A producer in a food chain is an organism that produces its own food through a process called photosynthesis. Producers are also known as autotrophs and are usually plants or algae. Since they make their own food, they are at the bottom of the food chain. Other organisms in the food chain, known as consumers, must eat either plants or animals to obtain energy. Consumers are divided into four types: herbivores, carnivores, omnivores, and decomposers. Herbivores eat only plants, carnivores eat only other animals, and omnivores eat both plants and animals. Decomposers break down dead organisms and waste material, returning nutrients to the soil. The food chain shows the relationships between producers, consumers, and decomposers, and who eats whom with arrows.