Unit Overview
7.4 Matter Cycling & Photosynthesis

Where does food come from and where does it go next?

Unit Summary

This unit on matter cycling and photosynthesis begins with students reflecting on what they ate for breakfast. Students are prompted to consider where their food comes from and consider which breakfast items might be from plants. Then students taste a common breakfast food, maple syrup, and see that according to the label, it is 100% from a tree.

Based on the preceding unit, students argue that they know what happens to the sugar in syrup when they consume it. It is absorbed into the circulatory system and transported to cells in their body to be used for fuel. Students explore what else is in food and discover that food from plants, like bananas, peanut butter, beans, avocado, and almonds, not only have sugars but proteins and fats as well. This discovery leads them to wonder how plants are getting these food molecules and where a plant’s food comes from.

Students figure out that they can trace all food back to plants, including processed and synthetic food. They obtain and communicate information to explain how matter gets from living things that have died back into the system through processes done by decomposers. Students finally explain that the pieces of their food are constantly recycled between living and nonliving parts of a system.

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Unit Examples


Additional Unit Information

Next Generation Science Standards
Performance Expectations

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

  • MS-LS1-6: Construct a scientific explanation based on evidence for the role of photosynthesis in the cycling of matter and flow of energy into and out of organisms.
  • MS-LS2-3: Develop a model to describe the cycling of matter and flow of energy among living and nonliving parts of an ecosystem.
  • MS-PS1-3: Gather and make sense of information to describe that synthetic materials come from natural resources and impact society. 

Partial NGSS Performance Expectations (PEs) addressed by this unit:

  • 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. (Specifically, chloroplasts and mitochondria.)
Disciplinary Core Ideas

The unit expands students’ understanding of matter cycling and photosynthesis, which include these Grade 6-8 DCI elements:

LS1.C: Organization for Matter and Energy Flow in Organisms

  • Plants, algae (including phytoplankton), and many microorganisms use the energy from light to make sugars (food) from carbon dioxide from the atmosphere and water through the process of photosynthesis, which also releases oxygen. These sugars can be used immediately or stored for growth or later use.

LS2.B: Cycle of Matter and Energy Transfer in Ecosystems

  • Food webs are models that demonstrate how matter and energy is transferred between producers, consumers, and decomposers as the three groups interact within an ecosystem. 
  • Transfers of matter into and out of the physical environment occur at every level. Decomposers recycle nutrients from dead plant or animal matter back to the soil in terrestrial environments or to the water in aquatic environments. 
  • The atoms that make up the organisms in an ecosystem are cycled repeatedly between the living and nonliving parts of the ecosystem.

PS1.A:  Structure and Properties of Matter

  • Each pure substance has characteristic physical and chemical properties (for any bulk quantity under given conditions) that can be used to identify it.

PS1.B: Chemical Reactions

  • Substances react chemically in characteristic ways. In a chemical process, the atoms that make up the original substances are regrouped into different molecules, and these new substances have different properties from those of the reactants.

PS3.D: Energy in Chemical Processes and Everyday Life

  • The chemical reaction by which plants produce complex food molecules (sugars) requires an energy input (i.e., from sunlight) to occur. In this reaction, carbon dioxide and water combine to form carbon-based organic molecules and release oxygen. (secondary)

The placement of this OpenSciEd Unit 7.4 and associated units are shown in the OpenSciEd Middle School Scope and Sequence.

Focal Science & Engineering Practices
  • Developing and Using Models
  • Constructing Explanations and Design Solutions
  • Engaging in Argument from Evidence
  • Obtaining, Evaluating, and Communication Information
Focal Crosscutting Concepts
  • Systems and System Models
  • Energy and Matter
Unit Placement Information
What are prerequisite math concepts necessary for the unit?

In Lesson 6 students use a NetLogo simulation to discover the relationship of how the inputs within the plant interact and affect the amounts of outputs and represent the process of photosynthesis in a plant. 

Prerequisite math concepts that may be helpful include:

  • CCSS.MATH.CONTENT.6.NS.C.8: Solve real-world and mathematical problems by graphing points in all four quadrants of the coordinate plane.
  • CCSS.MATH.CONTENT.6.SP.B.5.B Describing the nature of the attribute under investigation, including how it was measured and its units of measurement.
  • CCSS.MATH.CONTENT.6.SP.B.5.C: Giving quantitative measures of center (median and/or mean) and variability (interquartile range and/or mean absolute deviation), as well as describing any overall pattern and any striking deviations from the overall pattern with reference to the context in which the data were gathered. 

In addition, within the domain of Measurement and Data in the Common Core Mathematics Standards, students will be drawing on what they have learned across a number of standards under the category of Represent and Interpret data for grades 1-5 when they are generating and interpreting the tables and graphs of their data collected from the simulation and during analysis of several input/output graphs in many lessons across the unit.

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

This is the fourth unit in 7th grade in the OpenSciEd Scope and Sequence. 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 7.1 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 7.1.)
  • This unit is designed to come after two units involved in the foundations of chemical reactions and explicitly builds on those understandings. It is critical to note that students need the idea of chemical reactions and the idea that matter can be rearranged through these reactions yielding resultant materials with different properties to develop the explanations in this unit. Without these ideas, the questions raised make no sense to students, and they don’t have what they need to develop the disciplinary core ideas. If not being done in the standard OpenSciEd sequence, teachers would need to make sure there are other ways students have developed these foundational ideas, reflected in the PEs MS-PS1-1: Develop models to describe the atomic composition of simple molecules and extended structures and MS-PS1-2: Analyze and interpret data on the properties of substances before and after the substances interact to determine if a chemical reaction has occurred. Students will also need an understanding that all matter is made of particles, which is foundational ideas for these PEs. MS-PS1-5: Develop and use a model to describe how the total number of atoms does not change in a chemical reaction and thus mass is conserved.
  • The unit is also designed to come after the extension of chemical reactions to living things that occurs in OpenSciEd Unit 7.3. If students have not done that unit before taking this unit on, there will need to develop the idea that there are chemical reactions in living things, reflected in the PE MS-LS1-7: Develop a model to describe how food is rearranged through chemical reactions forming new molecules that support growth and/or release energy as this matter moves through an organism. 
  • Supplemental teaching of 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 and 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. This unit does not introduce cells to students. It uses that prerequisite knowledge to build understanding that living things are made of cells and those cells have structures for specific jobs. This unit will add to that knowledge by looking at the role of chloroplasts and mitochondria. 
Unit Acknowledgements
Unit Development Team
  • Jamie Noll, Unit Lead, Northwestern University
  • Tara McGill, Field Test Unit Lead and Reviewer, Northwestern University
  • Dawn Novak, Writer, BSCS Science Learning
  • Meghan McCleary, Writer, University of Illinois Extension
  • Sue Gasper, Writer, University of Illinois Extension
  • Katy Fattaleh, Writer, The Nora Project
  • Michael Novak, Writer, Northwestern University
  • Kate Cook-Whitt, Writer, Maine Mathematics and Science Alliance
  • Emily Harris, Writer, BSCS Science Learning
  • Tyler Scaletta, Writer, Chicago Public Schools
  • Katie Van Horne, Assessment Specialist
  • Kelsey Edwards, Project Coordinator, Northwestern University
  • Christina Murzynski,  Project Coordinator, Northwestern University
  • Misty Richmond, Pilot Teacher, James Ward School 
  • Mary Colannino, Teacher Advisor, Hugh B. Bain Middle School
  • Elizabeth Xeng de los Santos, Advisory Team, University of Nevada – Reno
  • Chris Griesemer, Advisory Team, University of California – Davis
  • Cindy Passmore, Unit Advisory Chair, University of California – Davis
Production Team

BSCS Science Learning

  • Christine Osborne, Copyeditor, Independent Contractor
  • Valerie Maltese, Marketing Specialist & Project Coordinator
  • Alyssa Markle, Project Coordinator
  • Chris Moraine, 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.