Materials:

• 1 set of 30 food web cards
• 1 roll of colored yarn from lesson 3
• 1 class set of Activity Sheet #7 Investigating Food Chains (teacher provided)
• 1 clump of grass (teacher provided)
• scissors (teacher provided)

Objectives:

• Students will list the basic components of a cheeseburger.
• Students will trace common food chains found in nature.
• Students will demonstrate the interdependence of organisms through a class food webbing activity.

Background:

Every organism is dependent upon other organisms for survival. Plants that capture energy from the sun are consumed by animals that, in turn, are eaten by other animals. This linkage, or webbing of different species is key to understanding the interdependence of living organisms (including humans) to their environment.

This activity explores how seemingly unrelated, independent organisms are, in fact, highly dependent upon each other for survival. This interdependence of organisms within an ecosystem is often represented as a food web. In a food web, one organism is linked to another organism in a web-like fashion.

While food webs simplify a very complex series of interdependent relationships, the basic concept is central to environmental education.

This activity is written in two parts. The first part explores the concept of food chains while the second section discusses food webs. Depending on your available time, you may prefer to break this lesson into two class periods.

Before You Begin This Lesson:

• Run off enough copies of Activity Sheet #7, Investigating Food Chains for each child in class.
• If necessary, untangle the blue yarn from lesson 3 -Fishing For Food. This yarn is used to construct a student food web.
• Locate the "Sun" card from the food web cards and place it at the top of the stack. If this card is missing, make a copy of the card from this page.
• Collect a clump of grass to show students.
• Read and understand the class food webbing activity before teaching the lesson.

Activity:

Part I - Food Chains

1. Begin by asking students to silently think about all of the "parts" that make up a "typical" cheese burger.

2. As a class, or in small groups, generate a list on the front board of cheese burger "parts. Your list might look something like that shown below:

Cheeseburger Ingredients: meat patty, bun, lettuce, cheese, tomato, mustard, ketchup

3. Ask students:

• Where did the meat patty come from (a cow)?
• What did the cow need to grow (food and water)?
• What kind of food did the cow eat (grass)?
• What did the grass need to grow? (water and sunlight).

4. Illustrate this general flow on the front board.

• meat patty
• cow
• grass
• sunlight & water

5. Challenge students to expand out each component of their cheeseburger in a manner similar to the meat patty diagram you just drew. The expanded list might look something like this:

6. Explain that the students have constructed a food chain for each cheeseburger ingredient. A food chain shows the transfer of energy from the sun to plants to animals.

7. Ask students what all of these food chains seem to have in common. (Sunlight is the primary food energy source).

8. Explain that food chains are found throughout nature. They help us to better understand what living things need to survive and grow.

9. Hold up the clump of grass. Explain that sheep eat grass like this in order to survive. Write out the following food chain on to the front board:

11. Next, ask students what animal(s) might eat sheep (humans, mountain lions, etc) . Add humans to the top of your food chain diagram.

12. Finally, ask where the grass gets its energy from (sunlight).

13. Add sunlight to the bottom of the food chain diagram.

14. Draw arrows connecting sunlight with the organisms in your food chain. Explain that energy from the sun is used by the grass which is eaten by the sheep which is consumed by humans.

15. Pass out Activity Sheet #7, Investigating Food Chains to each child. Complete the first example on the activity sheet with your class.

16. Once you think your students understand how to build their own food chains, instruct them to complete the other three problems shown on the activity sheet.

17. Once students have completed the sheet, reveal the correct (or most likely) solutions. Explain that, in a food chain, plants are called producers because they produce food. Also, explain that consumers are organisms that eat the food producers.

Teacher Key:

a. b c d

Part II - Food Webs

1. Explain that plants and animals that live in the same general area live in a community. Animals living in communities depend on the plants and animals of the community for survival. In communities, the plants depend on dead animals and rotting plants to replace the nutrients into the soil. All organisms living in communities depend on the sun as the primary energy source.

2. The ancient Washoe were members of this natural community. They depended on the native plants and animals for survival. Much of the Washoe culture is based on this interdependence with the natural environment.

3. Ask students what might happen if all the grass disappeared from the earth. (Grass eaters would either have to find a new food source, or become extinct. This would cause a heavy burden on the rest of the edible plant world. With fewer plants, there would be fewer plant eaters, which would cause fewer animal eaters.)

4. Explain that scientists call this dependence of one species on another species interdependence. Point out that mountain lions do not depend on zebras because they do not live in the same community, however each depends on other organisms within their own community to survive.

5. Draw the following food chain on the front board:

wolf

sheep

grass

sunlight

6. Ask if sheep are the only animals that eat grass (no, horses, cattle, zebras, etc.) Add the following chains to the list (you may want to modify the list based on student suggestions).

wolf mt. lion

sheep elk

grass

sunlight

7. Now ask students if the sheep, cow, or elk might eat other kinds of foods. You may want to add clover, or other foods suggested by students to enlarge the web.

human

wolf cow mt. lion

(calf)

sheep elk

grass

clover

sunlight

8. Lead students in building a food web using oats.

golden eagle snake red-tailed hawk

horse mouse

oats

sunlight

-----------------------------------------------

A Student Food Web

Note: You may prefer to conduct this activity outdoors, or in the multipurpose room.

9. Invite the class to build their own food web through the following activity:

a. Gather students into a circle. (You may have to rearrange some classroom furniture).

b. Pass out one food web card to each student, making sure a "responsible" student receives the sun card.

c. Hand the ball of yarn to the "sun" student and ask him or her to read their card out loud for the rest of the class. (The card reads, "I am the sun and I give energy to plants.)

d. Next, ask if any student(s) hold a card that uses the sun. (There should be several early on in the activity. Pick only one student.)

e. Have one student who uses sunlight read their card to the class.

f. Explain that these two students are dependent on each other. To show this dependance, use the yarn to connect the "sun" student with the other student (The student who used sunlight should now be holding on to the ball of yarn.)

g. Next, ask if anyone in class holds a card stating that they "eat" the student now holding the ball of yarn.

h. The ball of yarn should then be passed to the third person.

At this point, your classroom web might look something like that shown below.

i. At some point, you will reach a dead end. Cut the string and return the ball of yarn to the "sun" person to begin again.

j. The activity ends when everyone in class holds a part of the web.

k. To help demonstrate the interdependence within a food web, have one student tug gently on the yarn segment (s) they are holding. Any student who feels the tug should begin gently tugging their own yarn. Hopefully, all students will eventually feel the tug of other students.

l. Finally, try removing one person from the web by having them release their yarn. What happens to the web? How many organisms can be removed before the entire plant and animal community breaks down.

m. Collect all yarn segments and discard. (If supply of yarn is low, please order more for the next teacher).

Closure:

1. To help focus students on the importance of a single plant to the ancient Washoe, guide students into building the following food chain/web.

Washoe

Willow

Sunlight

Option:

Try having students design their own ecosystem using the following activity.

1. Begin by asking students to think about the school and all of the people who are hired to make it run. In some ways, a school is similar to an ecosystem, where everyone is dependent upon everyone else.

2. Brainstorm a class list of groups of people found at the school. Your list might look something like this:

cafeteria workers office workers teacher aides the teachers

the nurse principal's secretary parent helpers students

the principal playground aids the librarians the custodian

the crossing guard

3. Try linking each of the names generated by the class, similar to how organisms are linked in a food web.

4. Once all names have been linked, try erasing one name at a time, discussing how the disappearance of this group might effect everyone in the school. At what point would the school no longer function?

5. Close this optional lesson by leading a discussion that examines how the disappearance of a single species might effect a real ecosystem. You might prefer encouraging students to write their thoughts down as a journal entry.

Evaluation:

Because the construction of the food web incorporates the concepts of the food chain, the ability of the students to construct a web and extrapolate on the interactions of community members demonstrates an understanding of interdependence.

Food Chains & Food Webs Activity Sheet 7:

NAME:

DATE:

Investigating Food Chains

a. Draw out a food chain that includes: mouse, hawk, sunlight and grass seed.

c. Draw out a food chain that includes: sunlight, rainbow trout, minnows, Washoe and algae.