Question

With the help of a suitable diagram describe the logistic population growth curve.

Answer 1

Logistic growth curve of population

1. Resources like food and space are not always unlimited. They may be plenty in the beginning; but as the population density increases, competition for those resources starts, resulting in a slowdown in the rate at which the original population was growing. This results in a logistic or sigmoid growth curve.
2. Competition between individuals for limited resources will weed out the ‘weaker' ones. Only the ‘fittest’ individuals will survive and reproduce.
3. A given habitat has enough resources to support a maximum possible number, beyond which no further growth is possible. This limit can be called nature’s carrying capacity (K) for that species in that habitat.
4. A population growing in a habitat with limited resources shows initially a lag phase, followed by phases of acceleration and deceleration, and finally an asymptote when the population density reaches the carrying capacity.
5. A plot of population density (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 the growth of most animal populations, are finite and become limiting sooner or later, the logistic growth model is considered a more realistic one.

Answer 2

In nature, No population of any species in nature has at its disposal unlimited resources to permit exponential growth. This leads to competition between individuals for limited resources. Eventually, the ‘fittest’ individual will survive and reproduce. In nature, a given habitat has enough resources to support the maximum possible number, beyond which no further growth is possible. Let us call this limit nature’s carrying capacity (K) for that species in that habitat.

A population growing in a habitat with limited resources initially shows a lag phase. This is followed by acceleration and deceleration and finally an asymptote phase. Population density feeding capacity type of population growth is called Verhulst-Pearl Logistic Growth. The following equation represents it –

`(dN)/(dt) = rN ((K - N)/K) = rN (1 - N/K)`

where `(dN)/(dt)` = rate of change in population size

where N = population density at time t,

r = rate of natural increase,

K = feeding capacity