Logistic population growth curve

Unlimited resources result in exponential growth. Many countries have realized this fact and introduced various restraints to limit human population growth. In nature, a given habitat has enough resources to support a maximum possible number, beyond which no further growth is possible. This limit is called as carrying capacity (K) for that species in that habitat.

A population growing in a habitat with limited resources shows initially a lag phase, followed by phases of increase and decrease and finally the population density reaches the carrying capacity. A plot of N in relation to time (t) results in a sigmoid curve. This type of population growth is called Verhulst-Pearl Logistic Growth as explained by the following equation :

S-shaped Population growth curve (Verhulst-Pearl logistic growth curve)

where N = Population density at a time t ; r = Intrinsic rate of natural increase and ; K = Carrying capacity, = Environmental resistance.

Since resources for growth for most animal populations become limiting sooner or later, the logistic growth model is concerned a more realistic one.