Question

In which of the following options, both the processes in the pair have a positive effect on population density?

• A. Natality and emigration
• B. Mortality and immigration
• C. Mortality and emigration
• D. Natality and immigration

Answer 1

The correct option is D Natality and immigration

Population density is the number of individuals of a species per unit area at a given time. If the initial population density at time t is $N_t$, then the population density at time t+1 can be represented as

$N_{t+1}$ = ${N_t}^{}$ + [(B+I)-(D+E)]

Where,

B is natality i.e. number of births during a given time period

I is immigration i.e. number of individuals of the same species that enter a population from elsewhere during a given time period

D is mortality i.e. number of deaths during a given time period

E is emigration i.e. number of individuals of the same species that leave a population during a given time period.

Both natality and immigration add individuals to a population and have a positive effect on the population density whereas, mortality and emigration deduct individuals from a population and have a negative effect on it.