Students learn about energy flow in food webs, including the roles of the sun, producers, consumers and decomposers in the energy cycle. They model a food web and create diagrams of food webs using their own drawings and/or images from nature or wildlife magazines. Students investigate the links between the sun, plants and animals, building their understanding of the web of nutrient dependency and energy transfer.
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- Colorado: Science
- International Technology and Engineering Educators Association: Technology
- Next Generation Science Standards: Science
- Use models to describe that energy in animals' food (used for body repair, growth, motion, and to maintain body warmth) was once energy from the sun. (Grade 5)  ...show
- Develop a model to describe the movement of matter among plants, animals, decomposers, and the environment. (Grade 5)  ...show
- Compare and contrast producers and consumers in a food chain or food web.
- Diagram the flow of energy through simple food chains and food webs.
- Explain how engineers use knowledge of energy flow through food chains and webs to work with new energy sources, technologies and designed environments.
Each group needs:
- 1 piece of cardboard or construction paper
- 1 or 2 nature or wildlife magazines (such as National Geographic, Natural History, Ranger Rick, etc.)
For the entire class to share:
- Several balls of string or yarn (can be re-used for future projects)
|Biodome:||A human-made, closed environment containing plants and animals existing in equilibrium.|
|Consumer:||An organism requiring complex organic compounds for food, which it obtains by preying on other organisms or by eating organic matter.|
|Decomposer:||Organisms such as bacteria and fungi that decompose dead plants and animals.|
|Ecosystem:||A functional unit consisting of all the living organisms (plants, animals and microbes) in a given area, and all the nonliving physical and chemical factors of their environment, linked together through nutrient cycling and energy flow. An ecosystem can be of any size — a log, pond, field, forest or the Earth's biosphere — but it always functions as a whole unit.|
|Energy:||The capacity for vigorous activity; available power; the capacity to do work. For example, I eat chocolate to get quick energy.|
|Engineer:||A person who applies scientific and mathematical principles to creative and practical ends such as the design, manufacture and operation of efficient and economical structures, machines, processes and systems.|
|Environment:||The surroundings in which an organism lives, including air, water, land, natural resources, flora, fauna, humans and their interrelationships. (Examples: Tundra, coniferous forest, deciduous forest, grassland prairie, mountains and rain forest.)|
|Food chain:||A sequence of organisms, each of which uses the next, lower member of the sequence as a food source. Source: U.S. Environmental Protection Agency: http://www.epa.gov/OCEPAterms/fterms.html.|
|Food web:||A complex network of many interconnected food chains and feeding interactions.|
|Photosynthesis:||The process in green plants by which carbohydrates are made from carbon dioxide and water using sunlight as the energy source.|
|Producer:||Any organism that is capable of producing its own food, usually through photosynthesis.|
Before the Activity
- Gather materials.
- Hold a class discussion. Explain the idea that food chains are sometimes too simple to show what is actually going on in an environment. For example, humans eat more than chicken; they also eat fish, vegetables, fruit, grains, cheese and other types of meat. Bears and mountain lions eat birds and fish, and bears also eat berries. Skunks eat insects, bird eggs, baby birds, as well as fruit and berries. If possible, have the class research food webs in a variety of ecosystems online or in natural history books.
- Consider using the attached Example Food Web Worksheet to acquaint students with the concept before beginning the activity.
With the Students: Part 1 — Human Food Web
- Divide the class into teams of eight students each. (Groups may be larger or smaller, if desired, but they must be at least five students each.)
- Have all the students stand in a circle.
- Distribute a ball of string or yarn to one member of each group. This person represents the sun and starts each food web.
- Have the first student hold tightly to the end of the string and toss the ball of string to another person in the group, across the circle.
- Have the second person name one thing in the ecosystem that uses energy from the sun. Next, have this person clasp the string with one hand and toss the ball of string on to another student in the circle with his/her other hand.
- Have the third student name something that eats or is eaten by the previous item named.
- Continue until all students in the circle are connected with the ball of string at least once.
- Have the student groups stop and look at the web they have created. Are some webs more complex than others? Why? (Answer: Some species may have been named twice because they are consumers of multiple things; some ecosystems have more variety of food sources, etc.) Point out to students how they have modeled a food chain or food web.
With the Students: Part 2 — Drawing Food Chains and Webs
- Divide the class into teams of two students each.
- Ask each pair to think of a terrestrial food chain and an aquatic food chain, and create each of these with words on one side of a piece of paper, using arrows to show the energy flow.
- Discuss the food webs they created as a class in Part 1, and tell them that they are now going to construct a food web in their pairs using pictures.
- Pass out an assortment of nature and wildlife magazines.
- Instruct the groups to make food webs on the other side of their paper by either drawing pictures of the living things in their food chains or finding them in the magazines and gluing them onto the paper. Suggest that they use arrows to show the direction of the flow of energy between the images.
- Conclude with an informal discussion using the questions and answers provided in the post-activity assessment of the Assessment section.
Activity Embedded Assessment
- How do we use the energy that is in the food we eat? (Discussion points: We use energy to move, keep warm [we give off heat all the time, and this heat energy comes from the food we eat] grow, think, stay healthy, and stay alive. What is left is stored in our bodies.)
- If only a fraction of the energy that an herbivore (plant eater) gets from plant food becomes part of the herbivore's body (its biomass), what happens to the rest of it? (Discussion points: The rest of the energy from the plant food is lost as waste [in droppings] or is used up for movement, keeping warm or just staying alive.)
- Is the same true for carnivores? (Discussion points: Yes, when a carnivore eats another animal, only a fraction of the energy from its animal food is incorporated into the carnivore's body.)
- Introduce the class to the idea that energy is lost at each link in the food chain or web because the living things pass on much less energy than they receive. This energy loss means that most food chains are only four or five links long. Can they find any long food chains within the food webs they made today?
- Which item on their food web probably had the most energy? Which item had the least? (Discussion points: Many engineers work with energy efficiency and conservation. Engineers pay attention to when energy is gained and energy is lost. Engineers design technologies for alternate sources of energy and ways to keep more energy in a system.)
- How do you think an engineer might use information about a food chain or web when designing a biodome or space station in which humans live? (Discussion points: To figure out how much energy is needed to grow plants in the artificial environment. To find out how much food is needed to provide enough energy to the organisms or people living in the environment. To make sure to include plants, animals and other organisms that are part of the same food web. To make sure the artificial ecosystem conditions provide the right kind and amount of resources [sunshine, air, nutrients, soil, water, climate, etc.] to support all the food web organisms. To conserve and re-use resources because they are important to survive and in limited supply.)
- For lower grades, make less complicated food chains instead of food webs. For example, have students make paper food chains by drawing or gluing pictures of food chain components onto separate pieces of paper. Then tape them together in the appropriate order.
- For upper grades, have students prepare their food webs and present them to the class discussing the interconnectedness and relationships of the animals and plants. Also, have students consider the effect of other nutrient cycles on their food web, such as carbon, nitrogen and water.
Bush, Mark B. Ecology of a Changing Planet, Second Edition. Saddle River, NJ: Prentice Hall, 2000.
Dictionary.com. Lexico Publishing Group, LLC. Accessed December 5, 2006.
Food Chains and Webs, Making a Food Chain. Cornwall Wildlife Trust, UK. http://www.cornwallwildlifetrust.org.uk/ Accessed December 5, 2006. (Source of part of this activity; also includes additional fun and easy classroom and student activities)
Christopher Valenti, Malinda Schaefer Zarske, Denise Carlson
© 2004 by Regents of the University of Colorado.
Integrated Teaching and Learning Program, College of Engineering, University of Colorado Boulder
Last modified: March 3, 2015