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Population density (in agriculture: standing stock or plant density) is a measurement of population per unit land area. It is mostly applied to humans , but sometimes to other living organisms too. It is a key geographical term.
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).
In ecology, a population is a group of organisms of the same species which inhabit the same geographical area and are capable of interbreeding. [2] [3] 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.
species density, take into account the number of species in an area; species richness, take into account the number of species per individuals (usually [species]/[individuals x area]) diversity indices, take into account the number of species (the richness) and their relative contribution (the evenness); e.g.: Simpson index; Shannon-Wiener index
When a cell population reaches a certain density, the amount of required growth factors and nutrients available to each cell becomes insufficient to allow continued cell growth. [citation needed] This is also true for other organisms because an increased density means an increase in intraspecific competition. Greater competition means an ...
The distinction between the two terms is based on whether or not the population in question exhibits a critical population size or density. A population exhibiting a weak Allee effect will possess a reduced per capita growth rate (directly related to individual fitness of the population) at lower population density or size.
Neo-Malthusians and eugenicists popularised the use of the words to describe the number of people the Earth can support in the 1950s, [9] although American biostatisticians Raymond Pearl and Lowell Reed had already applied it in these terms to human populations in the 1920s.
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 effect . [ 1 ]