Productivity and energy transferEdexcel International A Level Biology: Flashcards
What these 13 flashcards ask
- What is GPP?
- What is NPP?
- State the equation linking GPP, NPP and R.
- What is R in productivity calculations?
- Give units for productivity.
- How is efficiency of energy transfer calculated?
- What is a typical efficiency of transfer between trophic levels?
- Give two reasons why not all the biomass of one trophic level passes to the next.
- How is energy lost in an animal's metabolism?
- Why is transfer from plants to herbivores often less efficient than from herbivores to carnivores?
- Why do food chains rarely have more than four or five trophic levels?
- Why do crop plants convert only 1 to 3% of light energy to NPP?
- Why does eating plants directly feed more people than eating animals?
Exam questions on Productivity and energy transfer
- In a grassland ecosystem the gross primary productivity (GPP) of the plants is 14 500 kJ m⁻² year⁻¹. The plants lose 6 000 kJ m⁻² year⁻¹ as a result of respiration (R).Calculate the percentage of the GPP that is lost in respiration. Show your working.2 marks
- In a food chain in a freshwater ecosystem, the net primary productivity of the producers is 12 000 kJ m⁻² year⁻¹. The energy stored in the biomass of the primary consumers (zooplankton) is 1 080 kJ m⁻² year⁻¹ and the energy stored in the biomass of the secondary consumers (small fish) is 130 kJ m⁻² year⁻¹.The efficiency of transfer from the primary to the secondary consumers is 12.0%, which is greater than the efficiency from the producers to the primary consumers. Suggest why.2 marks
- Over one year a field of maize receives 30 000 kJ m⁻² of light energy. The maize fixes 600 kJ m⁻² in gross primary productivity and loses 200 kJ m⁻² in respiration.Calculate the net primary productivity of the maize and the percentage of the light energy that is converted to net primary productivity. Show your working.3 marks
Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).