Teacher sheet · Ages 10–11 · about 45–50 minutes
Bacteria, viruses and fungi
Lesson page: echoesof.science/school/microbes/ages-10-11/ · Pupil worksheet: echoesof.science/school/microbes/ages-10-11/print/
Learning aims
- Describe bacteria, viruses and fungi and how they differ.
- Know that most microbes are harmless or useful.
- Know that antibiotics work against bacteria but not viruses.
- Plan and carry out a fair test with yeast.
Lesson plan
| Time | Activity |
|---|---|
| 5 min | Starter: true or false? 'All microbes are germs.' |
| 10 min | Read the text; compare sizes of a bacterium and a virus. |
| 20 min | Yeast fair test in groups. |
| 5 min | Game: Which microbe am I? |
| 5 min | Quiz and results discussion. |
Materials for the experiment
- Three identical small plastic bottles and three balloons
- Dried baker's yeast and sugar
- Measuring spoons and a measuring jug
- Cold tap water, room-temperature water and warm tap water (about hand-warm)
- A thermometer
- A piece of string and a ruler
Safety: Use tap water no hotter than hand-warm; no kettles. Do not taste the mixture. Wash hands afterwards. Use latex-free balloons for anyone with a latex allergy. Do not try to grow other microbes from hands or surfaces.
Common misconceptions
| Pupils may think… | Actually… |
|---|---|
| Viruses are just small bacteria. | Viruses are not cells and can only reproduce inside a host cell. |
| Antibiotics cure every infection. | They only work on bacteria, and overuse makes bacteria resistant. |
| Yeast makes bread rise by getting bigger itself. | The yeast gives off carbon dioxide gas, which makes bubbles in the dough. |
Worksheet answers
- A bacterium is a living cell; a virus is not a cell and can only copy itself inside another cell (also: viruses are much smaller).
- Any two of bread, cheese, yoghurt, chocolate, vinegar.
- Usually the warm one, because the yeast worked faster and made more carbon dioxide; any answer backed by their data is fine.
- Antibiotics only work against bacteria, not viruses; using them when not needed helps bacteria become resistant.
Quiz answers
- What does a bacterium NOT have? A nucleus. Bacteria are single cells without a nucleus.[5]
- How do viruses make copies of themselves? Only inside the cells of another living thing. Viruses need a host cell to reproduce.[6]
- Which microbe makes bread rise? Yeast, a fungus. Yeast gives off carbon dioxide gas.[5]
- What are disease-causing microbes called? Pathogens. Pathogens are less than 1% of microbe species.[3]
- Do antibiotics work against viruses? No, they only work against bacteria. Antibiotics are not effective against viruses.[9]
- In the yeast fair test, what must you keep the same? Amount of yeast, sugar and water. Only the variable being tested should change.[2]
Going further
Repeat the test with different amounts of sugar (0, 1, 2 and 3 teaspoons). Predict and test what happens.
Sources used in this lesson
- [1] KS1: Introduction to Microbes (e-Bug, UK Health Security Agency): reliability High
- [2] KS2: Useful Microbes (e-Bug, UK Health Security Agency): reliability High
- [3] What is microbiology? (Microbiology Society (UK)): reliability High
- [4] What Counts as a Microbe? (American Society for Microbiology): reliability High
- [5] Microbiology: Types of microorganisms (Encyclopaedia Britannica): reliability Medium-high
- [6] Microbiology, 6.1 Viruses (OpenStax, Rice University): reliability High
- [9] Antibiotic and antimicrobial resistance (NHS (UK)): reliability High
Full list with links and a note on each source's reliability: echoesof.science/school/microbes/sources/
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