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Darwin Snail SimulationNATURAL SELECTION LAB · BIOLOGY 30
THE ROCKY COASTLINE

Who survives to reproduce?

Paused
A MODEL POPULATION
Generation1
Snails alive50
Mean thickness4.00
Crab happiness0
0 crabs

Inspect a snail, or select Claw to become the predator.

Shell thickness distribution

Thin shells Thick shells

View counts as a table

Across generations

Each point shows a new generation, before predation.

Parent–offspring evidence

Inspect each offspring before predation. A survivor never changes thickness in Exercises 1–5.

Your evidence notes

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Stylized snail illustration

How it works

Select: click a snail to inspect its shell and parent. Claw: click repeatedly to crack a shell. Thicker shells take more clicks.

Run: snails move and added crabs feed. Predation pauses automatically at 25 survivors. Click Snails reproduce to create two offspring per survivor; the parents die.

Reset trial: a new random trial with your current settings. Save evidence first. Changes to starting variation apply on reset.

Shell colours: a visual key for thickness, not a claim about real snail colours. Thickness units are arbitrary. This model simplifies real biology.

Research: select individuals, transfer them into tanks and advance days. Banded crabs supply cues without eating snails.

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