Every ecosystem depends on the movement of energy. Most energy begins with the Sun, which plants use during photosynthesis to make food.
Plants are called producers because they make their own food. Animals that eat plants are called primary consumers, while animals that eat other animals are secondary or tertiary consumers. Decomposers such as fungi and bacteria break down dead organisms and return nutrients to the soil.
A food chain shows one path of energy flow, while a food web connects many food chains together, showing how organisms depend on one another.