Igcse Model Questions Vol1 2023 Biology Question 24

In a grassland ecosystem primary production is 8000 kJ m\(^{-2}\) yr\(^{-1}\). Herbivores convert 10 % of the energy they ingest into biomass, and secondary consumers convert 15 % of the energy they ingest into biomass. The measured herbivore biomass is 150 kJ m\(^{-2}\).\n\n(a) Estimate the biomass of secondary consumers in the grassland.\n\nIn a forest ecosystem primary production is 6000 kJ m\(^{-2}\) yr\(^{-1}\). Herbivores convert 12 % of ingested energy into biomass and secondary consumers convert 20 % of ingested energy into biomass.\n\n(b) Calculate the ratio (as a percentage) of secondary‑consumer biomass to primary production for each ecosystem and state which ecosystem has the higher overall trophic efficiency.