Neco Model Questions Vol1 2017 Biology Question 47

Lake A and Lake B are freshwater ecosystems. In each lake, the biomass of producers, primary consumers and secondary consumers is given in g m⁻² as follows: - Lake A: producers 2000, primary consumers 300, secondary consumers 50. - Lake B: producers 1800, primary consumers 360, secondary consumers 60. All organisms have an energy content of \(4\ \text{kJ}\,\text{g}^{-1}\). (a) Calculate the total energy (in kJ m⁻²) stored in each trophic level for both lakes. (b) Assuming that the energy transferred from one trophic level to the next is the ratio of the consumer energy to the producer (or preceding consumer) energy, compute the ecological efficiency (%) for the transfer from producers to primary consumers and from primary to secondary consumers in each lake. (c) Determine the overall efficiency from producers to secondary consumers for each lake and state which lake has the higher overall efficiency. (d) If 60 % of the producer energy is used for respiration, calculate the net primary productivity (NPP) for each lake. Which lake has the greater NPP?