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In population genetics and population ecology, population size (usually denoted N) is the number of individual organisms in a population.

The effective population size (Ne) is defined as "the number of breeding individuals in an idealized population that would show the same amount of dispersion of allele frequencies under random genetic drift or the same amount of inbreeding as the population under consideration." Ne is usually less than N (the absolute population size) and this has important applications in conservation genetics.

Small population size results in increased genetic drift. Population bottlenecks are when population size reduces for a short period of time.

Overpopulation may indicate any case in which the population of any species of animal may exceed the carrying capacity of its ecological niche.

See also[edit]

Original courtesy of Wikipedia: http://en.wikipedia.org/wiki/Population_size — Please support Wikipedia.
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Population Size

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9300 news items

Nature World News

Nature World News
Wed, 17 Dec 2014 11:14:32 -0800

Despite popular belief, humans did not entirely hunt giant lemurs living on Madagascar into extinction thousands of years ago. Ancient DNA has revealed that their small population size is partly to blame, shedding light on what factors put today's ...

NerdWallet (blog)

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Wed, 17 Dec 2014 15:00:21 -0800

Half of the top 10 places for Cuban-Americans by population size are outside Florida, and include the metro areas in Los Angeles, Chicago, Atlanta and Las Vegas. Florida comes back into clear focus when ranking by percentage of population with Cuban ...


Tue, 16 Dec 2014 08:18:45 -0800

Peter Wagner, executive director of the Prison Policy Initiative, said we should set the raw numbers aside because they are not as useful as comparing each country's incarceration rate, which factors in population size. The U.S. prison population rate ...


Thu, 04 Dec 2014 14:30:00 -0800

Both genetic variation and PSMC inference is sensitive to population structure, he said, in addition to population size changes, and "if there is a lot of population structure, say, in the ancestors of the Khoe-San, that could give the same signal as a ...


Wed, 10 Dec 2014 04:29:34 -0800

The average number of children per couple in the reproductive age has dropped from 6.4 children in 1960 to 2.1 children in 2013; the population growth rate per year decreased from 3.5 percent in 1960 to 1.05 percent in 2013; the population size in 2013 ...


Thu, 18 Dec 2014 05:16:57 -0800

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Thu, 18 Dec 2014 08:30:00 -0800

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Wed, 17 Dec 2014 13:28:33 -0800

Polar bears are largely dependent on sea ice to travel, hunt and mate, making their population size an indicator of how climate change is affecting wildlife in the region. The number of polar bears in the entire Arctic is not known because the area is ...

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