Learning about the
Nature of Science
with Case Studies
Kathy Gallucci
Elon University
Elon, NC
September 27, 2008
9th Annual Conference on
Case Study Teaching in Science
SUNY Buffalo
“scientists are just basically trying to figure out the
universe, how the world works, trying to [understand]
that in as much logic as possible and in the end trying to
help mankind and the earth….”
Nature of Science
• scientific enterprise (process)
– discovery, inquiry
• scientific knowledge (justification)
– knowledge claims
(Duschl, 1990)
Why teach the justification of knowledge claims?
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How does science know what it knows?
Is there a difference between scientific knowledge and opinion?
If science is tentative, why should we accept what it says?
Are there limits to the kind of questions science can ask?
What about the public perception of science?
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“only a theory”
“teach the controversy”
“when science speaks, let no dog bark”
science as a faith
• Do many politicians understand science?
• Why do we require non-science majors to take science?
• Why is astrology so popular?
Context of justification
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hypothesis-testing
tentativeness
observation vs. inference
empirical evidence
social & cultural embeddedness
“The Dragon in my Garage”
"A fire-breathing dragon lives in my garage."
Suppose I seriously make such an assertion to you. Surely you'd want to check
it out, see for yourself. There have been innumerable stories of dragons over
the centuries, but no real evidence. What an opportunity!
"Show me," you say. I lead you to my garage. You look inside and see a ladder,
empty paint cans, an old tricycle--but no dragon.
"Where's the dragon?" you ask.
"Oh, she's right here," I reply, waving vaguely. "I neglected to mention that she's
an invisible dragon."
You propose spreading flour on the floor of the garage to capture the dragon's
footprints.
"Good idea," I say, "but this dragon floats in the air."
Then you'll use an infrared sensor to detect the invisible fire.
"Good idea, but the invisible fire is also heatless."
You'll spray-paint the dragon and make her visible.
"Good idea, but she's an incorporeal dragon and the paint won't stick."
And so on. I counter every physical test you propose with a special explanation
of why it won't work.
Now, what's the difference between an invisible, incorporeal, floating dragon
who spits heatless fire and no dragon at all?
(Sagan 1996)
“[by] taking this science class, … the more I learn about
science, the more I learn what we don’t know about
science. It seems like…everything has to be falsifiable…
It’s just really interesting, the more you learn, the more
you learn what you don’t know.”
Are these statements falsifiable (F) and/or testable (T)?
1. Students who attend class do better than students
who do not attend class.
2. God created the world.
3. Life exists in other solar systems.
4. In one million years, there will be no humans on earth.
5. There is an invisible, heatless, weightless dragon in
my garage.
6. The earth is flat.
http://urbanlegends.about.com/b/2004/01/28/man-finds-pickled-dragon-in-garage.htm
“I really respect the field of science but I think that it
is so much… under the microscope…everybody just
…looks at it for all the right answers, I think. Science
might be right at the moment, but science always
evolves. That’s kind of what I’ve learned…. It’s cool
to know there’s not just one golden rule in science.
There’s a lot of different people interpreting things
differently.”
“Using Family Photos
to Gather Evidence”
Using Photos to Gather Evidence
• An inference is a conclusion that is arrived at by reasoning
from evidence.
• Our inferences are only as good as our knowledge bases.
• Even small clues can yield a significant amount of information.
(inferences)
(adapted from Dickey, 2000)
“Mystery Disease”
“We…were the detectives, we were the scientists,
trying to figure out what was wrong with these people.”
Chamorros in Guam & ALS-PDC
Neurologists observed that many of the Chamorro
people had a disease that resembled ALS, Parkinson’s
disease, and Alzheimer’s disease.
In one village, Umatac, 1/3 to 1/4 of all adult deaths
between 1944-1953 were caused by this disease.
Guam has the highest rate of ALS-type disease on earth.
Group Discussion 1
1.
Based on the information given, what do you think is causing the high
incidence of ALS-PDC in Guam? Make a list of possible causes.
2.
What information not provided would help you investigate the reason
for the high incidence Of ALS-PDC in Guam?
3.
Write a testable and falsifiable hypothesis about the cause of ALS-PDC.
Scientists considered these possible causes of the disease:
Genetics?
• The disease seems clustered in families
• But a spouse, even from a different country, sometimes gets it
Aluminum in the water?
• Water tests showed low levels of aluminum in the water
Calcium and magnesium levels low in the soil?
• Calcium and magnesium were not deficient in soil
Infectious agents?
• The disease is not transmitted from person to person
Diet?
• What are some possibilities…
Photo by Paul Cox
Cycads produce large seeds, high in
starch. These are prepared by
soaking in water several times to
remove the toxin.
Chamorro people have made the
fadang into flour to make
Photo by Paul Cox
tortillas since before WW II.
The flour is made into thin cakes or Recently scientists have isolated 2
neurotoxins from the cycad seeds…
tortillas.
Group discussion 2
4.
Based on this new information, write another
hypothesis regarding the cause of ALS-PDC.
5.
How do you think you could test your hypothesis?
More experiments…, and the results…
Researchers conducted experiments to determine if eating cycad
seeds was a possible cause of ALS-PDC.
Seeds and flour were fed to laboratory animals and similar
neurological disorders were not observed.
Chemists analyzed the seeds and found low concentrations of
neurotoxins.
Cycad flour did not seem to be the cause of ALS-PDC.
What is another unique Chamorro food?
The annual incidence of ALS-PDC in
Guam has dropped.
Correlated with this decline, is the
availability of a unique Chamorro food…
Photo by Paul Cox
© Paul Alan Cox
• Eat fruits, seeds, nectar,
pollen
• Cycad seeds are a favorite
food
• Eat 2 times their body
weight daily
One species is extinct.
The other is endangered
(only about 100-200 left).
Photo credit: Dr. Merlin Tuttle, Bat Conservation International
Are flying foxes important to
Chamorro diets?
More observations and experiments…
The researchers concluded that the consumption of flying foxes in
Guam drastically increases the chances of an individual getting
ALS-PDC.
They noted that men ate the whole flying fox more often than
women.
A population study on flying foxes in Guam was conducted…
Group discussion 3
6. Why should eating flying foxes cause
disease in humans?
Source of toxin:
Coralloid roots that contain nitrogen-fixing cyanobacteria
http://www.botan.su.se/Fysiologi/Terrestrial_Biodiversity/Cycad%20project%20coralloid2.jpg
http://plantnet.rbgsyd.gov.au/PlantNet/cycad/nitrogen/figure23.jpg
(Cox, et al., 2003)
(Cox, et al., 2003)
YOU ARE WHAT YOU EAT…
…what’s on your plate?
Photo by Merlin Tuttle
“The Fish Kill Mystery”
1. What are some of the possible causes of the fish kill?
2. What are some of the observations they made?
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temperature
dissolved oxygen
turbid water
light penetration
sores on fish
3. What inferences did they make from these observations?
New knowledge from observations and experiments
“Nutrient influx doesn’t only have the potential to stimulate
the overpopulation of photosynthesizers, it can also stimulate
some plankton species to produce toxins and may indirectly
stimulate some to change body forms.”
Tentativeness of science
“… don’t lead these ladies into thinking that scientists know
for sure what is happening with this interesting
species…Wayne Litaker and his colleagues have evidence
supporting a much more simplistic life cycle for Pfiesteria,
one without all the amoeboid forms”
Tentativeness of science
“… don’t lead these ladies into thinking that scientists know
for sure what is happening with this interesting
species…Wayne Litaker and his colleagues have evidence
supporting a much more simplistic life cycle for Pfiesteria,
one without all the amoeboid forms.”
“The point is that science doesn’t always have a clear-cut
answer to questions immediately. The Pfiesteria controversy
is far from over …”
research evidence & inferences
• nutrients + sunlight = high photosynthesis
• phytoplankton on surface block sunlight
• decomposition of dead phytoplankton uses O2
• fish die from lack of oxygen
• nutrients stimulate plankton to produce toxins &
change body forms
• large schools of fish may “cue” plankton to
produce a deadly toxin
tentativeness of science
• different researchers have come to different conclusions
• absence of evidence cannot be used to make conclusions
social & cultural issues
• Who is responsible for the heavy nutrient influx into the estuary?
• What would be the viewpoint of a fisherman? a tourist? an
environmentalist? a homeowner? a waste water treatment operator?
a State Congressman? a pig farmer? a journalist?
• How would the scientists’ recommendations affect each of these
stakeholders?
“I kind of realize that…so much in science isn’t a definite.
It doesn’t have a definite answer, because it’s all
…theories. It’s not something exact, it’s not like a fact,
but it’s because of all these common theories, that all …
give you a certain idea of something.”
NOS Concepts in Case Studies
Sources of NOS cases
• NCCSTS: ignore the subject under which it is listed
(“Fish Kill” is listed under Ecology/Environment and
“Child Bed Fever” is listed under Medicine)
• Historical examples (McComas, 2008)
• National Inquirer
• Mythbusters
• CSI
• Popular media
• Student answers
References
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Abd-El-Khalick, F., Bell, F.R. & Lederman, N.G. (1998). The nature of science and instructional
practice: making the unnatural natural. Science Education 82: 417-436.
Cox, P.A., Banack, S.A, & Murch, S.J. (2003). Biomagnification of cyanobacterial neurotoxins and
neurodegenerative disease among the Chamorro people of Guam. Proceedings of the National
Academy of Sciences 100(23): 13380-13383.
Dickey, J. (2000). Using family photographs to introduce human evolution. Paper presented at the
National Association of Biology Teachers Annual Convention, Orlando, Florida. October 25-28.
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Duschl, R.A. (1990). Restructuring science education: the importance of theories and their development.
New York: Teachers College Press.
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Gallucci, K. (2006). Learning concepts with cases. Journal of College Science Teaching 36(2): 16-20.
Gallucci, K. (2007). The case method of instruction, conceptual change, and student attitude. Ph.D.
dissertation, available at http://www.lib.ncsu.edu/theses/available/etd-10112007-132733/
Kosal, E.F. (2003). The fish kill mystery. Journal of College Science Teaching 33(4): 36-40.
McComas, W. (2008). Seeking historical examples to illustrate key aspects of the nature of science.
Science & Education 17: 249-263.
Sagan, C. (1996). The dragon in my garage. In The demon-haunted world: science as a candle in the
dark (pp. 169-173). New York: Random House.
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