$(b)$

Exponential growth curve is also called $J-$shaped curve or geometric growth curve.

Logistic curve is also called sigmoid growth curve $J-$shaped curve.

Exponential Growth Model When the resources availability is unlimited in the habitat, the population grows in an exponential or geometric fashion. As resources are unlimited than there is no inhibition from crowding.

The equation is; $d N / d t=(b-d) \times N i$ Birth rate, $d=i$, Death rate

$N=i$ Population density, $\frac{d n}{d t}=$ Rate of change of population

Let $(b-d)=r$, then the equation is, $d N / d t=R n$

$r=i$ Intrinsic rate of natural increase

When a population shows exponential growth, the curve plotted with $N$ in relation to time, assume J shape

In this there is no fix carrying capacity

Logistic Growth Model No population can continue to grow exponentially, as the resource availability become limiting at certain point of time. Logistic growth model have fixed carrying capacity

It is described by the equation $\frac{d N}{d t}=r N\left(\frac{K-N}{K}\right)$ Rate of change of population density

$N=$ Population density at time

$N=$ Population density

$r=$ Intrinsic rate of natural increase

$K=$ Carrying capacity

Population growth curve $A$ when resources are not limiting. Plot is exponential or geometrical curve $B$. When resources are limiting the growth, plot is logistic

$^{\prime} K ^{\prime}$ is carrying capacity