The correct option is 10 %.
Explanation
The flow of energy through an ecosystem is unidirectional and governed by the laws of thermodynamics. The efficiency of energy transfer between trophic levels is described by the Ten % Law, proposed by Raymond Lindeman in 1942.
Detailed Analysis
According to this law, during the transfer of organic food energy from one trophic level to the next higher level, only about 10 % of the energy is stored as flesh (biomass) and becomes available to the next consumer. The remaining energy is utilized or lost through various processes:
- Metabolic Activities: A significant portion is used for respiration, movement, and reproduction.
- Heat Loss: Energy is dissipated into the environment as heat (consistent with the second law of thermodynamics).
- Unassimilated Waste: Some energy is lost in excretion and non-digestible matter.
Consequently, 10 % is correct, while options 1 %, 50 %, and 90 % are incorrect representations of ecological efficiency.
Key Takeaway: Energy flow in an ecosystem follows the 10% law, meaning energy diminishes at each successive trophic level, which restricts the length of food chains to usually 3 to 5 levels.