Scientists Say: Food web

This is what you get when you combine all of an ecosystem’s food chains

A cheetah chases a gazelle in the Masai Mara National Reserve in Kenya. This predator-prey relationship represents one connection in the overall food chain of this African food web.

James Warwick/Getty Images

Food web, (noun, “FOOD WEB”)

A food web is a map of what organisms eat what other organisms in a given area. Those life forms include all the species in that area, such as plants, animals and even microbes. Food webs represent feeding relationships with arrows. Each arrow points from the species getting eaten (the prey) to the species feeding on them (the predator).

Most species in a food web have feeding relationships with many other species. For example, a rabbit may eat grass, wheat or lettuce. That same rabbit may be eaten by a fox or a hawk. Or it may die of natural causes and be eaten by microbes in the soil. Each possible pathway is called a food chain. And each species is a link in that chain. A food web combines all the individual food chains between every species in a given place, or an ecosystem.

a food web of a freshwater ecosystem shows connections between underwater plants, fish, birds and even a boy sitting onshore, fishing
This food web shows the feeding relationships between species in a freshwater environment. Organisms are grouped according to major feeding categories — primary producers (which get energy from sunlight), primary consumers (which eat primary producers), secondary consumers (which eat primary consumers) and decomposers.K. Schulz, M. Smit, L. Herfort and H. Simon/Front. Young Minds. 2018 (CC-BY)

By showing who eats who, food webs illustrate how energy travels through an ecosystem. Energy enters most ecosystems through plants or algae, which get their energy from sunlight.

Food webs can focus on different aspects of an ecosystem. For example, a food web of a rainforest ecosystem might start with plants, such as Brazil nut trees (Bertholletia excelsa). Those organisms are, in turn, shown being eaten by animals, such as sloths and monkeys. The end of this food web is likely to be top predators, such as jaguars.  

But there are other types of food webs. For example, a detrital food web focuses on decomposers, such as fungi and soil bacteria. For the same rainforest ecosystem, the starting point for a detrital food web would be dead animals and plants.

Scientists use food webs to model the often-complicated feeding relationships between species. That can help scientists predict how changes to one species might affect other species in the ecosystem.

In a sentence

Researchers in Peru’s Amazon rainforest study opossum-eating spiders to learn about this ecosystem’s unusual food web.

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Katie Grace Carpenter is a science writer and curriculum developer, with degrees in biology and biogeochemistry. She also writes science fiction and creates science videos. Katie lives in the U.S. but also spends time in Sweden with her husband, who’s a chef.

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