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 http://seawifs.gsfc.nasa.gov/OCEAN_PLANET/HTML/education_lesson1.html)
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."

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.

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...)