Invisible Travelers
Learning Objectives
Students will be able to:
- Explain that germs are too small to see without a microscope
- Name different types of germs (bacteria and viruses)
- Describe that some germs help us while others make us sick
- Understand that germs are everywhere around us
The Big Question
"What are germs, and why can't we see them?"
Opening Hook (5 minutes)
Think about this: Have you ever gotten a cold? One day you felt fine, the next day your nose was running and your throat was sore. But you couldn't SEE anything that made you sick. So what happened?
You were invaded by tiny, invisible travelers called germs!
What Are Germs?
Germs are tiny living things (or almost-living things) that are too small to see without a microscope. There are different types:
Bacteria
- Tiny single-celled living things
- Can be good OR bad
- Some live in your gut and help you digest food!
- Others can cause infections like strep throat
- Can be killed by soap and antibiotics
Viruses
- Even smaller than bacteria!
- Not quite alive - need a host to survive
- Cause colds, flu, COVID-19, and more
- Cannot be killed by antibiotics
- Your body fights them with your immune system
How Small Are Germs?
Size Comparison:
| Thing | Size | Can You See It? |
|---|---|---|
| Period at end of sentence (.) | About 350 micrometers | Yes! |
| Human hair width | 70 micrometers | Yes! |
| PM2.5 particle | 2.5 micrometers | No |
| Bacteria | 1-5 micrometers | No - need microscope! |
| Virus | 0.02-0.3 micrometers | No - WAY too small! |
Amazing fact: You could fit thousands of viruses on the period at the end of this sentence!
Not All Germs Are Bad!
Good Germs (Helpful!)
- Bacteria in your gut help digest food
- Some bacteria make vitamins for your body
- Bacteria help make yogurt, cheese, and bread
- Some bacteria help plants grow
- Good bacteria fight off bad bacteria!
Bad Germs (Make us Sick)
- Cold viruses - runny nose, cough
- Flu virus - fever, body aches
- Strep bacteria - sore throat
- Stomach viruses - vomiting, diarrhea
- COVID-19 virus - respiratory illness
Activity: Germs Are Everywhere! (15 minutes)
The Glitter Germ Demonstration
Materials: Fine glitter, hand lotion, various classroom objects
- Put a small amount of lotion on one student's hands
- Sprinkle glitter on the lotion - the glitter represents germs!
- Have the student shake hands with another student
- Have them both touch objects - doorknob, pencils, desk
- Look at where the "germs" (glitter) ended up!
- Try to wash off the glitter - notice how you need soap and lots of scrubbing!
What Did We Learn?
Germs spread quickly from person to person and to surfaces we touch. We can't see real germs like we can see glitter, but they spread the same way!
Where Do Germs Live?
Germs are everywhere! They live on:
Our Bodies
Hands, skin, mouth, gut
Surfaces
Doorknobs, phones, desks
In the Air
When people cough or sneeze
Water & Food
If not clean or cooked properly
Animals
Pets, farm animals, wildlife
Soil
Gardens, playgrounds
Your Body's Defenses
Your body has ways to fight germs:
- Skin - acts like a wall to keep germs out
- Nose hairs and mucus - trap germs before they get to your lungs
- Stomach acid - kills many germs you swallow
- White blood cells - your body's germ-fighting army!
- Immune system - remembers germs so it can fight them faster next time
Science Notebook (10 minutes)
Draw and answer:
- Draw a picture comparing the size of a bacteria and a virus to something you CAN see
- List 2 helpful things germs do
- List 2 sicknesses caused by germs
- Why can't we see germs with just our eyes?
Key Takeaways
- Germs are tiny - too small to see without a microscope
- Bacteria and viruses are two main types of germs
- Some germs help us, some germs make us sick
- Germs are everywhere and spread easily from person to person
- Our bodies have defenses to fight germs
Vocabulary Words
Germs
Tiny living things that can make us sick. Includes bacteria and viruses.
Bacteria
Single-celled germs. Some are helpful, some cause illness.
Virus
Tiny germs that need to be inside a living cell to survive. Cause colds and flu.
Microscope
A tool that makes very small things look bigger so we can see them.