Reaction-Diffusion
Classroom worksheet · Interactive simulation: https://lkforge.com/tools/physics/reaction-diffusion/
Name: Date:
Learning objectives
- Explain how patterns emerge from reaction and diffusion.
- Describe the activator–inhibitor mechanism.
- Connect the patterns to nature.
Variables to change
- Feed rate
- Kill rate
- Diffusion rates
Procedure
- Start the simulation and watch spots or stripes emerge from near-uniform starting conditions.
- Adjust the feed and kill rates and observe how the pattern changes.
- Compare patterns that form spots versus mazes/stripes.
Observations
Describe the patterns that form and how parameter changes shift them between spots, stripes, and mazes.
Questions
- What two processes create the patterns?
- What is an activator–inhibitor system?
- Do the patterns require a pre-drawn template?
- Who first proposed this mechanism for biological patterns?
- Give a natural example of such patterns.
Answer key (instructors)
- 1. Local chemical reaction and diffusion (spreading) of the reacting substances.
- 2. One substance promotes its own production (activator) while another suppresses it (inhibitor) and diffuses faster, producing spaced patterns.
- 3. No — they self-organize from small fluctuations; the pattern is emergent.
- 4. Alan Turing — these are called Turing patterns.
- 5. Animal coat markings (spots, stripes), seashell patterns, and vegetation patterning.
Reaction–diffusion systems pair a self-activating chemical with a faster-diffusing inhibitor. From near-uniform starts they self-organize into spots, stripes, and mazes — Turing patterns that model animal markings and other natural patterning.