MS-LS4-4LS4.B: Natural Selection — how natural selection leads to adaptation of populations over generations. MS-LS4-6LS4.B: Mathematical representations of proportional changes in traits over time. SP2: ModellingScience Practice 2: Developing and using models — using a simulation as a model for natural selection in a population.
Simulation & ModellingSimulations allow students to manipulate variables and observe outcomes — a key science practice that builds causal reasoning. — NGSS Science and Engineering Practices Pattern RecognitionObserving patterns across multiple runs builds inductive reasoning — students construct the rule from evidence rather than being told it. — Kirschner et al., 2006 Low-Stakes ExplorationLow-stakes exploration reduces anxiety and increases engagement — students are more willing to take risks and test hypotheses. — Dweck, 2006
Simulation

Beetle Island

Watch natural selection happen in real time. Set the environment, run the simulation, and track how beetle populations shift over generations — then find out if your prediction was right.

① Read
② Simulate
③ Graph
④ Reflect
Phase 1
Before You Investigate
Unlock all four concepts to understand what drives natural selection — then make a prediction before the simulation begins.
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What is this simulation showing?
You are watching natural selection happen in real time. The beetle population starts with two coat colors — this is called variation. Beetles that blend into their environment are harder for predators to spot, so they survive longer, reproduce more, and pass their heritable trait (coat color) to offspring. Over many generations, the population shifts toward whichever color helps survival. This is adaptation through natural selection.
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Why are there two beetle colors?
Variation exists naturally in every population — no two individuals are exactly identical. Both light and dark beetles have always lived on this island. Their color is encoded in their genes and passed from parent to offspring. Before the simulation starts, neither color has an advantage. Once you choose an environment, the environmental pressure changes — and natural selection begins acting on that existing variation.
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Why does the environment change?
The beetles did not move anywhere. The island itself changed around them. Environments change all the time: droughts turn forests into deserts, volcanic ash darkens soil, floods shift ground cover. This is exactly what happened to the peppered moths in England — the Industrial Revolution changed the trees they already lived on. The island changes, and the population must adapt or decline.
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Why do wrong-color beetles still survive?
Because natural selection is probabilistic, not guaranteed. Even a poorly-camouflaged beetle might get lucky and avoid a predator. And even a well-camouflaged beetle might still get eaten. What changes over generations is the probability of survival — not a guarantee. This is why the wrong-color beetles never disappear entirely; they just become rarer as the better-adapted trait becomes more common. Chance is always part of the process.
Key Insight