Food web

What is a food web?	A network showing how plants and animals are connected through feeding relationships.
Why is it important?	It helps us understand how energy moves through nature and why every living thing matters.
Example	A rabbit eats grass, a fox eats the rabbit, and a bird might eat the fox.

A food web is the natural way that different plants and animals are connected through what they eat and what eats them. It shows how energy moves through an ecological community. Every living thing has a place in this web, called a trophic level. Some organisms make their own food, like plants, and these are called autotrophs. Others, like animals, need to eat to get energy, and these are called heterotrophs.

A freshwater aquatic food web. The blue arrows show a complete food chain (algae → daphnia → gizzard shad → largemouth bass → great blue heron)

Food webs help us understand how different species depend on each other. For example, a bird might eat a bug, and the bug might eat a plant. This creates a chain of who eats whom. There are many ways this can happen, such as herbivory, where animals eat plants, or carnivory, where animals eat other animals. Some organisms, like carnivorous plants, can even do both, making them mixotrophs.

The idea of food webs was developed by scientists like Charles Elton and Raymond Lindeman, who studied how energy flows in nature. They showed that even though food webs are simple pictures, they help explain complex relationships in ecosystems. Today, scientists use math and models to study food webs and discover patterns that help us understand how nature works together.

Taxonomy of a food web

Food webs show how plants and animals are connected by what they eat. They can look very complicated, but they follow some basic patterns.

In a food web, animals and plants are linked by who eats whom. We can group living things into two main types: autotrophs and heterotrophs. Autotrophs, like plants, make their own food using sunlight or chemicals. Heterotrophs, like animals, must eat other organisms for food. Some plants can also act like animals by eating other creatures.

Trophic levels

Main article: Trophic level

Food webs have levels called trophic levels. The bottom level is made up of plants and other producers that make their own food. Above them are animals that eat the plants, and at the top are animals that eat other animals. Some animals eat from many levels, which makes the food web complex.

A trophic pyramid (a) and a simplified community food web (b) illustrating ecological relations among creatures that are typical of a northern Boreal terrestrial ecosystem. The trophic pyramid roughly represents each level's biomass (usually measured as total dry weight).

Trophic dynamics and multitrophic interactions

The idea of trophic levels helps us understand how energy moves from one part of an ecosystem to another. Sometimes, animals that eat plants also affect the plants indirectly by controlling the numbers of animals that eat the plants. This can help plants grow more.

Energy flow and biomass

Multitrophic interaction: Euphydryas editha taylori larvae sequester defensive compounds from specific types of plants they consume to protect themselves from bird predators

Energy flows through a food web from plants to animals. Each time energy moves from one level to the next, some energy is lost. This is why there are usually only a few levels in a food chain. The amount of energy gets smaller at each level, which can be shown in diagrams called ecological pyramids.

Food chain

Main article: food chain

Energy flow diagram of a frog. The frog represents a node in an extended food web. The energy ingested is utilized for metabolic processes and transformed into biomass. The energy flow continues on its path if the frog is ingested by predators, parasites, or as a decaying carcass in soil. This energy flow diagram illustrates how energy is lost as it fuels the metabolic process that transform the energy and nutrients into biomass.

A food chain is a simple line showing who eats whom. It shows the steps between plants and top animals. The length of a food chain can vary, and it helps scientists understand how changes in one part of the web can affect the whole system.

Ecological pyramids

Ecological pyramids show how the number of animals or the amount of weight gets smaller at each level of the food web. In some water systems, the pyramid can be upside down because small plants can support larger animals if they grow very quickly. But energy pyramids always show energy getting smaller at each level because of the laws of nature.

Material flux and recycling

Main article: Nutrient cycle

Many of the Earth's elements and minerals are found in the bodies and food of living things. These minerals and nutrients follow the same paths as energy in food webs. Scientists study the amounts of carbon (C), nitrogen (N), and phosphorus (P) in organisms to understand how these elements move and change. Minerals are important for plants and animals to grow and stay healthy. Food webs show how these minerals move through the environment. Most of the food made by plants is not eaten, but it helps recycle nutrients back into the soil. Tiny microorganisms help create and recycle minerals, playing a big role in keeping the Earth healthy. While food webs and nutrient cycles are often studied separately, they are closely connected in how they support life and balance nature.

Kinds of food webs

Food webs show how different plants and animals are connected through eating and being eaten in nature. They are simplified versions of real ecosystems, which are very complex. Most studies look at the biggest influences where most of the energy moves.

There are different kinds of food webs:

Paleoecological studies can reconstruct fossil food-webs and trophic levels. Primary producers form the base (red spheres), predators at top (yellow spheres), the lines represent feeding links. Original food-webs (left) are simplified (right) by aggregating groups feeding on common prey into coarser grained trophic species.

Source web - starts with one or more plants or animals and shows all the animals that eat them, and what those animals eat, and so on.
Sink web - starts with one or more plants or animals and shows all the animals they eat, and what those animals eat, and so on.
Community (or connectedness) web - shows a group of plants and animals and all the connections of who eats whom.
Energy flow web - measures the amount of energy that moves between plants and animals.
Paleoecological web - reconstructs old ecosystems from fossils.
Functional web - focuses on the important connections that strongly affect how the community works.

Food webs can also be organized based on different types of ecosystems, like human food webs, agricultural food webs, marine food webs, soil food webs, and microbial food webs.

An illustration of a soil food web.

Detrital web

In a detrital web, plants and animals that have died are broken down by decomposers, such as bacteria and fungi. This dead material then becomes food for detritivores, and later for carnivores. Often, there are links between the detrital web and the grazing web. For example, mushrooms from the detrital web can be eaten by deer, squirrels, and mice in the grazing web. Earthworms, which eat decaying leaves, are eaten by robins.

Quantitative food webs

A simplified version of a food web in the Gulf of Naples in eutrophic (green) and oligotrophic (blue) summer conditions. In the Green system state, both copepods and microzooplankton exert a strong grazing pressure on phytoplankton, while in the Blue state, copepods increase their predation over microzooplankton, which in turn shifts its predation from phytoplankton to bacterial plankton or picoplankton. These trophic mechanisms stabilize the delivery of organic matter from copepods to fish.

Ecologists study food webs by collecting data and using math to understand patterns in nature. They look at things like the types of species, how many there are, and how much they weigh. This helps them see how changes in one species can affect others.

Food webs are very complex, with many connections between different species. Scientists use math to simplify these connections and understand how stable food webs are. They also study how food webs change over time and space, showing that each type of ecosystem, like land or water, has its own unique food web structure.

History of food webs

Victor Summerhayes and Charles Elton's 1923 food web of Bear Island (Arrows point to an organism being consumed by another organism).

Food webs help scientists understand how different animals and plants connect by eating each other in nature. One of the first ideas about this came from an Afro-Arab scholar named Al-Jahiz a long time ago, who wrote that every animal needs food, and even hunters can become hunted. The first picture of a food web was made by Lorenzo Camerano in 1880.

Later, scientists like Charles Elton wrote important books about how animals eat each other. After that, food webs became a key idea in the study of nature, helping scientists see how all living things are linked together. This idea grew even more when studies showed that complex food webs help keep many different species safe and the environment balanced.