Life Science · California Grade 7

MS-LS2-2

Construct an explanation that predicts patterns of interactions among organisms across multiple ecosystems.

Clarification statement: Emphasis is on predicting consistent patterns of interactions in different ecosystems in terms of the relationships among and between organisms and abiotic components of ecosystems. Examples of types of interactions could include competitive, predatory, and mutually beneficial.

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

Chapters

Chapter 20: Resources in Living Systemspractice

Students see competition within a species (horses for grass), between species (yaks and horses; cattle and deer in Lab 3) and in a cup of duckweed, and they predict the same pattern in a new ecosystem. Predator and mutualist interactions are Lesson 21, so this chapter builds toward the PE rather than assessing it.

Chapter 21: Interactions Among Organismsassesses

The lesson's core claim is that predation, competition, mutualism, commensalism and parasitism recur in every ecosystem even though the species change. Lab 2, the slide task, W6 and W9 ask students to classify interactions from evidence, state the pattern, and use it to predict an interaction or a population change in an ecosystem they have not studied, which is evidence toward this PE as written.

Worksheets (15)

Chapter	Worksheet	Role	How it connects
Ch. 20	W2 · Resource, Condition or Competitor? Sorting the Words of a Pond Vocabulary in action	supports	Competition is one of the interaction patterns this PE asks students to predict across ecosystems. Here students only learn to recognize and name it.
Ch. 20	W7 · Fixing Sam's Review Packet: A Frog, a Pond and Eight Claims Error analysis	supports	One statement mistakes competition for fighting. Correcting it builds the accurate idea of competition for a shared limited resource, one of the interaction patterns this PE asks students to predict; the sheet does not ask for predictions across ecosystems.
Ch. 20	W8 · What Sets the Limit? A Twelve-Ecosystem Evidence Jigsaw Collaborative investigation	practice	Teams compare competition in a rocky shore, a savanna and a culture tube, and compare what limits life in deserts, forests, lakes and reefs, then predict the same pattern in a new ecosystem (California coastal upwelling). Predator and partner interactions come in Lesson 21, so this builds toward the PE rather than assessing it.
Ch. 20	W10 · Resources in Living Systems: Mastery Check Retrieval and mastery check	practice	Item 8 asks students to predict competition between two seed-eating species in a new ecosystem, in plentiful and scarce years. One item on one interaction type builds toward the PE but does not assess it.
Ch. 21	W1 · The Tree That Hires Bodyguards: Ants, Thorns and Nectar Phenomenon exploration	practice	Students meet one interaction up close, rate its effect on each partner and ask whether the same kind of partnership could exist elsewhere. That is the first step toward explaining and predicting patterns of interaction across ecosystems; no prediction across ecosystems is assessed yet.
Ch. 21	W2 · Plus, Minus, Zero: Sorting Interactions by Who Gains and Who Loses Vocabulary in action	practice	Classifying unfamiliar interactions by their effect on each partner is the vocabulary and reasoning students need before they can explain why the same patterns of interaction appear in ecosystem after ecosystem.
Ch. 21	W3 · The Ten-Year Puzzle: Hares, Lynx and a Pattern That Almost Repeats Reading with evidence	practice	The passage shows one predator-prey pattern, explains the cause-and-effect behind it and then shows the same shape in other ecosystems with different species. Citing that evidence builds toward explaining and predicting patterns of interaction across ecosystems.
Ch. 21	W4 · Reading the Waves: Rabbits, Foxes and the Lag Between Them Diagrams and models	practice	Interpreting the lagged predator-prey pattern and then sketching it for a different pair of species in a different ecosystem is the model-building half of predicting consistent patterns of interaction across ecosystems.
Ch. 21	W5 · Twelve Years at Hollow Creek: Graphing Voles and Owls Data and graphing	practice	Students quantify the lagged predator-prey pattern in one meadow and then argue whether the same pattern should appear in a different ecosystem with different species, which is the core of predicting interaction patterns across ecosystems.
Ch. 21	W6 · Why Are the Quail Disappearing? A Claim-Evidence-Reasoning Case Claim, evidence, reasoning	assesses	Students construct an explanation that identifies a predatory interaction from data, rules out competition and parasitism with evidence, and uses the known pattern of predation to predict the outcome of a management action; this is the explanation-that-predicts the PE asks for, applied to one ecosystem with a comparison to others in the reasoning.
Ch. 21	W7 · Fixing Talia's Field Notebook: Nine Claims About Interactions Error analysis	practice	Diagnosing and repairing a flawed account of predator-prey timing, interaction labels and population consequences exercises the reasoning students need before they can construct explanations that predict patterns of interaction across ecosystems. No new cross-ecosystem prediction is assessed on this sheet.
Ch. 21	W8 · If One Partner Changes: A Jigsaw on Interaction Rules Collaborative investigation	practice	The twelve cards come from oceans, islands, deserts, forests, grasslands and pastures. Teams turn them into one set of rules for how each interaction type moves populations, then use the rules to predict changes in an unfamiliar mountain ecosystem. That builds the explanation-that-predicts the PE asks for; students are assessed on it individually in W6 and W9.
Ch. 21	W9 · Listening Past the Highway: Choose a Shield for the Frog Recorders Transfer and design	assesses	In Part C students predict what corrected frog counts should show at ponds with, without and after removal of an introduced predator and competitor, and justify the prediction with the same pattern in at least one other ecosystem. That is an explanation that predicts patterns of interaction across ecosystems, applied to a system the chapter does not teach.
Ch. 21	W10 · Interactions Among Organisms: Mastery Check Retrieval and mastery check	assesses	Items 6, 7 and 10 ask students to predict population changes from stated interactions in a kelp forest, a coral reef and a desert, and the synthesis asks them to explain one interaction, predict a change, and name the same pattern in a different ecosystem. Together these give evidence of explaining and predicting patterns of interaction across ecosystems.
Ch. 28	W1 · Trucks Full of Bees: The Almond Bloom Puzzle Phenomenon exploration	supports	Part B asks students to recall the bee-and-flower relationship as a mutually beneficial interaction from earlier lessons, which is the pattern the orchard's harvest depends on.

Labs (5)

Chapter	Lab	Role	How it connects
Ch. 20	Lab 1 · The Bead Meadow: Deal the Grass, Count the Deer Collaborative systems modeling	practice	Deer compete for a fixed number of lush patches, and the two-species question asks students to predict what happens when elk share the same deck. This builds the competition pattern that the PE asks students to predict across ecosystems; predator and partner interactions are Lesson 21.
Ch. 21	Lab 1 · Beads, Cards and Cycles: A Fox-and-Vole Simulation Collaborative systems modeling	practice	Students generate predator-prey data from a model, identify the lag pattern, and predict what the same rules would do in a different ecosystem. It is practice rather than assessment because the model covers one interaction type; the cross-ecosystem explanation comes in Lab 2 and W6.
Ch. 21	Lab 2 · Who Is Doing What to Whom? Case Files from Four Ecosystems Evidence-based mystery	assesses	Students classify sixteen interactions from evidence in four ecosystems that share no species, explain why all five interaction types recur (q8), predict the missing interaction in each ecosystem before the reveal (q3), and predict interactions in a Sierra Nevada ecosystem none of the cards describe (q10). That is evidence toward the PE as written; the competitive, predatory and mutually beneficial examples named in the clarification statement all appear.
Ch. 21	Lab 3 · Shield the Frog Listener: A Noise Barrier for a Pond Sensor Engineering design challenge	supports	The shield exists so a frog population can be counted accurately; q10 asks students to name the frogs' interactions and predict a ripple effect that would go unnoticed without good counts, connecting the design to the chapter's interaction patterns.
Ch. 28	Lab 1 · The Cotton-Swab Orchard: How Do Bees Turn Blossoms into Almonds? Physical model	supports	The service rests on the bee-blossom mutualism from Lesson 21: bees get nectar and pollen as food, and the plants get pollen carried to other plants. The lab uses that interaction as background rather than asking students to predict interaction patterns across ecosystems.