Lesson 2 of 5 · Evolution
Antibiotic Resistance Is Selection You Can Watch
🐒
🎯 Your mission
Set it up. Test it. Be amazed.
⚡ The twist
Nature loves to surprise the careful watcher.
What you'll learn
Antibiotics do not produce resistant bacteria. Rare resistant mutants are already present in a large population, and the antibiotic kills everything else, leaving them to inherit the whole environment. With generation times near twenty minutes, a strain can go from rare to dominant within days. Finishing a prescribed course matters for exactly this reason: stopping early leaves the partly-resistant survivors alive and hands them the population.
Key words
antibiotic resistance
A heritable ability of bacteria to survive an antibiotic, which selection makes common once the antibiotic is applied.
selection pressure
An environmental factor that makes one heritable variant reproduce more successfully than another.
Make a hypothesis first
Before you start: write down what you think will happen, and why.
Say your guess out loud — then find out if you were right.
Get ready
🧰 What you need
- 200 dried beans
- marker pen
- tray
- graph paper
⚠️ Safety first
- Small beans are a choking hazard — keep them away from young children and wash hands afterwards.
Step 1 of 4 · Read
Think about what you just learned: say what "antibiotic resistance" and "selection pressure" mean in your own words before you start.
Step 2 of 4 · Do
Model resistance with 200 beans, two of them marked as resistant. Remove all the unmarked beans to represent one course of treatment, let the survivors double three times, and record how the marked proportion changes at each step.
Step 3 of 4 · Observe
Record what actually happened, including anything that did not match what you expected.
Step 4 of 4 · Record
Write a conclusion that answers the question this lesson opened with, and state your uncertainty.
Question 1 of 3
Question 2 of 3
Question 3 of 3
Mind = blown
🔬 The more you look, the more nature shows you.
Nice work!
You got 0 of 3 right.
Next Smart Experiment
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✨ More to explore
🌍 Where you see this in real life: This shows up in your everyday life more than you'd think.
🏆 Stretch challenge (try it this week): Try one experiment in real life this week — even a tiny one.
👨👩👧 For the dinner table: “What's the most surprising thing you learned today?”
Share this experiment
Send it to a parent who's looking for a 10-minute kitchen science win.
Ready?
Antibiotic Resistance Is Selection You Can Watch
Set it up. Test it. Be amazed.
Full screen — no distractions
Done with science? Try something else
Print the whole Evolution track
All 8th Grade Evolution lessons as a printable PDF, with worksheets and answer keys.