$J$-shaped growth curve depicts:

The exponential growth equation is $N_{t} = N_{0}e^{rt}$,where $N_{t}$ is the population density after time $t$. What do $N_{0}$ and $r$ refer to,respectively?

Given below are two statements: one is labelled as Assertion $A$ and the other is labelled as Reason $R$.
Assertion $A$: The logistic growth model of populations is considered more realistic than the exponential growth model.
Reason $R$: Resources are finite.
In the light of the above statements, choose the most appropriate answer from the options given below:

Graph $A$ and $B$ indicate:

The apex of the age pyramid of a stationary population is

When births are equal to deaths,it is called: