Conceptual Change in the Fly Room:

A Lesson for Undergraduate Biology Education

M. Frances RoweEdgewood CollegeMadison, WisconsinUSAfrowe@edgewood.edu

Undergraduate Biology Education:A Challenge

Common Misconception Associated with

Learning Genetics:

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:

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.

The belief that changes in environmental conditions direct changes in organisms’ phenotypes, “need” drives evolution.

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.

The belief that acquired characteristics may be inherited.

The role of mutation in evolution

Thomas Hunt Morgan1866- 1945

Thomas Hunt Morgan1891-1904

Bryn Mawr College

Edmund B. Wilson

Nettie Stevens

Thomas Hunt Morgan1904-1928

Columbia University

Schermerhorn Hall

Thomas Hunt MorganNaples

1894-1895

Hans Driesch

• 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

Thomas Hunt MorganGenetics 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 MorganEvolution 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

Alfred Sturtevant

Hermann Muller

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

Theodosius DobzhanskyNettie Stevens

Edmund B. Wilson

Thomas Hunt MorganGenetics Post-1910

• Mendel’s factors must reside on 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 MorganEvolution 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 BiologyInstruction

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?

• 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 White-eyed 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 ?