Question

The graph shows two types of population growth curves. A is exponential and B is logistic. Which one is the following growth model considered as a more realistic one?
               

(a) Exponential growth curve
(b) Logistic growth curve
(c) Both the growth curve
(d) None of the above

Answer 1

Hint: This shows an S-shaped curve in which the population is ever-changing and its growth refers to the change in the number of individuals in a population with time.
Formula used:
\frac { dN }{ dt } =rN\left( \frac { K-N }{ N } \right)
Where, N= population density at time t; r= Intrinsic rate of natural increase; K= carrying capacity

Complete answer:
The logistic growth curve is the more realistic one because the resources for growth for most animal populations are finite and become limiting sooner or later.

Additional information:
-As we know the resources for the population in nature are limited this means that a given habitat has enough resources to support a maximum possible number and beyond that no further growth is possible.
-This limitation is known as the carrying capacity of that habitat.
-So, this will lead to a competition between individuals for limited resources, and hence, the fittest individual will survive and reproduce.
-A population growing in such habitat with limited resources shows initially a lag phase, followed by phases of acceleration then deceleration, and finally an asymptote when the population density reaches the carrying capacity.
-In case of an exponential growth curve, the habitat has unlimited resources. So, each species has the ability to realize its innate potential to grow in number which will lead to enormous population densities in a short time, and resources may become depleted.
-Exponential growth curve shows the J-shaped curve and the Logistic growth curve shows an S-shaped or sigmoid curve. It can be obtained when population size is plotted over time.

So, the correct answer is ‘Logistic growth curve’.

Note:
-Exponential growth is also known as geometric growth.
-Logistic growth curve is called Verhulst Pearl Logistic Growth.
-Population growth generally depends on factors like food availability, predation threat, weather, and competition.