Which beetles would survive best on this island — and how would the population change over time? Set the environment and find out.
This page is a three-step scientific investigation. Complete each step in order.
Beetles don't choose to change color. Individual beetles stay the same their whole lives. It's the population that changes — because survivors reproduce and pass on their traits.
Read all four questions and answers before touching anything. They explain what the simulation is showing and why.
Choose an environment, press Run, and watch what happens. A predator event will occur mid-simulation — pay attention to how the population responds.
Switch to Graph Mode to plot your results by hand, then answer the reflection questions and submit.
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 in that environment. This is adaptation through natural selection.
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 to act on that existing variation.
No — the beetles didn't move anywhere. The island itself changed around them. Environments change all the time: droughts turn forests into deserts, volcanic ash darkens soil, floods change ground cover. This is exactly what happened to the peppered moths in England — they didn't move to a sootier environment. The Industrial Revolution changed the trees they already lived on. The beetles here experience the same thing: the island changes, and the population must adapt or decline.
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 in the population as the better-adapted trait becomes more common. Chance is always part of the process.
Select a beetle color on the right, then click on each even-numbered generation (G0, G2, G4…) to plot that color's percentage. One point per color per generation.
| Gen | % Light | % Dark |
|---|---|---|
| Run simulation first… | ||
Plot one point per color at G0, G2, G4… Click a filled slot to replace it.