Unit Overview
6.6 Cells & Systems*

How do living things heal?*

Unit Summary

*This unit is still being revised based on the feedback from the field test.
This unit on cells and systems begins with students reflecting about activities they do with their bodies and a time when something happened inside their body that prevented them from doing those activities. Students then obtain information from doctor’s notes and images about an injury and recovery of a middle school student. This prompts them to develop an initial model to explain, What happens during the healing process so the student was able to use his foot again to walk, run, jump, and dance? This initial work sets students up to ask questions about: “How does the foot (or body) heal?”

Throughout this unit, students will do the following:
•Ask questions that arise from careful observation of an example of healing to seek additional information about how healing happens.
•Plan and carry out investigations to observe the microscopic structures of cells and what is happening inside living systems and subsystems, at different scales.
•Critically read scientific texts adapted for classroom use to obtain information about the structure and function of systems in the human body as well as unicellular organisms.
•Develop and use models to describe the healing process and other related phenomena.
•Engage in argument from evidence that single-celled organisms grow and split in similar ways to animal cells.
•Apply science ideas from the evidence collected by investigating healing to construct an explanation for how growth is happening at the bones in growth plates.

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 the parts of cells contribute to the function. 
    • Other aspects of this PE, such as mitochondria and chloroplasts, are developed in additional OpenSciEd units: 7.3 Metabolic Reactions, 7.4 Matter Cycling & Photosynthesis, and 8.5 Genetics.
  • MS-LS1-3: Use argument supported by evidence for how the body is a system of interacting subsystems composed of groups of cells.
    • Other aspects of this PE, such as the digestive system, are developed in additional OpenSciEd unit: 7.3 Metabolic Reactions.

Partial NGSS Performance Expectations (PEs) addressed by this unit and built into other OpenSciEd units:

  • 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.
    • Other aspects of this PE are developed in additional OpenSciEd units, beginning their initial work on MS-LS1-8 in the Unit 6.1 Light & Matter. The current version of this unit, 6.6 Cells & Systems, 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 7.1 Chemical Reactions & Matter unit in 7th grade and the 8.2 Sound unit in 8th grade.
Focal 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: Structure and Function 

  • 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). 
  • Within cells, special structures are responsible for particular functions, and the cell membrane forms the boundary that controls what enters and leaves the cell.
  • 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.
Science and Engineering Practices
  • Developing and Using Models
  • Planning and Carrying Out Investigations
  • Engaging in Argument from Evidence
Crosscutting Concepts
  • Scale, Proportion, and Quantity
  • Systems and System Models
  • Structure and Function
Unit Information
What should my students know from earlier grades or units?

This unit reinforces and builds from the following elementary DCI elements.

LS1.A: Structure and Function

  • Plants and animals have both internal and external structures that serve various functions in growth, survival, behavior, and reproduction. (Boundary: Stress at this grade level is on understanding the macroscale systems and their function, not microscopic processes.)   

LS1.B Growth and Development of Organisms

  • Reproduction is essential to the continued existence of every kind of organism. Plants and animals have unique and diverse life cycles that include being born (sprouting in plants), growing, developing into adults, reproducing, and eventually dying.

LS1.C Organization for matter and energy flow in organisms

  • Animals and plants alike generally need to take in air and water, animals must take in food, and plants need light and minerals; anaerobic life, such as bacteria in the gut, functions without air. Food provides animals with the materials they need for body repair and growth and is digested to release the energy they need to maintain body warmth and for motion. Plants acquire their material for growth chiefly from air and water and process matter they have formed to maintain their internal conditions (e.g., at night).

Students would benefit from having prior experience using the following focal science and engineering practices (SEPs) at the 3-5 grade-band level. 

  • Developing and Using models 
    • Develop and/or use models to describe and/or predict phenomena.  
    • Develop a diagram or simple physical prototype to convey a proposed object, tool, or process. 
    • Use a model to test cause and effect relationships or interactions concerning the functioning of a natural or designed system.
  • Planning and Carrying Out Investigations
    • Plan and conduct an investigation collaboratively to produce data to serve as the basis for evidence, using fair tests in which variables are controlled, and the number of trials considered.
  • Engaging in Argument from Evidence
    • Construct and/or support an argument with evidence, data, and/or a model.  

It will be helpful to have students familiar with these focal crosscutting concepts (CCCs) from the 3-5 grade-band level.  

  • Scale, Proportion, and Quantity
    • Natural objects and/or observable phenomena exist from the very small to the immensely large or from very short to very long time periods.  
    • Standard units are used to measure and describe physical quantities such as weight, time, temperature, and volume.
  • Systems and System Models
    • A system can be described in terms of its components and their interactions.
  • Structure and Function
    • Different materials have different substructures, which can sometimes be observed. 
    • Substructures have shapes and parts that serve functions.
What are some common ideas students might have?

Students may come to this unit with prior knowledge and experiences that can be leveraged to your advantage. Some of these ideas include the following:

  • Students might come into the unit thinking that there are smaller parts and/or structures in the body. If they do, they might think that those smaller parts are all the same size and shape. They may even say that the body is made of cells but not have a deeper understanding of what that means at a microscopic level. Student questions about what happens as the injury heals will motivate the need to look at the body in closer and different ways.
  • While students might understand that there are different parts inside the body, students might not connect those parts to different microscopic functions. Students can build off the work they did in grades K-5, understanding macroscale systems and their function in living things, to support their work figuring out the microscopic structures within living things during this unit. 
  • Students may not consider that plants or single-celled organisms are made of similar structures as humans and other animals. Students may not even be aware that single-celled living organisms exist. 
  • Students are experts in their lived experiences which makes these experiences educative resources for the science classroom. Students’ experiences with their own healing of common childhood injuries, such as scraping a knee on a sidewalk, allows students to engage in the anchoring phenomenon of healing and to describe the healing process they witnessed. While students may not initially describe all of the components and interactions of healing, their macroscopic understanding of personal healing can be leveraged to motivate the need to understand the microscopic structures and multi-system and subsystem components and interactions of healing, that might not be directly visible from the outside of the body with just their eyes. 
  • Students have a deep understanding of how the large-scale structures of their body move to complete daily tasks. This understanding can be leveraged when students investigate the body’s microscopic structures of cells and the structures within cells in coordination with their particular functions.
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 7.3 Metabolic Reactions, 7.4 Matter Cycling, and 8th grade unit 8.5 Genetics 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 prerequisite math concepts are necessary for the unit?

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 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.