Unit Overview
6.6 Cells & Systems

How do living things heal?

Unit Summary

This unit launches with students hearing about an injury that happened to a middle school student that caused him to need stitches, pins, and a cast. They analyze doctor reports and develop an initial model for what is going on in our body when it heals. Students investigate what the different parts of our body are made of, from the macro scale to the micro scale. They figure out parts of our body are made of cells and that these cells work together for our body to function.

Once students have figured out what their bodies are made of and how the parts of their body work together to be able to move, they wonder how the parts of our body heal. They start by watching a timelapse of a knee scrape and notice that over time the part that was scraped is filled in with new skin cells. Students investigate what happens when cells make more cells, what cells need to make more cells, and how cells get what they need to make more cells. Students return to the healing timeline they made at the start of the unit and apply what they have figured out about the interactions between the different systems in the body to explain the various events of healing that took place for the injury at the start of the unit. Finally, they apply their model for healing to explain growth at growth plates in children's bodies as they become adults.

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Unit Examples


Additional Unit Information

Building Toward the Following Standards and Practices
Performance Expectations

This unit builds towards the following NGSS Performance Expectations (PEs): 

  • MS-LS1-1. Conduct an investigation to provide evidence that living things are made of cells; either one cell or many different numbers and types of cells.
  • MS-LS1-2.* Develop and use a model to describe the function of a cell as a whole and ways parts of cells contribute to the function.
  • MS-LS1-3.* Use argument supported by evidence for how the body is a system of interacting subsystems composed of groups of cells.
  • MS-LS1-8.* Gather and synthesize information that sensory receptors respond to stimuli by sending messages to the brain for immediate behavior or storage as memories.

*PEs marked with an asterisk are partially developed in this unit and shared with other units, as explained in the DCI column.

Regarding the strike through in LS1.D–“and synthesize… or storage as memories”–this PE is revisited in multiple units in OpenSciEd. In order to support students in having a genuine need to figure out things about each of the different receptors, they will engage with this PE in the OpenSciEd Unit 6.1: Why do we sometimes see different things when looking at the same object? (One-way Mirror Unit) unit in reference to receptors in the eye, in the OpenSciEd Unit 7.1: How can we make something new that was not there before? (Bath Bombs Unit) unit in reference to receptors in your nose, in the OpenSciEd Unit 8.1: Why do things sometimes get damaged when they hit each other? (Collisions Unit) unit in reference to receptors in your skin and brain, and in the Sound Unit unit in reference to the receptors in your ears. In this unit, students will be engaging with this PE as they gather more information about nerves in general–what they do, how they look, and how they function.

Disciplinary Core Ideas

The unit expands students’ understanding of cells, systems, and structure and function which include these Grade 6-8 DCI elements: 

  • LS1.A: All living things are made up of cells, which is the smallest unit that can be said to be alive. An organism may consist of one single cell (unicellular) or many different numbers and types of cells (multicellular).
  • LS1.A: Within cells, special structures are responsible for particular functions, and the cell membrane forms the boundary that controls what enters and leaves the cell.
  • LS1.A: In multicellular organisms, the body is a system of multiple interacting subsystems. These subsystems are groups of cells that work together to form tissues and organs that are specialized for particular body functions
  • LS1.D: Information Processing. Each sense receptor responds to different inputs (electromagnetic, mechanical, chemical), transmitting them as signals that travel along nerve cells to the brain. The signals are then processed in the brain, resulting in immediate behaviors or memories.
    • Other aspects of this PE are developed in additional OpenSciEd units, beginning their initial work on MS-LS1-8 in the One-way Mirror Unit. The current version of this unit, OpenSciEd Unit 6.6: How do living things heal? (Healing Unit), primarily addresses the role of nerve cells in sending signals to the brain. Students will revisit and expand on their understanding of this DCI in later units in the OpenSciEd program, including returning to it in the OpenSciEd Unit 7.1: How can we make something new that was not there before? (Bath Bombs Unit) unit in 7th grade and the Sound Unit unit in 8th grade.
Science & Engineering Practices
  • Developing and Using Models: This unit intentionally develops this practice. While students engage in aspects of the modeling practice they have explored in prior units, this is a different context. This is the first biological system context that students investigate in the program, and is their first experience tying physical mechanisms to phenomena that occur in living things. Beginning in Lesson 1, students are developing a model for healing. They revise this model throughout the unit, and use their elaborated model to explain how the body heals from an injury (Lesson 12). In Lessons 2 through 6, the class develops a model of the structure and function of the different parts of the body. In Lesson 8, students apply what they have figured out about the different parts of the body to develop a model for how skin heals from a scrape at the cellular level. In Lessons 9 through 11, students continue to revise the healing model to include what is happening at the cellular level.
  • Planning and Carrying Out Investigations: This practice is key to the sensemaking in this unit. Students plan and carry out investigations across multiple lessons to help figure out how healing occurs. Students watch a demonstration of a chicken wing dissection in Lesson 2. They brainstorm how they would revise this dissection to “injure” the chicken wing in a similar manner to the injury the student in Lesson 1 had incurred. In Lesson 4, students carry out an investigation using microscopes to look at a blood sample. In Lesson 7, students plan for an investigation that could provide evidence as to whether other things in our world are made of cells. In Lesson 11, students carry out an investigation to figure out if things, like food particles, can get into an onion cell.
  • Analyzing and Interpreting Data: This unit intentionally develops this practice. While students have engaged with this practice in earlier units, in this unit students analyze different kinds of data (including images at different scales) in a different type of context, living things. Students identify the macro-level functions of skin, bone, and muscle, and figure out that the microscopic structures (cells) in blood and nerves support the functions of those body parts. Students analyze and interpret observational data, videos, and images to provide evidence that cell growth occurs. Students analyze second-hand data from an investigation of E.coli to collect evidence that the bacteria need food to make more cells and the more food the bacteria are provided, the more the bacteria make more cells.
  • Engaging in Argumentation: This practice is key to the sensemaking in this unit. Students engage in argumentation many times throughout the unit as they explain what is happening in the body for it to heal. In Lesson 2, they argue orally for the interactions between the bone and muscle and skin for a part of the body to function. In Lesson 7, students argue from evidence whether the living things they analyzed are made of cells or not. In Lesson 10, students argue for what human cells need to grow and make more cells and argue for what bacteria need to grow and make more of themselves. In Lesson 12, students argue from evidence for what caused the different healing events on the Healing Timeline from Lesson 1. In Lesson 13, students argue for whether the healing process is similar or different from the growth process and why.
  • The following practices are also key to the sensemaking in the unit:
    • Asking Questions and Defining Problems
    • Constructing Explanations and Designing Solutions
    • Obtaining, Evaluating, and Communicating Information
Crosscutting Concepts
  • Scale, Proportion, and Quantity: This crosscutting concept is key to the sensemaking in this unit. Students use different spatial scales to observe and make sense of phenomena, from macroscopic (parts of the body, systems within the body) to the microscopic (cell level). They also consider different temporal scales (4 months of healing for the student in Lesson 1 to the quick timelapse in Lesson 8) to figure out what the body is made of and how the different structures in the body are interconnected (ie: cells are part of tissues).
  • Systems and System Models: This crosscutting concept is key to the sensemaking in this unit. Beginning in Lesson 2, the class develops a poster titled Our Body as a System. Students incrementally revise and extend the systems model poster in the next four lessons as they figure out more about the different systems and subsystems within our body ranging from our body as a whole down to the system of the cell.
  • Structure and Function: This crosscutting concept is key to the sensemaking in this unit. As students figure out how parts of the body heal, they investigate the way different parts are structured, how these parts function and how the way these parts are structured is related to the function of the part. Students look at structures both macroscopically in the body as well as microscopically down to the cell. Students figure out that the different parts of the body are made of cells that are unique in shape and composition to that part of the body and that the structure of the cell is related to the structure and function of the part of the body the cell comes from.
  • The following crosscutting concepts are also key to the sensemaking in this unit:
    • Patterns
    • Cause and Effect
Connections to the Nature of Science

Which elements of NOS are developed in the unit?

  • Science investigations use a variety of methods and tools to make measurements and observations. (NOS-SEP)
  • Science assumes that objects and events in natural systems occur in consistent patterns that are understandable through measurement and observation. (NOS-CCC)

How are they developed?

  • Students make observations about the structure and function of different parts of the body at different scales through watching a dissection and then using microscopes to see the cellular level.
  • Students use microscopes to make observations of what different parts of living things are made up of. Through a small sample on a slide, they find these parts are made of cells and conclude the entire body part is made of the same type of cells.
Unit Information
How is the unit structured?

The unit is organized into two lesson sets.

  • Lesson Set 1 consists of Lessons 1-7. The anchor lesson is about an injury case that happened to a middle school student. The class hears about his story and then analyzes some different images representing people with disabilities. Using these images, students reflect on and think about what is meant by disability and how both the injury and some of these disabilities can affect how a person can function or do things. The class decides at the end of Lesson 1 to focus on figuring out more about the parts of the body that were injured in the case of the student with the broken foot. In this first lesson set we carry out investigations and critically read articles while incrementally changing spatial scales to figure out that the body can be thought of as a system, that there are different systems within the body that interact, and that all these systems are made up of cells. This first lesson set also serves to help students shift scales from the macro scale of the body to the micro scale of the cells that make up the parts of the body.
  • Lesson Set 2 consists of Lessons 8-14. The class remains at the microscopic scale at the beginning of this lesson set and then shifts from the micro back to the macro to explain the healing process. The focus of this lesson set is to explain that in order for our body to heal from an injury, it needs to make more cells. In order to make more cells, our cells need nutrients or food just like we do. We figure out that the structure of our cells is such that food particles which are carried around our body through our blood vessels can get into our cells and be used to make more cells. In the last lesson we engage with five disability stories through audio and video to reflect on what the word disability means and how it relates to our healing story. Students brainstorm areas in the classroom and school that could be adapted or redesigned to make them more accessible to people with different disabilities.

Where does this unit fall within the OpenSciEd Scope and Sequence?

This unit is designed to be the first life science focused unit in OpenSciEd. This unit will serve to set a foundation for students around the ideas of cells, body systems, and the interactions between these systems for the body to function. These ideas will be built upon and revisited in future units: OpenSciEd Unit 7.3: How do things inside our bodies work together to make us feel the way we do? (Inside Our Bodies Unit), OpenSciEd Unit 7.4: Where does food come from, and where does it go next? (Maple Syrup Unit), and OpenSciEd Unit 8.5: Why are living things different from one another? (Muscles Unit). Students will use and build on Systems and System Model supports that were established in Cup Design Unit and Storms Unit. In addition, they will build upon supports for Structure and Function that were established back in Cup Design Unit. For more information, visit the Scope and Sequence page.

What modifications will I need to make if this unit is taught out of sequence?

This is the sixth unit in 6th grade in the OpenSciEd Scope and Sequence and the first life science unit. OpenSciEd 7th grade units Unit 7.3, Unit 7.4, and 8th grade Unit 8.5 will all build off the Disciplinary Core Ideas (DCIs) that students develop by working on the following NGSS performance expectations MS-LS1-1, MS-LS1-2, MS-LS1-3 in this unit. If this unit is taught later in the OpenSciEd sequence, be mindful that elements of these DCIs might need additional scaffolding in the other life science units.

Given this placement, several modifications would need to be made if teaching this unit earlier in the middle school curriculum. These include:

  • If taught before OpenSciEd Unit 6.1 or at the start of the school year, supplemental teaching of classroom norms, setting up the Driving Question Board, and asking open-ended and testable questions would need to be added. (These supports are built into 6.1.) In this unit, students will build on the crosscutting concepts of system thinking, scale and proportion (moving from macroscopic to microscopic), and patterns from earlier 6th grade OpenSciEd units.
  • If taught before 6.1 and 6.2, students will benefit from additional scaffolding for structure and function.
  • If taught before, 6.4, students will benefit from additional scaffolding for scale, proportion, and quantity.
  • If taught before, 6.2 and 6.4, students will benefit from additional scaffolding for systems and system models. In this unit, students will build on the science and engineering practices of modeling, planning and carrying out investigations, and engaging in argument from evidence from earlier 6th grade OpenSciEd units.
  • If taught before 6.1 students will benefit from additional scaffolding for developing and using models.
  • If taught before, 6.2 and 6.3, students will benefit from additional scaffolding for planning and carrying out investigations. If taught before, 6.2 students benefit from additional scaffolding for engaging in argument from evidence.
What mathematics is required to fully access the unit’s learning experiences?

In Lesson 4, students calculate the total magnification of their microscope’s view, such as a 40x objective times a 10x eyepiece is 400x total magnification. In Lesson 4, students also use millimeter graph paper to help gain perspective about how close-up they’re seeing things with the microscope and to estimate the field of view at different magnifications. Prerequisite math concepts that may be helpful include the following:

  • CCSS.MATH.CONTENT.4.NBT.B.5 Multiply a whole number of up to four digits by a one-digit whole number, and multiply two two-digit numbers, using strategies based on place value and the properties of operations.
  • CCSS.MATH.CONTENT.5.NBT.A.2 Explain patterns in the number of zeros of the product when multiplying a number by powers of 10, and explain patterns in the placement of the decimal point when a decimal is multiplied or divided by a power of 10. Use whole-number exponents to denote powers of 10.
  • CCSS.MATH.CONTENT.4.MD.A.1 Know relative sizes of measurement units within one system of units including km, m, cm; kg, g; lb, oz.; l, ml; hr, min, sec. Within a single system of measurement, express measurements in a larger unit in terms of a smaller unit.

Also in Lesson 4, you may choose to take time to explore the mathematics of ratios of blood cells based on the percentages of each type mentioned in the reading. If you choose to extend the investigation in this way, the prerequisite math concepts that may be helpful include the following:

  • CCSS.MATH.CONTENT.6.RP.A.1: Understand the concept of a ratio and use ratio language to describe a ratio relationship between two quantities.
  • CCSS.MATH.CONTENT.6.RP.A.3.C: Find a percent of a quantity as a rate per 100 (e.g., 30% of a quantity means 30/100 times the quantity); solve problems involving finding the whole, given a part and the percent.
How do I shorten or condense the unit if needed? How can I extend the unit if needed?

The following are example options to shorten or condense parts of the unit without completely eliminating the important sensemaking for students.

  • Lesson 4: If you do not have microscopes available, you can shorten this lesson by one day by taking out the orientation to the microscopes.
  • Lesson 6: This is a two day lesson that includes using the microscopes to look at skin, bone and muscle slides. These images are in the Link on OpenSciEd Interactive website . If you have the technology available, you could have students make observations of the images as home learning and do the sense making over the course of one day afterwards.
  • Lesson 7: This is meant as a mid-point assessment to gauge where students are at in their thinking about whether all living things are made of cells. It could be done as home learning which could gain you a class period. In addition, this assessment only begins to build towards this key science idea at this point in the unit but is more deeply built upon and assessed in Lesson 10.
  • Lesson 13: This lesson is used as a transfer task in which students apply what they have figured out about how our body heals from a biological perspective through making new cells to repair the injured tissues, to a growth scenario. Students look at images of growth plates and think about whether a similar process to healing might also be what is happening when we grow. Since the anchoring phenomena and the PEs will have been fully addressed and assessed prior to this unit you could choose to delete this lesson.

To extend or enhance the unit, consider the following:

  • Lesson 2: If you wish, you could conduct the dissection as a demonstration investigation with your students instead of watching the video of the dissection. This would allow students to make closer observations and ask questions about the structures of the chicken wing that might be able to be answered through closer investigations of the parts of the chicken wing.
  • Lesson 5: Instead of sharing microscopic images of nerves with students, if you have slides of nerve smear available, you could allow students to use the microscopes and look at them with a partner to make observations.
  • Lesson 7: The first part of the assessment asks students to plan for an investigation that would help them figure out whether other things in their world are made of cells. Due to the open-ended nature of this question, in the second part of the assessment students analyze microscopic images of 6 different objects to look for evidence of whether they are made of cells or not. If you have the materials and time, you could allow students to carry out the investigation they plan for in part 1 of the assessment.
What are recommended adult-level learning resources for the science concepts in this unit?

The OpenSciEd instructional model focuses on the teacher being a member of the classroom community, supporting students to figure out scientific ideas motivated by their questions about phenomena. Students iteratively build their understanding of phenomena as the unit unfolds. To match the incremental build of a full scientific explanation across the unit, the science content background necessary for you to teach individual lessons incrementally builds too. Throughout the unit, we provide just-in-time science content background for you that is specific to the Disciplinary Core Ideas (DCIs) that will be figured out in a lesson. Places to look for this guidance include the “Where we are going” and “Where we are not going” sections for each lesson. Additionally, the expected student responses, keys, and rubrics have illustrated important science ideas that should be developed in each lesson. In addition to this information, the K-12 Science Framework is a great resource to learn more about the DCIs in this unit (LS1.A; LS1.D), including what students have learned previously and where they are headed in high school. In addition to the science content background information embedded in the lesson resources, below we provide recommended resources that can help build your understanding of phenomena and Performance Expectations bundle for this unit:

How does this unit support disability, inclusion, and social emotional learning?

This unit focuses on how parts of our body systems work together to perform functions, such as healing. In this unit, teachers and students will be exploring the ways that injury impacts the human body and how the body recovers from injury. Related to this phenomenon of healing is the topic of disability. Many students and teachers have not had the opportunity to learn about disability in any formal way despite the fact that many students have directly experienced a temporary or lifelong visible or invisible disability. 

This unit makes an intentional effort to support students’ and teachers’ approach to this topic with sensitivity and confidence when you discuss disability, as it pertains to injury and healing with your students. Additionally, injury and healing can trigger trauma for some students. Therefore, be sure you plan ahead and consider how to support your students before and during the unit to ensure that they feel comfortable discussing, viewing, and figuring out what is happening as the body heals from injury.

Unit Acknowledgements
Unit Development Team
  • Dawn Novak, Unit Lead, BSCS Science Learning
  • Jamie Deutch Noll, Field Test Unit Lead, Northwestern University
  • Sue Gaspar, Writer, University Of Illinois Extension
  • Gail Housman, Writer, Northwestern University
  • Ari Jamshidi, Writer, University of California, Berkeley
  • Meghan McCleary, Writer, University Of Illinois Extension
  • Tracey Ramirez, Writer, The Charles A. Dana Center, The University of Texas at Austin
  • Wayne Wright, Writer, BSCS Science Learning
  • Gretchen Brinza, Pilot Teacher, Sauganash Elementary School
  • Keetra Tipton, Pilot Teacher, Aptakisic Junior High School
  • Abe Lo, Reviewer, PD design, BSCS Science Learning
  • Tara McGill, Conceptual design, Northwestern University
  • Katie Van Horne, Assessment Specialist, Concolor Research
  • Barbara Hug, Unit Advisory Chair, University of Illinois Urbana‐Champaign
  • Stina Krist, Unit Advisory Chair, University of Illinois Urbana‐Champaign
  • Molly Reisz, Advisory Team, Dennison Middle School
Production Team

BSCS Science Learning

  • Maria Gonzales, Copyeditor, Independent Contractor
  • Kate Herman, Copyeditor, Independent Contractor
  • Rachel Poland, Copyeditor, Independent Contractor
  • Renee DeVaul, Project Coordinator
  • Valerie Maltese, Marketing Specialist & Project Coordinator
  • Chris Moraine, Multimedia Graphic Designer
  • Kate Chambers, Multimedia Graphic Designer
Unit External Evaluation
NextGenScience’s Science Peer Review Panel

An integral component of OpenSciEd’s development process is external validation of alignment to the Next Generation Science Standards by NextGenScience’s Science Peer Review Panel using the EQuIP Rubric for Science. We are proud that this unit has earned the highest score available and has been awarded the NGSS Design Badge. You can find additional information about the EQuIP rubric and the peer review process at the nextgenscience.org website.