Overview

Plants 'R ' Us is a lesson plan targeted to third or fourth grade students. It primarily focuses on science. The lesson plan will enable students to explore trophic levels of organisms by creating a food web that originates with autotrophs, or p lants.

Science process skills used:
observation, analysis
Concepts learned:
Plant/animal interdependencies, food webs, trophic levels

Purpose
Objectives:

• students will discover the interdependencies of plants and animals
• students will learn what a food web is
• students will learn what trophic level are, and how components of a food web relate to them
• students will discover the importance of plants to life on earth

TEKS addressed: Science, 3^rd grade
Process Skills:
3C:   Represent natural world using models, identifying limitations.
Systems (Content Knowledge):
5A:   Observe and identify simple systems
8B:   Observe and identify organisms with similar needs that compete for resources.
8C:   Describe environmental changes which cause organisms to thrive, become ill, or perish.

Materials
Yarn, metal shower curtain rings, notecards with the name of an organism and its food source written on each one, and a chart or poster showing the trophic levels of organisms.

Getting Ready (Background Information)
(Note. I would use the handout "Energy and Nutrient Flow in Ecosystems" to accompany this background information, and perhaps a simplified version of it as a classroom visual aid.) A food web links organisms with their food sources, as well as the organisms for which they are a food source. The circles radiating out from the center of a web correlate with the trophic levels. Plants are primary producers at the center of the web. They are autotrophs, which means that they make their own food.

The next circle of the web consists of the primary consumers, or herbivores, which eat plants. Primary consumers include such animals as deer (eat grass), squirrels (eat nuts), and earthworms (eat dead plant matter). The next layer of the web is the se condary consumers, or carnivores, which eat the primary consumers. This includes animals such as wolves (eat deer), foxes and hawks (eat squirrels), and robins (eat earthworms). Both primary and secondary consumers are called heterotrophs. This is because they do not make their own food, but must rely on another source for food.

Some organisms eat both plants and animals. They are called omnivores, because they eat whatever is available. These include bears, coyotes, and people.

Motivate! (Engage)
Ask students if they like to eat plants. Most children do not think of their food, even fruits and vegetables, as plants, so this should stimulate some discussion. Ask students to name plants that they like to eat as they think of them. Some common fr uits and vegetables like lettuce, carrots, apples, bananas, and strawberries will probably be suggested.

Ask students to pretend that they are a squirrel. Now what would they eat? The answer, of course, is still plant material such as nuts and seeds.

Now ask students to pretend that they are a fox or a hawk. Now what do they eat? The answer will be meat, such as squirrels and other small animals.

Introduce the food game, described below.

Activity (Explore)

• Have students take a card with an organisms name on it. (Use different colored cards for the different trophic levels.) Give each student two pieces of yarn and a metal ring.
• Ask students to find two different food sources, and to connect themselves to their food sources by tying a piece of yarn to the food sources' metal ring.
• Let students create their own food web.

Note: for the purposes of creating a viable food web, use organisms from the same type of habitat for all of the cards in one game. For example, one game could use a meadow habitat, one could use a forest habitat, etc.

Safety Tips
Show students how to loop their yarn through the metal ring of another student who represents a food source for them. This will prevent them from tying their yarn to another student's wrist or around their neck and cutting off circulation, and will al so prevent tightly tied knots which cannot be easily untied.

Concept Discovery (Explanation)

• After food web is created, have students look around the room to see what food relationships were created. Ask each student to name their organism, and their food sources. Students should be able to see that all food sources can be traced back to plan ts.
• Create a habitat disruption, such as a drought or a disease, that disrupts part of the habitat. How is the rest of the habitat affected?
• Introduce the concept of trophic levels. Discuss each level with students. Show them the chart illustrating the trophic levels.
• Now go back through the classroom food web, and have each student name their organisms' trophic level.

Going Further: Elaboration

• Give students a recipe for Grass Bread. As a group, ask students to trace back the source of each ingredient. Ex: flour is ground up wheat, which is a plant; eggs come from chickens, which eat grains from plants, etc. (Note. Use a multi-grain recip e, so that a variety of grains and nuts are used.) At the end, students should be able to see that each ingredient of the bread can be traced back to a plant. Ask students again how important plants are to people.
• Make Grass Bread with students, if possible. If not, make the bread ahead of time and slice it and eat it with students.

Closure:

• Ask students again how important plants are. What would happen down the food web if there were no plants?
• Discuss how the classroom food web is similar to a real one, and how it is different.

Assessmenet: Evaluation
This activity is participatory in nature and involves the teacher as a facilitator, rather than an instructor. The teacher can observe students during the activity, and use the rubric below to determine student scores. This will eliminate some of the subjectivity of attaching grades to hands-on activities which are not standard "question-answer/scored" activities. A maximum score of 25 is possible, and would be considered mastery of concepts involved. The first evaluation score is based on participati on in the activity. The four other score areas are based on masterv level of subiect content.

Description of skill or task (Can be graded by group or by student)	1 (poor)	2 (fair)	3 (average)	4 (good)	5 (excellent)
Participated in actvity. (On task)
Mastery of concept of a food web, and how the radiating circles of the web are connected conceptually.
Mastery of concept of plant/animal interdependencies.
Able to construct a simple food web, with one organism at each level.
Mastery of concept of trophic levels.

Connections: Integration with other content areas

• Social Studies: Discuss some of the ways that people use plants. Ex: vegetables for food, wood for houses, rubber for shoes, cotton for clothes, foxglove and willow as medicines.
• Social Studies and Geography: Discuss world food sources using a map or globe to identify continents/countries. Discuss the Irish Potato Famine, which was a plant shortage-caused food crisis.

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