5 original questions · Application and evidence

Respiration: apparatus, controls and interpretation

Use the context and data to draft a response, then compare your reasoning with an explanatory example.

Context and data

An illustrative respirometer comparison uses equal masses of germinating seeds at two temperatures. Carbon dioxide is absorbed in the apparatus. Matched control apparatus contains inert material of comparable displaced volume. Each displacement is measured over six minutes, with positive displacement defined as movement consistent with gas uptake. Use test minus control for the stated correction.

Six-minute displacements in matched apparatus
Temperature / °C	Seed apparatus displacement / mm	Control displacement / mm
15	2.4	0.3
25	4.8	0.6

Original illustrative data. Use the stated assumptions and units; these are not examination-board questions.

This worksheet includes questions and data, with space for your responses. Answers are omitted.

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Respiration: apparatus, controls and interpretation

Context and data

Five questions

1. Calculate the control-corrected displacement rate at each temperature.

2. Compare the corrected rates and explain why the correction matters to interpreting the apparatus readings.

3. Explain how oxygen consumption can produce the measured displacement when carbon dioxide is absorbed.

4. A student claims that the table proves ATP production exactly doubled at 25 °C. Evaluate this conclusion.

5. Suggest two changes that would strengthen the comparison and explain their purposes.