Practise calculating the efficiency of biomass and energy transfer between trophic levels. Read values from pyramids of biomass, find what is lost, and work across several levels. New numbers every time, with a worked solution for each step.
The rules
- Efficiency of transfer = biomass at the higher level ÷ biomass at the lower level × 100. The same works for energy.
- Higher level on top. The answer is always less than 100%, because each level has less biomass than the one below it.
- Biomass lost = biomass at the lower level − biomass at the higher level.
- Percentage lost = 100 − efficiency.
- Biomass at the next level = biomass at the lower level × efficiency ÷ 100.
- Use the right pair of levels. Primary consumers eat producers, secondary consumers eat primary consumers. Across two transfers, multiply the efficiencies as decimals.
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