The document outlines the basic steps of the scientific method, using Louis Pasteur's experiment on bacterial growth as an example. It discusses the key components of an experiment, including manipulated, controlled, and responding variables. Pasteur's experiment aimed to test his hypothesis that airborne particles caused bacterial growth in broth by preventing or allowing air to reach sterilized broth samples. The results supported his hypothesis, as bacterial growth only occurred in samples exposed to air. This experimentation contributed to the development of the broader theory of germ theory.

1. Scientific Method

2. Science works by
using the scientific
method to prove that
ideas are wrong.
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3. Steps in the scientific method:
Step 1 - observation,
questioning
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4. Steps in the scientific method:
Step 1 - observation,
questioning
Why are these
bacteria growing
here?
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5. Step 2 - Research, Experimentation
Types of variables in an experiment:
• manipulated (independent) - are changed as part of
experiment
• controlled - held constant during the experiment
• responding (dependent) - conditions that are
observed to change during the experiment

6. In Pasteur’s experiment

7. In Pasteur’s experiment
• manipulated - allowing/
preventing particles in air to
reach broth

8. In Pasteur’s experiment
• manipulated - allowing/
preventing particles in air to
reach broth
• controlled - sterile broth, same
kind of container, same kind of
broth,location of flask, how
long was the broth left, volume
of broth

9. In Pasteur’s experiment
• manipulated - allowing/
preventing particles in air to
reach broth
• controlled - sterile broth, same
kind of container, same kind of
broth,location of flask, how
long was the broth left, volume
of broth
• responding - growth of
bacteria

10. An experiment tests a hypothesis (proposed
explanation for the phenomenon)
Pasteur suggested
bacteria in the air
caused the bacterial
growth.
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11. Step 3 - Observation
What were the results of the experiment
Pasteur saw
bacterial growth
only after the broth
was infected by the
dust from the air.

12. Step 4 - Development of a theory
After repeated experimentation, a theory is
developed which might then be tested
further (back to Step 2)

13. A good theory:
• explains observed phenomenon
• makes predictions
• is (scientifically) testable

14. Is cell theory a good theory?