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.
Famous quotes containing the words population and/or size:
“O for a man who is a man, and, as my neighbor says, has a bone in his back which you cannot pass your hand through! Our statistics are at fault: the population has been returned too large. How many men are there to a square thousand miles in this country? Hardly one.”
—Henry David Thoreau (1817–1862)
“Delusions that shrink to the size of a woman’s glove,
Then sicken inclusively outwards:
. . . the incessant recital
Intoned by reality, larded with technical terms,
Each one double-yolked with meaning and meaning’s rebuttal:
For the skirl of that bulletin unpicks the world like a knot....”
—Philip Larkin (1922–1986)