# A student is investigating the effect of pH on the germination of seeds. Describe the steps the student should take to ensure the pH of the soil is accurately measured and controlled throughout the experiment.

> OCR A-Level Biology A (H420) — 1 Development of practical skills in biology · Describe · 4 marks

## Mark scheme (4 marks)

1. The student should calibrate the pH meter
2. The student should use buffer solutions to control the pH
3. The student should take multiple pH readings over time
4. The student should consider the potential for pH drift or variation

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Source: [GradeNine](https://www.gradenine.co.uk/q/a-student-is-investigating-the-effect-a4a7ffef) · Published by Druglandscape Ltd.