Feeding Positions in a Food Chain or Food We
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Maybe you've studied a little ecology and come across the terms "food chain" and "food web." Both help ecologists explain the ways that energy from food travels through an ecosystem. In this post, we will dive into the differences between food chains and food webs, and look at some examples of both!
Food Chains
In an ecosystem, organisms are connected to one another through feeding relationships: basically, who eats whom. There are feeding relationships between plants and plant-eating animals and feeding relationships between prey and predators. A food chain is an ordered list of who eats whom in an ecosystem. It is just one of the many paths that allow energy to move through an ecosystem, from organism to organism.
Food chains will always start with a producer, a plant or microorganism that can make its own food through photosynthesis, the process of creating sugar and oxygen from water, carbon dioxide gas, and sunlight. The next organism on every food chain will be the primary consumer – a plant-eating animal, also known as an herbivore. Following the primary consumer are one or more additional consumers, called the secondary (2nd) consumer, tertiary (3rd) consumer, quaternary (4th) consumer, etc…. Secondary and higher consumers will always be omnivores or carnivores. The final consumer on any food chain is also known as a top predator, because it has no predators of its own.
We visually represent food chains with a list of organisms connected by arrows to show the movement of energy through food (see above). Food chains are also sometimes represented as pyramids (see below), because it takes many producers to feed each primary consumer, many primary consumers to feed each secondary consumer, and so on. This is why ecosystems have many plants but few top predators. Each layer on the pyramid represents a position in the food chain, called a trophic level.
Food chains vary in length. Some may be short, with as few as two tropic levels. Others have more trophic levels due to many different producers eating one another. Below, you will find a few examples of food chains.
Food Chain Examples:
Clover -> Rabbit -> Fox
Willow -> Elk -> Wolf
Leaf-> Grasshopper -> Songbird -> Owl
Flower nectar -> Butterfly -> Frog -> Heron
Phytoplankton -> Bivalve -> Walrus -> Orca
Algae -> Caddisfly larva -> Minnow -> Trout-> Bear
Food Webs
A food chain is just one of the many paths that allow energy to flow through an ecosystem. But ecosystems are more complicated than a single food chain: every ecosystem includes many food chains that overlap and connect. For example, several different herbivores might all feed on one large field of grass. One predator might eat several types of prey to get enough food. The result is a complex network of feeding relationships between organisms in an ecosystem, called a food web. Food webs map the many paths for the movement of energy between all the organisms in an ecosystem.
In addition to the producers and consumers, decomposers are an important part of any food web. Decomposers are ecosystem members who have an important role of recycling nutrients back into the soil. They consume waste and decaying plant and animal matter. Usually, decomposers are fungi, microorganisms, or invertebrate animals like worms. Thanks to decomposers, nutrients are returned to the soil to help plants grow.
The difference between food chains and food webs? In summary, food chains are a single path showing how energy moves from organism to organism through an ecosystem, while a food web is a more complex network that maps the multiple feeding relationships of each organism in an ecosystem.
Food Web Example:
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References and Further Reading
- EPA (n.d.). EPA EcoBox Tools by Exposure Pathways – Food Chains. Available: https://www.epa.gov/ecobox/epa-ecobox-tools-exposure-pathways-food-chains
- National Geographic (n.d.). Food Web. Available: https://www.nationalgeographic.org/encyclopedia/food-web/
- National Oceanic and Atmospheric Administration (2019). Aquatic Food Webs. Available: https://www.noaa.gov/education/resource-collections/marine-life/aquatic-food-webs
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Source: https://wildearthlab.com/2021/08/06/food-chains-and-webs/
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