Explain why eating food from higher trophic levels is less efficient for feeding large human populations than eating food from lower trophic levels.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Global food security is an increasing concern. Scientists suggest that humans eating more plant-based diets could help feed more people worldwide.
Model answer (4 marks)
Biomass is lost at each trophic level due to energy conversion inefficiencies.
Respiration, movement and heat loss further reduce the energy that can be transferred to the next level.
Consequently, the amount of biomass available at higher trophic levels (animals) is much lower than that of producers (plants).
Eating plants directly therefore provides more biomass per unit area for a large human population.
Respiration, movement and heat loss further reduce the energy that can be transferred to the next level.
Consequently, the amount of biomass available at higher trophic levels (animals) is much lower than that of producers (plants).
Eating plants directly therefore provides more biomass per unit area for a large human population.
Examiner tips
- Use the term ‘trophic level’ and ‘biomass’. Explain the loss of energy at each step. Show the final comparison of plant vs animal biomass. Keep the answer concise and to the point.
Common mistakes
- Confusing ‘energy’ with ‘biomass’. Failing to mention respiration/heat loss. Giving examples that are not directly related to the question.
Mark scheme (4 marks)
- Biomass is lost at each trophic level
- Biomass is lost through respiration / movement / heat
- So less biomass is available at higher trophic levels (e.g. animals) compared to producers / plants
- Therefore eating plants / producers directly means more biomass is available to feed more people
Key terms in this question
Related
- Revision notes: Food production (Bio only) →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →