Which process do both plants and animals perform to add carbon to the atmosphere?

• A. Transpiration
• B. Photosynthesis
• C. Nitrogen fixation
• D. Cellular respiration

Answer: (D)

Verified step by step guidance

1. Understand the question: The problem asks which process adds carbon to the atmosphere and is performed by both plants and animals. This requires knowledge of biological processes that release carbon dioxide (CO₂).
2. Review the options: Transpiration involves water movement in plants, photosynthesis absorbs CO₂ to produce glucose, and nitrogen fixation converts nitrogen gas into usable forms. Cellular respiration is the process where organisms break down glucose to release energy, producing CO₂ as a byproduct.
3. Focus on cellular respiration: Cellular respiration occurs in the mitochondria of both plant and animal cells. During this process, glucose (C₆H₁₂O₆) reacts with oxygen (O₂) to produce energy, water (H₂O), and carbon dioxide (CO₂). The chemical equation for cellular respiration is: $C_6{H}_{12}{O}_6+6O_2\to 6{\mathrm{CO}}_2+6H_{2}O$.
4. Explain why cellular respiration adds carbon to the atmosphere: During cellular respiration, CO₂ is released as a waste product and diffuses into the atmosphere. This process is common to all aerobic organisms, including plants and animals.
5. Conclude: Cellular respiration is the correct answer because it is the process by which both plants and animals release carbon dioxide into the atmosphere, contributing to the carbon cycle.