1. How would you feel about touching this?
2.1a Would you touch it?
How would you feel about touching this?
fine I’d prefer not to disgusted
Slide 1

2. How would you feel about touching this?
2.1a Would you touch it?
How would you feel about touching this?
fine I’d prefer not to disgusted
Slide 2

3. How would you feel about touching this?
2.1a Would you touch it?
How would you feel about touching this?
fine I’d prefer not to disgusted
Slide 3

4. How would you feel about touching this?
2.1a Would you touch it?
How would you feel about touching this?
fine I’d prefer not to disgusted
Slide 4

5. 2.1a Would you touch it?
Why is it useful for some things to be so disgusting that we won’t touch them?
What was wrong with the cucumber soup?
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6. 2.1a Would you touch it?
Disgust keeps us away from things which look as if they could make us ill…
…waste like faeces, vomit, pus infected wounds, decaying food and the animals found with it.
All these contain microbes.
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7. 2.1a Alien cells
Ben spit out his apple when he found it was rotten inside, so he didn’t eat any microbes.
But 100 trillion microbes call Ben home. Luckily they are too small to see?
Where would you expect to find most of those microbes?
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8. 2.1a Alien cells
Microbes like these coat your skin and line openings like your mouth.
The largest, a fungus, is as big as a red blood cell.
The blue and yellow cells are bacteria.
How could we make bacteria easier to see?
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9. 2.1a Alien cells
When bacteria grow and divide on surfaces, they stick together…
...so the crowd of bacteria soon becomes visible.
These bacteria are common in faeces.
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10. Each dot is a crowd, or colony, of bacteria formed from a single cell.
2.1a Alien cells
Each dot is a crowd, or colony, of bacteria formed from a single cell.
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11. 2.1a Multiplying by dividing
Delayed reaction
Why is Kuba’s finger getting more and more painful?
Bacteria have infected it...
...and they’re multiplying fast
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12. 2.1a Multiplying by dividing
Multiplying by two
If these bacteria have enough food they can split into two and grow back to full size every 20 minutes.
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13. 2.1a What’s this?
Bacteria
These bacteria cause cholera
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14. 2.1a What’s this?
Virus
This virus infects horses
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15. Plant cells 2.1a What’s this? Only plant cells have green chloroplasts
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16. Animal cell 2.1a What’s this? Animal cells have no cell wall Slide 16

17. Virus 2.1a What’s this? This virus gives children diarrhoea Slide 17

18. Bacteria in animal cells 2.1a What’s this?
These human lung cells have bacteria in them which cause pneumonia
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19. Viruses in animal cells 2.1a What’s this?
These human cells have herpes virus particles inside them
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20. Bacteria in animal cells 2.1a What’s this?
These salmonella bacteria are invading human gut cells
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21. Questions to answer
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28. 2.1a Multiplying by dividing
Modelling fast growth
Start with 2 cubes.
These are your bacteria.
Let 1 second = 1 minute
So the number doubles every 20 seconds.
When the cubes get too hard to count, just record the numbers.
How many cubes do you have after 3 minutes?
How many real bacteria can grow in 3 hours?
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29. 2.1a Multiplying by dividing
Which graph?
Number of bacteria
time
Which line shows how their numbers grew?
Plot your results to check your decision.
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30. 2.1a Multiplying by dividing
Is there a limit?
Eventually the bacteria are so crowded that they can’t get enough nutrients.
Growth slows and the number of bacteria may plummet.
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