Carbon enters the food chain through the work of plants and other photosynthetic organisms, like plants for an example, they can take in carbon dioxide from the air, and fix it. Life on Earth is carbon based. All of the organic molecules we use contain the element carbon. It is incredibly versatile and important to living things. Carbon is found in carbohydrates, lipids, proteins, and nucleic acids. Without carbon, life on Earth would probably not exist. Hope this helps!