Energy Efficiency

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•  Energy losses between trophic levels restrict the length of food chains and the biomass of higher trophic levels

When energy transformations take place in living organisms the process is never 100% efficient

  • Most of the energy is lost to the organism – either used in respiration, released as heat, excreted in faeces or unconsumed
  • Typically energy transformations are ~10% efficient, with about 90% of available energy lost between trophic levels
  • The amount of energy transferred depends on how efficiently organisms can capture and use energy (usually between 5 – 20%)

As energy is lost between trophic levels, higher trophic levels store less energy as carbon compounds and so have less biomass

  • Biomass is the total mass of a group of organisms – consisting of the carbon compounds contained in the cells and tissues
  • Because carbon compounds store energy, scientists can measure the amount of energy added to organisms as biomass
  • Biomass diminishes along food chains with the loss of carbon dioxide, water and waste products (e.g. urea) to the environment 

Because energy and biomass is lost between each level of a food chain, the number of potential trophic levels are limited

  • Higher trophic levels receive less energy / biomass from feeding and so need to eat larger quantities to obtain sufficient amounts
  • Because higher trophic levels need to eat more, they expend more energy (and biomass) hunting for food
  • If the energy required to hunt food exceeds the energy available from the food eaten, the trophic level becomes unviable

Representation of Energy Flow Along a Food Chain

energy efficiency