Life Science · California Grade 7

MS-LS2-3

Develop a model to describe the cycling of matter and flow of energy among living and nonliving parts of an ecosystem.

Clarification statement: Emphasis is on describing the conservation of matter and flow of energy into and out of various ecosystems, and on defining the boundaries of the system.

Assessment boundary: Assessment does not include the use of chemical reactions to describe the processes.

Source: California Department of Education, NGSS Preferred Integrated Course Model, Grade 7 (accessed 2026-10-18)

Chapters

Chapter 4: Capturing the Sun's Energypractice

Lab 2 has students build a token model with a defined system boundary showing atoms moving from air and water into a producer, then into a consumer, while energy enters as light and leaves as heat. This builds the model-making practice that Lessons 6 and 7 extend to whole ecosystems, so the role is practice rather than assesses.

Chapter 5: Using Stored Energysupports

The closing comparison of the two processes shows matter looping between carbon dioxide and sugar while energy enters as light and leaves as heat. That is the organism-scale idea that Lessons 6 and 7 scale up to ecosystems, where this PE is addressed.

Chapter 6: Food Webs and Trophic Pyramidsassesses

Lab 1 and W4 require students to build a food-web model that adds air, soil and sunlight as nonliving parts, shows matter returning through decomposers, and shows energy entering as light and leaving as heat. Lab 2 makes students account for every unit of energy at each transfer. Both produce direct evidence toward this PE without using chemical equations, which the assessment boundary excludes.

Chapter 7: Global Cycles of Matterassesses

The chapter's core product is a student-built model of how matter cycles among living and nonliving parts of an ecosystem, with the boundary of the system stated. Lab 1 (atom passports), Lab 2 (sealed jar), W4 and the presentation task produce that evidence directly. The assessment boundary is respected: no task asks students to use chemical equations; atoms are traced by name and process.

Chapter 10: Energy in Earth's Systemssupports

The biosphere section restates the Lesson 6 idea that energy enters as sunlight, passes from producers to consumers and leaves as heat, while decomposers return matter. The chapter uses it to contrast energy flow with matter cycling across all four systems rather than to assess ecosystem models.

Worksheets (30)

Chapter	Worksheet	Role	How it connects
Ch. 4	W4 · Reading the Leaf: Inputs, Outputs and a Balanced Equation Diagrams and models	supports	The drawing extends the leaf model to a consumer, a first step toward modeling matter cycling and energy flow among living and nonliving parts of an ecosystem.
Ch. 4	W8 · Follow the Evidence: A Photosynthesis Jigsaw Collaborative investigation	supports	Several cards trace matter between the nonliving air and living producers, and from producers to the organisms that eat them, which is background for modeling matter cycling in an ecosystem.
Ch. 5	W8 · Twelve Clues About Food: An Evidence Jigsaw on Energy and Matter Collaborative investigation	supports	Several cards (fungus on a log, exhaled breath, sprouting seeds) show carbon dioxide leaving organisms, which is background for the ecosystem-scale cycling of matter studied in later chapters.
Ch. 5	W9 · The Antlion's Budget: Dig, Wait, or Move? An Energy Decision Transfer and design	supports	The budget treats the antlion as one link through which matter and energy from ants pass; this is background for ecosystem-scale energy flow in later chapters and is not assessed here.
Ch. 6	W1 · A Valley of Grass, a Dozen Deer, One Mountain Lion Phenomenon exploration	supports	Students observe the pattern (shrinking mass at each feeding level, food eaten without mass gained) that the chapter's model of matter cycling and energy flow will have to explain. This sheet activates the question; it does not yet build the model.
Ch. 6	W2 · Thirteen Words, One Ecosystem: Using the Language of Food Webs Vocabulary in action	supports	Students need a precise working vocabulary before they can build or read a model of matter cycling and energy flow. Sorting the terms by what kind of thing each names (an organism, a model, an interaction, a quantity) prepares them for the modeling tasks in W4 and W8.
Ch. 6	W3 · The Otter, the Urchin and the Kelp: Reading a Food Web from the Top Down Reading with evidence	practice	The passage traces energy from sunlight through kelp, urchins and otters to heat in cold water, and follows kelp matter into decomposers; students pull those pathways out of the text, which builds the ideas their own model will need.
Ch. 6	W4 · Draw the Pond: Building a Food Web and Tracing Matter and Energy Diagrams and models	assesses	Students construct a model of a pond that shows where matter goes (including the air, water and mud) and where energy goes, and they define what is inside and outside the system. That is the PE's own task. The sheet stays within the assessment boundary: no chemical reactions are written.
Ch. 6	W5 · How Much Gets Through? Energy per Level and a Caterpillar's Matter Budget Data and graphing	practice	Calculating transfer fractions and balancing a matter budget gives students the quantitative reasons behind the model they build for this PE: energy shrinks at every level because most of it leaves as heat, while the matter that leaves an animal is still in the ecosystem.
Ch. 6	W6 · When the Coyotes Left: A Claim-Evidence-Reasoning Case Claim, evidence, reasoning	supports	The reasoning section asks students to explain the pattern using the food web as a model of how matter and energy move from grass to jackrabbits to coyotes, which is the model this PE develops.
Ch. 6	W7 · Fixing Mateo's Desert Notebook: Arrows, Energy and Matter Error analysis	practice	Diagnosing a flawed model of matter cycling and energy flow, and rewriting it, exercises exactly the ideas the PE's model must get right: arrow direction, matter conserved and recycled, energy leaving as heat, and nonliving parts in the cycle.
Ch. 6	W8 · Bear Creek Jigsaw: Twelve Cards, One Stream Food Web Collaborative investigation	practice	Teams build a physical food web model that includes producers, consumers and decomposers and trace matter to the decomposers and energy to heat; this is the modeling practice the PE calls for, done collaboratively before the individual assessment.
Ch. 6	W9 · Clearing Alder Reservoir: Choose a Food-Web Fix and Plan the Test Transfer and design	practice	Every prediction must come from the reservoir's trophic pyramid: how a change in one level moves matter and energy flow through the others. Students apply the chapter's model to a new system rather than building it from scratch.
Ch. 6	W10 · Food Webs and Trophic Pyramids: Mastery Check Retrieval and mastery check	assesses	Items ask students to describe where matter and energy go, to draw and label a pyramid model, and to include nonliving parts and the system's energy input; the synthesis item is a compact version of the PE's model. No item requires chemical reactions.
Ch. 7	W1 · Two Ponds, One Rainstorm: Why Did Only One Turn Green? Phenomenon exploration	practice	Students build a first, rough model of matter moving from a fertilizer bag through water into the bodies of algae. It starts the practice of modeling matter cycling between nonliving and living parts of an ecosystem; it is not yet evidence toward the PE.
Ch. 7	W2 · Reservoirs, Routes and Rules: Sorting the Language of Cycles Vocabulary in action	practice	Every arrow in a matter-cycle model is a process and every box is a reservoir. Sorting the terms this way builds the vocabulary students need to construct and explain their own cycling-of-matter models later in the chapter.
Ch. 7	W3 · The Air Is Full of Nitrogen, and Almost Nobody Can Eat It Reading with evidence	practice	The passage follows nitrogen atoms through nonliving reservoirs (air, soil, water) and living ones (bacteria, plants, animals). Reading and citing it builds the understanding students need to construct a cycling-of-matter model; it does not itself produce a model.
Ch. 7	W4 · Reading the Carbon Loop, Drawing the Nitrogen Loop Diagrams and models	assesses	The drawing task asks students to construct a model of nitrogen cycling in a peanut field with reservoirs, labeled process arrows and a drawn system boundary. A complete drawing is direct evidence toward the PE. No chemical equations are required, which respects the assessment boundary.
Ch. 7	W5 · Carbon by the Hour, Nitrogen by the Week: Two Teaching Datasets Data and graphing	practice	The terrarium data let students see carbon moving between the air inside a sealed system and the plants, hour by hour, and reason about conservation of matter within a defined boundary. They analyze the model's behavior rather than build the model.
Ch. 7	W6 · The Vanishing Log: Where Did 9.6 Kilograms Go? Claim, evidence, reasoning	assesses	Students compare an open system (the cage) with a closed one (the jar) and argue, from data, that the log's mass moved to the air and soil rather than disappearing. The argument addresses conservation of matter and system boundaries directly, without chemical equations.
Ch. 7	W7 · Fixing Marco's Cycle Poster: Seven Claims That Break the Rules Error analysis	practice	Each of Marco's claims misreads a cycle model: matter destroyed, a single required route, plants built from soil, Earth closed to energy. Diagnosing and repairing them sharpens the understanding students need to build and defend accurate cycling-of-matter models.
Ch. 7	W8 · Who Turned Miller Pond Green? An Evidence Jigsaw Collaborative investigation	practice	The group task is to build a flow model that follows nitrogen from a fertilizer bag through water into algae, decomposers and back, with each arrow backed by an evidence card. It builds the modeling practice of the PE at the scale of one pond.
Ch. 7	W9 · Where Should the Trees Go? Judging Three Carbon-Capture Plans Transfer and design	supports	The whole challenge rests on the carbon-cycle idea that photosynthesis moves carbon from the air into a living reservoir, and that burning or decay returns it. The science is applied here, not modeled.
Ch. 7	W10 · Global Cycles of Matter: Mastery Check Retrieval and mastery check	assesses	Items ask students to trace matter between living and nonliving reservoirs, apply conservation of matter inside a defined boundary, and draw a small cycling model. Together they produce evidence toward the PE without requiring chemical equations.
Ch. 10	W6 · Where Did the Oxygen Go? A Sealed-Jar Claim-Evidence-Reasoning Case Claim, evidence, reasoning	supports	Explaining the oxygen drop requires tracing matter (oxygen, carbon dioxide) and energy (sunlight in, heat from decomposition) among living and nonliving parts of a closed model, which is background for the ecosystem model this PE asks for.
Ch. 10	W7 · Heat Does Not Float: Fixing Mateo's Quiz Error analysis	supports	One item repairs the idea that energy cycles through a food chain. Correctly stating that matter cycles while energy flows through is background for this PE's ecosystem model.
Ch. 10	W8 · Follow the Energy: A Twelve-Card Jigsaw Across Earth's Systems Collaborative investigation	supports	The kelp, compost and plankton cards show sunlight entering living systems and leaving as heat, which is background for this PE's model of energy flow in ecosystems.
Ch. 10	W9 · Design Challenge: A Sealed Mini-World That Survives Twenty-One Days Transfer and design	supports	Choosing plants, soil and animals so that matter cycles inside a sealed boundary while energy flows in and out draws on the ecosystem ideas of this PE as background.
Ch. 10	W10 · Energy in Earth's Systems: Mastery Check Retrieval and mastery check	supports	Item 9 checks the accurate statement that matter cycles while energy flows through a food chain, background for this PE's ecosystem model.
Ch. 28	W7 · Fixing Priya's Report on Nature's Services Error analysis	supports	Statement 4 confuses matter cycling with energy flow, revisiting the ecosystem model from earlier lessons.

Labs (10)

Chapter	Lab	Role	How it connects
Ch. 4	Lab 1 · The Rising Disks: What Makes a Sunken Leaf Float? Evidence-based mystery	supports	The cup is a small bounded system; students name what crosses into the leaf and what comes out, which is background for the ecosystem-level model in Lab 2 and Lessons 6 and 7.
Ch. 4	Lab 2 · Follow the Atoms, Follow the Energy: A Sealed-Jar Model Collaborative systems modeling	practice	The jar is a tiny ecosystem with a drawn boundary, a producer, a consumer, air and water. Students show matter cycling inside the boundary and energy flowing through it. The chemical equation is used only to count atoms, not to describe the process, and the full ecosystem model with decomposers and reservoirs comes in Lessons 6 and 7, so the role is practice.
Ch. 5	Lab 1 · The Jar That Warmed Up: What Are the Seeds Doing in the Dark? Evidence-based mystery	supports	The sealed jar is a closed system for matter; students must decide what crossed into the indicator and what the seeds' stored starch became, which is the organism-scale version of ecosystem matter tracking in Lesson 6.
Ch. 6	Lab 1 · Build the Web, Then Break It: A Model of an Oak Woodland Collaborative systems modeling	assesses	Students build a model with living parts, nonliving pools (air and soil), an energy input (sunlight) and an energy output (heat), connect every organism to decomposers, and write what is inside and outside the system. That is the model this PE asks for, without any chemical reactions.
Ch. 6	Lab 2 · Pouring Energy Up the Pyramid: A Water Model of Trophic Levels Physical model	assesses	Students run a physical model in which energy enters once, a measured fraction moves to each next level, and the remainder leaves to heat or decomposers. The accounting table and the graph are evidence that they can model energy flow through an ecosystem, within the PE's boundary (no chemical reactions).
Ch. 6	Lab 3 · Fixing Lake Vesipuro: Test a Restoration Plan on Paper Data-driven decision	supports	The nutrient rule in the model makes visible that the matter arriving in sewage and runoff becomes algae; this reinforces the matter-cycling model from Lab 1 without being the main target of the lab.
Ch. 7	Lab 1 · Passport of a Carbon Atom: Where Do the Atoms Pile Up? Collaborative systems modeling	assesses	Students run, record and then revise a model of carbon cycling among producers, consumers, decomposers, soil, water, air and fossil fuels, state the boundary of the modeled system, and use the pooled data to explain conservation of matter and the effect of fossil-fuel burning. No chemical reactions are used, which respects the assessment boundary.
Ch. 7	Lab 2 · Two Jars, One Lid: Does a Closed System Keep Its Mass? Physical model	assesses	Students define the boundary of each jar system, record what can and cannot cross it, and use measured masses to describe conservation of matter among the living and nonliving parts (seeds, leaves, soil, water, air). This is the conservation-and-boundary emphasis named in the PE's clarification statement, without chemical reactions.
Ch. 7	Lab 3 · Feed the Field, Keep the Pond: Choosing a Fertilizer Plan Data-driven decision	practice	Students trace fertilizer nitrogen from the bag through soil, runoff, pond, algae and decomposers to explain why nitrate and oxygen move together in the data; the cycle model is used, not built, so the role is practice.
Ch. 10	Lab 2 · Strings Across the Spheres: Modeling Energy and Matter Flows Collaborative systems modeling	supports	Four of the cards trace sunlight through kelp, a consumer, decomposers and heat loss, so students restate the Lesson 6 ecosystem model inside the larger Earth-systems model.