Question

If natality is represented by $-B$
If mortality is represented by $-D$
If immigration is represented by $-I$
If emigration is represented by $-E$
If population density is represented by $-N$
Then, population density at time $t +1$ is represented by

• A. $N_{t+1}=N_{t}-[(B+I)-(D+E)]$
• B. $N_{t+1}=N_{t}+[(B+I)-(D+E)]$
• C. $N_{t+1}=N_{t}+[(B+I)+(D+E)]$
• D. $N_{t+1}=N_{t}-[(B+I)+(D+E)]$

Answer 1

Answer: (B)

Option (b) gives the correct representation for population density at time $t+1 . ' N$ ' is the population density at time $t$ then its density at time $t+1$ is
$N_{t+1}=N_{t}+[(B+I)-(D+E)]$
We can see from the above equation that population density increases if the number of birth plus number of immigrants $(B+I)$ is more than the number of death plus the number of emigrants $(D+E)$.