country, or the world. Governments typically quantify the size of the resident population within their jurisdiction by a process called a ce ...
*
Population geography 300px, Map of world population density in 1994 Population Geography relates spatial variations in the distribution, composition, migration, and growth of populations to the terrain. Population geography involves demography Demography (from ...


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 The World Health Organization (WHO) is a specialized agency of the United Nations United Nations Specialized Agencies are autonomous organizations working with the United Nations and each other through the co-ordinating machinery of the Unite ...

WHO
and
FAO The Food and Agriculture Organization of the United Nations (FAO)french: Organisation des Nations unies pour l'alimentation et l'agriculture; it, Organizzazione delle Nazioni Unite per l'Alimentazione e l'Agricoltura is a specialized agency ...

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 territorial body or political entity A polity is an identifiable political entity—any group of people who have a collective identity, who are organized by some form of Institutionalisation, institutionalized social ...
Population ecology Population models