A student investigates the rate of respiration in germinating seeds and dry (non-germinating) seeds by measuring the temperature change inside sealed containers over 30 minutes. The germinating seeds show a larger temperature increase than the dry seeds. Explain why the germinating seeds produce more heat energy than the dry seeds during this investigation.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Germinating seeds are seeds that have begun to grow. Dry seeds are dormant and show very little biological activity. Both types of seed are kept in sealed containers at the start of the investigation.
Model answer (5 marks)
1. Germinating seeds are actively respiring, so their rate of respiration is higher than that of dry seeds.
2. Respiration releases energy stored in glucose and other food reserves.
3. A portion of this released energy is transferred as heat to the container and its surroundings.
4. The germinating seeds need this energy for growth, cell division, active transport and synthesis of new molecules.
5. Dry seeds are dormant; their metabolic and enzyme activity is very low, so little respiration and consequently little heat is produced.
2. Respiration releases energy stored in glucose and other food reserves.
3. A portion of this released energy is transferred as heat to the container and its surroundings.
4. The germinating seeds need this energy for growth, cell division, active transport and synthesis of new molecules.
5. Dry seeds are dormant; their metabolic and enzyme activity is very low, so little respiration and consequently little heat is produced.
Examiner tips
- Use the word "actively" to show higher respiration. Mention that heat is a by‑product of respiration. Explain the need for energy in growth. Show the contrast with dormant seeds’ low activity.
Common mistakes
- Confusing heat production with the temperature of the seeds themselves. Forgetting to link respiration to energy release. Saying the dry seeds “do not produce heat” instead of “produce little heat”.
Mark scheme (5 marks)
- Germinating seeds are actively respiring / have a higher rate of respiration than dry seeds
- Respiration releases energy (from glucose/food stores)
- Some of the released energy is transferred as heat (to the surroundings / container)
- Germinating seeds require energy for growth / cell division / active transport / building new molecules
- Dry seeds are dormant so metabolic activity / enzyme activity is very low, meaning little respiration occurs and little heat is produced
Key terms in this question
Related
- All Pearson Edexcel A-Level Biology A (9BI0) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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