Biology · Grades 8–11
Quadrat density estimate
Divide the total counted organisms by the total sampled area. Density is not the same as total population size.
Rule and assumptions
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
Worked examples
A supplied survey counts 82 plants in 5 non-overlapping quadrats, each 0.5 m². Find the mean density in the sampled area. Round to 3 decimal places if needed. Answer in plants/m².
density = total count / total sampled area 82/(5 × 0.5) = 32.8
32.8 plants/m²
A supplied survey counts 112 plants in 12 non-overlapping quadrats, each 0.5 m². Find the mean density in the sampled area. Round to 3 decimal places if needed. Answer in plants/m².
density = total count / total sampled area 112/(12 × 0.5) = 18.667
18.667 plants/m²
Try two questions
A supplied survey counts 97 plants in 6 non-overlapping quadrats, each 2 m². Find the mean density in the sampled area. Round to 3 decimal places if needed. Answer in plants/m².
A supplied survey counts 195 plants in 3 non-overlapping quadrats, each 2 m². Find the mean density in the sampled area. Round to 3 decimal places if needed. Answer in plants/m².
Answers and reasoning
Answers and marking notes
- 8.083 plants/m²
density = total count / total sampled area 97/(6 × 2) = 8.083
- 32.5 plants/m²
density = total count / total sampled area 195/(3 × 2) = 32.5
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.