Example of Food Chain and Food Web: How Ecosystems Connect

A food chain is a single, linear path of energy transfer that starts with a producer—an organism like grass or algae that makes its own food—and ends with an apex predator, a detritivore, or a decomposer. A food web is the interconnected network of many such chains within one ecosystem. The most familiar illustration of both is grass → grasshopper → frog → snake → hawk as a single chain, and that same chain woven together with dozens of others as a web. The distinction matters because real ecosystems rarely run in straight lines; energy branches, overlaps, and loops back through the soil.

Food Chain Basics

A food chain describes energy moving in one direction, one link at a time, with no branching. Each link sits at a trophic level, meaning its position in the feeding sequence. The first level is always the primary producers, or autotrophs—plants, algae, and some bacteria that convert sunlight or inorganic chemicals into stored energy. Every level above them holds consumers: primary consumers (herbivores) eat producers, secondary consumers eat herbivores, and tertiary consumers eat other carnivores. At the top sits an apex predator with no natural predators in that chain, such as a killer whale or a grizzly bear.

When organisms at any level die, detritivores like earthworms and decomposers like fungi and bacteria break down their remains, returning simple nutrients to the soil for producers to reuse. This closes the loop rather than ending it. The modern concept of these feeding relationships is often associated with the ecologist Charles Elton, though the underlying idea traces back much further, as outlined in Wikipedia’s overview of food chains.

A Simple Grassland Chain

Consider a prairie:

• Producer: prairie grass captures sunlight.
• Primary consumer: a grasshopper eats the grass.
• Secondary consumer: a meadowlark eats the grasshopper.
• Tertiary consumer: a prairie falcon eats the meadowlark.
• Decomposers: bacteria and fungi break down the falcon’s remains after death.

Each arrow represents energy passing from one organism to the next—and a large share of that energy is lost as heat along the way.

Food Web Explained

A food web connects multiple food chains into one non-linear map of who eats whom. Because most animals eat more than one thing, and most are eaten by more than one predator, a single chain is really just one thread pulled from a much larger fabric. A meadowlark might eat grasshoppers, beetles, and seeds; a falcon might hunt meadowlarks, mice, and snakes. Draw all of those links together and you have a web.

This realism has a practical payoff: resilience. If one prey species declines in a web, a predator can often shift to another. In a lone chain, that same decline can cut the line entirely. Food webs also let ecologists estimate chain length—the number of links between a consumer and the base of the chain—which is one common way to quantify these systems, as noted by the National Geographic Society.

Real Ecosystem Examples

Different ecosystems build their webs from different foundations, but the underlying logic stays the same.

Grasslands. A savanna web includes grasses, acacia leaves, zebras, gazelles, lions, cheetahs, and vultures, with termites and dung beetles recycling nutrients. Remove the grasses and the entire structure collapses upward.

Oceans. In open water, phytoplankton form the base, consumed by zooplankton, then small fish like sardines, then larger predators such as tuna, and finally apex predators like killer whales. Near hydrothermal vents, chemosynthetic bacteria use hydrogen sulfide instead of sunlight to produce energy, forming the base of a chain in total darkness—an exception that shows life does not always need the sun.

Forests. A temperate woodland web runs from oak leaves and acorns to caterpillars, mice, and deer, then to owls, foxes, and hawks. Fallen leaves feed earthworms and fungi, whose waste returns nitrogen and phosphorus to the trees. The U.S. National Park Service documents how these interlocking roles sustain protected habitats across its park ecosystems.

Why Connections Matter

Energy enters every ecosystem through its producers, and the total energy available at each higher level shrinks because organisms use most of what they consume for their own metabolism. This is why top predators are relatively rare and why a web with more pathways tends to be more stable than a single chain.

Keystone species deserve special attention. A keystone species has an outsized effect on its ecosystem relative to its abundance—remove it and the balance can fail. Sea otters, for example, control sea urchins that would otherwise graze kelp forests to nothing. Encyclopaedia Britannica notes that even one missing component can raise extinction risk or sharply cut a species’ survival odds (Encyclopaedia Britannica).

The lesson is straightforward: connections, not isolated links, determine whether an ecosystem thrives.

Energy Flow and the Ten Percent Idea

Not all the energy an organism eats becomes usable growth. Most is spent on movement, body heat, and basic metabolism, so only a fraction—commonly taught as roughly 10 percent—passes to the next trophic level. That rough figure, often called the ten percent rule, explains a lot about ecosystem shape. It is why biomass pyramids taper: you need many acres of grass to feed a modest herd of gazelles, and far more gazelles to support a single pride of lions.

This energy loss, not aggression or competition alone, sets a natural ceiling on how many links a chain can hold. Those uneaten parts—bones, shells, and roots—are not truly lost; they re-enter the system through the recycling work of fungi, bacteria, and detritivores.

Producers: Two Ways to Start a Chain

Most chains begin with photosynthesis, where plants, algae, and cyanobacteria convert sunlight, water, and carbon dioxide into sugars. But a smaller set of ecosystems starts differently. At hydrothermal vents and cold seeps, chemosynthetic bacteria and archaea use hydrogen sulfide and methane as their energy source, building carbohydrates without any sunlight. These microbes anchor food chains in the deep ocean where photosynthesis is impossible.

Ecologists often split webs into two channels:

• Grazing food web: living plants are eaten by herbivores, which are eaten by predators.
• Detrital food web: dead leaves, fallen logs, and animal remains feed detritivores and decomposers first.

In many forests the detrital channel carries more energy than the grazing one. A single fallen oak log can support beetle larvae, millipedes, fungi, and the salamanders that hunt them—an entire web running on death and decay rather than fresh greenery.

Trophic Cascades in Practice

A trophic cascade happens when a change at one level ripples through the others. When wolves were restored to Yellowstone, elk changed how they browsed near streams, willow and aspen recovered, and beavers and songbirds returned. The predator did not just eat prey; it reshaped the habitat. Such cascades show that a web’s connections run both downward and upward, and that a single species can steer the fate of many others.

Key Takeaways

• A food chain is a single linear path of energy from producers to consumers, ending at an apex predator, detritivore, or decomposer.
• A food web links many food chains together and better reflects how real ecosystems function, which is why it is more resilient.
• Trophic levels describe an organism’s feeding position: producers at the base, then primary, secondary, and tertiary consumers above.
• Decomposers and detritivores recycle nutrients back to producers, closing the energy loop.
• Only a small fraction of energy—often cited near 10 percent—moves to the next trophic level, which limits chain length.
• Chains can begin with photosynthesis or, in the deep sea, with chemosynthesis.
• Keystone species hold webs together; removing one link, as in a trophic cascade, can destabilize an entire ecosystem.