In a salt marsh ecosystem, the gross primary productivity (GPPGPPGPP) of the vegetation is 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 plants lose 55% of this energy through respiration.
The primary consumers in this ecosystem ingest 40% of the resulting net primary productivity (NPPNPPNPP). Of this ingested chemical energy, 60% is lost as faeces and urine, and 25% is lost to the environment through consumer respiration.
Calculate the net secondary productivity (NNN) of these primary consumers in kJ m−2 yr−1\text{kJ m}^{-2} \text{ yr}^{-1}kJ m−2 yr−1.
9.72×102 kJ m−2 yr−19.72 \times 10^2 \text{ kJ m}^{-2} \text{ yr}^{-1}9.72×102 kJ m−2 yr−1
1.19×103 kJ m−2 yr−11.19 \times 10^3 \text{ kJ m}^{-2} \text{ yr}^{-1}1.19×103 kJ m−2 yr−1
2.16×103 kJ m−2 yr−12.16 \times 10^3 \text{ kJ m}^{-2} \text{ yr}^{-1}2.16×103 kJ m−2 yr−1
2.43×103 kJ m−2 yr−12.43 \times 10^3 \text{ kJ m}^{-2} \text{ yr}^{-1}2.43×103 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.