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Conceptual Change in the
Fly Room:
A Lesson for Undergraduate
Biology Education
M. Frances Rowe
Edgewood College
Madison, Wisconsin
USA
[email protected]
Undergraduate Biology Education:
A Challenge
Common Misconception Associated with
Learning Genetics:
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Students inability to relate meiosis to allele
segregation
Students lack understanding of genetic terms (gene,
allele, chromosome, gamete, trait)
Seeing dominant and frequent as the same
The perception that genetic ratios are determinate,
not probabilistic
The relationship between genes and chromosomes,
The mechanisms for determining gender
Common Misconception Associated
with Learning Evolution:
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The belief that natural selection is both the production of
variation and the selection of variations by environmental
forces, rather than two separate processes affecting
populations.
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The belief that changes in environmental conditions direct
changes in organisms’ phenotypes, “need” drives evolution.
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A view of evolution as a change in an individual within its
lifetime rather than evolutionary change seen as a changing
proportion of individuals within a population over time.
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The belief that acquired characteristics may be inherited.
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The role of mutation in evolution
Thomas Hunt Morgan
1866- 1945
Thomas Hunt Morgan
1891-1904
Nettie Stevens
Bryn Mawr College
Edmund B. Wilson
Thomas Hunt Morgan
1904-1928
Schermerhorn Hall
Columbia University
Thomas Hunt Morgan
Naples
1894-1895
• Embraced epigenesis as an
explanatory theory for embryonic
development
• Introduced to
Entwickungsmechanik, the German
flavor of biology research, a
mechanistic experimental approach
• Converted from an observational
research program to an
experimental one, hypothesis
testing
Hans Driesch
Thomas Hunt Morgan
Genetics Pre-1910
• He believed chromosomes were uniform, and
questioned whether chromosomes changed during
synapse
• He felt that if many traits are on the same
chromosome, it contradicted Mendel’s claim of
independent assortment
• Mendel’s theory of dominance and recessive
variations could not account for the inheritance of sex
in the observed one-to-one ratio
• He did not believe continuous variation could be
explained by Mendelian principles
• There was no experimental evidence to support the
existence of Mendel’s postulated “factors”
Thomas Hunt Morgan
Evolution Pre-1910
• Darwin had provided no acceptable explanation
for the origin of variation in organisms;
• Believed that species were a human construction;
• Morgan believed natural selection could only sort
out the negative, not preserve the positive;
• He did not believe natural selection could act on
small adaptations to improve the function of
particular organs, like the eye;
• Darwin’s work was not supported by experiment;
• Morgan questioned the role of chance in the
process of natural selection
The Fly Room
The Fly Room
Calvin Bridges
Hermann Muller
Alfred Sturtevant
The Fly Room
Fly Room
• Genes are located on
Chromosomes
• The allele determining red
or white eyes is located on
the X chromosome
Fly Room
• Linked genes tend to
be inherited together
because they are
located on the same
chromosome
• Crossing over shuffles
genes producing
genetic recombinants
Fly Room
• Recombination frequencies
reflect the distance between
genes on a chromosome
• Recombinant data can be
used to construct
chromosome maps: an
ordered list of the genes
along a particular
chromosome
Thomas Hunt Morgan
1910- 1930
Nettie Stevens
Theodosius Dobzhansky
Edmund B. Wilson
Thomas Hunt Morgan
Genetics Post-1910
• Mendel’s factors must reside on
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•
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chromosomes
Each factor resides on a particular
chromosome
The eye color trait is positioned on the
X chromosome
The red eye color variation is dominant
to the white variation.
Chromosomal Theory of Heredity
Thomas Hunt Morgan
Evolution Post-1910
• Mendelian genetics, which he now
embraced, provided an acceptable
explanation for the origin of
variation;
• He supported natural selection
• He supported common descent
The Fly Room
The investigator must . . . cultivate a
skeptical state of mind toward all hypothesis
–especially his own- and be ready to
abandon them the moment the evidence
points the other way.
T.H. Morgan, 1927
In 1933 Thomas Hunt Morgan was the first
geneticist to be awarded the Nobel Prize. He
received the prize for Physiology or Medicine for
demonstrating that genes were located on
chromosomes via hereditary transmission in
Drosophila melanogaster
Undergraduate Biology
Instruction
Intended Learning Outcomes
• Development of content knowledge in the areas of
transmission genetics, molecular biology,
evolution, natural selection, and population
genetics;
• Development of content knowledge and
understanding of the history of biology;
• Understanding that biology is an accumulated, yet
impermanent body of knowledge.
Instructional Strategies
Reading Significant Episodes in the
History of Science
Instructional Strategies
Engage Students with Phenomena
Instructional Strategies
Challenge students to think about their ideas
(create dissatisfaction)
Instructional Strategies
Discussion of ideas theirs and those of others
Student discussion
Session
Discussion Questions
• What is required to believe a concept or an idea?
• What “got in the way” for Morgan to embrace
Mendel’s ideas?
• What does it mean to be an experimentalist?
• What counts as evidence in a scientific
investigation?
• How does one know when enough data/evidence
has been collected to support a theory?
• What does it mean for information to be internally
consistent?
• What does it mean for information to be
externally consistent?
Instructional Strategies
Require students to justify their ideas; create
written arguments grounded in and
supported by data
General Biology II
Student Assessment
Productive Synthesis
Concept Map
Obstructive Synthesis
Concept Map
Semi-Productive Synthesis
Concept Map
What does this mean for
biology instruction?
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Biology instruction is enhanced and strengthened by the
inclusion of history of science in the biology curriculum
Linking the history of biology, genetics, and evolution opens
the door for students to “give up” their misconceptions
Linking the history of biology, genetics, and evolution
enables students to construct their biology content
knowledge and increases the likelihood of understanding
both the process of science and the products it has produced
Knowledge of the history of biology aids students in
understanding that biology (as well as the other sciences) is
an accumulated, yet impermanent body of knowledge
Picture Resources
• Kohler, R.E. (1984). Lords of the Fly: Drosophila Genetics and the
Experimental Life. Chicago, IL: The University of Chicago Press
• Hagen, J., Allchin, D. & Singer, F. (1996). Thomas Hunt & the Whiteeyed Mutant. In Doing Biology. New York, NY: HarperCollins
College Publishers.
• Edgewood College General Biology II students.
• Campbell, N.A. & Reece, J.B. (2003). Biology, 6th ed. San Francisco,
CA: Benjamin Cummings.
• Google Images
Questions ?