In a grassland ecosystem, the gross primary productivity (GPPGPPGPP) of the plant community is measured as 4.0×104 kJ m−2 yr−14.0 \times 10^4 \text{ kJ m}^{-2}\text{ yr}^{-1}4.0×104 kJ m−2 yr−1. The plants lose 65% of this energy as heat through cellular respiration.
Primary consumers in this ecosystem ingest 2.8×103 kJ m−2 yr−12.8 \times 10^3 \text{ kJ m}^{-2}\text{ yr}^{-1}2.8×103 kJ m−2 yr−1 of the producer biomass. Of this ingested energy, 1.5×103 kJ m−2 yr−11.5 \times 10^3 \text{ kJ m}^{-2}\text{ yr}^{-1}1.5×103 kJ m−2 yr−1 is lost in faeces and urine, while 6.0×102 kJ m−2 yr−16.0 \times 10^2 \text{ kJ m}^{-2}\text{ yr}^{-1}6.0×102 kJ m−2 yr−1 is lost through cellular respiration.
What is the net secondary productivity (NNN) of the primary consumers expressed as a percentage of the net primary productivity (NPPNPPNPP) of the producers?
1.75%1.75\%1.75%
5.00%5.00\%5.00%
9.29%9.29\%9.29%
20.00%20.00\%20.00%
67 exam-style questions on OCR GCSE Biology 4.1 Ecosystems, covering 4.1.1 Cycling of materials in ecosystems, 4.1.2 Microorganisms in cycling materials, 4.1.3 The carbon and water cycles, 4.1.4 Factors affecting decomposition, 4.1.5 Levels of organisation in an ecosystem, 4.1.6 Abiotic and biotic factors affecting communities, 4.1.7 Interdependence and competition, 4.1.8 Trophic levels, 4.1.9 Pyramids of biomass, and 4.1.10 Efficiency of biomass transfers. Each one has a worked solution and a mark scheme showing where the marks go.