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Project title or topic of activity

The Web of Life

Author(s): Kasi Kiehlbaugh

Date: Fall 1999


Summary of Activity
50-100 words

By making use of common household foods, this activity presents the concepts of food chains and food webs. It teaches students about the differences between a producer and a consumer, and emphasizes that humans are just one piece of this very complicated web of life. It illustrates that the ocean is part of our food web, and that marine algae are an important ingredient in many of our foods.


Grade levels

5th & 6th grade

General description or introduction
The scientific principles that the activity is founded on.

The activity investigates the topic of ecology and ecosystems, with a specific focus on how energy and materials flow through these ecosystems. It examines this flow by tracing the way food is produced and consumed in food chains and food webs. The ecosystem of interest is the marine environment as related to humans.

Background information

Food web background (taken from Castro, pg. 204-205)
"The flow of energy and matter through an ecosystem can be traced by observing the food, or trophic, relationships among its organisms: who makes the food and who eats it. The organisms can be divided into two broad components: primary producers, the autotrophs that make the food, and consumers, the heterotrophs that eat it. Not all consumers feed directly on producers. Many animals eat other animals rather than primary producers. Thus, the transfer of energy through the system usually takes place in several steps known as a food chain. Each of the steps in the food chain is known as a trophic level.

Most ecosystems have a number of different primary producers. Furthermore, many animals eat more than just one kind of food, and many change their diet as they get older and larger. For these reasons, trophic structure is usually a complex, interwoven food web instead of a simple, straight-line food chain. Such food webs are often difficult for biologists to unravel and understand, but their complexity is one reason for the tremendous diversity of life." (additional material can be found in Castro, pg. 205-212)

Seaweed background
(taken from
Although fish and other seafood products make delicious, healthy meals for people all over the world, many American children would not mind if they never had to eat tuna casserole again. But they would mind if suddenly there were no more cheese and chocolate milk, peanut butter and pudding, frozen desserts and fruit drinks. What could such different foods have in common? Along with hundreds of other common foods and household items, they contain the aquatic autotroph known as seaweed.

Many kinds of seaweed are edible and rich in vitamins and iodine. They are as common in many Asian countries as green beans and carrots are in the United States. But until more people here develop a taste for sea vegetables, it is alginates, carrageenan, and beta carotene -- seaweed derivatives that act as stabilizers, thickeners, and colorants -- that end up on our dining room tables.

Seaweeds are not really weeds but large forms of marine algae that grow in the coastal ocean waters of many countries. They include thousands of species ranging from microscopic algaes called phytoplankton to giant floating or anchored varieties.

The three main groups of seaweed are brown, red, and green algae, each providing important ingredients for the manufacture of food and other products. Carrageenan is a generic term for compounds extracted from species of red algae. Carrageenans are used in stabilizing and gelling foods, cosmetics, pharmaceuticals, and industrial products. From brown algae come alginates. They make water-based products thicker, creamier, and more stable over extreme differences in temperature, pH, and time. For example, alginates prevent ice crystals from forming in ice cream. Beta Carotene, a natural pigment derived from green algae, is used as a yellow-orange food coloring and may help prevent certain types of cancers.

These seaweed derivatives represent only a small part of the many living and nonliving products we derive from ocean algaes, animals, minerals, and sea water. Together, they provide an important reason to protect the oceans."

Credit for the activity

This activity was an original idea, but in the process of searching the internet for background information, I came across several web sites with similar themes which I have utilized:

Estimated time to do the activity


Goals of Activity:

Goal A
Familiarize students with the concept of a food chain/food web

Goal B
Understand the biological differences between a producer and a consumer

Goal C
Recognize that producers (both marine and terrestrial) are the heart of the food web

Goal D
Identify our place in the food web as consumers of autotrophs both directly and indirectly; Show that many of the foods that we eat every day contain algae from the sea.


National Science Education Standards. (NSES)

Two content standards that this lesson plan covers:

Standard 1
Science as Inquiry
Content Standard A: As a result of activities in grades 5-8, all students should develop
-Abilities necessary to do scientific inquiry
-Understandings about scientific inquiry

Standard 2
Life Science
Content Standard C: As a result of activities in grades 5-8, all students should develop understanding of
-Structure and function in living systems
-Reproduction and heredity
-Regulation and behavior
-Populations and ecosystems
-Diversity and adaptations of organisms


Materials Needed

Note: For all processed food items, make sure to bring the original package/container so that the students can examine the ingredients.

  • Jar of Pickles
  • Cucumber
  • Marshmallows
  • Ear of corn
  • Can of Tuna
  • Cheese
  • Peanut Butter
  • Brownie mix
  • Chocolate milk (& paper cups)
  • Ice cream (& bowls, spoons, napkins)
  • McDonalds milkshakes (this could be served in place of the milk and ice cream)
  • Mayonnaise
  • Toothpaste
  • Whipped topping
  • Gravy packet
  • Samples or pictures of brown, red and green algae Nori (can be purchased from a Japanese food store)
  • Loaf of bread
  • Overhead transparency of an example food web (see Figure 9.11 (a) and (b) from pg. 206-7 of Castro text)
  • Table to display items during activity
  • Chalkboard or overhead projector


Before class, the instructor should obtain all of the materials listed and read the background information to become familiar with the topic of the lesson.

Place all the food items in an easily accessible but hidden location (paper bag) so that the students can't see them before they are presented in the activity.

If the instructor plans on allowing the students to eat some of the foods (ice cream and chocolate milk are suggested), he or she may want to prepare the portions ahead of time, or have a helper prepare them while the instructor is going through the lesson.

Step-by-Step Procedure for the Activity

Discussion with entire class:
(1) Begin by asking the students to do a concept map related to food chains. Give them several key words to get them started. Once the students have completed their maps, discuss the maps and determine how much knowledge the students already possess about the topic. Try to make use of prior knowledge as much as possible through the activity.
(2) Ask for several specific examples of food chains, both terrestrial and marine. Draw these food chain diagrams on the chalkboard or overhead projector so that students who learn visually can see them. Guide the students to produce food chains that contain a plant as the initial link.
(3) Ask students to identify what the difference is between plants and the rest of the animals in the food chain. Discuss the ideas of producers (plants) and consumers (animals), emphasizing the fact that producers utilize energy directly from the sun to generate food, while consumers are dependent on the producers for their food. Point out that not all animals eat plants directly, but sometimes eat other animals to get their energy. Be sure to use examples throughout this discussion to make the concepts easy to understand.
(4) Next, ask the students to define a food web. If possible, connect the examples that were given by the students into a food web, or if the examples are unrelated, generate a food web based on one of the examples. Show the overhead of the marine food web that is listed in the materials section and point out the different food chains that work together to make the food web. Have the students identify the producers and consumers in the food web examples.
(5) Ask the students to identify their own place in the food web. Do they eat plants, or animals, or both? Where do the plants come from? Ask them if there are producers in the ocean. Do they eat them? If they say no, tell them you may have a surprise for them, but don't say any more than this. Have them give examples of what types of plants and animals they eat.
(6) Show students the jar of pickles. Ask the students to identify what is in the jar. Is it a producer or consumer? What plant was used to make the pickles? (cucumber) Show students the cucumber.
(7) Show students the bag of marshmallows. Ask them if they know what is in the marshmallows. Hint that there are two types of plants in them (sugar cane and corn) and see if they can figure it out. Show them the ear of corn during the discussion.
(8) Show the can of tuna. Is it a producer or consumer? Where does it live?
(9) Display all of the remaining food items (cheese through gravy packet from materials list) and ask the students to identify what all of these items have in common. Hint that they all contain a type of producer, one that comes from the ocean.
(10) Explain that each product contains algae, an autotroph, in the form of seaweed. Display the seaweed samples or pictures and talk about the ingredients that come from the three types of algae (red-carrageenan, brown-alginates, and green-beta carotene) and what each is used for.
(11) Choose one of the products and show students where to find the nutritional label and ingredients. From the label, point out the algae derivative contained in the chosen sample (example: chocolate milk contains carrageenan). Emphasize that this means chocolate milk contains red seaweed, and that when they drink it they are eating algae from the ocean!
(12) Split the class into small groups of 3 to 5 students and provide each group with one of the food products. Ask them to identify the seaweed derivative found in the food they were given. Point out that some of the foods contain more than one type of seaweed. Go around the room and have each group report on what is in their food. As an added challenge, ask them to identify any other plants that are contained in their food (i.e. corn from high fructose corn syrup, sugar from sugar cane, etcÉ)
(13) As a wrap-up, pass out the ice cream and chocolate milk to each student, reminding them that these foods contain seaweed.

Images, work sheets, additional web pages

non available}

Items for discussion or conclusion

1st question

What is a food chain/food web and where do you fit into it?

2nd question
What is the difference between a producer and a consumer?

3rd question
Which of these (producer and consumer) is the most important part of the food web?

4th question
Are there producers in the ocean and are they part of the food web? How?


Because everything is connected together in a complex food web, we are all affected by harmful things that are done to the environment. Our environment includes the ocean. Since the producers and consumers from the ocean are such an important part of many of the foods that we eat every day, we need to work hard to protect the ocean.

Beyond the Activity
Further activities which relate to and extend the complexity of the experiment.

Give a more detailed discussion of the trophic structure as described in Castro, pg 205-212. Include how important nutrients such as carbon and nitrogen are cycled through the food web.

Give a talk on the basic engineering processes involved in turning plants (such as corn) into the products that people buy in the grocery store (corn syrup, corn starch). Introduce the field of food engineering, which is a relatively new branch of engineering concerned with the application of engineering principles and concepts to the handling, manufacturing, processing, and distribution of foods. It encompasses the knowledge required to design processes and systems for an efficient food chain extending from the producer to the consumer (which ties directly back into the topic of the activity).

Have a hands-on experiment where the students use powdered forms of carageenan and alginate to see what effects they have in food (thickening, color, etc...)

Web Resources
A web address with information on the topic of the activity.

Web Address

Additional References

Chapman, V. J., and D. C. Chapman. Seaweeds and Their Uses. New York: Chapman and Hall, 1970.