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Science In Action
The Strange Case of BeriBeri
In 1887 a strange nerve disease attacked the people in the Dutch East Indies. The disease was
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 whole-grain 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
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 Lysozymes were Discovered
November 1921. Alexandar Fleming had a terrible cold. He was working in his lab. He was a
Scottish scientist fascinated with bacteria. He was looking at some harmless airborne bacteria that
he had grown on special plates called petri dishes when a drop from his nose fell into the dish. YUK!
He was a keen observer and noticed that immediately these yellow colonies of bacteria became
cloudy, glassy, and lifeless in appearance. What happened? The bacterial cells had burst open
(lysed)!!!! A substance that your body produces is able to burst open bacterial cells. What did he
find? He had discovered lysozymes, a naturally occurring enzyme present in mucus, tears, and
saliva that works as an antibacterial agent.
6. What were his observations?
7. What did he discover and what was its function?
8. Why are observations important in science?
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.
9. Identify the problem.
10. What was Fleming's hypothesis?
11. How was the hypothesis tested?
12. Should the hypothesis be supported or rejected based on the experiment?
13. This experiment lead to the development of what major medical advancement?
Scenario 1: Perfumes and Bees’ Behavior
JoAnna read that certain perfume esters would agitate bees. Because perfume formulas are secret,
she decided to determine whether the unknown Ester X was present in four different perfumes by
observing the bee’s behavior. She placed a saucer containing 10 mL of the first perfume 3 m from
the hive. She recorded the time required for the bees to emerge and made observations on their
behavior. After a 30-minute recovery period, she tested the second, third, and fourth perfumes. All
experiments were conduced on the same day when the weather conditions were similar; that is, air
temperature and wind were constant.
14. What is the hypothesis?
15. What is the independent variable?________________________________
16. What is the dependent variable?_________________________________
17. What were the control variables (the variables that were kept the same)
18. What was JoAnna’s experimental design? (what did she do? ….her procedure)
Scenario 2: Aloe vera and Planaria
Jackie read that Aloe vera promoted healing on burned tissue. She decided to investigate the effect
of various amounts of Aloe vera on the regeneration of planaria. She bisected the planaria to obtain
10 parts (5 heads and 5 tails) for each experimental group. She applied concentrations of 0%, 10%,
20%, and 30% Aloe vera to the groups. Fifteen mL of Aloe vera solutions were applied. All planaria
were maintained in a growth chamber with identical food, temperature, and humidity. On day 15,
Jackie observed the regeneration of the planaria parts and categorized development as full, partial, or
none.
19. What is the hypothesis?
20. What is the independent variable?_____________________________
21. What is the dependent variable?_______________________________
22. What were the control variables (those variables that were keep the same)?
Scenario 3: Ants and Tunnel Length
A student investigated whether ants dig more tunnels in the light or in the dark. She thought that ants
used the filtered light that penetrated the upper layers of earth and would dig more tunnels during the
daytime. Ten ant colonies were set up in commercial ant farms with the same number and type of
ants per ant farm. The same amount of food was given to each colony, and the colonies were in the
same temperature. Five of the colonies were exposed to normal room light and five were covered
with black construction paper so they did not receive light. Every other day for three weeks the length
of the tunnels was measured in millimeters using a string and a ruler. Averages for the light and dark
groups for each measured were then computed. The averages are listed in the following chart.
Length of Tunnels (mm) Constructed by Ants in Different Light Conditions
Day
1
3
5
7
9
11
13
15
17
19
21
23. What is the problem/observation?
24. What is the hypothesis?
Light
5
10
20
26
32
50
61
66
90
95
103
Dark
7
15
25
32
47
62
93
110
115
120
136
25. Explain the experimental design (what is the procedure?).
26. What is the Independent Variable?
27. What is the Dependent Variable?
28. What are the control variables?
29. What is the control group? (group whether nothing was changed)