J-shaped growth curve (2024)

Quick Reference

A curve on a graph that records the situation in which, in a new environment, the population density of an organism increases rapidly in an exponential or logarithmic form, but then stops abruptly as environmental resistance (e.g. seasonality) or some other factor (e.g. the end of the breeding phase) suddenly becomes effective. The actual rate of population change depends on the biotic potential and the population size. It may be summarized mathematically as: dN/dt = rN (with a definite limit on N) where N is the number of individuals in the population, t is time, and r is a constant representing the intrinsic rate of increase (biotic potential) of the organism concerned. Population numbers typically show great fluctuation, giving the characteristic ‘boom and bust’ cycles of some insects, or the ones seen in algal blooms. This type of population growth is termed ‘density-independent’ as the regulation of growth rate is not tied to the population density until the final crash. Compare S-shaped growth curve.