Summary:

In this lesson the students model a complex food web by passing a string to one another. The string activity follows a class discussion of food webs and the parts that make them up; producers, consumers, and decomposers.

Learning Goals / Objectives:

The students will demonstrate an understanding of how producers, consumers, and decomposers are interrelated in a complex food web.

The students will categorize plants and animals according to what they eat.

The students will model how parts of an ecosystem effect all others.

Background

In all ecosystems energy is produced and consumed. Plants and animals are connected through a web of eating relationships. Plants, the producers, create simple sugars, through photosynthesis, from sunlight, carbon dioxide, and water. Primary consumers, the plant eaters or herbivores, obtain all their energy needs by eating producers. Omnivores get their food by eating the producers or eating one or more consumer. The carnivores consume animals that have received their energy from somewhere else in the web.

A food web is a simple graphic representation of theses relationships. It shows how all parts of an ecosystem, no matter how unrelated they seem, are connected.

Setup:

Make the producer, consumer, and decomposer cards. Laminate them for future use. Have a ball of string or yarn ready to go. A very bright color works the best. Write consumer, producer, and decomposer on the display board.

Anticipatory Set:

Review the concept of food chains, consumers, producers, and decomposers. Introduce the picture cards. As a review have the students sort cards according to producer, consumer or decomposer. Display them on the board. Have goups of two teams or more use their cards to review and create food chains. Tell them that they won’t necessarly use every card. Pass out the picture cards and ask students to create simple food chains. Compliment groups that are successful and guide others into a food chain. Choose one of the simple food chains to discuss and place their cards on display. Ask the class if there are any other relationships that were overlooked. Guide the discussion toward the idea of one consumer eating a variety of foods. Discuss the idea that not all ecosystems are as simple as a food chain. Introduce the concept of a food web.

Instructions / Activities:

1. Step 1: Introduce the lesson with the set. Have students get out science notebooks and clear desks. Pass out minerals to each group. Allow them a few minutes of free exploration and discussion about the minerals.

2. Step 2: Using the picture cards construct and discuss a simple food web on the board. Emphasis that in an ecosystem the relationships and dependencies are not as simple as a food chain.

3: Randomly give each student a picture card. Have them read and discuss their card with their team members. They should identify where the energy used by the item on their card comes from, food or photosynthesis.

4: The students now put their cards around their necks and move to a large open space. and form a large circle. The circle should be random and need not be in any order. Have the sun stand in the center of the circle.

5: Give the sun the string and call one of the producers to present their card. They stand anywhere in the circle and the sun passes the string to them. Have other students present their cards and take a stand anywhere in the circle. They receive the string from their food source. Some consumers may eat more than one thing. Anytime a new producer is introduced go back to the sun. The sun should be the only one that feeds the producers.

6: Once every student is part of the web have a discussion about the similarities and differences of food chains and webs. Propose the question “What happens in a food web if something is disrupted?” Propose different scenarios. For example; “What would happen if their was a fire and all the grass was destroyed?” Have the grass lower the string and squat down. Now talk about who received their energy from the grass. With no grass they too will die. Continue until the sun is the only one left standing. Have stuents stand and try different scenarios.

7: Collect materials and have students return to their desks for a class discussion. Discuss food webs and the interrelationships between all the parts. Give them a writing prompt and sentence starter and have them write in their science journals.

8: Working in teams or individually, have the students draw their own food webs and label the parts. Present their drawings and post.

Assessment:

Formative assessments include:
Class discussion
Journal entries
Individual and team interviews
Have students draw and present their own food web posters to be displayed on the wall
An “I know…….because….” writing, drawing, or etc.

Summative assessments include.
Test; written short answer, multiple choice, and matching.
Vocabulary test.

Wrap-up / Closure:

Pass out organized (a complete web in each set in random order) cards to each group. Have them construct food webs. Present one of the webs on the board.

Attachments: