The different age groups in a population are classified by:

The given age pyramid for human population indicates:

The following figure shows the age pyramids for human populations. What types of populations are represented by $P$,$Q$,and $R$?
$P \quad\quad Q \quad\quad R$

Consider the birth rate and death rate per year in a given population.
Total population after $5$ years $\rightarrow 100$
Number of individuals dying per year $\rightarrow 10$
Number of individuals born per year $\rightarrow 20$

What makes a population stable?

Define 'zero population growth rate'. Draw an age pyramid for the same.