Which of the following is $NOT$ a primary factor affecting population density?

The crude number of births by a population per unit time is called:

Which of the following equations correctly represents the calculation of population density?

$(a)$ Label the three tiers $1, 2, 3$ given in the above age pyramid.
$(b)$ What type of population growth is represented by the above age pyramid?

In the given figure,which factors are responsible for the increase in population density?

Under a particular set of selection pressure,organisms evolve towards the most efficient reproductive strategy. For example:
$A$) Oysters produce a large number of small-sized offspring.
$B$) Mammals produce a small number of large-sized offspring.
In the light of the above statements,choose the correct option.