Step 2: Recognize the role of photosynthesis in gas recycling. Photosynthesis is a biological process where plants, algae, and some bacteria use sunlight to convert carbon dioxide (CO₂) and water (H₂O) into glucose (C₆H₁₂O₆) and oxygen (O₂). This process removes CO₂ from the atmosphere and produces organic matter, which is essential for life.