Biology · Grades 7–12
Ecology & populations · Formula reference
Formula reference
Rule and assumptions
Quadrat density estimate
Divide the total counted organisms by the total sampled area. Density is not the same as total population size.
density = total count / total sampled area
Population balance
Add births and immigration; subtract deaths and emigration. All counts refer to the same interval.
N₂ = N₁ + births + immigration − deaths − emigration
Food-web transfer model
Convert the supplied transfer efficiency to a fraction. Do not assume that all food webs have a fixed 10% efficiency.
transferred energy = available energy × stated efficiency/100
Population estimate from supplied records
Use supplied records only. Assume a closed population, equal capture probability, mixing and retained marks. The estimate has sampling uncertainty.
N ≈ MC/R
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.