Download Lets`s Get Small

Lets’s Get Small
In this activity we will be making a model to compare the sizes of various viruses and bacteria to the
width of a human hair. A model is used as a tool for humans to be able to visualize things that are
either very very tiny or very very large. (The globe is a model)
What to do…
1. Run your hand through your hair to find a loose hair. Examine the hair under a magnifying glass.
Does it look larger under the glass? Examine the hair from another participant under the magnifying
glass. Compare its thickness, or width, to your own hair. If you were going to make a model of a
piece of human hair, would you make it larger or smaller than a real piece of hair? Do you think
microbes are smaller than the width of a piece of hair? If you needed to make a model of a microbe,
would you make it larger or smaller than the original?
2. Lay your meter stick or ruler out in front of you. What kinds of things do you measure in meters?
Viruses, bacteria and protozoa are so small that we use much smaller measurements for them. They
are even so small that we cannot use any sort of “stick” to measure them at all.
3. Move to the area set aside for your group to create models to compare the sizes of viruses,
bacteria and protozoa with the width of a piece of hair. That would be the tiny space between your
fingers where you held a piece of hair earlier. You will need a legnth of paper that is 10 meters long
to represent the width of a human hair. Select one of the microbes from the following list:
Poliovirus, Adenovirus, Vaccina Virus, Bacteriophage, Cold Virus, Yellow Fever Virus, Flu Virus,
Cold Sore Virus, Smallpox Virus, Staphylococcus, Streptococcus, E.Coli, Human Hair, Human red
Blood Cell; and draw what you think it might look like and its size in comparison to the width of a
human hair. Label this one with the microbe name and a big G for “Guess.”
4. Now go back to the Microbe reference Chart and what size the microbe you selected really is.
Return to your drawing and make another drawing the proper size. How does it compare to your
original?
5. Circulate among the drawings made by the other groups. Compare the microbe sizes and shapes.
Are you surprised by the different sizes of microbes? How could you see these microbes? Did you
create a good model of microbial size? Why do viruses and bactera have such different shapes?
How many bacteria do you think could fit into a teaspoon?
6. Why do scientists need to use models? Why can’t they just look under a microsope to see what
they need to see?
Please answer these questions on loose leaf. Be sure to RAP.
1. Do viruses and bacteria vary in shape and size? (Do they come in various sizes and
shapes?)
2. How do models help scientists study things that are very small, like viruses?
Microbe
Effect on the
Body
Actual Size
Model Size
Poliovirus
Diseases of the
digestive tract,
brain and spinal
cord
20 nanometers
2mm
Adenovirus
Diseases of
respiratory tract
and digestive
tract
90 nm
9mm
Vaccina Virus
Cowpox
200 nm
20mm
Bacteriophabe
Useful, transfers
genes from one
organism to
another helping
survival and
biotechnology
Causes food
poisoning
60 nm
6mm
0.0005 mm
5 cm
Causes diseases
and helps with
digestion
0.002 mm
2 cm
0.1 mm wide
10 m
Staphylococcus
E. Coli
Human Hair
Shape (not to
scale)
Human red
blood cell
carries oxygen in
our bodies
0.01 mm
1m
Streptococcus
causes disease
750 nm
75 mm
Smallpox Virus
causes disease
250 nm
25 mm
Cold Sore Virus
causes disease
130 nm
13 mm
Influenza Virus
causes disease
90 nm
9mm
Cold Virus
causes disease
75 nm
7.5 mm
Yellow Fever
Virus
causes disease
22nm
2.2mm