Name: Gracie Villacis______ Class: __BIOL-101-301-243________ Date: ___5/21/2024__________
Famous Examples of the Scientific Method
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.
Experiment #1:
Scientists thought the disease might be caused by bacteria found in blood. They injected chickens
with blood from patients with the beriberi disease. The injected chickens became sick. However,
so did the other group of chickens that were not injected with bacteria.
1. What was the initial hypothesis in this example?
The beriberi disease might be caused by bacteria found in the blood.
2. What independent variable were the scientists studying in this case?
The injection of blood from patients with the disease into chickens.
3. What dependent variable were the scientists measuring?
The health condition of the chickens—whether they became sick or not as a result.
4. What was the experimental group in their study? What was the control group?
The experimental group in the study was the chickens who were injected with blood from the
patients with beriberi. The control group was the chickens that were not injected with the blood.
5. Why is a control group important? What conclusion might the scientists have reached if they did
not use a control group in this example?
A control group is important because it helps determine if the changes in the experimental group
are actually due to the independent variable and not other factors. Without a control group, the
scientists might have incorrectly concluded that the blood injection was the cause of the illness in
chickens and that the disease is caused by bacteria found in blood, ignoring other possible factors.
6. Would this first experiment be considered a failure? Explain why or why not.
This first experiment would not necessarily be considered a failure because it provided vital
information based on the results. The fact that both groups of chickens became sick suggests that
the cause of beriberi might not be from bacteria in the blood, which then leads scientists to explore
other possible causes. It isn’t a failure, more of a redirection.
Experiment #2:
One of the scientists studying Beriberi was named Dr. Eijkman. He realized that before the experiment,
all the chickens had eaten whole-grain rice, but during the experiment, the chickens were fed only
polished (white) rice. Dr. Eijkman researched this further by testing two new groups of chickens. One
group was fed the polished rice, the other group was fed the whole-grain rice. Only the polished rice
chickens got the illness. As a result, he believed that the polished rice was missing a nutrient needed to
prevent the disease.
7. What observation did Dr. Eijkman make during the first Beriberi experiment?
During the first experiment, Dr. Eijkman observed that the chickens who were fed polished
(white) rice during the experiment had gotten sick, while those previously fed whole-grain rice did
not.
8. What independent variable was Dr. Eijkman studying in this case? What dependent variable
did he measure?
The independent variable he was studying in this case was the type of rice that the chickens were
fed—polished rice vs. whole-grain rice. The dependent variable he measured was the occurrence
of the illness in the chickens.
9. What was the experimental group in this study? What was the control group?
The experimental group in this study was the group of chickens fed polished rice and the control
group was the group of chickens fed whole-grain rice.
10. Explain what Dr. Eijkman would need to do next in order to share his discovery with other
scientists and have his conclusions be considered valid.
To share his discovery with other scientists and have his conclusions be considered valid, Dr.
Eijkman would need to publish his findings in a scientific journal. He would need to include
details descriptions of his experiments, data, and results/conclusion. Additionally, other scientists
would need to replicate his experiments to confirm the results.
The Discovery of Penicillin
In 1928, Sir Alexander Fleming was studying Staphylococcus bacteria growing in culture dishes. He
noticed that a type of 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 died.
Experiment #3:
Fleming thought 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 liquid broth
solution. This solution contained all the materials the mold needed to grow. After the mold grew, he
removed it. He then grew two identical groups of bacteria. He then took the mold-infused broth and
added it to of the groups of bacteria. Those bacteria died. Fleming then added a liquid broth that did not
contain mold to the second group of bacteria. This group survived.
11. What independent variable were the scientists studying in this case? What dependent variable
were the scientists measuring?
The independent variable in this case was the presence of the mold-infused broth. The dependent
variable that was measured was the state of the bacteria – survival or death.
12. What was the experimental group in their study? What was the control group?
The experimental group in the study was the group of bacteria that the mold-infused broth was
added to. The control group was the group of bacteria in which the broth without mold was added
to.
13. When an experiment is designed, all variables between the experimental group and control group
must be held constant. How did Fleming’s experimental design meet this requirement?
Fleming’s experimental design met this requirement by ensuring that both groups of bacteria were
identical and grown under the same conditions. By doing so he was able to keep all variables
between the experimental and control group constant, except for the addition of the mold-infused
broth to the experimental group and the plain broth to the control group.