In the context of energy flow through ecosystems, which of the following best explains why less than 0.1% of the energy from the sun ultimately reaches decomposers in a food chain?

• A. Most energy is lost as heat at each trophic level due to metabolic processes.
• B. Producers absorb nearly all the solar energy, leaving none for higher trophic levels.
• C. Energy is destroyed as it moves through the food chain.
• D. Decomposers are unable to utilize any energy from organic matter.

Answer: (A)

Verified step by step guidance

1. Step 1: Understand the concept of energy flow in ecosystems. Energy enters ecosystems through producers (e.g., plants, algae) that capture solar energy via photosynthesis. This energy is then transferred through various trophic levels (primary consumers, secondary consumers, etc.) in the food chain.
2. Step 2: Recognize that energy transfer between trophic levels is inefficient. According to the 10% rule, only about 10% of the energy at one trophic level is passed on to the next level. The rest is lost as heat due to metabolic processes such as respiration, movement, and maintaining body temperature.
3. Step 3: Consider the role of decomposers. Decomposers (e.g., fungi, bacteria) break down organic matter from dead organisms and waste products, recycling nutrients back into the ecosystem. However, the energy available to decomposers is a fraction of the original solar energy because most of it has already been lost as heat through the food chain.
4. Step 4: Evaluate the incorrect options. Energy is not destroyed as it moves through the food chain (violating the law of conservation of energy). Producers do not absorb all solar energy; they only capture a small portion. Decomposers can utilize energy from organic matter, but the amount is minimal due to prior energy losses.
5. Step 5: Conclude that the correct explanation is: 'Most energy is lost as heat at each trophic level due to metabolic processes.' This aligns with the principles of energy flow and the inefficiency of energy transfer in ecosystems.