1. Animals Unit Activity 5.3: Explaining How Cows Grow: Digestion
Carbon: Transformations in Matter and Energy
Environmental Literacy Project Michigan State University
Animals Unit Activity 5.3: Explaining How Cows Grow: Digestion
Lead a discussion about how student ideas have changed over time.
Show slide 23 of the 5.3 Explaining How Cows Grow: Digestion PPT. Have students look back over their process tools for this unit.
Have students consider how their ideas changed with regard to scale, movement, and carbon.
What do they know now about how cows use food to move and function that they didn’t know before the investigation?

2. Unit Map
You are here
Use the instructional model to show students where they are in the course of the unit.
Show slide 2 of the 5.3 Explaining How Cows Grow: Digestion and Biosynthesis PPT.

3. Revisit your arguments
Think about what you know now that you didn’t know before. What have you learned?
Remind students of their unanswered questions.
Using slide 3 of the PPT have students revisit their arguments and unanswered questions from the Mealworm Investigation by looking at 3.3 Evidence-Based Arguments for Mealworms Eating.
Remind students that after explaining cellular respiration in Lesson 4.2 there were still unanswered questions about how animals grow and where the glucose needed for cellular respiration comes from.
In today’s lesson, students will use what they learned in Lesson 5.1 (and 5.2) to explain how cows get food to their bodies’ cells.

4. How do animals use food as materials for growth?
Image Credit: Craig Douglas, Michigan State University
Use slides 4-5 of the 5.3 Explaining How Cows Grow: Digestion PPT to guide students through a review of digestion.
Use Slide 4 to review how animals use food to grow. Ask students for their ideas about what they remember from the previous activity.
Use slides 5 to remind students what happens to the food that IS digested: Large organic molecules (polymers) are divided into small organic molecules (monomers) that go into the blood.
Display the following posters in your classroom to help students visualize the digestion of polymers to monomers.
Carbohydrates: Use the Digestion and Biosynthesis of Carbohydrates 11 x 17 Poster to offer students a visualization of how polymers like starch (which is a type of carbohydrate) are broken apart into monomers like glucose.
Fat: Use the Digestion and Biosynthesis of Fat 11 x 17 Poster to offer students a visualization of how polymers like fat are broken apart into monomers like fatty acids and glycerol.
Proteins: Use the Digestion and Biosynthesis of Protein 11 x 17 Poster to offer students a visualization of how polymers like proteins are broken down into amino acids.
Note: If you only taught 5.1, you can use the posters to help students visualize the process, but do not need to focus on the names of the small organic molecules.

5. Step 1: Digestion Materials for growth: Biosynthesis Food Digestion
Energy: Cellular respiration
Image Credit: Craig Douglas, Michigan State University
Use slides 4-5 of the 5.3 Explaining How Cows Grow: Digestion PPT to guide students through a review of digestion.
Use Slide 4 to review how animals use food to grow. Ask students for their ideas about what they remember from the previous activity.
Use slides 5 to remind students what happens to the food that IS digested: Large organic molecules (polymers) are divided into small organic molecules (monomers) that go into the blood.
Display the following posters in your classroom to help students visualize the digestion of polymers to monomers.
Carbohydrates: Use the Digestion and Biosynthesis of Carbohydrates 11 x 17 Poster to offer students a visualization of how polymers like starch (which is a type of carbohydrate) are broken apart into monomers like glucose.
Fat: Use the Digestion and Biosynthesis of Fat 11 x 17 Poster to offer students a visualization of how polymers like fat are broken apart into monomers like fatty acids and glycerol.
Proteins: Use the Digestion and Biosynthesis of Protein 11 x 17 Poster to offer students a visualization of how polymers like proteins are broken down into amino acids.
Note: If you only taught 5.1, you can use the posters to help students visualize the process, but do not need to focus on the names of the small organic molecules.

6. Constructing explanations
Consider the following as you construct your explanation:
Evidence from the investigation
What you learned from the molecular modeling or tracing activity
Three Questions Handout
Have students complete their Explanations Process Tool for Digestion.
Show slide 6 of the 5.3 Explaining How Cows Grow: Digestion PPT. Give each student one copy of 5.3 Explanations Tool for Cow Digestion.
Tell students that in this part of the investigation, they will combine everything they learned about how cows get food to their body’s cells into an explanation.
Remind them to consider both their evidence from the investigation as well as what they learned in the molecular modeling (or tracing) activity to construct their explanations.
Give students about 10 minutes to complete the Explanations process tool.

7. Comparing Ideas with a Partner
Compare your explanations for each of the Three Questions.
How are they alike?
How are they different?
Check your explanation with the middle- and right-hand columns of the Three Questions handout.
Consider making revisions to your explanation based on your conversation with your partner.
Have students share explanations with each other.
Show slide 7 of the 5.3 Explaining How Cows Grow: Digestion PPT. Divide students into pairs and have them compare explanations for the Three Questions and the final explanation on the process tool.
Have students use the Three Questions 11 x 17 Poster (or Handout) as a reference. Have students check their explanations with the middle and right-hand columns of the poster or handout to make sure they are following the “rules.”

8. The Matter Movement Question
Digestion:
The Matter Movement Question
How do molecules move to the location of the chemical change?
How do molecules move away from the location of the chemical change?
Image Credit: Craig Douglas, Michigan State University
Have students think about how digestion answers the Matter Movement question.
Use slides 8-14 in the PPT to have the students discuss what is happening to matter during digestion and to have them check their answers to the Matter Movement Question on their 5.3 Explanations Tool for Cow Digestion.
Show students slides 8-11 to have them think about where atoms are moving from and moving to during digestion.
Display slides to have students compare their answers to the Matter Movement Question with the answers on the slides. Have students use a different colored writing utensil to make any needed changes to their answers. Allow students to ask questions if they do not understand why their ideas are incorrect.
If students have model explanations to share, display student work and discuss. If students have common areas of weakness in their explanations, ask for a volunteer to share, display student work, and discuss ways of strengthening the response.

9. Which atoms and molecules move when an animal digests food?
Small organic molecules (monomers: amino acids, glucose, fatty acids, glycerol)
Large organic molecules (polymers: proteins, carbs, fats)
Image Credit: Craig Douglas, Michigan State University
Have students think about how digestion answers the Matter Movement question.
Use slides 8-14 in the PPT to have the students discuss what is happening to matter during digestion and to have them check their answers to the Matter Movement Question on their 5.3 Explanations Tool for Cow Digestion.
Show students slides 8-11 to have them think about where atoms are moving from and moving to during digestion.
Display slides to have students compare their answers to the Matter Movement Question with the answers on the slides. Have students use a different colored writing utensil to make any needed changes to their answers. Allow students to ask questions if they do not understand why their ideas are incorrect.
If students have model explanations to share, display student work and discuss. If students have common areas of weakness in their explanations, ask for a volunteer to share, display student work, and discuss ways of strengthening the response.

10. Large organic molecules (polymers: proteins, carbs, fats)
How do large and small organic molecules move when an animal digests food?
Small organic molecules (monomers: amino acids, glucose, fatty acids, glycerol)
Large organic molecules (polymers: proteins, carbs, fats)
Image Credit: Craig Douglas, Michigan State University
Have students think about how digestion answers the Matter Movement question.
Use slides 8-14 in the PPT to have the students discuss what is happening to matter during digestion and to have them check their answers to the Matter Movement Question on their 5.3 Explanations Tool for Cow Digestion.
Show students slides 8-11 to have them think about where atoms are moving from and moving to during digestion.
Display slides to have students compare their answers to the Matter Movement Question with the answers on the slides. Have students use a different colored writing utensil to make any needed changes to their answers. Allow students to ask questions if they do not understand why their ideas are incorrect.
If students have model explanations to share, display student work and discuss. If students have common areas of weakness in their explanations, ask for a volunteer to share, display student work, and discuss ways of strengthening the response.

11. What happens to food that animals can’t digest?
Our digestive systems cannot break down some large organic molecules (such as fiber).
These molecules leave our bodies as feces.
Image Credit: Craig Douglas, Michigan State University
Have students think about how digestion answers the Matter Movement question.
Use slides 8-14 in the PPT to have the students discuss what is happening to matter during digestion and to have them check their answers to the Matter Movement Question on their 5.3 Explanations Tool for Cow Digestion.
Show students slides 8-11 to have them think about where atoms are moving from and moving to during digestion.
Display slides to have students compare their answers to the Matter Movement Question with the answers on the slides. Have students use a different colored writing utensil to make any needed changes to their answers. Allow students to ask questions if they do not understand why their ideas are incorrect.
If students have model explanations to share, display student work and discuss. If students have common areas of weakness in their explanations, ask for a volunteer to share, display student work, and discuss ways of strengthening the response.

12. Matter Movement Do you have:
arrows showing large organic molecules or polymers (carbohydrates, proteins, fat/lipids) going through the small intestine?
Large Organic Molecules
Image Credit: Craig Douglas, Michigan State University
Display slides to have students compare their answers to the Matter Movement Question with the answers on the slides. Have students use a different colored writing utensil to make any needed changes to their answers. Allow students to ask questions if they do not understand why their ideas are incorrect.
If students have model explanations to share, display student work and discuss. If students have common areas of weakness in their explanations, ask for a volunteer to share, display student work, and discuss ways of strengthening the response.
Small Intestine
Blood
Large Organic Molecules

13. Matter Movement Do you have:
an arrow showing small organic molecules going into the blood?
Large Organic Molecules
Small Organic Molecules
Image Credit: Craig Douglas, Michigan State University
Display slides to have students compare their answers to the Matter Movement Question with the answers on the slides. Have students use a different colored writing utensil to make any needed changes to their answers. Allow students to ask questions if they do not understand why their ideas are incorrect.
If students have model explanations to share, display student work and discuss. If students have common areas of weakness in their explanations, ask for a volunteer to share, display student work, and discuss ways of strengthening the response.
Small Intestine
Blood
Large Organic Molecules

14. Matter Movement Do you have:
An arrow showing undigested large organic molecules continuing through the intestine
Large Organic Molecules
Large Organic Molecules
Small Organic Molecules
Image Credit: Craig Douglas, Michigan State University
Display slides to have students compare their answers to the Matter Movement Question with the answers on the slides. Have students use a different colored writing utensil to make any needed changes to their answers. Allow students to ask questions if they do not understand why their ideas are incorrect.
If students have model explanations to share, display student work and discuss. If students have common areas of weakness in their explanations, ask for a volunteer to share, display student work, and discuss ways of strengthening the response.
Small Intestine
Blood
Large Organic Molecules

15. The Matter Change Question
Digestion:
The Matter Change Question
What molecules are carbon atoms in before and after the chemical change?
What other molecules are involved?
Image Credit: Craig Douglas, Michigan State University
Have students think about how digestion also answers the Matter Change Question.
Show slide 15 to begin discussion the Matter Change Question.
Display slides to have students compare their answers to the Matter Change Question on the 5.3 Explanations Tool for Cow Digestion with the answers on the slide. Have students use a different colored writing utensil to make any needed changes to their answers. Allow students to ask questions if they do not understand why their ideas are incorrect.
If students have model explanations to share, display student work and discuss. If students have common areas of weakness in their explanations, ask for a volunteer to share, display student work, and discuss ways of strengthening the response.
Note: digestive cells produce molecules (enzymes) that can break large organic molecules up into small organic molecules.

16. Matter Change
Name the chemical change that a cow uses to break down food: Digestion
Display slides to have students compare their answers to the Matter Change Question on the 5.3 Explanations Tool for Cow Digestion with the answers on the slide. Have students use a different colored writing utensil to make any needed changes to their answers. Allow students to ask questions if they do not understand why their ideas are incorrect.
If students have model explanations to share, display student work and discuss. If students have common areas of weakness in their explanations, ask for a volunteer to share, display student work, and discuss ways of strengthening the response.

17. Matter Change
What molecules are carbon atoms in before the chemical change? Large organic molecules (or polymers: carbohydrates, fats/lipids, and proteins) What other molecules are needed? (Water)
What molecules are carbon atoms in after the chemical change? Small organic molecules (or monomers: amino acids, sugars, and fatty acids) What other molecules are produced? None
Chemical Change
Display slides to have students compare their answers to the Matter Change Question on the 5.3 Explanations Tool for Cow Digestion with the answers on the slide. Have students use a different colored writing utensil to make any needed changes to their answers. Allow students to ask questions if they do not understand why their ideas are incorrect.
If students have model explanations to share, display student work and discuss. If students have common areas of weakness in their explanations, ask for a volunteer to share, display student work, and discuss ways of strengthening the response.

18. Digestion: The Energy Change Question
What forms of energy are involved?
Image Credit: Craig Douglas, Michigan State University
Discuss how digestion helps to answer Energy Change questions.
Display slide 18 to begin discussion the Energy Change Question.
Display slide 19 to have students compares their answers to the Energy Change Question on the 5.3 Explanations Tool for Cow Digestion with the answers on the slide. Have students use a different colored writing utensil to make any needed changes to their answers. Allow students to ask questions if they do not understand why their ideas are incorrect.
If students have model explanations to share, display student work and discuss. If students have common areas of weakness in their explanations, ask for a volunteer to share, display student work, and discuss ways of strengthening the response.
What energy transformations take place during the chemical change?

19. Energy Change
What forms of energy go into this chemical change? Chemical Energy
What forms of energy come out of this chemical change? Chemical Energy
Energy Transformation
Display slide 19 to have students compares their answers to the Energy Change Question on the 5.3 Explanations Tool for Cow Digestion with the answers on the slide. Have students use a different colored writing utensil to make any needed changes to their answers. Allow students to ask questions if they do not understand why their ideas are incorrect.
If students have model explanations to share, display student work and discuss. If students have common areas of weakness in their explanations, ask for a volunteer to share, display student work, and discuss ways of strengthening the response.

20. Telling the Whole Story
Question: How does a cow get small organic molecules to its cells?
Does your story include these parts? (Check the Back of the Three Questions Handout.)
Matter movement: Large organic molecules (or polymers: carbohydrates, fats/lipids, proteins) enter into the cow and move through the digestive system to the small intestine.
Matter change: Large organic molecules are separated into small organic molecules (or monomers: amino acids, sugars, fatty acids, glycerol).
Energy change: The chemical energy of the C-C and C-H bonds in the large organic molecules remains in the small organic molecules.
Matter movement: The small organic molecules pass through the intestinal lining into the blood stream.
(Optional) Have students critique example explanations.
Display slide 20 of the PPT for the full story of digestion. Have students look at two handouts: (a) The Three Questions Handout, and (b) the Animals Example Explanations Handout.
Ask students to evaluate the two example explanations of cow digestion on the Animals Example Explanations Handout: Which explanation is better? Why?
Have students use the Three Questions Explanation Checklist on the back of the Three Questions Handout to justify their critiques of the explanations.
Have students critique and improve their full explanations.
Display slide 20 of the PPT for the full explanation. Have students use the Three Questions Explanation Checklist on the back of the Three Questions Handout to check that their story includes each of the parts (matter movement, matter change, energy change, and matter movement).
If students don’t have all four parts in their explanation, instruct them to add to their explanation using a different colored writing utensil.
If students have model explanations to share, display student work and discuss. If students have common areas of weakness in their explanations, ask for a volunteer to share, display student work, and discuss ways of strengthening the response.

21. Discuss with a partner
(Optional) Have students read about digestion and complete part of the graphic organizer.
Pass out 5.3 How do Animals Digest Food? Reading. The reading provides a summary explanation of digestion and additional information about the digestion of fiber. Higher level students may not need the review of content provided in this reading, but you may want them to add to the graphic organizer started in Activity 4.2.
Students can complete the reading individually or in pairs.
After reading, students can complete the digestion section of the Matter and Energy in Animals Graphic Organizer that they started completing in Activity 4.2.
Have students connect their atomic-molecular explanations to the macroscopic scale by referring to the cow poster.
Show slide 22. Have students look at the Cow 11 x 17 Poster and discuss with a partner the parts of a cow involved in digestion on a macroscopic scale.
Tell students that digestion occurs in the small intestines.
Tell students that in the next activity they will explain what happens to food after digestion.