Question

Explain different types of growth models.

Answer 1

i. Exponential Growth model

1. Resources like food, space are essential for any growth of a population.
2. Ideally, when resources in the habitat are unlimited, each species has the ability to fully realize its innate potential to grow in numbers. Then the population grows in an exponential or geometric proportion.
3. Every species is capable of growing exponentially under unlimited resource conditions, and reach enormous population densities in a short time.

ii. Logistic Growth model

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 slowdown in the rate at which the original population was growing. This results in 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 as nature’s carrying capacity (K) for that species in that habitat. 
4. A population growing in a habitat with limited resources show initially a lag phase, followed by phases of acceleration and deceleration and finally an asymptote, when the population density reaches the carrying capacity.