1. Naturally all populations of any species always have limited resources to permit exponential growth. Due to this there is always competition between individuals for limited resources. The most fit organisms succeed by survival and reproduction.
2. A given habitat has enough resources to support a maximum possible number, but beyond a particular limit the further growth is impossible.
3. This limit is called nature’s carrying capacity (K) for that species in that habitat.
4. A population growing in a habitat with limited resources show following phases in a sequential manner, (a) A lag phase (b) Phase of acceleration (c) Phase of deceleration (d) An asymptote, when the population density reaches the carrying capacity.
5. A plot of N in relation to time (t) results in a sigmoid curve. This type of population growth is called VerhulstPearl Logistic Growth.
6. Since resources for growth for most animal populations are finite and become limiting sooner or later, the logistic growth model is considered as a more realistic one.
7. Logistic growth thus always shows sigmoid curve.
