An ecological study of a grassland ecosystem measures the energy flow through a population of grasshoppers (primary consumers). The grasshoppers ingest grass containing 2.40×106 kJ m−2 yr−12.40 \times 10^6 \text{ kJ m}^{-2} \text{ yr}^{-1}2.40×106 kJ m−2 yr−1 of energy. They lose 1.08×106 kJ m−2 yr−11.08 \times 10^6 \text{ kJ m}^{-2} \text{ yr}^{-1}1.08×106 kJ m−2 yr−1 in faeces and excretion, and lose 9.60×105 kJ m−2 yr−19.60 \times 10^5 \text{ kJ m}^{-2} \text{ yr}^{-1}9.60×105 kJ m−2 yr−1 through respiration.
What percentage of the energy ingested by the grasshoppers is converted into biomass available for transfer to the next trophic level (secondary consumers)?
15%15\%15%
40%40\%40%
45%45\%45%
60%60\%60%
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.