The population of any species is:

If there were $30$ lotus plants in a pond last year and through reproduction $10$ new plants were added, taking the current population to $40$, then the birth rate = $.........$ offspring per lotus per year.

Which of the following is not a controlling factor of population density?

$A$ group of individuals living in a particular geographical area at a particular time is called:

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

Define population and community.