Question 1Warm-upFoundation
Daisies counted in 10 quadrats: 3, 5, 2, 4, 6, 0, 3, 5, 4, 8. Calculate the mean number per quadrat.
Total ÷ 10.
Worked solution
- Total
Answer:
GCSE & IGCSE biology practice
Quadrats questions and answers
Ecologists use quadrats to estimate how many of a species live in an area. Count the organisms in several randomly placed quadrats, find the mean per quadrat, convert to the number per m², then multiply by the total area: estimated population .
15 questions · Foundation tier · Every answer is checked as you type it, with a full worked solution. Updated .
Where quadrats comes up
| GCSE (AQA) | Biology and Combined Science, Foundation and Higher: use quadrats and transects; calculate means; required practical to measure the population size of a common species using sampling. |
|---|---|
| Cambridge IGCSE (0610) | Quadrat sampling isn't in the 2026 to 2028 syllabus. |
The method
- Place quadrats randomly (e.g. random coordinates) to avoid bias.
- Mean per quadrat = total count ÷ number of quadrats.
- Per m²: divide by the quadrat's area (a 0.5 m × 0.5 m quadrat is 0.25 m²).
- Population = mean per m² × total area (m²).
- Use a transect to see how distribution changes across a habitat.
Quadrats questions
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Warm-up
Question 2Warm-upFoundation
The mean is 4 daisies per 1 m² quadrat. The field is 50 m × 20 m. Estimate the number of daisies in the field.
Area = 1000 m².
Worked solution
- Area m²
- daisies
Answer:
Question 9Warm-upFoundation
Plants counted in 5 quadrats: 6, 8, 5, 9, 7. Calculate the mean number per quadrat.
Add the counts and divide by the number of quadrats.
Worked solution
Answer:
Question 10Warm-upFoundation
The mean is 3 plants per m². The area is 120 m². Estimate the number of plants.
Mean per m² × area.
Worked solution
Answer:
Exam-style
Question 3Exam-styleFoundation
A 0.25 m² quadrat has a mean of 3 dandelions. What is the mean number per m²?
Divide by 0.25 (or × 4).
Worked solution
- per m²
Answer: per m²
Question 4Exam-styleFoundation
A 0.5 m × 0.5 m quadrat gives a mean of 2.5 plants. The lawn is 200 m². Estimate the number of plants.
Quadrat area = 0.25 m².
Worked solution
- Per m²:
Answer:
Question 5Exam-styleFoundation
Why should quadrats be placed randomly?
What if you chose spots by eye?
Worked solution
- Choosing positions yourself could favour areas with more (or fewer) plants. Random placement gives a representative sample.
Answer: To avoid bias, so the sample represents the whole area
Question 6Exam-styleFoundation
Counts in 7 quadrats: 2, 3, 3, 4, 5, 7, 9. What is the median?
The middle value of the ordered list.
Worked solution
- Seven values in order: the 4th is .
Answer:
Question 11Exam-styleFoundation
A 0.25 m² quadrat has a mean of 6 buttercups. What is the mean number per m²?
There are four 0.25 m² quadrats in 1 m².
Worked solution
- per m²
Answer: per m²
Question 12Exam-styleFoundation
A field is 30 m × 40 m. 1 m² quadrats give a mean of 2.5 daisies. Estimate the number of daisies in the field.
Find the area of the field first.
Worked solution
- Area m²
Answer:
Question 13Exam-styleFoundation
Why should a student use many quadrats rather than just a few?
Think about how representative the sample is.
Worked solution
- More quadrats reduce the effect of unusual results, so the mean is more representative of the whole area.
Answer: A larger sample gives a more reliable mean
Challenge
Question 7ChallengeFoundation
Five 1 m² quadrats on an 80 m² lawn contain 12, 15, 9, 14 and 10 clover plants. Estimate the clover population.
Mean, then × area.
Worked solution
- Mean per m²
Answer:
Question 8ChallengeFoundation
A student wants to see how the number of a plant changes from the edge of a pond out into a field. What should they use?
Random sampling estimates numbers; a transect shows change across a habitat.
Worked solution
- A line transect, with quadrats at regular intervals, shows how distribution changes with distance from the pond.
Answer: A transect: sample at regular intervals along a line from the pond outwards
Question 14ChallengeFoundation
Eight 0.5 m × 0.5 m quadrats contain 36 buttercups in total. The meadow is 500 m². Estimate the buttercup population.
Mean per quadrat, then per m², then × area.
Worked solution
- Mean per quadrat
- Each quadrat is m², so per m²
Answer:
Question 15ChallengeFoundation
A plant was found in 7 out of 10 quadrats. What is its percentage frequency?
Number of quadrats with the plant ÷ total quadrats × 100.
Worked solution
Answer:
Common mistakes
- Forgetting to convert to per m² when the quadrat isn't 1 m².
- Choosing quadrat positions by eye (biased).
- Dividing by the area instead of multiplying.
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Sources
The questions are our own. The “where it comes up” notes are from each board's published specification, checked on 27 October 2026:
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