Question

Which of the following statements best describes the effect of natality and immigration on population density?

• A. Neither of them affect population density
• B. Natality has a positive effect whereas immigration has a negative effect on population density
• C. Both have a negative effect on population density
• D. Both have a positive effect on population density

Answer 1

The correct option is D Both have a positive effect on population density

Population density is the number of individuals present per unit area.

Natality (B) is the number of births during a given period that is added to the already existing population.
Immigration (I) refers to the number of individuals of the same species that move into the population, from elsewhere, during a given time period.

In both these processes, individuals are added to the population and hence it results in an increase in population density. If the population density at time t is $N_t$ and the population density at time t+1 is $N_{t+1}$, then the effect of mortality and immigration on population density can be represented as -
$N_{t+1}$ = [$N_t$ + (B+I)]
This shows that both natality and immigration have a positive effect on population density.