The study of human populations in a biological community is called...........

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

Emigration is:

Which factors influence the change in population density?

Define the following terms:
$(1)$ Immigration
$(2)$ Emigration
$(3)$ Mortality

List any four characters that are employed in human population census.