The Scientific Method in Action
Name: ___________________________________ Period: _______ Date: ___________
The Strange Case of BeriBeri
In 1887 a strange nerve disease attacked the people in the Dutch East Indies. The disease was called BeriBeri.
Symptoms of the disease included weakness and loss of appetite, victims often died of heart failure. Scientists
thought the disease might be caused by bacteria. They injected chickens with bacteria from the blood of
patients with beriberi. The injected chickens became sick. However, so did a group of chickens that were not
injected with bacteria.
One of the scientists, Dr. Eijkman, noticed something. Before the experiment, all the chickens had eaten wholegrain rice, but during the experiment, the chickens were fed polished rice. Dr. Eijkman researched this
interesting case. He found that polished rice lacked thiamine, a vitamin necessary for good health.
1. State the Problem or question.
2. What was the hypothesis?
3. How was the hypothesis tested?
4. Should the hypothesis be supported or rejected based on the experiment?
5. What should be the new hypothesis?
How Penicillin Was Discovered
In 1928, Sir Alexander Fleming was studying Staphylococcus bacteria growing in culture dishes. He noticed that
a mold called Penicillium was also growing in some of the dishes. A clear area existed around the mold because all
the bacteria that had grown in this area had died. In the culture dishes without the mold, no clear areas were
present.
Fleming hypothesized that the mold must be producing a chemical that killed the bacteria. He decided to isolate
this substance and test it to see if it would kill bacteria. Fleming transferred the mold to a nutrient broth
solution. This solution contained all the materials the mold needed to grow. After the mold grew, he removed it
from the nutrient broth. Fleming then added the nutrient broth in which the mold had grown to a culture of
bacteria. He observed that the bacteria died. The isolated chemical that killed the bacteria was later named
penicillin after the mold that produced it.
6. Identify the problem or question.
7. What was Fleming's hypothesis?
8. How was the hypothesis tested?
9. Should the hypothesis be supported or rejected based on the experiment?
10. This experiment led to the development of what major medical advancement?
Spontaneous Generation
In 1862, Louis Pasteur, despite criticism from other scientists of the day, believed that all life came from life
and that even microbes did not spontaneously generate. He observed that bacteria would grow in open
containers of meat broth. He also observed that if the broth was boiled for an hour in a sealed container that
remained sealed, no bacteria grew. However, if the container was later opened, the broth grew bacteria. Finally,
He discovered that bacteria were present in dust particles that float in the air.
He thought that the air carried bacteria into the broth, and if there was a way to keep the dust from getting to
the broth while still allowing air to reach the broth, then the broth would not grow bacteria. He designed an
experiment with two flasks with s shaped necks filled with broth which he boiled for an hour to sterilize it. The
two flasks were open to the air, but from below, so dust was trapped in the neck and never reached the broth.
The broth in the flasks did not grow bacteria.
Next, Pasteur broke the s curved neck off one of the flasks, exposing the broth to the air from above, while
leaving the other flask alone. Dust particles fell into the broken flask and the broth grew bacteria, while the
dust particles could not go up the neck of the s curved flask against gravity to get in the broth, and the broth
remained free of bacteria.
11. Identify the problem
12. What was Pasteur’s hypothesis?
13. How was the hypothesis tested?
14. Should the hypothesis be supported or rejected based on the experiment?
15. What can be concluded from this experiment?
16. What would have happened in the experiment if bacteria really did grow spontaneously?
Review: Write 3-5 complete sentences explaining how the scientific method
works.