Energy Flow and the Second Law of Thermodynamics

Steps:

• Energy enters ecosystems via sunlight captured by producers through photosynthesis.
• It transfers through trophic levels as organisms consume each other, with only 10% efficiency per level.
• At each transfer, most energy is lost as heat from metabolic processes.
• Ultimately, all energy dissipates as heat, leaving the ecosystem.

Why A is correct:

• The second law of thermodynamics states that energy transformations increase entropy, resulting in irreversible loss as heat, preventing full recycling.

Why the others are wrong:

• B: Decomposers recycle nutrients, not energy, which cannot be reused once lost as heat.
• C: Producers capture new solar energy but do not account for the total energy already in the system.
• D: Top carnivores use a tiny fraction of energy, which is still lost as heat after their metabolism.

Final answer: A