In the context of energy transfer in ecosystems, what does the $10\%$ rule refer to, and why is energy lost at each trophic level?

• A. The $10\%$ rule indicates that $10\%$ of energy is converted into biomass, with energy lost due to gravitational forces.
• B. The $10\%$ rule states that only $10\%$ of energy is transferred to the next trophic level, with energy lost primarily as heat.
• C. The $10\%$ rule implies that $10\%$ of energy is used for reproduction, with energy lost due to friction.
• D. The $10\%$ rule suggests that $10\%$ of energy is stored in chemical bonds, with energy lost through nuclear reactions.

Answer: (B)

Verified step by step guidance

1. Understand the concept of the '10% rule' in ecology: It refers to the observation that, on average, only about 10% of the energy at one trophic level is transferred to the next level in an ecosystem.
2. Recognize that energy is lost at each trophic level primarily as heat due to metabolic processes. Organisms use energy for growth, reproduction, and maintenance, and much of this energy is dissipated as heat.
3. Clarify that the energy transfer is not due to gravitational forces or friction, as these are not significant factors in energy loss in biological systems.
4. Note that the energy is not lost through nuclear reactions in biological contexts. Instead, it is the inefficiency of energy transfer in biological processes that leads to energy loss.
5. Conclude that the 10% rule highlights the inefficiency of energy transfer in ecosystems, emphasizing the importance of energy conservation and the role of producers in capturing solar energy.