Some populations climb. Some collapse. The clues are hidden inside real data. Read the graphs, find the patterns, and use the numbers as evidence to explain what drives a population up or down.
Resources · Competition · Predation · Population Size
📋 MA STE Standards · Grade 77.MS-LS2-1SEP: Analyzing DataSEP: Constructing ExplanationsCCC: Cause & EffectCCC: Stability & Change
Before You Begin
Read this first, then investigate
This is a data investigation, not a reading. Your job is to analyze real population data, interpret the patterns, and use evidence to explain what you find. Work through each phase in order.
What will I actually do?
You will analyze real population graphs and tables, interpret the trends you see, and provide evidence for how resource availability changes population size. You are the scientist here.
What should I already know?
From your lessons you already understand populations, carrying capacity, limiting factors, food webs, and predator-prey relationships. This investigation puts those ideas to work on real data.
Where does the data come from?
Real long-term studies: the Isle Royale wolves and moose, the boreal forest lynx and hare records, and the Yellowstone wolf reintroduction. Scientists tracked these for decades.
How is this scored?
Checkpoints ask you to read the data, not memorize a definition. In Classroom Mode your quiz and written work go to your teacher. In Practice Mode nothing is sent.
1 · Observe
2 · Analyze
3 · Explain
4 · Reason
5 · Challenge
Phase 1 · Mission & Observe
Why do some populations crash while others climb?
On Isle Royale, an island in Lake Superior, scientists have tracked two populations for over 60 years: moose (which eat plants) and wolves (which eat moose). Read the graph and table below. Do not skim. Look for where each line rises, where it falls, and how the two lines move in relation to each other.
Isle Royale: Moose and Wolves
Source: Long-term field study
Moose are counted in hundreds. Wolves are counted as individual animals. Watch how a change in one population is followed by a change in the other.
Moose (hundreds)Wolves (individuals)
Read the graph
When the moose population was high, what happened to the wolf population a few years later? When wolves grew, what happened to moose? The two lines do not peak at the same time.
Make a prediction
Before you analyze the rest, commit to an idea. When a prey population (moose) grows for several years, what usually happens to its predator population (wolves) afterward?
Prediction saved. Now let's test it against more data.
Checkpoint 1 · Read the data
In the years right after the moose population peaked, the wolf population:
Make a prediction, then answer Checkpoint 1 to unlock Phase 2.
Phase 2 · Analyze
Find the pattern: lynx and hare
For nearly a century, fur-trade records tracked snowshoe hare (a plant-eater) and Canada lynx (a predator that hunts hare) across the boreal forest. This is one of the most famous datasets in ecology. Analyze it the same way: where are the peaks, where are the crashes, and which population leads the other?
Boreal Forest: Snowshoe Hare and Lynx
Source: Long-term trapping records
Both populations are shown in thousands. Notice the repeating cycle, and notice which curve reaches its peak first.
Hare (thousands)Lynx (thousands)
Look for the trend
The hare is a resource for the lynx. Every time hare numbers crash, the lynx crash follows close behind. The predator peak lags the prey peak by a few years, over and over again.
Checkpoint 2 · Interpret the trend
Each time the hare population crashed, the lynx population:
Answer Checkpoint 2 to unlock Phase 3.
Phase 3 · Explain
Connect resources, competition, and predation
In 1995, wolves were brought back to Yellowstone after being gone for about 70 years. With wolves missing, the elk population had grown very large and overgrazed the young willow trees along the rivers. Analyze what happened after the wolves returned, then explain the chain of cause and effect.
Yellowstone: Wolves, Elk, and Willow
Source: National park monitoring
Wolves shown as individuals. Elk shown in thousands. Willow shown as an index of plant cover (0 = bare, 100 = full recovery). Wolves were reintroduced in 1995.
Wolves up → elk down. Elk down → willow recovers. The elk had been a limiting factor for willow. Removing too many predators let one population grow until it ran the shared resource down for everyone.
Checkpoint 3 · Explain the chain
Why did willow cover increase after wolves returned?
Answer Checkpoint 3 to unlock Phase 4.
Phase 4 · Claim, Evidence, Reasoning
Build your argument from the data
You have analyzed three real datasets. Now use them as evidence. Write a short, scientific argument answering the mission question: how does resource availability affect population size? Pull actual numbers from the graphs you read.
Claim
In one sentence: what is the relationship between the amount of resources available and the size of a population?
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Evidence
Use specific numbers or trends from at least one dataset (Isle Royale, lynx and hare, or Yellowstone).
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Reasoning
Explain why your evidence supports your claim. Connect resources, competition, and predation to population size.
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Write a claim, evidence, and reasoning to unlock the Final Challenge.
Phase 5 · Final Challenge
A new graph, on your own
Here is a dataset you have never seen. A herd of deer was introduced to a fenced range with plenty of grass and no predators. Analyze the graph, then decide what most likely happened to the food supply over time. No hints this time, you are the scientist.
Mystery Range: Deer Herd
Source: Wildlife survey
Deer counted as individuals. The grass-supply line is an index of how much food was available (0 = bare ground, 100 = full grass cover).
Deer (individuals)Grass supply (index)
Your analysis
Based only on the data, which statement best explains the deer crash?
Defend it with evidence
Use numbers from this graph. What did the grass index do just before the deer population peaked and crashed?
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Choose an explanation and defend it to finish the investigation.
Next Step
Choose Your Mode
You analyzed three real datasets and one mystery graph. Pick how to finish: Practice Mode to self-check, or Classroom Mode to send your work to your teacher.
Practice Mode shows the quiz so you can self-check. Nothing is sent to your teacher.Classroom Mode adds a submission panel so your work is sent to your teacher.
Evaluate · Quiz
Check Your Understanding
Ten questions on reading population data and explaining what drives populations up and down. Answer all ten, then click Score My Quiz. In Classroom Mode, fill in your name, teacher, and block to submit.