ALEX Lesson Plan

In this lesson which emphasizes hands-on, inquiry-based activities, students will create two models of the digestive system and determine the correct placement of various organs of the digestive system. Students will use the model to compare mechanical and chemical digestion. Students will use information provided by the model to explain why food spends various amounts of time in a particular organ. To extend the learning of this module, students will design an experiment to determine the effect of introducing new foods to a baby’s diet.  The module also includes a presentation, a word search puzzle, and a bingo game emphasizing vocabulary words related to the digestive tract.

Student Materials (per student)

Pencil or pen

Pre-/Post-Test (see attached document)

Digestive System Word Search (see attached document)

Bingo Cards-“Digestive System Vocabulary” (see attached document)

Bingo card covers/tokens

Student Procedure A-“Cracker and Avocado Activity” (see attached document)

Student Procedure B-“Cracker and Avocado Activity” (see attached document)

Note: Two variations of the Student Activity Procedure handout are provided, the teacher should choose the appropriate handout for his or her class. The “Student Procedure B” handout will allow students more creativity in designing a model of the digestive system, while the “Student Procedure A” handout provides more detailed instructions.

Student Handout for Part 1 and Part 2-“Cracker and Avocado Activity Reflection Questions” (see attached document)

Model the Digestive Tract (see attached documents)

Student Lab Guide-“Baby Burps: Now That’s Gas” (see attached document)

Student Materials (per group)

Cracker and Avocado Activity

Part 1

Saltine cracker

Timer

Part 2

Three saltine crackers

Half of a peeled ripe avocado

One pint size Ziploc bag

One quart size Ziploc bag

Five mL of water

Ten mL of orange juice

Ten mL of vinegar

Flexible tubing

Pantyhose cut at each end

Duct tape

Paper towels

Eight-ounce paper cup with a hole cut in the bottom of the cup

Plastic tub

Gloves

Aprons

Model the Digestive Tract

Masking tape

Yardstick

Digestive Organ Pictures (see attached documents)

• Stomach
• Large intestine
• Pharynx/Esophagus
• Mouth
• Small intestine

Teacher Materials

Teacher Preparation Guide (see attached document)

Pre-/Post-Test Answer Key (see attached documents)

Ins and Outs of Digestion Presentation (see attached PowerPoint presentation)

Rubric for Assessment-“Baby Burps: Now That’s Gas” (see attached document)

Teacher Technology Resources

Teacher computer

Interactive whiteboard or projector

Student Background:  As this lesson will introduce students to the organs and processes of the digestive system, students do not need to possess background knowledge about these concepts prior to participating in the lesson’s activities. This lesson will require students to participate in hands-on, inquiry-based lab activities. The students will need to be able to follow multi-step procedural instructions in order to complete the experiments. Students will be participating in lab activities in which household materials will be handled. Students should follow all appropriate safety precautions including wearing gloves, aprons, and goggles. All spills and splashes should be cleaned with water.  

Teacher Background: The teacher should preview the Teacher Preparation Guide prior to teaching the lesson to ensure that the lab activities are prepared for students before beginning the lesson’s activities. As written, the activities included in this lesson will require at least six class days to complete. The teacher can view the Ins and Outs of Digestion Presentation for additional background information about the concepts taught in this lesson. The teacher should review lab safety precautions with students and ensure students follow these procedures for the duration of the lesson.

Prior to completing the second portion of the Cracker/Avocado Activity, the teacher should tape large garbage bags to the floor to provide an area for each group. The teacher should ensure that all supplies for each group are prepared before beginning Part 2 of the activity. Detailed instructions for setting up this lab are provided in the Teacher Preparation Guide.

Before Strategy/Engage: 50 minutes (Day 1)

1. The teacher should give each student a copy of the Pre-/Post-Test (see attached document). The teacher should give students approximately ten to fifteen minutes to complete the pre-test. The teacher should stress to students that the purpose of the pre-test is to demonstrate the student’s background knowledge about the concepts of osmosis and diffusion.
2. After students complete the pretest, the teacher should check students’ answers to determine their current knowledge base of the concepts using the Pre-/Post-Test Answer Key (see attached document). Alternatively, the teacher could allow students to check their own paper or check a partner’s paper.
3. The teacher should use the Digestive System Word Search and the Bingo Cards to introduce the vocabulary words that will be used during this unit (see attached documents).

During Strategy/Explore & Explain: 100 minutes (Day 2 and 3)

1. For the next portion of the lesson, each student will need a copy of the Student Procedure A-“Cracker and Avocado Activity Instructions” and Handout for Part 1 and Part 2-“Cracker and Avocado Activity Reflection Questions” (see attached documents). The students should be divided into collaborative groups of approximately four students each.

Cracker and Avocado Activity

Part 1:

1. Have one representative from each group come to the front of the class to get a saltine cracker for each member of the group and a timer for the group.
2. Instruct each representative to take a small bite of the cracker but DO NOT CHEW or SWALLOW.  A designated student should start the timer and the representative should hold the cracker on the tongue for two minutes with mouth closed. After the two minutes, the cracker should be swallowed.
3. The teacher should ask the students discuss the Part 1 questions on the handout with their group members and write the answers in the appropriate place.

Part 2:

1. Prior to the second part of the Cracker and Avocado Activity, the teacher should tape large garbage bags to the floor to provide an area for each group.
2. At each area students should have the following: three saltine crackers, half of a peeled ripe avocado, one pint-size Ziploc bag, one quart size Ziploc bag, five mL of water, ten mL of orange juice, ten mL of vinegar, flexible tubing, pantyhose cut at each end, duct tape, paper towels, eight-ounce paper cup with a hole cut in the bottom of the cup, a plastic tub, gloves, and aprons.
3. Prior to the activity explain to the students they will be making a model of the digestive system to examine the features of the digestive system.  

Student Directions

1. In the pint-size Ziploc bag, place three saltine crackers and the avocado. Close the bag and squeeze the contents two times. Open the bag and add the water. Close the bag and squeeze the contents five times. Open the bag and add the orange juice. Close the bag and squeeze the contents eight times.
2. Unzip approximately one inch of ONE CORNER of the Ziploc bag. Insert approximately two inches of the flexible tubing into the corner opening and use the duct to tape to secure the tubing and to seal the connection between the tubing and the bag. Make sure the open end of the tubing is held upright.
3. Add vinegar to the quart size Ziploc bag and close the bag leaving approximately one inch of ONE CORNER open. Insert the open end of the flexible tubing and use the duct tape to secure the tubing and to seal the connection between the tubing and the bag.
4. Squeeze the pint size bag until all the mixture goes into the flexible tubing, then squeeze the flexible tubing until the mixture goes in the quart size bag.
5. On the opposite corner from the flexible tubing/Ziploc connection, open approximately one inch of the Ziploc bag and use duct tape to secure the pantyhose in order to seal the connection between the pantyhose and the bag.
6. Have one student hold the end of the pantyhose two-thirds of the way up. Then squeeze the contents of the quart size Ziploc into the top one-third of the pantyhose which is placed on paper towels in order to absorb liquids.
7. While holding the pantyhose, place the open end into the paper cup over the plastic tub, and continue to squeeze the pantyhose in order for the mixture to go into the paper cup.
8. Squeeze the paper cup allowing the remaining mixture to go through the hole in the paper cup into the plastic tub.
9. Remove the flexible tubing from your model. Clean up and dispose of your materials. Remove your gloves and wash your hands.
10. Discuss the questions for Part 2 on the Student Handout with your group members and write the answers in the appropriate place.

After Strategy/Explain & Elaborate: 150 minutes (Day 4, 5, and 6)

1. Each student will need a copy of the Model the Digestive Tract handout (see attached document). Students should be divided into collaborative groups of approximately four students each. Each group will need one set of the Digestive Organ Pictures (see attached documents).
2. Working with their group members, students should complete the activity described on the handout, in which students will create a model of the digestive tract and calculate how long food takes to pass through each organ.
3. After all groups have completed the lab activities on the digestive system, the teacher should lead a class discussion among all of the groups to compare each group’s digestive system models.
   Note: If the teacher identifies that students need additional review before the summative assessment, the teacher may show students the Ins and Outs of Digestion Presentation to review the concepts demonstrated during the lab activities (see attached PowerPoint presentation).
4. The teacher should give the students the Pre-/Post-Test, that students completed as a pre-test at the beginning of the lesson. The teacher should explain to students that this post-test will allow students to demonstrate the knowledge they acquired during the lab activities.
5. To extend the learning of this lesson, the teacher can allow students to create their own investigation pertaining to the human digestive system. For this portion of the activity, the teacher will need to give each student a copy of the Student Lab Guide (see attached documents). This handout will provide students with a real-world situation related to the human digestive system. Students will create a hypothesis and design an experiment to solve the scientific problem.

Formative: The teacher will informally assess student’s background knowledge by administering the Pre-/Post-Test prior to teaching the lesson. The teacher should carefully monitor students as they complete the lab activities with their groups to certify that students are correctly following the lab procedures. The teacher should review each group’s models of the digestive system to ensure that students are creating accurate models.

Summative: The teacher will formally assess students at the conclusion of each lab experiment by reviewing each student’s answers to the reflection questions on the Student Handout for Part 1 and Part 2. The teacher will administer the Pre-/Post-Test as a summative assessment at the end of the lesson. A rubric is provided to assess the extension activity discussed at the conclusion of the lesson’s procedures.

Students who have prior knowledge of the digestive system can use the Student Procedure B-“Cracker and Avocado Activity” lab sheet (see attached document). This lab sheet will allow students more personal creativity in creating the model of the digestive system and to further develop an understanding of the concepts taught in this lesson.

Students who require additional preparation prior to the lesson or review after the lesson can view the Ins and Outs of Digestion Presentation Presentation which succinctly summarizes the concepts demonstrated during this lesson’s lab activities (see attached PowerPoint presentation).