Microorganisms: helpful and harmful

Tiny living things - bacteria, viruses and fungi - and how they help or harm us

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Try each question. If you're stuck, leave it and come back. The answer key is on the last page.

1
What is a microorganism? A) A tiny living thing that can only be seen with a microscope B) A small insect like an ant C) A new kind of plant D) A small piece of rock
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2
True or false? Yeast is used to make bread rise because it produces carbon dioxide gas. A) True B) False
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3
True or false? Washing your hands helps stop harmful microorganisms spreading. A) True B) False
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4
What is a microorganism? A) A tiny living thing that can only be seen with a microscope B) A type of plant C) A small animal D) A type of rock
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5
Match each microorganism to a true description. Match each item on the left to one on the right. Left: Bacteria, Viruses, Fungi, Yeast Right: Single-celled living things, Much smaller and not really alive, Include yeasts and moulds, A fungus used to make bread rise
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6
True or false? Yeast is a type of fungus. A) True B) False
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7
True or false? All bacteria are harmful and cause disease. A) True B) False
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8
Why do scientists say viruses are 'not really alive'? A) They can't reproduce on their own - they need a living cell B) They have eyes but cannot see C) They live underwater D) They are made of plastic
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9
True or false? Antibiotics work against bacteria, not viruses. A) True B) False
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10
Which is an example of microorganisms being useful? A) Making yoghurt and cheese B) Causing colds C) Spoiling food D) Making teeth decay
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Answer key

Microorganisms: helpful and harmful · for parents and teachers

1
A tiny living thing that can only be seen with a microscope
Microorganisms are living things too small to see with the naked eye. We use microscopes to see them.
2
True
True. Yeast feeds on sugar in the dough and produces carbon dioxide gas. The gas bubbles make the bread rise.
3
True
True. Soap and water remove microorganisms from skin so they can't be passed to food, surfaces or other people.
4
A tiny living thing that can only be seen with a microscope
Microorganisms are living things too small to see without a microscope, like bacteria, yeasts and many fungi.
5
Bacteria → Single-celled living things; Viruses → Much smaller and not really alive; Fungi → Include yeasts and moulds; Yeast → A fungus used to make bread rise
Bacteria are single-celled microbes. Viruses are much smaller and can't reproduce on their own. Fungi include yeasts and moulds.
6
True
True. Yeast is a single-celled fungus, NOT a bacterium. It produces carbon dioxide that makes bread rise.
7
False
False. Most bacteria are harmless or helpful. We use them to make yoghurt and cheese, and 'good' bacteria live in our gut.
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They can't reproduce on their own - they need a living cell
Viruses are not made of cells and cannot reproduce by themselves. They must invade a living cell to make copies of themselves.
9
True
True. Antibiotics kill bacteria but do not work against viruses.
10
Making yoghurt and cheese
Microorganisms are used to make many foods, like yoghurt, cheese, bread and wine.