In a temperate grassland ecosystem, the gross primary productivity (GPPGPPGPP) is measured as 3.6×104 kJ m−2 yr−13.6 \times 10^4 \text{ kJ m}^{-2} \text{ yr}^{-1}3.6×104 kJ m−2 yr−1. The primary producers (grasses) lose 60% of this energy as heat during respiration. A population of primary consumers (sheep) grazing on this grassland ingests 15% of the net primary productivity (NPPNPPNPP). Of the energy ingested by these sheep, 55% is lost in faeces and urine (FFF), and 35% is lost through respiration (RRR). Calculate the net secondary productivity (NNN) of this sheep population in kJ m−2 yr−1\text{kJ m}^{-2} \text{ yr}^{-1}kJ m−2 yr−1.
216 kJ m−2 yr−1216 \text{ kJ m}^{-2} \text{ yr}^{-1}216 kJ m−2 yr−1
540 kJ m−2 yr−1540 \text{ kJ m}^{-2} \text{ yr}^{-1}540 kJ m−2 yr−1
1944 kJ m−2 yr−11944 \text{ kJ m}^{-2} \text{ yr}^{-1}1944 kJ m−2 yr−1
324 kJ m−2 yr−1324 \text{ kJ m}^{-2} \text{ yr}^{-1}324 kJ m−2 yr−1
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.