Biology · Grades 8–12
Population balance
Add births and immigration; subtract deaths and emigration. All counts refer to the same interval.
Rule and assumptions
Add births and immigration; subtract deaths and emigration. All counts refer to the same interval.
N₂ = N₁ + births + immigration − deaths − emigration
Worked examples
A fictional population starts at 518. During one interval: 48 births, 33 arrivals, 6 deaths and 28 departures. Find the final count. Round to 3 decimal places if needed.
N₂ = N₁ + births + immigration − deaths − emigration 518 + 48 + 33 − 6 − 28 = 565
565
A fictional population starts at 778. During one interval: 59 births, 18 arrivals, 34 deaths and 34 departures. Find the final count. Round to 3 decimal places if needed.
N₂ = N₁ + births + immigration − deaths − emigration 778 + 59 + 18 − 34 − 34 = 787
787
Try two questions
A fictional population starts at 189. During one interval: 73 births, 26 arrivals, 60 deaths and 1 departures. Find the final count. Round to 3 decimal places if needed.
A fictional population starts at 146. During one interval: 35 births, 38 arrivals, 34 deaths and 28 departures. Find the final count. Round to 3 decimal places if needed.
Answers and reasoning
Answers and marking notes
- 227
N₂ = N₁ + births + immigration − deaths − emigration 189 + 73 + 26 − 60 − 1 = 227
- 157
N₂ = N₁ + births + immigration − deaths − emigration 146 + 35 + 38 − 34 − 28 = 157
Further reading and review references
These are reference links, not copied exercises, institutional endorsement or proof of independent review.
Learning preview · independent educational and translation review required. Suggested grades are not official curriculum alignment.