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Tadpole sampling method improvement
Frogs are animals that lay their eggs in water. The eggs hatch as tadpoles. Students investigated the number of tadpoles in a pond for 8 weeks. This is the method used.
- Collect 10 dm³ of pond water in a bucket.
- Count the number of tadpoles collected.
- Put the tadpoles back into the pond.
- Repeat steps 1 to 3 another three times in different parts of the pond.
- Repeat steps 1 to 4 at intervals for 8 weeks.
Suggest one improvement to the method.
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Marking points
- 1 Suggests collecting more samples each time.
- 2 Suggests sampling more frequently with a sensible interval.
- 3 Suggests taking a larger sample.
- 4 Suggests preventing double counting before all four samples are collected.
- 5 Suggests sampling at the same time of day.
- 6 Suggests randomising collecting positions.
- 7 Suggests sampling at a range of depths.
- 8 Suggests standardised net sweeps.
Full-mark answer
Randomise the positions in the pond from which each sample is collected.
Why this answer loses marks
The students should be more careful when sampling.
This is not a specific method change; state how sampling frequency, volume, position, depth, timing or repeat handling would change.