Food Chain and Food Web

Food chain and food web represent how living organisms feed to get the energy that sustains their growth, reproduction, and movement in their respective ecological systems. It is because the various communities of organisms in an ecosystem have to feed on each other to survive. This feeding relationship in the ecosystem is thus what brings about the two terminologies food chain and food web. A food chain is one possible path that energy and nutrients may take as they move through the ecosystem and all the interconnected food chains in an ecosystem make up a food web.

Without sharks, you take away the apex predator of the ocean, and you destroy the entire food chain.
~ Peter Benchley


What is Food Chain?

A food chain represents the sequence of the feeding relationship as the energy transfers from one trophic level to the next. Simply put, a food chain defines “who is eating who.” Food chains often follow a sequence of one path, with an arrow pointing the eater – used to indicate the flow of energy or “who is eating who.”

Photosynthesis is only the beginning of the food chain. In a food chain, for instance, green plants make their own food by the process of photosynthesis, smaller insects, and some bigger animals feed on the green plants, predators and carnivores then feed on insects and other bigger animals that feed on grass, and the chain goes on through all the higher consumer categories. While these animals eat plants, food and organic compounds are transferred from the plants to the animals.

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These animals are then eaten by other animals which again transfers the energy from one animal to another. A food chain basically describes how energy and nutrients move through an ecosystem.

Wikipedia defines food chain as,

A food chain is a linear network of links in a food web starting from producer organisms (such as grass or trees which use radiation from the sun to make their food) and ending at apex predator species (like grizzly bears or killer whales), detritivores (like earthworms or woodlice), or decomposer species (such as fungi or bacteria). A food chain also shows how the organisms are related with each other by the food they eat. Each level of a food chain represents a different trophic level.

Here is a simple example where a grasshopper eats grass, a toad eats the grasshopper, a snake eats the toad, and then the snake is eaten by a hawk.

Grass —-> Grasshopper —-> Toad —-> Snake —-> Hawk

What is Food Web?

On the other hand, in the event that the same feeding organisms operate at more than one trophic level, then the feeding relationship is termed as a food web. A food web is comprised of many or complex food chains since the energy flow takes many different paths and shows how the ecosystem feeding relationship is interconnected by different paths. A food web basically consists of all the food chains in a single ecosystem and each living thing in an ecosystem is part of multiple food chains.

In a food web, organisms are eaten by any number of consumer populations. Therefore, a cycle of connection between food chains which are interlinked to form a web-like pattern is defined as a food web. Organisms in food webs are grouped into categories called trophic levels like producers (first trophic level which include green plants), consumers which is further divided into primary consumers (which includes deer, mice, rabbit), secondary consumers (includes snakes) and tertiary consumers (includes owl or eagle) and decomposers (includes scavengers such as vultures and eagles).

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In a food web, for instance, the hawk may also eat a squirrel, a bird, a frog, or even a mouse and other animals. The snake might also eat a caterpillar, a rabbit, a beetle or other animals. The toad may also eat a caterpillar and some other insects, and the feeding relationship occurs similarly for all other animals in the food chain.

Main Differences Between a Food Chain and a Food Web

The basic difference between food chain and food web is that flow of energy is in linear direction in food chain while in food web it is in multiple directions. Wikipedia says, “A food chain differs from a food web, because the complex network of different animals’ feeding relations are aggregated and the chain only follows a direct, linear pathway of one animal at a time. A common metric used to quantify food web trophic structure is food chain length. In its simplest form, the length of a chain is the number of links between a trophic consumer and the base of the web and the mean chain length of an entire web is the arithmetic average of the lengths of all chains in a food web.”

Food Chain

  • Food chain indicates the flow of energy in the ecosystem in one linear direction
  • Nutrients and energy are passed from one trophic level to the next
  • The eater at the higher trophic level feeds on a single type of organism of the lower trophic level
  • Isolated and separate food chains results in instability in the ecosystem, that is, when on organism is removed from the food chain energy and nutrient flow is hampered
  • Food chains have no implications for improving the competitiveness and adaptability of the organisms in the ecosystem because food energy travels in a single pathway
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Food Web

  • Food web indicates the feeding relationship between other organisms in different directions
  • Food web represents the number of interconnected food chains by which nutrients and energy flow in the entire ecosystem
  • The eater at the higher trophic level feeds on several types of organism of the lower trophic levels
  • Because the food web is complex and interlinked, isolation of a single organism category doesn’t hamper ecosystem stability. Thus, food webs often increase ecosystem stability
  • Since food webs are complex and interlinked, they can significantly improve competitiveness and adaptability of organisms in the ecosystem
Sources: National Geographic
Photo by: Cat Burton

Sonia Madaan is a writer and founding editor of science education blog EarthEclipse. Her passion for science education drove her to start EarthEclipse with the sole objective of finding and sharing fun and interesting science facts. She loves writing on topics related to space, environment, chemistry, biology, geology and geography. When she is not writing, she loves watching sci-fi movies on Netflix.