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

HS-LS1-5: Use a model to illustrate how photosynthesis transforms light energy into stored chemical energy. 

HS-LS1-6: Construct and revise an explanation based on evidence for how carbon, hydrogen, and oxygen from sugar molecules may combine with other elements to form amino acids and/or other large carbon-based molecules.

HS-LS1-7: Use a model to illustrate that cellular respiration is a chemical process whereby the bonds of food molecules and oxygen molecules are broken and the bonds in new compounds are formed, resulting in a net transfer of energy.

HS-LS2-3: Construct and revise an explanation based on evidence for the cycling of matter and flow of energy in aerobic and anaerobic conditions.

HS-LS2-4: Use mathematical representations to support claims for the cycling of matter and flow of energy among organisms in an ecosystem.

HS-LS2-5: Develop a model to illustrate the role of photosynthesis and cellular respiration in the cycling of carbon among the biosphere, atmosphere, hydrosphere, and geosphere.

HS-ESS2-6†: Develop a quantitative model to describe the cycling of carbon among the hydrosphere, atmosphere, geosphere, and biosphere. 

HS-ETS1-2†: Design a solution to a complex real-world problem by breaking it down into smaller, more manageable problems that can be solved through engineering.

*This performance expectation is developed across multiple OpenSciEd Biology units.

†This performance expectation is developed across multiple OpenSciEd courses.

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

• The process of photosynthesis converts light energy to stored chemical energy by converting carbon dioxide plus water into sugars plus released oxygen. (HS-LS1-5)
• The sugar molecules thus formed contain carbon, hydrogen, and oxygen; their hydrocarbon backbones are used to make amino acids and other carbon-based molecules that can be assembled into larger molecules (such as proteins or DNA), used for example to form new cells. (HS-LS1-6)
• As matter and energy flow through different organizational levels of living systems, chemical elements are recombined in different ways to form different products. (HS-LS1-6),(HS-LS1-7)
• As a result of these chemical reactions, energy is transferred from one system of interacting molecules to another. Cellular respiration is a chemical process in which the bonds of food molecules and oxygen molecules are broken and new compounds are formed that can transport energy to muscles. Cellular respiration also releases the energy needed to maintain body temperature despite ongoing energy transfer to the surrounding environment. (HS-LS1-7)

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

• Photosynthesis and cellular respiration (including anaerobic processes) provide most of the energy for life processes.
• Plants or algae form the lowest level of the food web. At each link upward in a food web, only a small fraction of the matter consumed at the lower level is transferred upward to produce growth and release energy in cellular respiration at the higher level. Given this inefficiency, there are generally fewer organisms at higher levels of a food web. Some matter reacts to release energy for life functions, some matter is stored in newly made structures, and much is discarded. The chemical elements that make up the molecules of organisms pass through food webs and into and out of the atmosphere and soil, and they are combined and recombined in different ways. At each link in an ecosystem, matter and energy are conserved. (HS-LS2-4)
• Photosynthesis and cellular respiration are important components of the carbon cycle, in which carbon is exchanged among the biosphere, atmosphere, oceans, and geosphere through chemical, physical, geological, and biological processes. (HS-LS2-5)

PS3.D: Energy in Chemical Processes

• The main way that solar energy is captured and stored on Earth is through the complex chemical process known as photosynthesis. (secondary)(HS-LS2-5)

ESS2.D: Weather and Climate

• Changes in the atmosphere due to human activity have increased carbon dioxide concentrations and thus affect climate. (HS-ESS2-6)

ETS1.C: Optimizing the Design Solution

• Criteria may need to be broken down into simpler ones that can be approached systematically, and decisions about the priority of certain criteria over others (trade-offs) may be needed. (HS-ETS 1-2)

This unit intentionally develops students’ engagement in these practice elements:

Developing and Using Models

• Develop, revise, and/or use a model based on evidence to illustrate and/or predict the relationships between systems or between components of a system. 
• Develop a complex model that allows for manipulation and testing of a proposed process or system.

Planning and Carrying Out Investigations

• Plan and conduct an investigation individually and collaboratively to produce data to serve as the basis for evidence, and in the design: decide on types, how much, and accuracy of data needed to produce reliable measurements and consider limitations on the precision of the data (e.g., number of trials, cost, risk, time), and refine the design accordingly. 
• Plan and conduct an investigation or test a design solution in a safe and ethical manner including considerations of environmental, social, and personal impacts.
• Select appropriate tools to collect, record, analyze, and evaluate data.
• Make directional hypotheses that specify what happens to a dependent variable when an independent variable is manipulated. 

Constructing Explanations and Designing Solutions: 

• Make a quantitative and/or qualitative claim regarding the relationship between dependent and independent variables. 
• Construct and revise an explanation based on valid and reliable evidence obtained from a variety of sources (including students’ own investigations, models, theories, simulations, peer review) and the assumption that theories and laws that describe the natural world operate today as they did in the past and will continue to do so in the future.
• Apply scientific reasoning, theory, and/or models to link evidence to the claims to assess the extent to which the reasoning and data support the explanation or conclusion.
• Design, evaluate, and/or refine a solution to a complex real-world problem, based on scientific knowledge, student-generated sources of evidence, prioritized criteria, and trade-off considerations.

Elements from the following practices are also key to the sensemaking in this unit:

• Asking Questions and Defining Problems
• Mathematics and Computational Thinking
• Obtaining, Evaluating, and Communicating Information

This unit intentionally develops students’ engagement in these crosscutting concept elements:

Systems and Systems Models

• Systems can be designed to do specific tasks. 
• Models (e.g., physical, mathematical, computer mo/dels) can be used to simulate systems and interactions—including energy, matter, and information flows—within and between systems at different scales.

Energy and Matter

• Changes of energy and matter in a system can be described in terms of energy and matter flows into, out of, and within that system. 
• Energy cannot be created or destroyed—only moves between one place and another place, between objects and/or fields, or between systems.
• Energy drives the cycling of matter within and between systems.

The following crosscutting concepts are also key to the sensemaking in this unit:

• Cause and Effect

Which elements of NOS are developed in the unit?

• Scientific Investigations Use a Variety of Methods. Science investigations use diverse methods and do not always use the same set of procedures to obtain data.
• Scientific Knowledge is Based on Empirical Evidence. Science knowledge is based on empirical evidence.
• Scientific Knowledge is Open to Revision in Light of New Evidence. Most scientific knowledge is quite durable but is, in principle, subject to change based on new evidence and/or reinterpretation of existing evidence.
• Scientific Knowledge Assumes an Order and Consistency in Natural Systems. Scientific knowledge is based on the assumption that natural laws operate today as they did in the past and they will continue to do so in the future.
• Science is a Human Endeavor. Science and engineering are influenced by society and society is influenced by science and engineering.

How are they developed?

• Students plan and carry out investigations in Lessons 2, 3, 5, and 8. These investigations have different methods and procedures.
• In Lessons 2, 3, 5, and 8, students use empirical evidence to create models of yeast systems to investigate cellular respiration and to establish the relationships between variables to explain the flow of matter and energy in systems.
• The unit gives many opportunities for students to revise their models with new ideas and evidence. Initially, models illustrate the interactions in the zombie fire system in the Arctic and how they release so much carbon into the atmosphere.
• These ideas are then revised in Lesson 6, where models show the flow of energy and matter throughout the zombie fire system, taking into account photosynthesis and cellular respiration at different scales. Then these models are revised and expanded in Lesson 9 to show that the Sun’s and wildfires’ energy drives carbon cycling and that increasing atmospheric carbon is increasing global temperatures explaining climate change which is one of the causes of zombie fires in the first place.
• In Lesson 4, students come to understand that the amount of solar radiation that hits the surface of the Earth has changed since 10,000 years ago. The increase of the angle of only 2° was enough of a change to increase the amount of energy to hit the surface of the Earth to produce the peat (matter) in the Arctic. Students use this evidence to make predictions of the amount of solar radiation that could be available in the future, as this change in tilt is cyclical.
• In Lesson 6, students bring together all of the ideas to update their consensus models to explain that in the past the peat was frozen under the permafrost but as temperatures increase, the permafrost thaws making the peat available to burn in zombie fires. Students make predictions based on trends that temperatures will continue to increase, permafrost will continue to thaw, and more peat will be available to burn.
• Students take what they understand about the flow of energy and matter and other fire management policies in Lesson 11 to create fire management systems for communities that they care about that they propose will balance the flow of energy and matter and to protect the humans and non humans of the ecosystem in the future.
• As society is changing how land is used and how natural resources are managed, it requires innovative ways of applying science and engineering tools for the management of these systems. Lesson 7 explores how people are influencing the health of several carbon sinks globally, making them vulnerable to wildfires, thereby affecting life for humans and more-than-humans in these places. Lesson 10 explores different approaches to fire management that encompass traditional ways of knowing alongside engineering and technology in various sites around the world. In Lesson 11, students design more inclusive fire management systems by balancing the criteria, constraints, and trade-offs to more effectively protect ecosystems they have a connection to.

This unit is anchored by a puzzling Earth science phenomenon: fires are burning under ice and snow in the Arctic. Scientists in Alaska discovered burn scars from fires appearing very close to each other, and that spring fires were starting very early in the year. Locals discovered smoke emerging from under the snow and ice in Yakutia. Siberia. At the same time, scientists and local people noticed changes in the permafrost. It was thawing, cracking, and falling apart. Once living things that had been trapped in ice for thousands of years became exposed to air and warmth. As these overwinter, or zombie fires burn, scientists measured massive amounts of carbon dioxide and other gasses being released into the atmosphere. This phenomenon provides the context in which to investigate the relationship between matter and energy within smaller-scale systems, ecosystems, and global-scale systems.  

The zombie fire phenomenon was chosen from a group of phenomena aligned with the target performance expectations based on the results of a survey administered to almost 3,000 students from across the country and in consultation with external advisory panels that include teachers, subject matter experts, and state science administrators. The zombie fire phenomenon was chosen for the following reasons:

• Students showed high interest in explaining fires in survey data.
• It provides a diverse suite of entry points for students across the unit to make local, cultural, and/or relevant community connections so that students’ background knowledge and frames of reference are assets for their sensemaking work.
• Teachers and administrators saw the phenomenon as interesting and on grade band.
• Explaining the phenomenon addresses all the DCIs in the bundle at a high school level.
• Explaining the phenomenon requires the use of both energy and matter in order to understand changes in ecosystems from an atomic to a global scale.

The unit is organized into three main lesson sets. Lesson Set 1 (Lessons 1-6) focuses on answering the question: What causes zombie fires to burn under the ice, and what are the consequences? In the first lesson set, students investigate what is happening when zombie fires burn in the peat/permafrost system, what peat/permafrost is, why there is so much peat, and how there can be so many plants in the Arctic that could become peat. Lesson Set 2 (Lessons 7-9) focuses on answering the question: How is global carbon cycling affected by fires? In the second lesson set, students apply their new ideas about the matter and energy flow in the peat/permafrost system to other fire-vulnerable carbon sinks and then to the global effects of increased carbon due to fires. Lesson Set 3 (Lessons 10-12) focuses on answering the question: How do we design solutions to manage the impacts of fires? The unit culminates by instilling hope in students through investigations of successful fire management and designing a system for fire management in a community they care about.

This unit is the second in the OpenSciEd High School Biology course sequence. It is designed to build on student ideas about ecosystem interactions from the course’s first unit, OpenSciEd Unit B.1: How do ecosystems work, and how can understanding them help us protect them? (Serengeti Unit). In the first unit of OpenSciEd HS Biology, students developed conservation plans driven by five big ideas that students figured out and use to inform their plans: 1) Natural and human-caused disruptions can have short- and long-term impacts on ecosystems. 2) The stability of ecosystems is influenced by the current ecosystem state, biodiversity, and intensity or longevity of disturbances. 3) Ecosystems have carrying capacities that are impacted by the availability of resources, spatial and temporal factors, and the behaviors and interactions of different nonhuman and human populations. 4) Group behaviors like migration, hunting in packs, and prioritizing the protection of young organisms can increase the chances of survival. 5) Conservation involves benefits and burdens that are influenced by the complexity of ecosystem components and interactions.  

This is the second unit of the High School Biology Course in the OpenSciEd Scope and Sequence. Given this placement, several modifications would need to be made if teaching this unit earlier in the Biology course. These include the following adjustments:

• If taught before OpenSciEd Unit B.1: How do ecosystems work, and how can understanding them help us protect them? (Serengeti Unit) or at the start of the school year, be sure to include these supports: supplemental teaching of community agreements and setting up the Driving Question Board. These supports are built into the Serengeti Unit and could be adapted accordingly for this unit if needed.
• If taught earlier in the school year, supplemental teaching around the components, interactions, and mechanisms between organisms in ecosystems and how to represent it may be required.

This unit requires knowledge of how to analyze and interpret information from data, graphs, and other representations. In addition, students will need to gather and represent data in ways that can help them identify patterns in investigation results..

This unit does not assume students are fluent with the mathematical practices listed below but that students develop these practices as part of the sensemaking.

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

• Lesson 8: In order to maximize time, have students begin discussions of how they will represent their data as they are collecting data so that developing them is a quicker transition.
• Lesson 10: If you are short on time, assign the investigation of a community of choice as part of the home learning. Students can complete the investigation with members of the community and discuss their findings when they return.
• Lesson 12: If you are short on time or benefit from being presented with information in smaller chunks, consider
  • waiting to hand out Nitrogen Pollution By State until students reach that part of the assessment
  • or not using it entirely (and cross off or deleting the text for question 12 that suggests using it.

To extend or enhance the unit, consider the following:

• Lesson 3: For students who do not have a middle school understanding of matter and energy flow through decomposition, it may be helpful to take extra time to review these concepts. Optional: Banana Investigation is provided as an optional investigation. Students will use photos of decomposing banana peels placed in different environments (open air, sealed in a bag with water, in soil, in a freezer) to make observations about changes they see over a 5-day period. Additional support for teaching about decomposition and cellular respiration at the middle school grade band is available in OpenSciEd Unit 7.3: How do things inside our bodies work together to make us feel the way we do? (Inside Our Bodies Unit) and OpenSciEd Unit 7.4: Where does food come from, and where does it go next? (Maple Syrup Unit). If students need support developing their middle school level planning and carrying out investigation practice, refer to OpenSciEd Unit 7.2: How can we use chemical reactions to design a solution to a problem? (Homemade Heater Unit).
• Lesson 3: High-interest students may be motivated to know more about the structure of sucrose and its relationship to glucose.
• Lesson 3: If students are motivated to go beyond the standards in this lesson, an optional reading Frozen in Time is available to extend their thinking about decomposition in peat that supports students in understanding other factors that contribute to peat being an effective carbon sink, such as pH, as the sphagnum moss that is the most abundant organic matter in peat creates acidic conditions in the peat, thereby making the environment less desirable for decomposers.
• If students need support developing their middle school-level planning and carrying out investigation practice, refer to OpenSciEd Unit 7.2: How can we use chemical reactions to design a solution to a problem? (Homemade Heater Unit).
• Lesson 7: There are complex histories that lead up to all of the events that occur in each case study presented. However, the lesson does not have time to pursue all of the details behind government policies and decisions involved. Students interested in pursuing more details about the human actions discussed should be encouraged to read more from the references provided at the end of each case study. Have students research supporting Indigenous rights, climate advocacy, and making sustainable choices to begin addressing some of the harm done to these communities.
• Lesson 8: By this time in the unit, students may be inquiring about how they can make different choices that could reduce the amount of carbon that they produce with their lifestyle (carbon footprint) and inspire student agency.

• Share EnergyStar.gov’s Carbon Footprint resources for students to collect baseline data to measure the impact of their decision-making (with their community members) on the flow of carbon in their area. https://www.energystar.gov/ia/products/globalwarming/downloads/GoGreen_Activities%20508_compliant_small.pdf

• Digital version that shares facts and figures, assesses feelings around the results with suggestions on how to relate those feelings to action, opportunities to explore your data, and potential solutions to reduce the number of Earths that are necessary for your lifestyle/personal Overshoot Day: https://www.footprintcalculator.org/home/en
• Lesson 9: If students want to better understand the relationship between photosynthesis and global atmospheric carbon dioxide levels, ask them to look at the patterns found in the data from the Mauna Loa Observatory. This shows that plants can cause seasonal fluctuations on a large scale. Play the animation at https://gml.noaa.gov/ccgg/trends/history.html (from the beginning until 1:36) or look at the static image of the data at https://gml.noaa.gov/ccgg/trends/ .

• Lesson 10: For students interested in cultural burning practices that follow up on California’s Carbon Sink, the Karuk Nation has a series of short videos about their programs. https://vimeo.com/458221338
• Lesson 11: If your students are interested in an additional historical example of a fire management system, investigate Smokey Bear Campaign to learn about the Smokey Bear campaign.
• Lesson 11: Spend additional time revising the proposed solutions and present them to decision-makers in the community who may be able to implement them.
• Lesson 11: Challenge students to research the latest fire management technology and include it in their solutions.

• Jamie Deutch Noll, Unit Lead, BSCS Science Learning
• Melissa Campanella, Writer, University of Colorado Boulder
• Kate Henson, Writer, University of Colorado Boulder
• Sara Krauskopf, Writer, University of Colorado Boulder
• DeAnna Lee-Rivers, Writer, University of Colorado Boulder
• Christina Torres, Writer, Columbia University 
• Sarah Donovan, PsyD, Consultant Expert, SafeSide Prevention

inquiryHub, University of Colorado Boulder

• Madison Hammer, Production Manager
• Amanda Howard, Copy Editor
• Erin Howe, Project Manager
• Celeste Moreno, Media Producer

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 been identified as a quality example of a science unit. You can find additional information about the EQuIP rubric and the peer review process at the nextgenscience.org website.