Question

At each trophic transfer, what percentage of energy is typically available to the next trophic level?

• A. A) 1-5%
• B. B) 10-20%
• C. C) 50-60%
• D. D) 90-95%

Answer 1

Answer:

B. B) 10-20%

Energy Transfer in Trophic Levels: The 10% Rule

• An ecosystem is a community of living organisms (biotic components) interacting with their non-living environment (abiotic components). Energy flows through an ecosystem in a unidirectional manner.
• Trophic levels represent the different feeding positions in a food chain or food web. They indicate how energy moves from one organism to another.
• The typical percentage of energy available to the next trophic level at each transfer is commonly referred to as the "10% Rule" or Lindeman's 10% Law, though in reality, it can range from 10% to 20%.
• This rule states that only about 10% of the energy from one trophic level is incorporated into the biomass of the next trophic level. The remaining 90% (or 80-90%) of energy is lost or utilized for various purposes.

• Reasons for Energy Loss:

  • A significant portion of energy is lost as heat during metabolic processes (respiration, digestion, movement) by the organisms at each trophic level.
  • Not all biomass from one trophic level is consumed by the next (e.g., bones, fur, wood).
  • Not all consumed biomass is assimilated or digested; some is egested as waste.

• Implications for Ecosystems:

  • Due to this significant energy loss at each transfer, the amount of energy available decreases progressively at higher trophic levels.
  • This energy loss limits the number of trophic levels in an ecosystem, typically to 4 or 5 levels, as there isn't enough energy to support a large population at very high trophic levels.
  • This concept is visually represented by Ecological Pyramids, especially the Pyramid of Energy.
  • The Pyramid of Energy is always upright because energy flow is always unidirectional and decreases at successive trophic levels. It can never be inverted.
  • Producers (autotrophs like plants) form the base (first trophic level) and have the largest amount of energy.
  • Primary Consumers (herbivores) consume producers (second trophic level).
  • Secondary Consumers (carnivores that eat herbivores) are the third trophic level.
  • Tertiary Consumers (carnivores that eat other carnivores) are the fourth trophic level.
  • This fundamental principle explains why there are usually fewer large predators at the top of the food chain compared to the vast number of producers at the base.