During photosynthesis, plants absorb carbon dioxide (CO₂) from the atmosphere. Through this process, plants utilize sunlight to convert carbon dioxide and water into glucose and oxygen, which they use for energy and growth. The absorbed carbon dioxide is crucial for the formation of glucose during the light-independent reactions (Calvin cycle) of photosynthesis. This transformation not only sustains the plant but also contributes to the oxygen levels in the atmosphere, making it vital for the survival of aerobic organisms, including humans. Overall, photosynthesis is fundamental to life on Earth, supporting the food chain and oxygen supply.