The gas released during photosynthesis is oxygen. Photosynthesis occurs in plants, algae, and some bacteria, allowing them to convert sunlight, carbon dioxide, and water into glucose and oxygen. The process primarily takes place in chloroplasts, where chlorophyll captures light energy. During photosynthesis, carbon dioxide is absorbed from the atmosphere, while water is taken up by roots. As a byproduct, oxygen is released into the atmosphere, significantly contributing to the planet's breathable air. This process is vital for sustaining life on Earth, as it provides oxygen for most living organisms and is foundational to the food chain.