Life Science · California Grade 7

MS-LS2-1

Analyze and interpret data to provide evidence for the effects of resource availability on organisms and populations of organisms in an ecosystem.

Clarification statement: Emphasis is on cause and effect relationships between resources and growth of individual organisms and the numbers of organisms in ecosystems during periods of abundant and scarce resources.

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

Chapters

Chapter 6: Food Webs and Trophic Pyramidssupports

The trophic pyramid explains why an ecosystem supports far fewer top predators than producers: the energy resource shrinks at every level. This gives background for the resource-availability reasoning of MS-LS2-1 without the data analysis that PE calls for.

Chapter 20: Resources in Living Systemsassesses

Lab 2 produces real duckweed counts and frond condition under different light, nutrient and crowding conditions, Lab 3 has students analyze a simulated twelve-year record of rainfall, forage, deer counts and fawn mass, and W5 a simulated record of rain, grass and pronghorn. Each asks students to use the data as evidence for how resource availability affects organisms and populations, which is the PE as written. Lab 1 builds the same analysis with model-generated data from abundant and scarce bead meadows.

Chapter 21: Interactions Among Organismssupports

Predator-prey cycles and competition only make sense if students already see food, space and nest sites as limited resources. Lab 1 builds that in with a meadow that can only feed sixty voles, and the chapter refers back to Lesson 20 rather than reteaching it.

Chapter 22: Changing Ecosystemssupports

Every cascading change in this chapter runs through resources: a beaver dam changes water depth and light, prairie dogs change shelter and soil, and succession changes soil and shade. Students use the resource-population relationship from Lesson 20 as background rather than producing new evidence for it.

Worksheets (21)

Chapter	Worksheet	Role	How it connects
Ch. 20	W1 · The Frog That Lost Its Poison Phenomenon exploration	practice	The phenomenon is a change in an organism caused by a change in the resources it can get (its wild diet). Students begin reasoning about cause and effect between resource availability and organisms, which is the heart of this PE, before they analyze population data later in the chapter.
Ch. 20	W2 · Resource, Condition or Competitor? Sorting the Words of a Pond Vocabulary in action	supports	Students cannot analyze data on resource availability until they can say precisely what a resource is and how a limiting resource differs from a carrying capacity. This sheet builds that language; it does not itself produce evidence toward the PE.
Ch. 20	W3 · Twenty-Nine Reindeer: Boom and Crash on St. Matthew Island Reading with evidence	practice	Students interpret real population counts alongside a description of the resource (winter lichen) that limited the herd, and explain the effects of abundant and then scarce resources. The data are few, so this builds the practice rather than fully assessing it.
Ch. 20	W4 · Reading an S-Curve: Two Tubs of Duckweed Diagrams and models	practice	Students interpret a graph of population size under two resource supplies and explain the leveling-off as the effect of a limiting resource. Reading a given curve builds toward analyzing their own data in W5 and the labs.
Ch. 20	W5 · Rain, Grass and Pronghorn: Ten Years on the Sage Flats Data and graphing	assesses	Students analyze and interpret a ten-year dataset to provide evidence that resource availability (grass, driven by rainfall) affects the size of a pronghorn population during abundant and scarce years. This is the PE as written, using clearly labeled simulated data.
Ch. 20	W6 · What Limits the Water Fleas? A Claim-Evidence-Reasoning Case Claim, evidence, reasoning	assesses	Students interpret population counts under three food supplies and use them as evidence for the effect of resource availability on a population, including a period of scarcity after a resource is withdrawn. The written argument is direct evidence toward this PE.
Ch. 20	W7 · Fixing Sam's Review Packet: A Frog, a Pond and Eight Claims Error analysis	practice	Students use the Hollis Pond dataset (bluegill counts and insect-larva samples) as evidence to correct a forecast, a cause-and-effect claim and a carrying-capacity claim, and use the frog facts to correct a claim about how a resource affects an organism. Because the mistakes frame the reasoning, this builds the PE's practice rather than assessing it.
Ch. 20	W8 · What Sets the Limit? A Twelve-Ecosystem Evidence Jigsaw Collaborative investigation	practice	The cards are qualitative summaries of real research, and several show a resource changing population size (wildflowers, woodpeckers, algae) or individual bodies (urchins, flamingos). Students interpret this evidence but do not analyze numerical data, so the sheet is practice for the PE.
Ch. 20	W9 · Ridgeback Reserve: Design a Drought Plan for a Fenced Elk Herd Transfer and design	practice	Students calculate the herd each kind of year can support from forage and water supplies, find the limiting resource, and predict what scarcity does to the herd. This applies the PE's cause-and-effect reasoning to a new problem, but the numbers are planning values rather than observed population data, so it is practice rather than assessment.
Ch. 20	W10 · Resources in Living Systems: Mastery Check Retrieval and mastery check	assesses	Items 3-7 and the synthesis ask students to interpret a dataset from years of abundant and scarce food, calculate a percent change and a carrying capacity, judge what evidence supports a cause-and-effect claim, and explain effects on both individual growth and population size. Together they produce direct evidence toward the PE as written.
Ch. 21	W5 · Twelve Years at Hollow Creek: Graphing Voles and Owls Data and graphing	supports	Voles are the owls' main food resource, so the owl counts show how the availability of a resource affects a population; the sheet also includes a dry year in which the voles' own food ran short.
Ch. 22	W1 · Gray to Green: What Happened at Mount St. Helens After 1980? Phenomenon exploration	supports	The initial explanation draws on the earlier idea that populations depend on resources such as soil, water and shelter, which the eruption removed and recovery slowly rebuilt.
Ch. 22	W4 · Reading a Succession Model, Then Building Your Own Diagrams and models	supports	Each succession stage is explained by the resources it makes available (soil, shade, nitrogen, shelter), which draws on the resource-availability idea from the earlier chapter.
Ch. 22	W5 · With and Without Beavers: What the Stream Surveys Show Data and graphing	supports	Still, deep water and fast, oxygen-rich water are resources that different populations need. Students use the resource-population link from Lesson 20 to explain why the counts moved in opposite directions.
Ch. 22	W6 · Did the Lupine Change the Pumice Plain? A Claim-Evidence-Reasoning Case Claim, evidence, reasoning	supports	Usable nitrogen is the limiting resource in the reasoning: students explain the rise in seedlings as plant populations responding to a resource that lupine made more available, an idea from Lesson 20.
Ch. 22	W7 · Fixing Jordan's Argument About the Pine Creek Dam Error analysis	supports	The rewrite explains the trout decline through a resource the dam changed, cold water rich in oxygen, using the resource-population link from Lesson 20.
Ch. 22	W8 · Prairie Dog Evidence Sort: Who Gains, Who Loses, and How Do We Know? Collaborative investigation	supports	Most of the cascading effects on the cards run through resources prairie dogs provide or remove: burrows for shelter, prey for ferrets, short nutritious grass for grazers, and bare ground for plovers.
Ch. 22	W10 · Changing Ecosystems: Mastery Check Retrieval and mastery check	supports	Items 4, 6 and 12 rely on the link between resources (usable nitrogen, still water, soil) and the populations they support, from Lesson 20.
Ch. 28	W5 · What Is a Bee Visit Worth? Orchard Data and Replacement Cost Data and graphing	supports	The harvest levels off when another resource, not pollination, becomes limiting; students meet the idea of a limiting factor from data, which this PE develops for populations.
Ch. 29	W1 · Two Graphs, Two Stories: Wild Cycles and a Rising Line Phenomenon exploration	supports	Part C asks students to recall from earlier Grade 7 lessons how food and predators limit a wild population. That prior idea is what makes the hare and lynx cycle a useful contrast with people.
Ch. 29	W5 · Reading the Fur Ledger: Peaks, Lags and a Rising Line Data and graphing	supports	Students interpret predator-prey records and a real food-and-predator experiment as evidence for how resource availability and predation affect a population, revisiting an earlier Grade 7 idea.

Labs (8)

Chapter	Lab	Role	How it connects
Ch. 6	Lab 2 · Pouring Energy Up the Pyramid: A Water Model of Trophic Levels Physical model	supports	The run shows that the energy resource shrinks so fast that a fifth or sixth level cannot be supported; this is background for reasoning about resource availability and population size.
Ch. 20	Lab 1 · The Bead Meadow: Deal the Grass, Count the Deer Collaborative systems modeling	practice	Students tabulate, graph and compare population data from an abundant meadow, a scarce meadow and a drought, and use them as evidence that resource availability controls how fast and how far a population grows. Because the data come from rules the students apply themselves, this builds the analysis toward the PE; Lab 2 and Lab 3 supply the evidence from real organisms and field records.
Ch. 20	Lab 2 · Four Cups of Duckweed: Which Resource Runs Out First? Classroom field investigation	assesses	Students collect and analyze their own counts of a living population under abundant and scarce resources, compute growth factors, compare against a full-resource cup and pooled class medians, and use the data as evidence for the effect of each resource on population size and on frond health. That is the PE as written.
Ch. 20	Lab 3 · The Cedar Hollow Case File: Deer, Cattle and the Next Dry Year Data-driven decision	assesses	Students analyze and interpret a simulated twelve-year record of rainfall, forage, deer counts and fawn mass, and use it as evidence that forage availability changes both the size of the population and how large individual fawns grow. The clarification statement's emphasis on cause and effect during abundant and scarce periods is met by the dry-year and wet-year comparisons and the skeptic's round.
Ch. 21	Lab 1 · Beads, Cards and Cycles: A Fox-and-Vole Simulation Collaborative systems modeling	supports	The meadow can feed only sixty voles and each fox needs at least three voles to survive a round, which carries the resource-availability idea from Lesson 20 into this model.
Ch. 22	Lab 1 · The Mixed-Up Field Notebooks: Two Zones, One Eruption Evidence-based mystery	supports	The lupine cards show plant populations growing where a pioneer added the nitrogen that bare pumice lacked. Students use the resource-limits-populations idea from Lesson 20 to explain the pattern rather than analyzing new resource data.
Ch. 22	Lab 2 · Pull One Thread: Testing a Prairie Web for Its Keystone Collaborative systems modeling	supports	Every rule in the model is a resource rule: a population goes down or is lost when its food, water or shelter shrinks or disappears. Students apply the resource-population relationship from Lesson 20 rather than producing new evidence for it.
Ch. 22	Lab 3 · Path or No Path? A Disturbed-Versus-Undisturbed Plot Survey Classroom field investigation	supports	Water that soaks into the soil is a resource for plants and small animals. Students link slower soaking on packed ground to lower plant cover, using the resource-population relationship from Lesson 20 as part of their mechanism.