A primary producer uses sunlight for photosynthesis, converting light energy into chemical energy stored in glucose and other organic compounds. This process occurs in chloroplasts, where chlorophyll captures sunlight, enabling the conversion of carbon dioxide and water into sugars and oxygen. Primary producers, such as plants and algae, are foundational to food chains, as they provide energy for herbivores and, subsequently, for higher trophic levels. Thus, photosynthesis is critical for sustaining life on Earth and maintaining ecosystem health.