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25-499: As of 2003, the town had an estimated population of 6,450 and a density of 646.29 persons per km. The total area was 9.98 km. On March 31, 2006, Kuchinotsu, along with the towns of Arie , Fukae , Futsu , Kazusa , Kitaarima , Minamiarima and Nishiarie (all from Minamitakaki District ), was merged to create the city of Minamishimabara . An Imperial decree in July 1899 established Kuchinotsu as an open port for trading with

50-437: A population is often defined as a set of organisms in which any pair of members can breed together. They can thus routinely exchange gametes in order to have usually fertile progeny, and such a breeding 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

75-523: A "factor of Panmixia" (P) to include in the equations describing the gene frequencies in a population, and accounting for a population's tendency towards panmixia, while a "factor of Fixation" (F) would account for a population's departure from the Hardy–Weinberg expectation, due to less than panmictic mating. In this formulation, the two quantities are complementary, i.e.  P  = 1 −  F . From this factor of fixation, he later developed

100-476: 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. Growing opposition to the narrow population control focus led to a significant change in population control policies in

125-408: A group of human beings with some predefined feature in common, such as location, race , ethnicity , nationality , or religion . In ecology , a population is a group of organisms of the same species which inhabit the same geographical area and are capable of interbreeding . The area of a sexual population is the area where interbreeding is possible between any opposite-sex pair within

150-621: A range of hundreds to thousands of miles, and thus breed with other members of the population. To signify the importance of this, imagine several different finite populations of the same species (for example: a grazing herbivore ), isolated from each other by some physical characteristic of the environment (dense forest areas separating grazing lands). As time progresses, natural selection and genetic drift will slowly move each population toward genetic differentiation that would make each population genetically unique (that could eventually lead to speciation events or extirpation ). However, if

175-609: 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. Population growth increased significantly as the Industrial Revolution gathered pace from 1700 onwards. 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

200-611: Is often referred to as the demographic transition . 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,

225-617: Is uniformly possible. Both the Wahlund effect and the Hardy Weinberg equilibrium assume that the overall population is panmictic. In genetics and heredity , random mating usually implies the hybridising ( mating ) of individuals regardless of any spatial, physical, genetical, temporal or social preference. That is, the mating between two organisms is not influenced by any environmental, nor hereditary interaction. Hence, potential mates have an equal chance of being contributors to

250-715: 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 former 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

275-561: The F statistics . In a panmictic species, all of the individuals of a single species are potential partners, and the species gives no mating restrictions throughout the population. Panmixia can also be referred to as random mating, referring to a population that randomly chooses their mate, rather than sorting between the adults of the population. Panmixia allows for species to reach genetic diversity through gene flow more efficiently than monandry species. However, outside population factors, like drought and limited food sources, can affect

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300-532: The United States and the United Kingdom . 32°36′N 130°11′E  /  32.600°N 130.183°E  / 32.600; 130.183 This Nagasaki Prefecture location article is a stub . You can help Misplaced Pages by expanding it . Population Population is the term typically used to refer to the number of people in a single area. Governments conduct a census to quantify

325-569: The 1960s, made by the Green Revolution . In 2017 the United Nations Population Division projected that the world's population would reach about 9.8 billion in 2050 and 11.2 billion in 2100. In the future, the world's population is expected to peak at some point, after which it will decline due to economic reasons, health concerns, land exhaustion and environmental hazards. According to one report, it

350-496: 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

375-482: The area and more probable than cross-breeding with individuals from other areas. In humans , interbreeding is unrestricted by racial differences, as all humans belong to the same species of Homo sapiens. 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. In genetics,

400-480: 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)

425-579: The early 1980s. Panmixia Panmixia (or panmixis ) means uniform random fertilization. A panmictic population is one where all potential parents may contribute equally to the gamete pool, and that these gametes are uniformly distributed within the gamete population (gamodeme). This assumes that there are no hybridising restrictions within the parental population: neither genetics , cytogenetics nor behavioural ; and neither spatial nor temporal (see also Quantitative genetics for further discussion). Therefore, all gamete recombination (fertilization)

450-490: The fertilizing gamete pool. If there is no random sub-sampling of gametes involved in the fertilization cohort, panmixia has occurred. Such uniform random mating is distinct from lack of natural selection : in viability selection for instance, selection occurs before mating. In simple terms, panmixia (or panmicticism) is the ability of individuals in a population to interbreed without restrictions; individuals are able to move about freely within their habitat , possibly over

475-691: 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. 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

500-463: 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

525-418: 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 and animal breeding , procedures have been developed which deliberately utilize the effects of dispersion (such as line breeding, pure-line breeding, backcrossing). Dispersion-assisted selection leads to the greatest genetic advance (ΔG=change in

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550-771: 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. According to the UN, the world's population surpassed 8 billion on 15 November 2022, an increase 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 UNFPA , growth to such an extent offers unprecedented challenges and opportunities to all of humanity. According to papers published by

575-459: The separating factor is removed before this happens (e.g. a road is cut through the forest), and the individuals are allowed to move about freely, the individual populations will still be able to interbreed . As the species's populations interbreed over time, they become more genetically uniform, functioning again as a single panmictic population. In attempting to describe the mathematical properties of structured populations, Sewall Wright proposed

600-549: The size of a resident population within a given jurisdiction. The term is also applied to non-human animals , microorganisms , and plants , and has specific uses within such fields as ecology and genetics . The word population is derived from the Late Latin populatio (a people, a multitude), which itself is derived from the Latin word populus (a people). In sociology and population geography , population refers to

625-591: The way any species will mate. When scientists examine species mating to understand their mating style, they look at factors like genetic markers, genetic differentiation, and gene pool. A panmictic population of Monostroma latissimum , a marine green algae, shows sympatric speciation in southwest Japanese islands. Although panmictic, the population is diversifying. Dawson's burrowing bee , Amegilla dawsoni, may be forced to aggregate in common mating areas due to uneven resource distribution in its harsh desert environment. Pantala flavescens should be considered as

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