"Population is an auto-regulated system" was said by

At one time,the number of cheetahs in a habitat is $80$. Their birth rate is $4$ and death rate is $2$. Among them,$6$ cheetahs are internal migrants (immigration) and $3$ cheetahs are migratory (emigration). Calculate the population density of cheetahs in that habitat.

Which of the following states has the highest population density?

$A$ biologist studied the population of rats in a barn. He found that the average natality was $250$, average mortality $240$, immigration $20$ and emigration $30$. The net increase in population is

Emigration is:

Under a particular set of selection pressure,organisms evolve towards the most $A$ reproductive strategy. Some organisms breed only $B$ in lifetime while others breed $C$ in lifetime. Choose the correct option for $A, B$ and $C$.