A food chain shows who eats whom in an ecosystem. It starts with producers — plants and other organisms that make their own food using sunlight — and moves through layers of consumers, each eating the layer below. A simple example: grass → rabbit → fox. The grass is eaten by the rabbit; the rabbit is eaten by the fox.
In reality, most ecosystems have food webs — overlapping, interlocking chains where most animals eat several things and are eaten by several things. The fox doesn't just eat rabbits; it also eats mice, voles, birds, and earthworms. The rabbit is eaten by foxes, hawks, stoats, and weasels. A web is a much more accurate picture than a simple chain.
Think of an ecosystem like a game of Jenga. Each species is a block in the tower. Removing one block (a species going extinct) might do nothing, or might destabilise the whole tower depending on how central that piece is. Removing a predator like wolves from Yellowstone Park, for example, caused elk populations to explode, which caused overgrazing of riverbanks, which caused river erosion, which reduced fish habitat. Everything is connected, even things that seem unrelated.
Producers, consumers, and decomposers
Producers (plants, algae, photosynthetic bacteria) make food from sunlight — they're the foundation. Primary consumers (herbivores) eat producers. Secondary consumers eat herbivores. Tertiary consumers (apex predators) eat secondary consumers. Decomposers (bacteria, fungi, worms) break down dead material at every level, returning nutrients to the soil. Without decomposers, dead bodies and fallen leaves would pile up indefinitely — and the nutrients locked inside them would be lost to the system.
Why are there usually more prey than predators?
Energy is lost at every level of the chain. Only about 10% of the energy in one level transfers to the next — the rest is used for movement, warmth, and biological processes. So to support one lion, you need roughly 10 times its body mass in prey animals, each of which needs 10 times its mass in plants. This is why grasslands full of grass can support large herds of herbivores, but those herds support only a small number of lions.
A food chain shows who eats who in nature. It starts with plants that make their own food using sunlight. Then it moves through animals that eat other animals. A simple example is: grass → rabbit → fox. The grass feeds the rabbit. The rabbit feeds the fox.
Most places in nature have food webs instead of simple chains. A web is like lots of chains mixed together. Most animals eat many different things. Most animals are also eaten by many different things. The fox doesn't just eat rabbits. It also eats mice and birds and worms. The rabbit gets eaten by foxes, hawks and weasels. A web shows nature much better than a simple chain.
Think of nature like a tower of building blocks. Each animal and plant is one block in the tower. Taking away one block might do nothing to the tower. Or it might make the whole tower fall down. It depends how important that block is. When wolves were removed from a park in America, too many deer appeared. The deer ate too much grass near rivers. This made the rivers wash away soil. This hurt the fish living there. Everything in nature is connected, even things that seem separate.
Producers, consumers, and decomposers
Producers are plants and tiny green things that make food from sunlight. They are like the bottom layer of a sandwich. Primary consumers are animals that only eat plants, like rabbits. Secondary consumers eat the plant-eaters, like foxes. Tertiary consumers are the biggest hunters that eat other hunters. Decomposers are bacteria, mushrooms and worms that eat dead things. They break down dead plants and animals. They put nutrients back into the soil. Without decomposers, dead bodies and leaves would pile up everywhere. The good stuff inside them would be wasted.
Why are there usually more prey than predators?
Energy gets lost at every step of the food chain. Only about 10% of energy moves from one level to the next. The rest gets used for moving around and staying warm. So one lion needs about 10 times its weight in prey animals. Each prey animal needs 10 times its weight in plants. This is why grasslands full of grass can feed big herds of plant-eaters. But those herds can only feed a few lions.