During photosynthesis, plants take in carbon dioxide (CO2) from the atmosphere. This process is essential for converting light energy into chemical energy, allowing plants to produce glucose and oxygen as by-products. In the presence of sunlight, chlorophyll in the chloroplasts absorbs light energy, facilitating the combination of carbon dioxide and water to create glucose. Photosynthesis plays a critical role in the Earth's ecosystem, as it provides food and energy for plants, which, in turn, support herbivores and higher trophic levels. Additionally, this process is vital for maintaining atmospheric oxygen levels.