To learn about the digestive system. To begin to explore where nutrients come from, as well as their importance for particular tasks in the body.
Students are starting to view the body as a system in these grades. One important thing they should start to understand is that in order for their "systems" to properly function, they need energy and materials from food (as the benchmark states). Though students know they must eat to live, they may not have made the distinct connections between food and the body properly repairing itself, or food and growth; even a connection as simple as a lack of iron or carbohydrates making one tired.
This lesson will focus on the digestive system in order to address the latter part of the benchmark-that undigested food is eliminated. In addition, it will begin to explore where nutrients come from and their importance for particular tasks in the body.
This Science NetLinks lesson is the first of a three part series. It works in conjunction with Nutrition 2: Good Food, Good Health, a lesson that teaches about the food groups and how vitamins and minerals help the body function properly, and Nutrition 3: Got Broccoli?, a lesson that encapsulates what students have learned about nutrition.
Note: Younger elementary school students might think that the contents of the body is what they have seen being put into it or coming out of it. Students know food is related to growing and being strong and healthy, but they are not aware of the physiological mechanisms. In upper elementary, students can list a large number of organs and by 5th grade, "students know that food undergoes a process of transformation in the body." (Benchmarks for Science Literacy, pp. 344-345)
Get students involved in the topics of this lesson by discussing their food intake.
Ask questions such as:
- What have you eaten today?
- Why did you choose to eat those foods?
- What happened to your food after you ate it?
Students should naturally begin talking about the digestive system in response to the final question listed above. Let them know that food and the digestive system are the topics for this lesson.
Now read aloud Your Digestive System found on The Yuckiest Site on the Internet (on the Discovery website).
Once students have done some preliminary exploration of the digestive system, ask the following questions:
- Where do people get energy? (from food)
- How does the energy from food get into the body? (Nutrients flow into the bloodstream from the small intestine)
- What happens to the indigestible parts of the food? (Leftovers go into the large intestine and are eliminated.)
Next, brainstorm answers to the following questions. There are many answers, many of which are not very obvious, but this will get students thinking beyond the basic processes of the digestive system.
- What do you think your body uses the energy from food for? (These answers can include just about anything the body does. The goal is to demonstrate that without food, the body would not function properly and if it went without food for a prolonged period, the health of that person would deteriorate.)
- If your body didn't get enough nutrients, what do you think would happen? (Ask students if they would grow, or think as well. Try to get students to think about this question in relation to junk food.)
In this part of the lesson students will learn about the digestive system in more detail.
Note: Depending on your students' ability, this article can be read online or printed out and read in class. Also, it is not necessary to click on the links within the text for this lesson.
Have students get into groups and with colored construction paper, cut out parts of the digestive system as they make their way through the article. On each organ, students can write a one to two sentence description of the organ's purpose. In the end they will have a recreated digestive system of their own.
Another way to approach this is for you to hand each group a "puzzle" which would consist of the different parts of the digestive system already cut out. Students could sequence the digestive system as they read through the site. This will give them the big picture.
After this exercise, have students write short answers to these questions:
- Where in the digestive system do nutrients enter the body?
- What happens to the indigestible parts of food?
Next, have students go to a digestive system activity on The Learning Site, the World Wide Web service of Harcourt School Publishers.
Follow these steps to access the digestive system activity:
- Click on "Health" on the left side of the page.
- Click "4" on the right side of the page.
- Scroll down to Chapter 4.
- Click the activity, "Digestion!"
Once at the activity, have students review what they've learned by clicking on the link, "Building Your System." Then have them study the digestive organs in more depth by clicking on the "Inside Story."
As the benchmark for this lesson states, it's important for students to realize that the indigestible parts of food are eliminated, and that people obtain energy and materials for body repair and growth from food. To continue to illustrate these ideas, have students follow the final link on The Learning Site, "Food Path." This activity depicts various foods traveling through the digestive system, and introduces students to nutrition terms such as carbohydrates, protein, fat, vitamins, and minerals.
Ask questions such as the following to assess student understanding of the benchmark ideas:
- How is protein in milk broken down? (By digestive juices in the stomach.)
- What happens once food enters the small intestine? (Nutrients are absorbed, and minerals and vitamins move into the bloodstream.)
- What does bile do? (Helps the small intestine break down fat so it can be absorbed into the bloodstream.)
- What is broccoli made up of? (Water, fiber, and vitamins.)
- What happens to fiber in the body? (It's not digested, and is eliminated.)
- What is chicken largely made up of? (protein)
- What does your body use the nutrients in protein for? (To repair or replace worn-out cells.)
- What is pasta largely made up of? (carbohydrates)
- What do carbohydrates offer the body? (long-lasting energy)
- Why do you feel a quick burst of energy after eating foods with a lot of sugar? (Because sugar is quickly absorbed into the bloodstream.)
In addition, assess student understanding of the digestive system by how well they recreated the digestive system in the Development, after reading the KidsHealth article.
To learn more about the food groups and how vitamins and minerals help the body function properly, visit the second and third lessons in this Science NetLinks series:
Have students play Grab a Grape from the Nutrition Café. Here, students select from categories such as Food & Sports, Bone Building, Weight Control, and Body Building to learn more about the nutrients in foods and what they can do for the body.