OpenSciEd Unit 7.3 · Lesson 07 · 7.A

Look for: The digestive system is a long tube with diff…

MS-LS1-5MS-LS1-7Assessment opportunity · Formative assessment

From Teacher Edition

Facilitation guidance from the lesson plan — what to notice in student thinking and how to respond while teaching.

Building towards

7.A.1 Develop a model based on multiple lines of evidence to represent the inputs, processes, and outputs of the digestive system and the role that the system, and the subsystems within it, play in breaking down matter inputs through chemical reactions, absorbing food, and excreting unused matter.

What to look / listen for

Students should identify the following ideas in their models:

The digestive system is a long tube with different parts to it.
In one part of the digestive system, the small intestine, small food molecules are absorbed, and large food molecules aren’t.
Absorption means that the molecules cross the lining of the small intestine.
Fiber is not digested at all and is excreted from the body.
Large food molecules can be broken down into smaller food molecules.
In another part of the digestive system, the mouth, some types of complex carbohydrates are broken down into smaller pieces through chemical reactions.
Other types of food molecules (proteins and fats) are broken down in other parts of the digestive system (stomach and small intestine).

What to do

If students are missing ideas, prompt them to revisit their Gotta-Have-It Checklist, Progress Trackers, or science notebooks for key ideas that they are missing. Also see the guidance that follows for prompting discussion in small groups as they develop their models.
As students work, circulate to provide support. If students become stuck, it may help to use the prompts below to get them started.

Suggested prompt

Sample student response

What happens to large food molecules? How does it happen? What evidence do you have to support this idea?

They break down into smaller molecules through chemical reactions. We saw that in the graphs of food changing in the mouth and stomach and in our investigation with the cracker and saliva. We think this is true for all food molecules, not just complex carbohydrates and sugars.

Where do you think the small molecules go?

We know that they can pass through the small intestine wall and that they disappear. We think they get absorbed, but we’re not sure where.

What leaves a healthy body as poop?

In a healthy body, fiber, a large molecule that doesn’t break down, leaves the system.