Energy Loss Through Biological Processes

Steps:

• Define processes: Excretion removes waste containing stored energy; photosynthesis captures solar energy to build biomass; respiration breaks down food, releasing energy with some lost as heat.
• Assess energy flow: In food chains, energy enters via photosynthesis but decreases at each trophic level due to inefficiencies.
• Identify losses: Excretion ejects undigested matter with energy out of the chain; respiration dissipates energy as heat, unavailable for transfer.
• Determine impact: Only excretion and respiration cause net energy loss from the chain's usable pool.

Why B is correct:

• Excretion and respiration both remove energy from the food chain—excretion via waste biomass and respiration via the second law of thermodynamics, where heat loss prevents 100% transfer efficiency.

Why the others are wrong:

• A: Photosynthesis inputs energy, not loses it.
• C: Photosynthesis adds energy to the chain.
• D: Excretion also causes energy loss through waste removal.

Final answer: B