The food chain describes who eats whom in the wild. Every living thing needs food to survive. Each food chain is a possible pathway that energy and nutrients can follow through the ecosystem. Different habitats and ecosystems provide many possible food chains that make up a food web. In a grassland ecosystem, a grasshopper might eat grass, a producer. The grasshopper might get eaten by a rat, which in turn is consumed by a snake. Finally, a hawk—an apex predator—swoops down and snatches up the snake.

Source: Natural Geographic