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26-409: In 2003, the city had an estimated population of 60,145 and a density of 175.29 persons per km. The total area was 343.12 km. On January 1, 2005, Kuroiso was merged with the towns of Nishinasuno and Shiobara (both from Nasu District ) to create the city of Nasushiobara . Kuroiso is located at the northernmost tip of Tochigi, bordering Fukushima Prefecture . Kuroiso Station serves as

52-471: 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

78-411: A new individual organism. The sexual fusion of haploid cells is called karyogamy , the result of which is the formation of a diploid cell called the zygote or zygospore. German zoologists Oscar and Richard Hertwig made some of the first discoveries on animal zygote formation in the late 19th century. The zygote is the earliest developmental stage. In humans and most other anisogamous organisms,

104-457: A zygote is formed when an egg cell and sperm cell come together to create a new unique organism. The formation of a totipotent zygote with the potential to produce a whole organism depends on epigenetic reprogramming. DNA demethylation of the paternal genome in the zygote appears to be an important part of epigenetic reprogramming. In the paternal genome of the mouse, demethylation of DNA, particularly at sites of methylated cytosines,

130-913: 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 ( 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

156-527: Is also located in the district. This Tochigi 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 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

182-528: 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 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

208-408: Is likely a key process in establishing totipotency. Demethylation involves the processes of base excision repair and possibly other DNA-repair–based mechanisms. In human fertilization , a released ovum (a haploid secondary oocyte with replicate chromosome copies) and a haploid sperm cell ( male gamete) combine to form a single diploid cell called the zygote. Once the single sperm fuses with

234-600: 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

260-611: 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,

286-703: 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

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312-555: The pre-embryo in legal discourses including relevance to the use of embryonic stem cells. In the US the National Institutes of Health has determined that the traditional classification of pre-implantation embryo is still correct. After fertilization, the conceptus travels down the fallopian tube towards the uterus while continuing to divide without actually increasing in size, in a process called cleavage . After four divisions,

338-812: The terminal station for two subsections of the JR East Tōhoku Main Line railway, making it a junction between the Kantō and Tōhoku regions of Japan. The station's bus terminal also makes Kuroiso a gateway to the neighboring town of Nasu , known in Japan for its mountain hot springs and as the location of the Nasu Imperial Villa . Kuroiso is popular in Northern Tochigi for its local cafes and restaurants, as well as for having northern Tochigi's only multiplex movie theater . A Bridgestone steel cord plant

364-547: 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

390-485: 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

416-480: 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)

442-616: The conceptus consists of 16 blastomeres, and it is known as the morula . Through the processes of compaction, cell division, and blastulation, the conceptus takes the form of the blastocyst by the fifth day of development, just as it approaches the site of implantation. When the blastocyst hatches from the zona pellucida , it can implant in the endometrial lining of the uterus and begin the gastrulation stage of embryonic development. The human zygote has been genetically edited in experiments designed to cure inherited diseases. In fungi, this cell may then enter meiosis or mitosis depending on

468-451: The early 1980s. Zygote A zygote ( / ˈ z aɪ ˌ ɡ oʊ t / ; from Ancient Greek ζυγωτός (zygōtós)  'joined, yoked', from ζυγοῦν (zygoun)  'to join, to yoke') 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

494-463: 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

520-628: The life cycle of the species. In plants, the zygote may be polyploid if fertilization occurs between meiotically unreduced gametes. In land plants , the zygote is formed within a chamber called the archegonium . In seedless plants, the archegonium is usually flask-shaped, with a long hollow neck through which the sperm cell enters. As the zygote divides and grows, it does so inside the archegonium. The zygote can divide asexually by mitosis to produce identical offspring. A Chlamydomonas zygote contains chloroplast DNA (cpDNA) from both parents; such cells are generally rare, since normally cpDNA

546-416: The oocyte, the latter completes the division of the second meiosis forming a haploid daughter with only 23 chromosomes, almost all of the cytoplasm, and the male pronucleus . The other product of meiosis is the second polar body with only chromosomes but no ability to replicate or survive. In the fertilized daughter, DNA is then replicated in the two separate pronuclei derived from the sperm and ovum, making

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572-418: 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

598-756: 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

624-466: 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, 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

650-410: 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 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,

676-413: The zygote's chromosome number temporarily 4n diploid . After approximately 30 hours from the time of fertilization, a fusion of the pronuclei and immediate mitotic division produce two 2n diploid daughter cells called blastomeres . Between the stages of fertilization and implantation , the developing embryo is sometimes termed as a preimplantation- conceptus . This stage has also been referred to as

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