Animals Wildlife What Is a Food Web? Definition, Types, and Examples By Regina Bailey Regina Bailey Writer Emory University Chattahoochee Technical College Regina Bailey is a science writer, educator, and board-certified registered nurse. Her work has been featured in "Kaplan AP Biology" and "The Internet for Cellular and Molecular Biologists." Learn about our editorial process Updated May 7, 2024 Treehugger / Ellen Lindner Animals Wildlife Pets Animal Rights Endangered Species In This Article Expand Food Web Definition Trophic Levels in a Food Web Energy Movement Food Web vs. Food Chain Types of Food Webs Importance of the Study of Food Webs A food web is a detailed interconnecting diagram that shows the overall food relationships between organisms in a particular environment. The simplest explanation is that food webs are "who eats whom" diagrams showing the complex feeding relationships for a specific ecosystem. The study of food webs is important, as such webs can show how energy flows through an ecosystem. It also helps us understand how toxins and pollutants become concentrated within a particular ecosystem. Examples include mercury bioaccumulation in the Florida Everglades and mercury accumulation in the San Francisco Bay. Food webs can also help us study and explain how species diversity is related to how they fit within the overall food dynamic. They may also reveal critical information about the relationships between invasive species and those native to a particular ecosystem. Key Takeaways: What Is a Food Web? Think of a food web as a "who eats whom" diagram showing an ecosystem's complex feeding relationships. Knowing the interconnectedness of organisms in energy transfer within an ecosystem is vital to understanding food webs and how they apply to real-world science. An increase in toxic substances, like man-made persistent organic pollutants (POPs), can profoundly impact ecosystem species. By analyzing food webs, scientists can study and predict how substances move through the ecosystem to help prevent the bioaccumulation and biomagnification of harmful substances. Food Web Definition The concept of a food web, previously known as a food cycle, is typically credited to Charles Elton, who first introduced it in his book Animal Ecology, published in 1927. He is considered one of the founders of modern ecology and his book is a seminal work. In this book, he also introduced other important ecological concepts like niche and succession. In a food web, organisms are arranged according to their trophic level. An organism's trophic level refers to how it fits within the food web and is based on how it feeds. There are two main designations: autotrophs and heterotrophs. Autotrophs make their food, while heterotrophs do not. Within this broad designation are five main trophic levels: primary producers, primary consumers, secondary consumers, tertiary consumers, and apex predators. A food web shows how the different trophic levels within various food chains interconnect and how energy flows through them within an ecosystem. Trophic Levels in a Food Web A lion is an example of an apex predator. Andrew_Deer / Getty Images Plus Primary Producers Primary producers make their food via photosynthesis, which uses the sun's energy to make food by converting its light energy into chemical energy. Examples of primary producers include plants and algae. These organisms are also known as autotrophs. Primary Consumers Primary consumers are animals that eat the primary producers. They are named as such because they are the first organisms to eat the primary producers who make their own food. Primary consumers are also known as herbivores. Examples of animals in this designation are rabbits, beavers, elephants, and moose. Secondary Consumers Secondary consumers consist of organisms that eat primary consumers. Since secondary consumers are animals that eat the animals that eat the plants, they are called carnivorous or omnivorous. Carnivores eat animals, while omnivores consume both other animals and plants. Bears are an example of a secondary consumer. Tertiary Consumers Similar to secondary consumers, tertiary consumers can be carnivorous or omnivorous. The difference is that secondary consumers eat other carnivores. An example is an eagle. Apex Predators Lastly, the final level is composed of apex predators. Apex predators are at the top because they do not have natural predators. Lions are an example. Decomposers and Detritivores Additionally, organisms known as decomposers consume dead plants and animals and break them down. Fungi are examples of decomposers. Other organisms known as detritivores consume dead organic material. A vulture is an example of a detrivore. Energy Movement Energy flows through the different trophic levels. It begins with the sun's energy, which autotrophs use to produce food. This energy is transferred up the levels as the different organisms are consumed by members of the levels above them. Approximately 10% of the energy transferred from one trophic level to the next is converted to biomass—the overall mass of an organism or the mass of all the organisms that exist in a given trophic level. Since organisms expend energy to move around and go about their daily activities, only a part of the energy consumed is stored as biomass. Food Web vs. Food Chain VectorMine / Getty Images While a food web contains all constituent food chains in an ecosystem, food chains are a different construct. A food web can be composed of multiple food chains, some very short and others much longer. Food chains follow the flow of energy as it moves through the chain. The starting point is the energy from the sun, and this energy is traced as it moves through the food chain. This movement is typically linear, from one organism to another. For example, a short food chain may consist of plants that use the sun's energy to produce their food through photosynthesis and the herbivore that consumes these plants. This herbivore may be eaten by two different carnivores, which are a part of this food chain. When these carnivores are killed or die, the decomposers in the chain break down the carnivores, returning nutrients to the soil that can be used by plants. This brief chain is one of many parts of the overall food web that exists in an ecosystem. Other food chains in the food web for this particular ecosystem may be very similar to this example or may be much different. Since it is composed of all of the food chains in an ecosystem, the food web shows how the organisms in an ecosystem interconnect. Types of Food Webs Blueringmedia / Getty Images There are several types of food webs, which differ in how they are constructed and what they show or emphasize about the organisms within the particular ecosystem depicted. Scientists can use connectance and interaction food webs, along with energy flow, fossil, and functional food webs, to depict different aspects of the relationships within an ecosystem. They can also further classify the types of food webs based on the ecosystem being depicted in the web. Connectance Food Webs In a connectance food web, scientists use arrows to show one species being consumed by another. All of the arrows are equally weighted. The degree of strength of the consumption of one species by another is not depicted. Interaction Food Webs Like in connectance food webs, scientists also use arrows in interaction food webs to show one species being consumed by another. However, the arrows used are weighted to show the degree or strength of consumption of one species by another. The arrows depicted in such arrangements can be wider, bolder, or darker to denote the strength of consumption if one species typically consumes another. If the interaction between species is weak, the arrow can be very narrow or nonexistent. Energy Flow Food Webs Energy flow food webs depict the relationships between organisms in an ecosystem by quantifying and showing the energy flux between organisms. Fossil Food Webs Food webs can be dynamic, and the food relationships within an ecosystem can change over time. Scientists attempt to reconstruct the relationships between species in a fossil food web based on available evidence from the fossil record. Functional Food Webs Functional food webs depict the relationships between organisms in an ecosystem by depicting how different populations influence the growth rate of other populations within the environment. Food Webs and Type of Ecosystems Scientists can also subdivide the above types of food webs based on the type of ecosystem. For example, an energy-flow aquatic food web would depict the energy flux relationships in an aquatic environment. In contrast, an energy-flow terrestrial food web would show such relationships on land. Importance of the Study of Food Webs Man-made synthetic chemicals do not break down readily and can accumulate in an animal's fatty tissues. pidjoe / Getty Images Food webs show us how energy moves through an ecosystem, from the sun to producers to consumers. The interconnectedness of how organisms are involved in this energy transfer within an ecosystem is vital to understanding food webs and how they apply to real-world science. Just as energy can move through an ecosystem, other substances can also move through. There can be devastating effects when toxic substances or poisons are introduced into an ecosystem. Bioaccumulation and biomagnification are important concepts. Bioaccumulation is the accumulation of a substance, like poison or a contaminant, in an animal. Biomagnification refers to the buildup and increase in the concentration of said substance as it is passed from trophic level to trophic level in a food web. This increase in toxic substances can profoundly impact species within an ecosystem. For example, man-made synthetic chemicals often do not break down easily or quickly and can build up in an animal's fatty tissues over time. These substances are known as persistent organic pollutants (POPs). Marine environments are common examples of how these toxic substances can move, such as from phytoplankton to zooplankton, then to fish that eat the zooplankton, then to other fish (like salmon) who eat those fish, and up to orca who eat salmon. Orcas have a high blubber content so the POPs can be found at very high levels. These levels can cause several issues like reproductive problems, developmental issues with their young as well as immune system issues. By analyzing and understanding food webs, scientists can study and predict how substances may move through the ecosystem. They can then better help prevent the bioaccumulation and biomagnification of these toxic substances in the environment through intervention. Sources “Food Webs and Networks: the Architecture of Biodiversity.” Life Sciences at the University of Illinois at Urbana-Champaign, Biology Department. “11.4: Food Chains and Food Webs.” Geosciences LibreTexts, Libretexts. “Terrestrial Food Webs.” Smithsonian Environmental Research Center. “Bioaccumulation and Biomagnification: Increasingly Concentrated Problems!” CIMI School.