A food chain shows the path that energy takes as it moves from one living thing to another through eating. It starts with the sun, which gives energy to plants. Then an animal eats the plant, another animal eats that animal, and so on, creating a chain of who eats whom.

Here's how it works: sunlight helps grass grow. A grasshopper eats the grass. A frog eats the grasshopper. A snake eats the frog. A hawk eats the snake. Each step is called a link in the chain. Scientists use arrows to show the direction energy flows: grass → grasshopper → frog → snake → hawk.

Every food chain starts with a producer, usually a plant that makes its own food from sunlight. Animals that eat plants are herbivores, animals that eat other animals are carnivores, and animals that eat both are omnivores. At the end of most chains are decomposers like bacteria and fungi, which break down dead plants and animals and return nutrients to the soil.

In nature, food chains overlap and connect into complex webs called food webs. If one link disappears, it affects everything connected to it. When wolves were removed from Yellowstone National Park, deer populations exploded and ate too many plants, which changed the entire ecosystem. Understanding food chains helps scientists protect environments and predict what happens when something changes.