The Germ Theory Revolution
How germ theory finally explained what causes disease: Pasteur showing that microbes cause it, Koch hunting the microbe behind each disease, and Ehrlich finding the first magic bullet.
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Finally, the real cause
For centuries people blamed illness on an imbalance of humours or on bad air. In the nineteenth century that changed for good. Scientists proved that tiny living things, microbes or germs, cause disease, and then learned to find and fight them. This module follows that revolution through Pasteur, Koch and Ehrlich.
Germ theory words to know
Learn these before you sort the discoveries.
Old idea against germ theory
Germ theory replaced the guesses of earlier eras.
Name the scientist and the step
In the exam, tie each scientist to their step forward: Pasteur proved germs cause disease, Koch found which microbe causes which disease, and Ehrlich made a chemical that kills a chosen microbe. The big point is that germ theory finally explained the real cause, which the humours and bad-air ideas never could.
Match the scientist
- Louis Pasteur
- Robert Koch
- Paul Ehrlich
- the old humours idea
- proved microbes cause disease
- found the microbe behind each disease
- made the first magic bullet
- the wrong idea germ theory replaced
Match the contribution
- proving germs cause decay
- identifying a specific microbe
- making a weakened-microbe vaccine
- finding a chemical cure
- the work of Pasteur
- the work of Koch
- a later step by Pasteur
- the work of Ehrlich
What did Pasteur prove?
What did Louis Pasteur prove about disease?
- That microbes, or germs, cause disease and decay.
- That the four humours must be balanced.
- That bad air alone causes every illness.
- That the stars control health.
Steps in the revolution
Select the TWO genuine steps in the germ theory revolution.
- Koch found the microbe behind a disease
- Ehrlich made a chemical that kills one microbe
- Doctors returned to balancing the humours
- Healers read the stars to cure illness
Years of the revolution
Imagine germ theory was set out around the year 1860 and the first magic bullet was found around 1910. Subtract to find how many years lay between them. What is the answer?
Order the breakthroughs
Put the germ theory breakthroughs in order, earliest first.
- Pasteur proves germs cause disease
- Koch hunts down specific microbes
- Vaccines are made from weakened microbes
- Ehrlich finds the first magic bullet
Complete the account
Louis _____ proved that microbes cause disease, ending the old idea that it came from an imbalance of the humours. Robert _____ then found which microbe caused which disease. Paul Ehrlich made the first magic _____, a chemical that kills one kind of microbe. At last medicine understood the real _____ of disease.
Spot the germ-theory scientists
Tap the TWO scientists who were central to the germ theory revolution.
- Louis Pasteur
- Robert Koch
- Galen
- Hippocrates
Whose work is it?
Read each achievement and choose whose work it was.
- A scientist proves that germs, not bad air, cause food to decay and people to fall ill. Whose work is this?
- A researcher identifies the exact microbe that causes a named disease. Whose kind of work is this?
- A chemist develops a substance that kills one microbe without harming the patient. What is this called?
Explain the revolution
Explain how germ theory changed the understanding of disease, naming the scientists and their contributions.
- Say what germ theory is and what Pasteur proved
- Explain what Koch and Ehrlich each added
- Explain why this was such an important change from earlier ideas