What organisms bring carbon from the atmosphere into the food chain?

Plants, specifically through the process of photosynthesis, are the primary organisms that bring carbon from the atmosphere into the food chain. They absorb carbon dioxide and convert it into organic matter, which serves as a food source for herbivores. These herbivores are then consumed by carnivores, thereby transferring carbon through various trophic levels within the ecosystem. Additionally, some algae and cyanobacteria also play a significant role in this process in aquatic environments.