Food webs and food chains

In a food chain or web, each arrow shows who eats whom. The arrow starts at the organism that is eaten and points to the organism that eats it. Grass → grasshopper reads: the grasshopper eats the grass. If you follow the arrows, you follow the energy. Each meal transfers energy and matter from one living thing to another, and the arrow is the road map of that transfer.

Think of the arrow as an energy road, not a size ranking. A snake is larger than a mouse, but the arrow goes from the mouse to the snake because the snake eats the mouse. The direction never changes with size, speed or strength; it changes only with what eats what. Reading arrows backward turns a food web into a map of a ghost meal.

Food chains all start the same way. Producers, mostly plants and algae, capture the Sun's energy with photosynthesis. They are the only living things that create food energy for the rest of the web. Every animal, from a grasshopper to a hawk, is a consumer that gets its energy by eating something whose energy traced back to a producer. An energy road without a producer at the start has no fuel.

A food web is many chains joined together, because most animals eat several foods and are eaten by several predators. The web is more realistic than a single chain: if one food disappears, the web shows which other meals can save the animal. Whatever organism you follow, the rule never changes: arrows point from the eaten to the eater, tracing exactly where the energy goes.