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Population density

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	Topics Population density Topic Home Population density is a measurement of populationFacts About Population In sociology and biology, a population is the collection of people, or organisms of a particular species, living in a given ... per unit area or unit volume. It is frequently applied to living organisms, and particularly to humanHuman Humans, or human beings, are bipedal primates belonging to the mammalian species *Homo sapiens* under the fami... s. It is a key term used in geology. Biological population densities Population density refers to the number of people per square kilometer of land area. It is a common biological measurement and is more often used by conservationists as a measure than population size. Low densities may cause an extinction vortexExtinction Vortex Extinction Vortices are a class of models through which conservation biologists, geneticists and ecologists can understand t... and lead to further reduced fertility. This is called the Allee effectAllee effect Summary The Allee effect is a phenomenon in biology named after W.... , after W. C. Allee who first identified it. Examples of the causes in low population densities include: Increased problems with locating mates Increased inbreedingInbreeding Inbreeding is breeding between close relatives, whether plant or animal.... Different species have different expected densities. R-selected species commonly have high population densities, while K-selected species may have lower densities. Low densities may be associated with specialised mate location adaptations such as specialised pollinators; as found in the orchid family (Orchidaceae). Human population density For humans, population density is the number of people per unit of area (which may include or exclude cultivated or potentially productive area). Commonly this may be calculated for a countyCounty Summary A county is generally a sub-unit of regional self-government within a sovereign jurisdiction.... , cityCity A city is an urban area that is differentiated from a town, village, or hamlet by size, population density, importance, or ... , countryCountry In political geography and international politics a country is a geographical territory.... , another territory, or the entire worldEarth Earth is the third planet in the solar system in terms of distance from the Sun, and the fifth largest.... . The world populationWorld population The world population is the total number of humans alive on the planet Earth at a given time.... is 6.6 billion, and EarthEarth Earth is the third planet in the solar system in terms of distance from the Sun, and the fifth largest.... 's area is 510 million square kilometers (200 million square miles). Therefore the world-wide human population density is 6.6 billion / 510 million = 13 per km² (33 per sq mi), or 43 per km² (112 per sq mi) if only the Earth's land area of 150 million km² (58 million sq mi) is taken into account. This density rises when the population grows. It also includes all continental and island land area, including AntarcticaAntarctica Antarctica is the southernmost continent and encompasses the South Pole.... . Considering that over half of the earth's land mass consists of areas inhospitable to human inhabitation, such as deserts and high mountains, and that population clusters heavily around seaports and fresh water sources, this number by itself significantly understates the level of human crowding. Several of the most densely-populated territories in the world are city-states, microstates, micronations, or dependenciesDependent territory A dependent territory, dependent area or dependency is a territory that does not possess full political independ... . These territories share a relatively small area and an exceptionally high urbanizationUrbanization Urbanization or urbanisation is the increase over time in population or extent of cities and towns.... level, with an economically specialized cityCity Overview A city is an urban area that is differentiated from a town, village, or hamlet by size, population density, importance, or ... population drawing also on rural resources outside the area, illustrating the difference between high population density and overpopulationOverpopulation Overview Overpopulation is the condition of any organism's numbers exceeding the carrying capacity of its ecological niche.... . Cities with exceptionally high population densities are often considered to be overpopulated, though the extent to which this is the case depends on factors like quality of housing and infrastructure or access to resources. Most of the most densely-populated cities are in southern and eastern AsiaAsia Summary Asia is the largest and most populous continent or region, depending on the definition.... , though CairoCairo Cairo translated the "land of Ra'" It comes from two Coptic words "Kahi"... and LagosLagos Lagos is the largest city in Nigeria.... in AfricaAfrica Africa is one of the greatest sized continents of the Earth.... also fall into this category. City population is however, heavily dependent on the definition of "urban area" used: densities are typically higher for the central municipality itself, than when more recently-developed and administratively unincorporated suburban communities are included, as in the concepts of agglomerationAgglomeration In the study of human settlements, an agglomeration is an extended city or town area comprising the built-up area of a centr... or metropolitan areaMetropolitan area A metropolitan area is a large population center consisting of a large city and its adjacent zone of influence, or of severa... , the latter including sometimes neighbouring cities. Other methods of measurement While arithmetic density is the most common way of measuring population density, several other methods have been developed which aim to provide a more accurate measure of population density over a specific area. Arithmetic density: The total number of peoples / area of land measured in km² or mi². Physiological density: The total population / the amount of arable land. Agricultural density: The total rural population / amount of agricultural land. Residential density : The number of people living in an urban area / the area of residential land. Urban densityUrban density Urban density is a term used in urban planning and urban design to refer to the number of people inhabiting a given urbanize... : The number of peoples inhabiting an urban area / the total area of urban land. Ecological optimum: The density of population which can be supported by the area's natural resources. See also List of countries by population densityList of countries by population density List of countries and dependencies by population density in inhabitants/km.... List of countries by populationList of countries by population This is a list of sovereign states and other territories by population,... List of cities by populationList of cities by population This is a list of the largest cities of the world estimated for the year 2005.... List of religious populationsList of religious populations Summary Of the 6,450,000,000 people on Earth as of June 2005, as published by the United States Census Bureau, 5,208,000,000 followed worl... List of U.S. states by population densityList of U.S. states by population density Overview This is a list of the 50 U.S. states, ordered by population density.... Human geographyHuman geography Human geography is a branch of geography that focuses on the systematic study of patterns and processes that shape human int... Idealised populationIdealised population In population genetics an idealised population, also sometimes called a Fisher-Wright population after R.A.... Optimum populationOptimum population Overview Optimum population is where the amount of resources available in a country is equal to the country's population, so there ar... Population bottleneckPopulation bottleneck A population bottleneck is an evolutionary event in which a significant percentage of a population or species is killed or o... Population geneticsPopulation genetics Population genetics is the study of the allele frequency distribution and change under the influence of the four evolutionar... Population healthPopulation health Population health is an approach to health that aims to improve the health of an entire population.... Population momentumPopulation momentum Population momentum is an effect which causes population growth.... Population pyramidPopulation pyramid A population pyramid is two back-to-back bar graphs, one showing the number of males and one showing females in a particular... Small population sizeSmall population size Species with a small population size are subject to a higher chance of extinction because they are more vulnerable to geneti... External links combines Google Maps and 2000 Census data to show the population densities of U.S. zip codes on an interactive map.