What Is the Food Chain?
How energy flows from the Sun through plants, animals, and decomposers — the invisible thread connecting every living thing.
Everything Eats Something
Think about what you had for lunch today. Maybe a sandwich with lettuce and turkey. That lettuce grew using sunlight. That turkey ate grain, which also grew using sunlight. No matter what you eat, if you trace it back far enough, it all starts with the Sun. A food chain is the path that shows how energy moves from one living thing to the next through eating.
Every food chain follows the same basic pattern: energy starts with the Sun, gets captured by plants, and then passes along as animals eat plants and other animals eat those animals. Let's meet the players.
Producers: Where It All Begins
Plants, algae, and some bacteria are called producers because they make their own food. They use sunlight, water, and carbon dioxide to create energy through photosynthesis. Producers are the foundation of every food chain on Earth — without them, nothing else could survive.
In a forest food chain, the producers might be oak trees and wildflowers. In the ocean, tiny floating algae called phytoplankton are the main producers. These microscopic organisms are so numerous that they produce roughly half of all the oxygen on Earth.
Primary Consumers: The Plant Eaters
Animals that eat producers are called primary consumers or herbivores. Think of rabbits munching grass, caterpillars chewing leaves, or deer browsing on shrubs. These animals get their energy directly from plants, so they're the first "link" in the chain after producers.
Primary consumers don't get all the energy the plant originally captured from the Sun. Most of the plant's energy was used by the plant itself to grow, breathe, and stay alive. Only about 10% of the energy stored in a plant gets passed on to the animal that eats it. This is called the 10% rule, and it's one of the most important ideas in ecology.
Secondary and Tertiary Consumers
Animals that eat herbivores are called secondary consumers. A frog eating a caterpillar, a snake eating a mouse, or a small fish eating zooplankton — these are all secondary consumers. Many secondary consumers are predators, meaning they hunt and catch their food.
Some food chains have a third level of consumers called tertiary consumers. A hawk eating a snake that ate a mouse that ate seeds — the hawk is a tertiary consumer. Animals at the top of the food chain with no natural predators are called apex predators. Eagles, great white sharks, and wolves are all examples.
Decomposers: Nature's Recyclers
When plants and animals die, their bodies still contain energy and nutrients. Decomposers like fungi, bacteria, and earthworms break down dead matter and return nutrients to the soil. Those nutrients feed new plants, and the whole chain starts over again. Without decomposers, dead material would pile up everywhere and plants would run out of nutrients to grow.
Food Chains vs. Food Webs
In reality, most animals eat more than one thing. A robin eats worms, berries, and insects. A bear eats fish, berries, honey, and roots. When you connect all the food chains in an ecosystem together, you get a food web — a complex network showing all the feeding relationships in a community. Food webs show why removing just one species can affect dozens of others.
Because of the 10% rule, it takes about 10,000 pounds of phytoplankton to support just 1 pound of tuna. That's why top predators are always rarer than the animals below them — there simply isn't enough energy to support huge populations at the top of the chain.
Last reviewed: April 2026