Ecological Efficiency

OCR A-level BiologyEcosystemsLesson 7 of 21

Ecological efficiency is the efficiency with which biomass or energy is transferred from one trophic level to the next.

Producers
Plants convert only about 1-3% of the light energy falling on them into chemical energy in biomass. The rest is lost because:
• much of the light is the wrong wavelength, is reflected, or misses chlorophyll entirely;
• photosynthesis is limited by other factors, such as low CO₂ concentration or temperature;
• energy is lost in the reactions of photosynthesis.

The total chemical energy made by plants is gross primary production (GPP). Plants use some of it in their own respiration (R). What remains, stored as new biomass and available to primary consumers, is net primary production (NPP):

More in Ecosystems

• Abiotic Factors
• Producers and Consumers
• Trophic Levels
• Biomass Transfer
• Calculating Efficiency of Biomass Transfer
• Human Activities and Biomass Transfer
• Decomposers
• The Nitrogen Cycle

All 21 lessons in Ecosystems · All OCR A-level Biology topics