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Ecosystems · trophic levels
Energy transfers and productivity
Calculate net primary production, consumer production, transfer efficiency and production per unit area from biological energy budgets.
Method and worked examples ↓Learn the method
How to approach these questions
- Keep energy quantities in matching units and over the same area and time interval.
- Distinguish gross primary production from the production remaining after producer respiration.
- Read what counts as the input and useful output in the supplied energy budget.
- For an area-normalised value, divide the total production by the measured area.
Worked examples
GPP is 18,000 kJ m⁻² year⁻¹ and producer respiration is 7,000 in the same units. Find NPP.
NPP = 18,000 − 7,000 = 11,000 kJ m⁻² year⁻¹.
Producer NPP is 10,000 kJ and herbivore production is 800 kJ for the same interval and area. Find transfer efficiency.
Efficiency = 800 ÷ 10,000 × 100 = 8%. Energy dissipated during respiration is not available as production at the next trophic level.
Keep practising
Topic map and study list · Practical data guides · Active recall decks
Course resources
AQA A-level Biology · OCR A A-level Biology · Textbook answers
Skill coverage follows the common A-level science subject content. Check your board’s current requirements: AQA 7402 and OCR A H420.