Which of the following best distinguishes an ecosystem driven by photosynthesis from one driven by chemosynthesis?

• A. Both photosynthetic and chemosynthetic ecosystems require sunlight to produce organic molecules.
• B. Photosynthetic ecosystems rely on sunlight as the primary energy source, while chemosynthetic ecosystems obtain energy from inorganic chemical reactions.
• C. Chemosynthetic ecosystems are only found on land, whereas photosynthetic ecosystems are only found in aquatic environments.
• D. Photosynthetic ecosystems do not produce oxygen, while chemosynthetic ecosystems do.

Answer: (B)

Verified step by step guidance

1. Understand the key terms: Photosynthesis is the process by which organisms, such as plants and algae, use sunlight to convert carbon dioxide and water into glucose and oxygen. Chemosynthesis, on the other hand, is the process by which certain organisms, such as bacteria, use energy derived from inorganic chemical reactions (e.g., oxidation of hydrogen sulfide) to produce organic molecules.
2. Identify the primary energy source for each process: Photosynthetic ecosystems rely on sunlight as the primary energy source, while chemosynthetic ecosystems derive energy from inorganic chemical reactions, often in environments where sunlight is unavailable (e.g., deep-sea hydrothermal vents).
3. Evaluate the statement about sunlight: The claim that both photosynthetic and chemosynthetic ecosystems require sunlight is incorrect because chemosynthetic ecosystems do not depend on sunlight at all.
4. Analyze the environmental context: The statement that chemosynthetic ecosystems are only found on land and photosynthetic ecosystems are only aquatic is incorrect. Photosynthetic ecosystems are found in both terrestrial and aquatic environments, while chemosynthetic ecosystems are often found in extreme environments, such as deep-sea vents, which are aquatic.
5. Assess oxygen production: Photosynthetic ecosystems produce oxygen as a byproduct of splitting water molecules during the light-dependent reactions. Chemosynthetic ecosystems do not produce oxygen as a byproduct, so the statement that chemosynthetic ecosystems produce oxygen is incorrect.