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Science

Tiny Living Things: Microorganisms

Overview

Students explore the world of microscopic living things, discovering that bacteria, fungi, and viruses play vital — and sometimes deadly — roles in our world.

Learning Objective
Students understand what microorganisms are, where they live, and their roles as both harmful pathogens and beneficial organisms.

Resources needed

  • Bread left out for several days to grow mould (optional but powerful)
  • None otherwise

Lesson stages

0 / 7 done
  1. 1 Ask: what is the smallest living thing you know of?
  2. 2 Introduce: microorganisms are living things too small to see without a microscope.
  3. 3 Three types: bacteria (single cell), fungi (mould, yeast), viruses (not technically alive, but cause disease).
  4. 4 Ask: are all microorganisms harmful? (No — many are beneficial).
  5. 5 Beneficial examples: bacteria in yogurt and cheese, yeast in bread, bacteria in soil breaking down dead matter.
  6. 6 Harmful examples: bacteria causing cholera and tuberculosis, viruses causing flu and COVID-19.
  7. 7 Ask: how do we protect ourselves? (Handwashing, cooking food, clean water, vaccination).

Tap a step to mark it as done.

Variations

  • Grow yeast: add warm water, sugar, and yeast in a bottle with a balloon on top — watch it inflate.
  • Observe mould growth on bread over several days.
  • Discuss the history of disease — how did germ theory change medicine?
More information

Teach: microorganism, bacteria, virus, fungus, pathogen, beneficial, decomposer, hygiene. The distinction between bacteria (living, can be killed by antibiotics) and viruses (not living, antibiotics do not work) is particularly important.

Focus on harmful vs beneficial rather than the three types initially.

Can students name the three types of microorganism and give one example of each? Can they explain one beneficial and one harmful role of microorganisms?

Mould on bread shows a real microorganism. Yeast in warm water bubbles visibly. No microscope needed to demonstrate that microorganisms are real and active.

Students often think all bacteria are harmful and should be killed. The vast majority of bacteria are harmless or beneficial — the human gut contains trillions of beneficial bacteria essential for health.

Microorganisms connect biology, medicine, and environmental science. Understanding them is essential for health literacy, including hand hygiene, food safety, and vaccination.

Activity details
Primary Medium 25 minutes no prep Whole Class, Small Group Indoor & Outdoor
Topics
Microorganisms Bacteria Disease