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Activity 4 (Explain): Modeling the Respiratory & Circulatory Systems

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Activity Overview

Activity Summary

In this activity, students use what they have learned so far in the module to create a model showing how the respiratory and circulatory systems interact.

Activity Objectives & Materials

Approximate Time: 45 minutes



  • Students will create a model to show how the respiratory and circulatory systems connect to each other

  • Students will use their models to explain how oxygen gets to the different parts of our bodies



  • Computer & projector

  • Speakers (optional for video)

  • Paper for student models

  • Respiratory/Circulatory System Model (sample)



  • None

Standards Connection

DCI: LS 1.A: Structure & Function

SEP: Developing & Using Models

CCC: Systems & System Models



Show students a simple scientific model like the water cycle model below:

Water Cycle model.jpg

Have students write down the answers to these three questions.

  • What kinds of things do you see in this model?

  • In what way does this model look realistic?

  • In what way does this model not look realistic?

Go over the first question, and write students responses on the board. Make sure students mention the arrows, words, and objects.  Afterwards, tell students that you will come back to these in a few minutes. Then go over questions two and three.

  • The purpose of this warmup is for students to recognize that scientific models often include things like words, arrows, and simplified drawings of real-world things. Scientific models are often not physical, and they are used to explain phenomena like rain and clouds. They often do not look realistic, and can be very abstract.


1. Frame the Activity

Tell students that when scientists are studying very complicated systems, like the human body, they use models to make the system easier to understand. We’re going to create models today based upon everything we’ve learned so far. We’ll use our models to help understand how oxygen gets to our bodies through the respiratory and circulatory systems. Hopefully this will help us to figure out what’s happening with Tatiana and Calvin.

2. Identify the Respiratory System Parts of the Model

Add a Mini-lesson: If students have not created scientific models before, it is worth taking time to discuss the difference between a scientific model and a traditional model. See this article from the Royal Society of Chemistry for some ideas on how to teach modeling to students.

On the board/chart paper, write: “Respiratory System” Ask students what they think needs to be in their models. They should use their notes from the previous activity and ideas from their warmup to help. Add their responses to the list.

  • Nose, lungs, bronchi, trachea, alveoli, air/oxygen, carbon dioxide

3. Modeling the Respiratory System

Have students (on their own or in small groups), create a simple model of the respiratory system. Remind them that models don’t need to look like the actual real world objects. For example, they can draw a box and write “lungs” on it. They can use the two lists on the board to help them (parts of models and respiratory system). As students work, circulate and support as needed.

Differentiation ideas: If students need extra support, consider these options:

  • Instead of having students make their own models from scratch, put components of the model on small slips of paper (words, arrows, boxes), and have students create the model using the parts and glue/tape it onto a sheet of paper or into their notebooks

  • Create a handout with boxes for body, respiratory system, and circulatory system, and have students fill in the rest of the model

You can use the sample Respiratory-Circulatory System Model below as a guide, but make sure students are all making their own models. Modeling is a valuable part of the sensemaking process, so student models will be similar, but will likely look different.

Respiratory Circulatory System Model.jpg

When students have gotten their models to a point where they make sense, have them partner with another student (or another group) to share and explain their models. This provides the benefit of giving students a chance to practice explaining their models, and also to get ideas from their classmates. You may also want to show one model to the class and have students give “warm and cool” feedback to help highlight strong points and improve weak points in the model. This is a great way to help students improve their modeling and peer feedback skills. Afterwards, give students time to revise their models if they want.

Step 4

4. Identify the Circulatory System Parts of the Model

Write “circulatory system” on the board and add student responses. Make sure they include:

  • Heart, arteries, veins, blood, blood vessels


They may also choose to include things like red blood cells or capillaries, but they should avoid getting into too many details like valves.

5. Modeling the Circulatory System

Have students use their list to add the circulatory system to their models. Support them in particular in creating two different pathways from the heart to the lungs and back and from the heart to the rest of the body and back. Also remind them that some things they wanted to put in their model should go in a few different places (ex. oxygen and carbon dioxide). See the sample model at the end of the activity for ideas to help students.


If students get stuck trying to draw a realistic model, remind them that their goal is to show how oxygen gets to all the parts of their bodies, not to draw the human body.


Again, once they are done, have students share their revised models to get feedback, and give them time to make revisions afterwards.

6. Model Discussion

Discuss with students how their models show how the human circulatory and respiratory systems are connected.

Key points:

  • oxygen gets into our bodies through the respiratory system (nose/mouse, trachea, lungs, alveoli)

  • The alveoli allow oxygen to get into our bloodstream.

  • The blood, pumped by the heart, delivers the oxygen to our cells.​

Teacher Tip: Before the discussion about the human body as a system of interacting systems (below), you may want to review what a system is with students. Keep the definition simple so as not to add confusion: ex. a system is a thing  made of parts that work together.

Write the sentence, “The human body is a system of interacting systems” in a place where students can see it such as on the board or a piece of chart paper. Make sure students know what the word “system” means (see below) and what the word “interacting” means, and then have them turn to a partner to decide if they agree or disagree with this statement, and what evidence they have to support their decision. After they have had time to talk, bring the class back together to talk. Students should be able to formulate the idea that the statement is true because the circulatory system and the respiratory system interact, and so do lots of other systems in the human body (even if they don’t know the names of other systems).

NGSS Connection: The concept that the human body is a system of interacting subsystems is a key component of this module’s focus Disciplinary Core Idea, and the focus Crosscutting Concept (Systems & System Models). While students may not have completely internalized the concept at this point in the module, having students discuss it and make connections to it whenever possible is a good way to reinforce the idea.

7. Formative Assessment: Return to the Phenomenon

Ask students how they can use their models to help understand Tatiana & Calvin’s problem. What do you think might be causing Tatiana & Calvin’s breathing problem? Why is it worse when they exercise?

  • Possible explanations: Something in the air is keeping them from getting enough oxygen to their bodies through her lungs, something is wrong with their lungs/respiratory system.

  • It is less important at this point that students have “correct” answers than that they are using their models to help make logical hypotheses.

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