Ecological Efficiency
Energy transfer between trophic levels (~10%).
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~10% per level
How it works
Ecological efficiency tells you what fraction of energy stored in one trophic level is passed on to the next level, such as from plants to herbivores or from herbivores to carnivores. It is usually low because organisms use most of the energy they take in for respiration, movement, growth, and heat loss, so only a small amount becomes new biomass available to the next level. The result is expressed as a percentage by comparing the energy at the higher trophic level to the energy at the lower one.
When to use it
Use this formula when analyzing food chains, food webs, or energy pyramids in ecology. It is also useful for comparing how efficiently different ecosystems or feeding relationships transfer energy between trophic levels.
Worked example, step by step
A meadow ecosystem has 8,000 kJ of energy stored in grass at the producer level. Deer eating the grass store 920 kJ of energy in their biomass. Use the formula: E = (energy at level n+1 / energy at level n) × 100 E = (920 / 8000) × 100 E = 0.115 × 100 E = 11.5% So, the ecological efficiency from grass to deer is 11.5%.
Common mistakes to avoid
- using energy lost as the numerator instead of energy transferred to the next level
- mixing up trophic levels and comparing organisms that are not directly linked in the chain
- forgetting to multiply by 100 so the result is left as a decimal instead of a percentage
Did You Know?
Bigger mammals generally have longer pregnancies, from a mouse's three weeks to an elephant's nearly two years.
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