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Population density is the number of people per unit of area, usually transcribed as "per square kilometer" or square mile, and which may include or exclude, for example, areas of water or glaciers. Commonly this is calculated for a county, city, country, another territory or the entire world. The world's population is around 8,000,000,000 [3 ...
The half-life of a population is the time taken for the population to decline to half its size. We can calculate the half-life of a geometric population using the equation: N t = λ t N 0 by exploiting our knowledge of the fact that the population (N) is half its size (0.5N) after a half-life. [20]
A demographic structure of a population is how populations are often quantified. The total number of individuals in a population is defined as a population size, and how dense these individuals are is defined as population density. There is also a population's geographic range, which has limits that a species can tolerate (such as temperature).
Population size. In population genetics and population ecology, population size (usually denoted N) is a countable quantity representing the number of individual organisms in a population. Population size is directly associated with amount of genetic drift, and is the underlying cause of effects like population bottlenecks and the founder ...
Allee effects are classified by the nature of density dependence at low densities. If the population shrinks for low densities, there is a strong Allee effect. If the proliferation rate is positive and increasing then there is a weak Allee effect. The null hypothesis is that proliferation rates are positive but decreasing at low densities.
A 1982 study by Templeton and Johnson showed that in a population of Drosophila mercatorum under K-selection the population actually produced a higher frequency of traits typically associated with r-selection. [37] Several other studies contradicting the predictions of r/K selection theory were also published between 1977 and 1994. [38] [39 ...
The effective population size (Ne) is the size of an idealised population that would experience the same rate of genetic drift as the real population, whereby the latter, due mainly to the limited proportion of breeding individuals, has a normally larger census population size N. Idealised populations are based on unrealistic but convenient ...
New Jersey is the most densely populated state. New York is home to the most populous city in the country, and ranks 8th among the states in density. Despite a small population, Vermont has fairly average population density because of its small area. Idaho 's population has increased rapidly in recent decades, but its population density is ...