A COMPARATIVE STUDY OF HOW HIGH SCHOOL STUDENTS
UNDERSTAND STEM CELLS
By
Jonathan Christian Rabe Moyer
B.S. University of Maine, 2003
A THESIS
Submitted in Partial Fulfillment of the
Requirements for the Degree of
Master of Science in Teaching
The Graduate School
The University of Maine
May, 2007
Advisory Committee:
John R. Thompson, Assistant Professor of Physics, Advisor
Mary S. Tyler, Professor of Zoology
Michael C. Wittmann, Assistant Professor of Physics
A COMPARATIVE STUDY OF HOW HIGH SCHOOL STUDENTS
UNDERSTAND STEM CELLS
By Jonathan Christian Rabe Moyer
Thesis Advisor: Dr. John R. Thompson
An Abstract of the Thesis Presented
in Partial Fulfillment of the Requirements for the
Degree of Master of Science In Teaching
May, 2007
In Spring 2004 an inquiry-based unit on stem cells was developed from chromatin
dynamics research at the Jackson Laboratory in Bar Harbor, Maine. The unit was
developed according to the backwards design model of curriculum development and
implemented in Bangor area high schools in April 2005 and June 2005. With slight
modifications, the stem cell unit was re-implemented in June 2006 and tested against a
traditional, lecture-based unit.
Open response pre- and post-tests were used to capture initial student conceptions
and measure learning gains. Pre-instruction interviews were conducted in order to gain a
deeper understanding of pre-test answers. In addition, a two-tailed matched-pair analysis
of post-test answers was performed in order to determine the effectiveness of inquirybased instruction versus lecture-based instruction.
Comparison of pre- and post-tests shows relatively large learning gains after
instruction. Analysis of pre-test responses and interview transcripts reveals many
misconceptions, such as a fairly widespread belief that abortions are done specifically to
obtain stem cells and beliefs that the amount of genetic information of stem cells is
different from differentiated cells. Other findings include how students use a variety of
terms to describe differentiation and the belief that stem cells are more prevalent early in
life and "used up" during development.
The results of the two-tailed, matched-pair analysis for the most part do not
indicate statistically significant differences between inquiry- and lecture-based
instruction. However, results for a question on controversial aspects of stem cell research
imply that the lecture-based instruction was more effective than the inquiry-based
instruction at helping students understand the controversy. This result suggests that,
given the limited time span of the unit, inquiry-based methods by themselves may not be
the most appropriate pedagogy for teaching about controversies in stem cell research. A
combination of lecture and inquiry, where the instructor gives a small series of initial
lectures before assigning students a genuine inquiry activity, may be a better approach.
ACKNOWLEDGEMENTS
I want to thank the Howard Hughes Medical Institute and Fleet Bank, a Bank of
America company and trustee of the Lloyd G. Balfour Foundation, for funding the
Jackson Laboratory research experience that inspired this thesis.
I also want to thank Dr. Barbara Knowles, Dr. Mimi de Vries, Dr. Alexi Evsikov,
Karen Fancher, Andrea Holbrook, Emily Radford, and Ellen Hawkins of the Knowles
Lab at the Jackson Laboratory for providing me with the opportunity to study biology and
for their support. In addition, I want to thank Dr. Jon Geiger of the Jackson Laboratory
for his encouragement and assistance.
I want to thank my committee members Dr. John Thompson, Dr. Mary Tyler, and
Dr. Michael Wittmann for their assistance in writing this thesis. I would also like to
thank Dr. Susan McKay and Dr. Molly Schauffler for their assistance and support.
Finally, I want to thank Bill Lopotro and Peggy Volek for allowing me to use
their classrooms for this research.
u
TABLE OF CONTENTS
ACKNOWLEDGMENTS
ii
LIST OF TABLES
vi
LIST OF FIGURES
vii
Chapter
1. INTRODUCTION
1
1.1. Background Information
2
1.1.1. Early Development
2
1.1.2. Stem Cells
4
1.1.3. Controversy over Stem Cells
6
1.2. Toward a Unit on Stem Cells
7
2. LITERATURE REVIEW
8
2.1. Student Understanding of Osmosis and Diffusion
8
2.2. Student Understanding of Genetics, Cell Division, and
Cell Biology
10
2.3. Biotechnological Progress and Challenges to Teaching
13
2.4. Bioliteracy and Biology Education Reform
15
2.5. Guidelines for Teaching about Stem Cells
19
2.6. Summary
21
in
3. UNIT DESIGN
22
3.1. The Backward Design Model
22
3.2. Backward Design of the Stem Cell Unit
25
3.3. Inquiry-based Unit Outline
28
3.4. Lecture-based Unit Outline
29
4. RESEARCH DESIGN
30
4.1. Student Population
30
4.2. Pre-and Post-tests
31
4.2.1. CHS05 Pre-/Post-test
31
4.2.2. JBHS05 Pre-/Post-test
32
4.2.3. JBHS06 Pre-/Post-test
33
4.3. Interviews
36
5. RESULTS AND DISCUSSION
37
5.1. Learning Gains
37
5.1.1. Comparison of JBHS06 Inquiry and Lecture Unit
Effectiveness
37
5.2. Results of Pre-/Post-tests
40
5.2.1. CHS05 Pre-test Responses
41
5.2.2. JBHS05 Pre-test Responses
41
5.2.3. JBHS06 Pre-test Responses.....
43
5.2.4. Post-test Responses
45
IV
5.3. Interview Results
45
5.3.1. Interview 2
46
5.3.2. Interview 3
47
5.3.3. Interview 5
50
5.3.4. Interview 6
51
5.4. Discussion
52
5.4.1. Inquiry Versus Lecture
52
5.4.2. DNA Content of Stem Cells
54
5.4.3. Stem Cells as a Finite Resource
56
5.4.4. Student Understanding of Cell Differentiation
57
5.4.5. Sources of Stem Cells
58
6. CONCLUSIONS
60
6.1. Future Work
60
6.2. Implications for Teaching
61
BIBLIOGRAPHY
63
APPENDICES
65
Appendix A. Learning Standards
65
Appendix B. Rubric
70
BIOGRAPHY OF THE AUTHOR
72
v
LIST OF TABLES
Description
Page
Table 1
CHS05 pre-/post-test grades by question (N=6)
38
Table 2
JBHS05 pre-/post-test grades by question (N=39)
38
Table 3
JBHS06 inquiry pre-/post-test grades by question (N= 15)
38
Table 4
JBHS06 lecture pre-/post-test grades by question (N= 15)
38
Table 5
Two-tailed, Matched Pair Analysis
39
Table 6
Answers to JBHS06 Q7 "I feel I learned a lot about stem cells."
45
VI
LIST OF FIGURES
Description
Page
Figure 1
Transition from zygote to blastocyst stage
Figure 2
Responses to JBHS06 Q5 "What makes stem cells different
from other cells?"
3
40
VII
Chapter 1
INTRODUCTION
The subject of stem cells should be of interest to biology teachers in secondary
education for many reasons. First, stem cells are an ideal context for important concepts
such as cell division, cell differentiation, and development. Knowledge of these concepts
fulfills U.S. National Standards Content Standard C ("Life Science, the Cell"). Second,
the potential medical applications of stem cell research add health and biotechnology
dimensions to the topic, reinforcing the idea of the cell as the basic unit of life. Finally,
the vigorous debate surrounding embryonic stem cell research highlights the ethical and
social aspects of science and is immediately engaging and relevant to students' daily
lives. This ethical and social components of stem cell research demand that students
learn other viewpoints and how to effectively communicate their own, presenting an
opportunity to satisfy National Standards Content Standard F ("Science in Personal and
Social Perspectives, ") and State of Maine Science and Technology Standard L8.
Despite being an ideal context of study, relatively little has been published on
how students understand stem cells. This thesis seeks to remedy this deficiency by
presenting the results of two stem cell units - one designed according to the principles of
inquiry-based teaching and another according to traditional lecture methods. Inspired by
chromatin dynamics research at the Jackson Laboratory, the unit took one week of class
time and was implemented in Bangor, Maine area high schools. The objectives of this
study are to identify student preconceptions of stem cells and stem cell research and to
determine the effect of the inquiry-based unit with traditional, lecture-based instruction.
1
1.1. Background Information
The topic of stem cells is closely connected to the early stages of an organism's
development. Therefore, this section presents a brief overview of early development in
placental mammals (with a focus on humans) before moving on stem cells in particular.
1.1.1. Early Development
Development concerns events and processes that occur as a single cell becomes a
more complex organism, but these same processes are also present when a young
organism grows into a mature form or when an organism heals wounds. Development
has three characteristics: growth, differentiation, and morphogenesis. Growth happens
when cells divide, get larger, and divide again. Differentiation is the process whereby
cells become specialized in structure and function. For example, a muscle cell looks and
acts differently than a skin cell. Finally, morphogenesis entails the shaping and
patterning of body parts into a certain form, such as how an arm is distinct from a leg
even though both limbs contain similar types of tissues.
Early development in humans consists of three main stages: cleavage,
gastrulation, and neurulation. The cleavage stage consists of cell division without
growth, and it begins soon after fertilization. The egg and sperm fuse, forming a onecelled embryo called the zygote. The zygote then becomes a two-cell embryo, which in
turn becomes a four-cell embryo, and so on, eventually producing a solid mass called the
morula. The morula then becomes a blastocyst (or "blastula," in nonhuman animals), a
"hollow ball" structure that has an inner cell mass (ICM) contained within an outer cell
2
layer called the trophoblast. Figure 1 depicts the transition from zygote to blastocyst
stage embryo.
Figure 1 - Transition from zygote to blastocyst stage
i
Zygote
Early 2 cell
Late 2 cell
8 cell
Blastocyst
During the cleavage stage, the dividing cells are said to be undifferentiated - that
is, the cells are not yet differentiated and their developmental fate is not completely set.
However, the formation of the blastocyst results in the first example of determination the cells of the ICM are determined to become the cells of the fetus, while trophoblast
cells are determined to become extra-embryonic tissue such as the placenta. During
gastrulation, further cell-fate determination occurs with the development of the three
germ layers - ectoderm, mesoderm, and endoderm. These three layers undergo further
cell growth and differentiation as an organism develops, being responsible for a variety of
cells unique to each layer. For example, cells of the ectoderm differentiate into cells in
the nervous system, mesoderm cells differentiate into cells in muscles and connective
tissues, and endoderm cells differentiate into cells in the lining of the gut and gut
derivatives, such as the liver and lungs.
3
The final stage of early development discussed here is neurulation, in which some
cells in the mesoderm become a structure called the notochord. The appearance of the
notochord is an early form of morphogenesis, inducing the development of the nervous
system from ectoderm cells above it.
1.1.2. Stem Cells
Stem cells are cells that exist in an undifferentiated state. They do not have more
or less genetic information (DNA) than other somatic cells. Rather, the genetic
information in stem cells exists in a state that allows them to differentiate into other cell
types. Readily observable during the early stages of development outlined above, stem
cells are present at all stages of an organism's life. In addition to their ability to become
other cell types, stem cells can divide and renew themselves many times.
Traditionally, stem cells are classified by three levels of potency - totipotent,
pluripotent, and multipotent. Totipotent stem cells have the potential to make every other
cell in the body, the placenta, and all extra-embryonic tissues, thus forming all cell types
in the entire organism. In humans, an example would be the cells of early cleavage stage
embryos. Pluripotent stem cells have the genetic potential to make every other cell in the
body except for the placenta and extra-embryonic tissues, thus being unable to form an
entire organism. The ICM of the blastocyst stage in humans is composed of pluripotent
stem cells. Multipotent stem cells can only differentiate into some types of cells (such as
blood cells or bone cells).
Stem cells are also classified by source. Embryonic stem (ES) cells specifically
refer to the pluripotent stem cells found in the inner cell mass of blastocyst stage
4
embryos. While ES cells can no longer become an embryo, they can be grown in cell
cultures as undifferentiated cells and have been shown to become many different cell
types (Amit et al., 2000). In addition, ES cells do not seem to exhibit the normal
processes of cellular aging and some speculate that they may be immortal (Donovan &
Gearhart, 2001). The most common sources of human ES cells for research are
supernumary (unused) embryos from in vitro fertilization (IVF) clinics and from cell
cultures of various ES cell lines.
Adult stem (AS) cells are multipotent stem cells found in a fully formed, adult
body, held in reserve until needed to replenish dying cells or repair damaged tissue.
Bone marrow and umbilical cord blood are both particularly rich source of adult stem
cells, but AS cells are relatively plentiful in tissues seeing a high cell replacement rate
(skin epidermis, blood, and epithelial lining of the gut). Although AS cells typically only
become a limited class of cells, depending on the type of AS cell a relatively wide variety
of cells can be produced. For example, bone marrow stem cells have been induced to
become muscle fibers, bone cells, neurons, liver cells, and other cells involved in the
lining of blood vessels and organs (Orlic, 2003). Indeed, some suggest that AS cells may
be as potent, or nearly as potent, as ES cells (Filip, English, & Mokry, 2004). While AS
cells show much promise, it is generally believed that ES cells are preferable to AS cells
for research and therapeutic uses, because ES cells possess a greater potential to become
other cells and a greater capacity for self-renewal.
Many find stem cells interesting primarily because of their potential for
regenerative medicine. If the process of cell differentiation becomes fully understood, it
may be possible to coax undifferentiated stem cells into desired tissue types. Examples
5
of this "regenerative medicine" include the following: bone marrow replacements for
patients whose bone marrow has been compromised by chemotherapy, removing
paralysis by re-growing nerve tissue, and repairing hearts damaged from heart attacks. In
addition to medical applications, other proposed uses for stem cells focus on advancing
basic biological and pharmaceutical research. For example, pharmaceutical companies
could test a drug on differentiated stem cells to determine the benefits or harmful sideeffects of the drug. This avoids ethical controversies such as human or animal testing and
insures that drug tests will be based on human models (as opposed to mouse or other
animal models, whose bodies do not always react to substances as human bodies would).
1.1.3. Controversy over Stem Cells
Despite excitement over these potential applications, research on ES cells is
highly controversial. The primary objection to ES cell research is that, in harvesting ES
cells, researchers must destroy embryos. Many groups that believe embryos have rights
vigorously object to this. Another concern is that injecting undifferentiated ES cells into
the human body carries a cancer risk (Gardner, 2002; Clarke & Becker, 2006). In this
case, the remarkable capacity for self-renewal of ES cells becomes dangerous, as the
injected ES cells can divide uncontrollably and form tumors. While differentiated cells
derived from ES cells carry less of a cancer risk, determining whether or not every cell
has been adequately differentiated could be problematic. An additional concern is the
integrity of ES cell lines available for research. For example, long-term culture of ES
cells can result in genetic abnormalities (Draper et al., 2004), and non-human animal
6
contaminants from ES cell cultures can corrupt ES cells and make future treatments
derived from those cells unsafe (Smith, 2005).
Finally, many oocytes (eggs) are needed for ES cell research and the collection
process may be unfair to women. During the collection procedure, a woman is given
hormones that induce superovulation in order to collect as many eggs as possible.
However, these hormones may cause cancer or other life-threatening condition. In
addition, there is concern that women will feel pressure to sell or donate oocytes. For
example, some allege that disgraced Korean biologist Hwang Woo-Suk - in addition to
falsifying data - pressured junior researchers into donating oocytes for his work (Chong
& Normile, 2006).
1.2. Toward a Unit on Stem Cells
The background information above shows that stem cells are indeed an ideal
context of study. Few other topics in science education provide such an opportunity to
learn important biology concepts while exploring ethical and social controversies. After
reviewing relevant biology education research literature in Chapter 2, Chapter 3 discusses
efforts to design a stem cell unit based on the principles of backward design. Chapter 4
provides an overview of the sample population and research instruments used in this
study and Chapter 5 presents and discusses the results of that research. Finally, Chapter 6
concludes with some remarks on future research and implications for teaching.
7
Chapter 2
LITERATURE REVIEW
Virtually no research has been published on how students understand stem cells.
As discussed below, biology education research has traditionally focused on osmosis and
diffusion. Other topics of study have included genetics, meiosis, the nature of the cell
and its biology, and the challenges to teaching presented by biotechnological processes.
Recent work details efforts at cultivating and improving bioliteracy in students and to
reform biology education. In addition, guidelines for teaching stem cells have been
released and curricula have been developed to assist teachers in this controversial and
engaging topic. The following section provides an overview of biology education
research literature, with a general focus on its relevance to understanding stem cells and
observations of the effectiveness of traditional instruction methods in teaching students
these concepts.
2.1. Student Understanding of Osmosis and Diffusion
Concepts such as osmosis and diffusion have long been sources of difficulty for
students, even after instruction. Odom (1995) developed the Diffusion and Osmosis
Diagnostic Test (DODT) to detect misconceptions in order to formally measure this
difficulty. The DODT is a multiple-choice test with each question written in a two-tier
format. In the first tier, students choose form two, three, or four answers to a content
question, while in the second tier students choose one of four possible reasonings for
their answers in the first tier. Distractors for the reasoning options were based on
8
misconceptions found in a multiple-choice pretest with free-response reasonings and
follow-up interviews.
The concepts investigated by the DODT include the particulate and random
nature of matter, concentration and tonicity, the influences of life forces on diffusion and
osmosis, the kinetic energy of matter, the process of diffusion, and the process of
osmosis. The test was given to 116 secondary school biology students, 123 non-biology
major college students, and 117 biology major college students. Before taking the
DODT, the students taking the test all participated in seven traditional laboratory
exercises focusing on the concepts of the DODT.
Odom found that the number of correct responses on the first tier was generally
much higher than the number of correct responses for the corresponding reasoning. In
addition, he observed that major misconceptions were detected in all but one conceptual
area covered by the test (the kinetic energy of matter). This led Odom to conclude that
traditional instruction of osmosis and diffusion emphasized rote memorization of facts
over the comprehension of concepts. He believed that more constructivist classrooms
would lead to more significant learning.
Similar results for student understanding of osmosis were found by Zuckerman
(1998). Upon recommendation of science teachers from five suburban high schools,
Zuckerman gave 18 students a problem. In this scenario, a funnel fitted with an inelastic
membrane permeable only to water is inverted and placed inside a vessel containing pure
water. At the start of the experiment, a dilute solution of sugar and water is inside the
funnel. Students are asked to graph the solution level in the stem of the funnel as a
9
function of time. The graph at early times should show solution level increasing rapidly
then, as time progresses, gradually leveling off and reaching a plateau.
From test results and interviews with all 18 students, Zuckerman found that only
seven students correctly attributed the movement of water to the concentration gradient
and membrane permeability. The other students either had an incomplete understanding
of osmosis, such as focusing on amounts of water in addition to concentration, or
completely misrepresented the problem, believing it to be a problem of air pressure
"difference," "displacement" of water in the beaker, or the equilibration between the
levels of the two liquids. Zuckerman believes that these misrepresentations arise from
the students' intuitive ideas and that, working in pairs or groups, students can work
together to negotiate a common representation.
2.2. Student Understanding of Genetics, Cell Division, and Cell Biology
Lewis and Wood-Robinson (2000) investigated the knowledge and understanding
of genetics among 482 secondary school students in England and Wales. Multiple choice
problems, short answer problems, and small group discussions revealed widespread
confusion over a variety of topics. These topics ranged from understanding the nature of
genetic information, understanding the transfer of genetic information, and understanding
how genetic information is interpreted. For the purposes of this work, the most relevant
topic is the transfer of genetic information because it pertains to mitosis and meiosis.
Most students in the study did not clearly distinguish between somatic cells and
sex cells. Only about 20% of the students believed that all cells from one individual
contain the same genetic information, suggesting that most students believe cells only
10
contain the information they need to perform their function. Perhaps due to their poor
understanding of meiosis, students were also generally unfamiliar with the mechanism of
fertilization. While 42% recognized that a fertilized egg has twice as many chromosomes
as an unfertilized egg, students were unsure of how this arose.
These and other difficulties led Lewis and Wood-Robinson to conclude that the
science education received by these students provides neither a firm basis for future study
as a scientist nor useful preparation for interaction with science in adulthood. They
conclude that for general science education to work it must have relevance and meaning
to students. This includes providing them basic information, developing their ability to
evaluate scientific information, and providing opportunities to develop these skills.
Flores et al. (2003) performed a comprehensive study of 1200 Mexican high
school students that focused on student conceptions of cell structure and cell processes.
The study analyzed the following topics: respiration, water in plants, water in animals,
plant nutrition, animal nutrition, cell shapes, cell size, and reproduction. The most
relevant results to this work pertain to student conceptions of the cell and its processes.
As did Lewis and Wood-Robinson, Flores et al. detected confusion among students with
mitosis and meiosis, specifically that students did not believe there was any distinction
between these two processes. Flores et al. also note that most students hold an
anthropomorphic view of the cell, one in which the cell "makes decisions" about its
requirements and one where "cell reproduction requires two cells," similar to sexual
reproduction in macroscopic animals.
Flores et al. believe that most student difficulties in this study can be remedied by
being aware of the use of multi-cellular analogies that may cause more harm then good.
11
For example, while both macroscopic animals and cells undergo respiration, it should be
made clear that cells do not breathe as macroscopic animals do. In addition, they
recommend grounding concepts of cell function in a firm context that is meaningful to
students and builds on their experiences and previous ideas.
Recognizing the difficulties students have with genetics and meiosis, Wynne et al.
(2001) conducted a nine-week elective genetics course open to high school juniors and
seniors. The 19 students solved a variety of genetics problems generated by computer
software. Initially, problems could be solved with a limited meiotic model introduced by
the teacher. As the class progressed, more complicated problems allowed students to
"invent" a more sophisticated model of meiosis.
Wynne et al. show how, over the course of the class, students used meiosis to
recognize anomalies, generate hypotheses, and assess hypotheses. Wynne et al. identify
three major implications from this work. First, unlike what is described in the literature,
students can and do use meiosis when solving genetics problems. Second, as students
were developing their model of meiosis, they tended to protect certain assumptions (such
as equal chromosomal contributions from both parents). This tended to constrain the
development on new theoretical knowledge. Third, the students were highly engaged in
these problems. Because the problems were not simply algorithmic, they required active
exploration, revising of explanations, and group work that resulted in student learning
about the actual practice of genetics research.
12
2.3. Biotechnological Progress and Challenges to Teaching
Bryce and Gray (2004) sought to understand how biology teachers saw science
and teaching in relation to increasingly demanding education standards covering the
social dimensions of science. Forty-one biology teachers attended a one-week summer
course that informed in-service teachers of recent advances in biotechnology and raised
awareness of social and ethical issues. Twenty of these teachers were about to teach an
advanced biology course in the fall (the authors note that they did not provide advice for
actually implementing these topics in the classroom). The teachers completed
questionnaires that, six months later, Bryce and Gray used to determine which issues
should be explored in individual interviews with 10 of the teachers teaching advanced
biology and group interviews with 61 of their students.
Five primary findings arose from interviews with the teachers. First, while most
teachers recognize that discussion and debate of controversial issues is inescapable, and
some felt this was part of the scientific process, a number of teachers believed that
discussion of the controversy was distinct from objective, fact-based science itself.
Second, the teachers found human testimony and contextualization very important, as
they helped clarify the use of biotechnological advances. They expressed a desire to have
more sources both supportive of and opposed to biotechnology so that students could
know of alternative views. Third, with regards to animal experimentation, all of the
teachers noted that students had strong concerns for animal rights. Fourth, teachers were
unsure of the pedagogical techniques or resources needed for teaching the social and
ethical implications of biotechnology. In particular, they were unsure of the role they
needed to play in class discussions. Finally, the teachers were sensitive to how
13
controversial and disturbing class discussions could be and felt pressured because of it.
Bryce and Gray argued that this sensitivity could arise from lack of knowledge of the
science concerned, unfamiliarity with a particular genetic disorder, being unaccustomed
to answering awkward questions, and not knowing good sources of information for
students who want to follow up challenging subject matter.
Student interviews revealed four primary findings. First, discussions seemed to
be triggered as often by students as by the teacher. Discussions were largely spontaneous
and related to something students heard in the news. In these discussions, students could
readily tell if a news item had a bias and were aware of the overt neutrality of the teacher.
Second, students were aware of the strength of their own feelings and beliefs, and they
believed scientists could likewise hold such beliefs. Third, some students believed
teachers veered away from highly controversial subjects. It may be that teachers tend to
show science as "linear" and "tidy." Lastly, several students preferred using class-time
for discussion as opposed to reading or studying, and many believed both scientific and
social dimensions had to be discussed. Thus discussions were important to students.
Bryce and Gray conclude that, in order to more effectively teach social and ethical
aspects of biotechnology, teachers need more guidance and materials for the following:
handling the discussion of controversial material; safeguarding neutrality, choice and
personal ethics; more concrete outlines for the purposes and outcomes of discussion of
controversial issues; and greater clarity concerning the relationship of between such
discussion and what is formally assessed. As the authors note, if debate and discussion
are not assessed, then they will not be a priority.
14
2.4. Bioliteracy and Biology Education Reform
Observing the ignorance, misinformation, and many misconceptions lay people
have regarding biology, Klymkowsky, Garvin-Doxas, and Zeilik (2003) set out to create
a Biology Concept Inventory (BCI) test to objectively assess bioliteracy. Bioliteracy is
higher order understanding according to Bloom's Taxonomy, the ability to not only know
scientific terms but to apply that knowledge in other settings and to make informed
judgments about new discoveries based on a strong understanding of fundamental
principles. In seeking a standardized way to measure bioliteracy, the objectives of the
BCI are similar to the objectives of the Force Concept Inventory (FCI) test developed by
Hestenes et al. (1992), which has revolutionized introductory physics education.
Like the FCI, the BCI is a multiple-choice test. But unlike many multiple-choice
tests, BCI test questions are carefully designed. Each question focuses on a particular
concept that has proven to be of difficulty to students. The answer choices for the
questions include the correct response and distractors based on common misconceptions
students have regarding the concept. After analyzing test results, instructors can see what
misconceptions students have and then address those misconceptions.
Klymkowski et al. discuss the construction of a useful BCI, focusing on two BCIs
in particular, basic bioliteracy and developmental biology. The basic bioliteracy BCI is
intended to measure the understanding our secondary biology education should produce.
The developmental biology BCI is used to test more advanced students of biology who
have taken a "reformed" course, primarily as a pre/post-test to determine the degree to
which the course is working. Other advanced BCIs focusing on genetics, cell biology,
and molecular biology are planned.
15
The format used for BCI questions enables instructors to observe what they think
they are teaching against what students are learning. For a given question, instructors
rate the concept importance and the relevance to the course and compare it to student
performance. This provides a useful feedback mechanism for instructors curious about
their teaching, either in general or when implementing a teaching innovation. In addition,
a manner similar to the DODT, student questions to the BCI are two-tiered. The first tier
asks a content question, while the second tier asks for a level of confidence. This method
allows the instructor to see not only student misconceptions, but also student confidence
in their answers.
Wright (2005) asserts that for non-major biology courses, a focus on the technical
and rote content knowledge of biology is not as important as basic bioliteracy. Nonmajor biology courses should follow a "lived curriculum," which primarily involves
focusing on topics that are interesting and engaging to students. To be a lived
curriculum, the course must not leave students disinterested in biology - it must
encourage students to develop a curiosity about the living world and experience the
vibrancy and utility of biology. In addition, the lived curriculum courses should focus on
a particular context of interest to students without it being "dumbed-down." Rather,
within this context, students should explore how biologists approach the problem, what
methods are used to provide relevant data, how to critically evaluate data, and in general
model how biologists answer the question. Finally, new methods of assessment should
be developed that more accurately measure student's ability to think and communicate in
biology, which includes the ability to pose relevant questions and to find, evaluate, and
16
use the information needed to answer them. According to Wright, this is the most
challenging aspect of effecting change in biology education.
Knight and Wood (2005) observed the effects of changing an upper-level lecture
course in developmental biology to a more interactive classroom format. A traditional,
lecture-based course taught in the 2003 fall semester (F03) served as a control for the
experimental, interactive course taught in the 2004 spring semester (S04). The F03
consisted of two 75-minute classes per week with three prelim exams and a cumulative
final. Although students were encouraged to ask questions, few did so. The S04 course
met twice a week for 75 minutes in a lecture hall. While lectures were still conducted,
lecture meetings were interspersed with various learning activities, presented group work,
employed undergraduate lecture assistants to facilitate group work, engaged in group
discussion, and conducted in-class formative assessments. Students were assigned to
groups that were composed of one "A" student, two "B" students, and one "C" student.
Because developmental biology courses are traditionally graded on a curve, the
authors maintained that practice in both the F03 and S04 course. Although the overall
distribution of point totals was higher in S04 than F03, because of the curve there were
fewer "A" grades in the interactive course than in traditional course. However,
normalized gain from pretest and posttest scores indicated a 16% difference between S04
and F03, implying a much improved student performance in S04 than in F03.
To determine the reproducibility of these results, Knight and Wood employed
many of the S04 modifications in the 2005 spring semester (S05). Notable differences
between S04 and S05 include allowing students to choose their own groups, no grading
on the curve, additional group activities, and web-based multiple choice quizzes of
17
weekly readings that allowed the instructors to address difficult concepts in class. Knight
and Wood found that the average normalized learning gains of S04 and S05 over F03
were nearly identical, indicating that the results of S04 are reproducible.
Knight and Wood go on to discuss several aspects of the interactive course of use
to instructors. First, the data clearly show that allowing even a small level of interaction
can lead to significant learning gains. Second, at the start of the course many students
(perhaps through years of conditioning) believed that the only meaningful time in class
was when the instructor was lecturing. Some of the students complained the instructors
"were not teaching them very much, but rather making them learn the material on their
own." Third, the focus of the interactive class shifted away from the transmission of
information to one of helping students understand and apply concepts from their readings
and homework. Finally, even teachers can develop pedagogical misconceptions that
impair their abilities and place them in a "comfort zone" where they resist changing their
instructional methods. From their personal experience, Knight and Wood found making
the shift from transmission to interaction occasionally difficult.
Allen and Tanner (2005) present seven strategies designed to realize the promise
of active learning and inquiry instruction in large-enrollment classes. The first is
"bookending" the lecture with questions that initiate student discussion. Periodically
through the lecture, the instructor can prompt a short, 3- to 4-minute discussions to a
question. The second is utilizing "on-the-spot-feedback" technology such as clickers. By
presenting a multiple-choice question, having the students "vote" on the correct answer,
and viewing student responses, instructors can immediately address student
misconceptions in class. A third strategy is having students do presentations and
18
projects. With such a strategy, the instructor maintains a "behind-the-scenes" presence,
assisting in presentation planning and coaching presentation teams.
Learning cycle instructional models are a fourth strategy. In this strategy,
learning a concept is divided into stages. In the initial stages, the teacher plays a
prominent role in guiding students through explanation and exploration of a concept. In
the later stages, students develop more confidence and can do higher-level activities.
After the assessment phase, the cycle begins anew with another concept.
A fifth strategy involves peer-led team learning. A peer or near-peer of the
students taking the course (generally, a student who completed the course recently) can
greatly assist inquiry-based learning. Peers provide support in moments of uncertainty
and attest to the effectiveness of the instructor's methods. A sixth strategy is modeling an
inquiry approach in the large class. This strategy involves having students design simple
experiments and analyze and interpret their experiments in class. Finally, the seventh
strategy utilizes case studies and problem-based learning.
2.5. Guidelines for Teaching about Stem Cells
Miller (2005) uses the FIRES strategy to teach middle school students about stem
cells. FIRES is an acronym standing for Facts, Incidents, Reasons, Examples, and
Statistics. This strategy allows students to sort the potentially bewildering amount of
information regarding stem cells into one of the acronym's six categories. The
categorization activity is intended to take place after the instructor present the
information to the class and after the students research the topic on their own. To assist
the presentation process, Miller discusses the state of stem cell research as of the article's
19
publication. She also suggests using the FIRES strategy on a topic that is easy to
categorize to practice applying it to more complex topics such as stem cells.
Cannard (2005) believes controversial topics such as stem cells are ideal contexts
of study for biology. To facilitate her teaching of middle school students, Cannard has
developed a five-item approach to discussion of controversial topics. These include solid
background information, multiple perspectives, guidelines for discussing issues as a
group, substantive discussion questions, and strong follow-up.
Solid background information consists of reputable, easy to grasp information
about stem cells. Such information can be found on websites of science museums,
research institutions, newspapers, and public television and radio stations. Cannard
advises that instructors should take care to insure students have a firm understanding of
stem cells before engaging in the discussion.
Familiarizing students with multiple perspectives is the next step. To do this,
Cannard has students interview at least three people with different perspectives on stem
cell research. In addition, students are asked to read several websites promoting different
sides of the issue. An important component of these activities is trying to find out which
factors may shape a person's or organization's position.
After putting students in groups, the teacher needs to clearly establish group
interaction protocols to avoid overly heated debate. Some of these protocols could be
staying on task, cooperating and participating, respecting others, and using a
conversational voice. Teachers also have protocols they must follow. Teacher must visit
with each group while keeping an eye on the others, answering questions and asking
substantive questions to apply their knowledge and explore new possibilities.
20
Substantive questions can include asking students to imagine how others might feel about
the topic.
A strong follow-up consists of a higher order activity that demonstrates a
student's understanding of other perspectives. Cannard bases her assessment on four
factors: success in understanding different perspectives, collaborative discussion,
communicating understanding of the underlying issues, and presenting one's own
educated perspective.
2.6. Summary
Several themes emerge from the preceding literature review that inform this study
of student understanding of stem cell research. First, traditional, lecture-based instruction
in several cases is shown to be less effective than more interactive, inquiry-based
methods. Second, students enter biology courses with well-defined misconceptions that
can be very persistent, even after instruction. Third, teachers of controversial topics such
as stem cells should take care to maintain impartiality. Finally, in order for meaningful
learning to take place the context of study should be meaningful and engaging to
students.
21
Chapter 3
UNIT DESIGN
This chapter details how the stem cell unit was developed. After briefly
discussing the backward design model of curriculum development, the chapter details the
application of the backward design model to the topic of stem cells. The result of this
effort is a five-period long inquiry-based instructional plan that was implemented in 2005
and 2006. The chapter ends by presenting a five-period long lecture-based unit on stem
cells that was implemented along with the inquiry-based unit in 2006.
3.1. The Backward Design Model
The stem cell unit was developed using the backwards design model of
curriculum development advocated by Wiggins and McTighe (2005). This model
requires that instructors first identify desired outcomes and results, then determine what
constitutes acceptable evidence that the outcomes and results have been achieved
(assessment), and then plan instructional strategies and learning experiences that bring
students to the required achievement level. This differs from traditional curriculum
design, where determining teaching methods, the sequence of activities, and necessary
resources are generally decided upon before desired results and assessment methods are
clearly articulated.
Step 1: Identify enduring understandings
What should students learn? In this step, instructors should consider not only
required learning goals and objectives, but also those understandings intended to remain
over the long term. Called "enduring understandings," these ideas should (a) possess
22
enduring value beyond the classroom, (b) reside at the heart of the discipline, (c) require
discovery of abstract or complicated concepts, and (d) offer potential for engaging
students. These enduring understandings should form the basis of the unit.
How can teachers frame enduring understandings as inquiry? To promote inquiry
and higher order thinking, instructors must ask deep, essential questions that target the
key issues. Good essential questions are open-ended, resisting a single answer. In
addition, they are deliberately thought-provoking, counterintuitive, or controversial, and
they inspire higher orders of cognition. Bloom's Taxonomy Essential questions also
require students to draw upon content knowledge and personal experience, and they can
be revisited throughout the unit as part of an evolving, ongoing dialogue. Finally, good
essential questions lead to other essential questions posed by students.
Step 2: Determine acceptable evidence.
How do we know students have achieved enduring understanding? Wiggins and
McTighe offer six criteria. The first is being able to explain, or to give thorough,
justifiable, and supportable accounts of phenomena, facts, and data. Second is being able
to interpret, to tell meaningful stories or give apt translations. The third is being able to
apply, or to use and adapt what is known in diverse contexts. Fourth is having
perspective on issues, seeing the big picture and possessing the ability to see and hear
points of view through critical ears and eyes. Fifth is the ability to empathize, to find
value in what others may find odd or implausible. The sixth criteria is having selfknowledge, knowing how to perceive the projections, prejudices, and habits of the mind
that both shape and impede our understanding.
23
Wiggins and McTighe identify a continuum of assessment tools, which, from
least to most formal, are: informal checks of understanding, observations and dialog, tests
and quizzes, academic prompts, and performance tasks. Importantly, instructors should
incorporate a variety of assessments into the unit to ensure evaluations of a student's
performance is more a collection of evidence over time instead of a single test at the end
of instruction. Of the various assessment methods listed above, performance tasks, such
as research projects, are the best assessment tools to develop and display evidence of
deep, enduring understandings. In general, these tasks are open-ended, are not secure
(the answer is not known beforehand), and are authentic, genuine activities that allow a
student to exhibit all six facets of understanding. More traditional tests and quizzes are
generally secure (the answer may be known beforehand) and are useful for keeping
instructors appraised of student progress and for testing things that are merely useful to
know (such as terminology, etc.).
Step 3: Plan instructional strategies and learning experiences.
Planning instructional activities includes determining (a) what knowledge and
skill students will need to perform effectively, (b) what activities will equip students with
the necessary knowledge and skills, (c) how students will best learn that knowledge and
skill, (d) what resources are necessary to accomplish these goals, and (e) a coherent and
effective overall unit design.
24
3.2. Backward Design of the Stem Cell Unit
In this section the backward design model is applied to the topic of stem cells.
Step 1: Identify enduring understandings.
When the unit was being designed at the end of 2004 and the beginning of 2005,
these items were deemed to be enduring understandings pertaining to stem cells:
•
Stem cells are cells that can become other cells. Depending on their potency, they
can become any cell required for life or cells of a limited type.
•
Stem cells are found from two main sources: within the bodies of adults and in the
early stages of embryo development. Embryonic stem cells are thought to possess
greater potency than adult stem cells.
•
Researchers hope that the ability of stem cells to become other cells can be
harnessed to treat a variety of medical conditions.
These items were deemed to be enduring understandings because they pass the
criteria established earlier as (a) possessing enduring value beyond the classroom; (b)
residing at the heart of the discipline; (c) requiring discovery of abstract or complicated
concepts; and (d) offering potential for engaging students. With respect to criterion (a),
stem cell research is highly controversial, has many potential applications, and appears
frequently on state and national ballots (some of which high school students may actually
vote on in the near future). As a result, a good understanding of stem cells is very
valuable beyond the classroom. Regarding criterion (b), stem cells are at the forefront of
modern biology research and intersect with important biology concept such as
development and cell differentiation. As such, the topic of stem cells resides at the heart
of biology. Because a variety of opinions on stem cell research exists and because the
25
subject touches upon abstract concepts such as development and cell differentiation,
achieving these enduring understandings is a genuine discovery experience and fulfills
criterion (c). Finally, stem cell research is highly controversial, inspires wonder with its
array of proposed applications, and is frequently mentioned by celebrities and politicians.
Thus, it has the potential to be highly engaging, as required by criterion (d).
The essential questions for the unit were based on the enduring understandings
delineated above. They were:
•
What are stem cells?
•
How are stem cells obtained?
•
Why are they so potentially useful?
While these questions are thought-provoking, require students to draw upon content
knowledge and previous experience, and can lead to other questions, they are not very
open-ended. That is, these questions have a single right answer and don't require the
higher order thinking skills (such as synthesis, application, or evaluation from Bloom's
Taxonomy). While this is a weakness in the design, these questions were thought to still
be useful because they are basic and fundamental to the subject of stem cells. In addition,
their broad scope would tend to elicit a variety of answers and serve as a "hook" to
capture student interest.
Step 2: Determine acceptable evidence
Two assessments were deemed sufficient to determine if students achieved the
desired level of understanding. To give students the opportunity to explain and interpret
stem cells, the first assessment is a brief (one- to two-page) essay of answers to the
essential questions. The second assessment is another short essay where students select
26
or propose a governmental policy toward stem cell research and explore the ramifications
of that policy. Students will need to describe their policy, consider the future applications
of stem cells under their policy, discuss the positive and negative consequences (social,
medical, ethical, etc.) of the policy, and state where the policy draws the line in terms of
ethical use of stem cell-derived technology. This activity requires students to apply their
understanding of stem cells to a real-world issue, have perspective on the myriad aspects
of stem cell research, and empathize with other viewpoints to understand where they
come from and strengthen their own arguments for their policy.
Step 3: Plan instructional strategies and learning experiences
The last step in the backward design process for stem cells involves planning the
instructional sequence and learning activities. The skills and knowledge required to
perform effectively in this unit are the ability to answer the essential questions and the
ability to describe and articulate a stem cell policy. The assessments are formative in
nature and incorporate group work, and are intended to equip students with the
knowledge and skills needed to explore the essential questions and to articulate an
argument about stem cell policy, as part of the instructional strategy. By working in
groups, students can assist each other in constructing ideas about stem cell research,
something they could not do if they worked alone. As they develop their positions,
students learn what stem cells are, classify stem cells by potency and source, identify
potential applications of stem cell research, and come to recognize various ways
governments can approach policies toward stem cell research. The best manner in which
to teach this is grounding instruction in initial student ideas with a class discussion,
engaging in a stem cell research activity, followed by a policy construction activity.
27
Resources required for this instruction include computers with access to the
internet, books and other media, and a classroom of sufficient size for students to work in
groups and give presentations comfortably. The activity was designed to take five days
of 45- to 80-minute class periods.
3.3. Inquiry-based Unit Outline
The following unit plan emerges from the above considerations:
Period 1
In the first period, students take pre-tests and engage in a class discussion
focusing on what they already knew about stem cells. During this activity the instructor
should write down student ideas for the whole class to see. These ideas would generally
consist of the various student responses to the pre-test; however, students would be
welcome to share any other contexts they may have heard about stem cells.
Period 2
During the second period, students work in groups of two to research answers to
the essential questions. They're primary source of information is various websites on the
Internet, but they may use other sources, such as books, encyclopedias, news articles, etc.
Period 3
Students discuss the results of their research during the third period, comparing
their research with the results of the class discussion on the first day. In addition to
discussing the various types of stem cells and the various applications, the class should
discuss why stem cell research is so controversial and the steps governments can take to
limit it.
28
Period 4
This leads into the fourth period of classes, where students engage in the policy
construction activity. Students are divided into small groups and may choose a stem cell
policy provided by the teacher (permissive, flexible, or regulated) or they may work out
their own. As with the writing of their research essays, students have access to the
Internet or other media to help develop their policy.
Period 5
During the fifth period, the groups present their policies and have a group
discussion of the policies. They take the post-tests and then the class discusses how the
unit went.
3.4. Lecture-based Unit Outline
The lecture-based unit consisted of a series of presentations given over the course
of five class periods. The first period focuses on the early stages of development,
covering fertilization, cleavage stage embryos, implantation, gastrulation, and
neurulation. During the second period, students are told what stem cells are and how
they are classified (by source and by potency). The third period covers current and
proposed applications of stem cell research. The fourth period focuses on the
controversial aspects of stem cell research, and the fifth period covers the policies various
nations have on stem cell research.
29
Chapter 4
RESEARCH DESIGN
This study investigated high school biology student understanding of stem cells
and compared an inquiry-based unit with a traditional, lecture-based unit. Pre- and posttests were used to capture initial student conceptions and measure any learning gains.
Pre-instruction interviews were conducted in an effort to gain greater insight on student
answers to pre-tests. Finally, post-test results were analyzed to determine if the
difference between lecture-based and inquiry-based instruction was statistically
significant. This chapter details the design of these research components.
4.1. Student Population
2005
Two different populations participated in the inquiry-based activity in 2005. The
first population (designated CHS05) consisted of six students from Academic Biology, a
sophomore level biology class at Central High School in East Corinth, Maine. The
second population (JBHS05) consisted of 39 students enrolled in Advanced Placement
(AP) Biology at John Bapst High Memorial School in Bangor, Maine. JBHS05 students
were juniors and seniors. Students in both populations were strong academically and
bound for college.
2006
The student population for 2006 (designated JBHS06) was similar to JBHS05 and
consisted of two groups of 15 juniors and seniors enrolled in AP Biology. One group
30
participated in the inquiry-based unit while the other group participated in the lecturebased unit.
4.2. Pre- and Post-tests
Pre-tests were given on the first day of the unit before instruction began. Posttests were given on the fifth day of the unit at the end of instruction. While these tests
were used to measure the effect of instruction, they were not a significant part of a
student's grade for the unit.
While pre- and post-test questions were essentially identical for each sample, the
exact wording of the pre- and post-tests was not exactly the same in CHS05, JBHS05,
and JBHS06. The unit was constantly being reevaluated and revised between
implementations to insure that the questions were easy to understand and broad enough to
elicit a variety of responses. To facilitate understanding of the rationale behind these
efforts, this section briefly mentions pre-test results that are described with greater detail
in Chapter 5. Appendix B details the four-point rubric used to grade answers to the pre/post-test questions.
4.2.1. CHS05 Pre-/Post-test
The pre- and post-test questions for CHS05 were:
Ql. What are stem cells?
Q2. How are they obtained?
Q3. Why are they so potentially useful?
31
These questions mirror the three essential questions of the stem cell unit, as developed
using the backward design method discussed in Chapter 3.
4.2.2. JBHS05 Pre-/Post-test
Because the CHS05 questions were very open-ended, it was decided that the
JBHS05 pre-/post-test questions should be slightly less broad in scope. In addition, after
the CHS05 implementation we wondered if students felt they achieved significant
learning gains and if exposure to the material changed their opinions of stem cell
research. Thus the three pre-/post-test questions from CHS05 were modified, and two
more questions were added to the post-test. The pre-test questions for JBHS05 were:
Ql. What are stem cells? How do they differ from other cells?
Q2. Biologists work with stem cells. Where do they get them? How do
they collect them?
Q3. What properties of stem cells make them of interest to scientists?
The JBHS05 post-tests included two more questions that weren't graded for the
purpose of measuring learning gains. These questions contained statements and students
were asked to circle their level of agreement with the statements on a five-point Likert
scale from " 1 " ("Strongly Agree) to "5" ("Strongly Disagree"). These questions were
intended to be a means with which to assess any changes in student opinions as a result of
instruction. They are as follows:
Q4. "You feel you learned a lot about stem cells."
Q5. "You have changed the way you think about stem cells."
32
Because it was felt that asking for student opinions was too intrusive, no effort
was made to establish initial student opinions on stem cell research using Q5 on the pretest. As a result, an answer of "2" ("Agree") could mean they initially opposed stem cell
research but now support it, initially supported stem cell research but now oppose it, or
initially supported/opposed stem cell research and now support/oppose it even more.
4.2.3. JBHS06 Pre-/Post-test
While JBHS05 pre-tests revealed several interesting insights, we decided to make
the JBHS06 pre-test questions more open-ended in order to elicit even more student
responses. In addition, few students mentioned why they thought stem cell research was
controversial; indeed, some student responses suggested that traditional methods for
harvesting stem cells weren't harmful to the embryo. This suggested that there was a
fourth enduring understanding that we overlooked in our initial unit development.
Namely:
•
Embryonic stem cell research is highly controversial because in order to
harvest embryonic stem cells a developing embryo must be destroyed.
Many people equate this with taking a human life.
There are other sources of controversy surrounding stem cell research (such as the
potential exploitation of women, safety concerns, and ownership issues), but the central
issue is one of defining what is human and when does human life begin. Much like the
enduring understandings outlined in Chapter 3, this enduring understanding has great
value beyond the classroom, resides at the heart of biology, requires discovery of
33
different viewpoints, and is by highly engaging. As such, it suggests this essential
question:
•
Why is stem cell research controversial?
This question is a good one because it's thought-provoking, requires students to
understand what technical aspect of the stem cell harvesting process is controversial, can
lead to other questions, and has no single right answer.
As a result of these considerations, the pre-test questions for JBHS06 were as
follows:
Ql. "What are stem cells?"
Q2. "Where do stem cells come from?"
Q3. "Why are scientists interested in stem cells?"
Q4. "Why is stem cell research controversial?"
In addition to these open response questions, the JBHS06 pre-tests included a
multiple-choice question that was as follows:
Q5. "What makes stem cells different from other cells? Circle all that
apply.
a) Stem cells contain all of an organism's DNA.
b) Stem cells contain information about an individual's genetic
tendencies.
c) Stem cells have the potential to become other cells.
d) Stem cells are used up as the organism grows older.
e) Stem cells are immature, undeveloped cells.
34
While choice "c" is the correct answer, students were allowed to choose as many
answers as they wished. Choices "a," "b," "d," and "e" are based relatively common or
notable responses from 2005 pre-tests. Choice "e" is confusingly worded, because while
stem cells may not necessarily be "immature," it may be fair to say they are
"undeveloped." However, the potential for confusion wasn't noticed until after the preand post-tests were implemented. The intent of this question was to see if student
preconceptions of stem cells tend to reliably fall in certain categories and if these
preconceptions were reproducible from year to year, much like how multiple choice
questions on a biology concept inventory would be designed.
Post-tests for JBHS06 had two extra questions designed to determine how
instruction affected student opinions on stem cell research and if students felt they
learned a lot about stem cells. These questions, Q6 and Q7, correspond to questions Q4
and Q5, respectively, from JBHS05. The questions were as follows:
Q6. Has this unit changed the way you think about stem cells? If so,
please explain how.
Q7. Circle the answer that best fits your response to the following
statement: "I feel I learned a lot about stem cells."
In order to elicit more student responses for JBHS06 Q6 the Likert scale in
JBHS05 Q4 was discarded, becoming an open response question. The Likert scale in Q7
dropped number rankings in favor of the phrases "Strongly Agree," "Agree," "Disagree,"
"Strongly Disagree."
35
4.3. Interviews
After doing the pretests but before any targeted instruction, one-on-one,
standardized, open-ended interviews were conducted to gain greater depth of student
preconceptions. Participation in the interviews was voluntary, but participating students
received a small amount of extra credit. The interviews were standardized in that
students were asked to answer questions similar to those found on the pre-tests, but the
interviews were open-ended in that there was considerable flexibility for the conversation
to drift from one topic to another. In addition to the pre-test questions, students were
asked:
•
What makes stem cells different from other cells?
•
When and where did you first hear about stem cells?.
•
What is the current federal policy regarding stem cell research?
•
What is your opinion on stem cell research?
•
What will stem cell research be like in the future?
•
Is there anything you would like to add?
36
Chapter 5
RESULTS AND DISCUSSION
5.1. Learning Gains
Pre- and post-test scores were used to measure learning gains in all three
implementations. To insure inter-operator reliability, the quiz grades were verified by an
expert in the field. Learning gains were calculated according to the following normalized
learning gain formula <g> = (p -po)/(pmax -po), where <g> is the normalized learning
gain, p is the post-test average for the given question, po is the pre-test average for the
given question, and pmax is the highest possible pre-/post-test score. For this work, pmax =
4. Tables 1 -4 list the pre-/post-test grades by question.
5.1.1 Comparison of JBHS06 Inquiry and Lecture Unit Effectiveness
Post-test results from JBHS06 were used to compare the effectiveness of the
inquiry-based and lecture-based unit. Because of the small numbers of students in each
group, for this experiment the appropriate statistical comparison method to make this
comparison is a two-tailed, matched-pair analysis (Kitchens, 1998). For this analysis, the
30 students were organized into 15 pairs, with each pair consisting of an inquiry student
and a lecture student. To ensure that the pairs consisted of students with roughly equal
levels of ability, pairs were assigned based on students' pre-test scores.
37
Table 1 - CHS05 pre-/post-test grades by question (N=6)
Question
Pre-test Average
Post-test Average
1.167
3.167
Q1
Q2
1.000
3.167
Q3
1.333
3.000
Gain (%)
71
72
62
Table 2 - JBHS05 pre-/post-test grades by question (N=39)
Question
Pre-test
Post-test Average
Q1
1.700
3.205
Q2
1.500
3.256
Q3
1.725
3.641
Gain (%)
65
70
40
T a b l e 3 - J B H S 06 inquiry pre-/post-test grades by question (N=15)
Question
Gain (%)
Pre-test Average
Post-test Average
62
Q1
1.733
2.6
Q2
1.933
58
3.133
61
Q3
1.800
3.133
Q4
1.667
2.867
51
Table 4 - JBHS06 lecture pre-/post-test grades by question (N=15)
Gain (%)
Question .
Pre-test Average
Post-test Average
1.867
2.267
19
Q1
Q2
42
1.933
2.800
3.067
Q3
1.667
60
Q4
3.333
64
2.133
For this analysis, the null hypothesis Ho is:
H0:
iii- fi2 = 0,
where \ii is the average post-test grade for a given inquiry question and /X2 is the average
post-test grade for the corresponding lecture question. In words, the null hypothesis says
there is no statistically significant difference between the average inquiry- and lecturebased post-test score for the given question. The alternative hypothesis Ha is:
Ha:
Hi- y.2* 0.
In words, the alternative hypothesis says there is a statistically significant difference
between the average inquiry- and lecture-base post-test score for a given questions.
38
The test statistic t0bs is given by the equation tobs = dVvf/sa, where arts the
average difference of scores, n is the number of students, and Sd is the standard deviation
of the difference of scores. Because the sample size is small, we can assume afis
approximately normally distributed. Therefore, the test statistic has a Student's t
distribution with degrees of freedom df equal to n -1. In our case, df= 14. For p = 0.05
(corresponding to a 97.5% confidence interval) and df= 14, our critical value tcaic is
1.761. If tobs is greater than tcak, we may reject the null hypothesis (that is, we may say
for that particular question that the difference between the inquiry and lecture grades is
significant). Table 5 lists tobs and for p = 0.05 and degrees of freedom df= 14.
Table 5 - Two-tailed, Matched Pair Analysis
Question
Q1
Q2
Q3
Q4
lobs
1.685
1.685
0.269
-2.432
The only statistically significant result listed on table 5 is for Q4. Thus while there
appears to be no difference between the two teaching methods for content questions such
as what stem cells are, where they come from, and why they are of interest, it appears that
students benefited more strongly from lecture-based instruction than from inquiry-based
instruction.
39
Figure 2 depicts the results for JBHS06 Q5. Distractors "c" and "e" appear to be
the most common before and after instruction. While "c" has a relatively unambiguous
interpretation (it shows most students are familiar with the idea of stem cells becoming
other cells), answer "e" is less clear. While it might be fair to say that stem cells
"undeveloped," it's less clear that they are "immature," because AS cells are found in
"mature" bodies. This question may show that students are drawn to ideas of immaturity
and being undeveloped, but two separate distractors are required to distinguish between
the options.
Figure 2 - Responses to JBHS06 Q5 "What makes stem cells different from other
cells?"
5.2. Results of Pre-/Post-tests
This section details the results of the pre- and post-tests for four implementations
of the stem cell unit. This includes the three inquiry-based implementations (CHS05,
JBHS05, and JBHS06) and the single lecture-based implementation (JBHS06).
40
5.2.1. CHS05 Pre-test Responses
Responses to pre-test questions were very vague or superficial for Ql and Q2,
such as Student 6's answer to Ql being "Stem cells are cells that have stems?" and
Student 4's answer to Q2 being "They are obtained by genetics and certain environmental
factors." Responses to Q3 were also generally vague, such as Student l's response to
Q3: "They are so potentially useful because they help people become more advanced in
specific aspects." But in most cases students indicated that products of stem cell research
might have positive or medical applications, even if they were unsure of what those
applications were.
Some responses suggested that stem cells were bad to have or were the byproduct
of disease. For example, Student 4 answered Ql with "Stem cells are cells that cause
certain problems within the body. Sometimes stem cells can be good and help with bad
cells." Student 6 answered Q2 with "Stem cells are obtained by getting a disease."
However, like most of the other students, their responses to Q3 suggested that stem cells
have valuable medical properties.
Students generally fared much better in the post-tests, achieving a "good idea" of
what stem cells are, where they come from, and why they are of interest.
5.2.2. JBHS05 Pre-test Responses
In general JBHS05 students seemed to be at least passingly familiar with stem
cells prior to instruction, perhaps by virtue of having some exposure to the topic in
previous classes. Indeed, although JBHS05 Q4 was not intended to be open response,
some students indicated they didn't learn much about stem cells as a result of this unit
41
because they already had previous exposure to the topic. A general discussion of each
pre-test question follows.
Question 1. Most student responses to Ql indicated, in one form or another, that
stem cells can become other cells. Students used a variety of terms to describe this
process. For example, one student says, "Stem cells are cells that regenerate into other
cells. Embryonic stem cells can generate into any type of cell." Another student says
"Stem cells are cells that have not yet developed so that they perform a specific function.
Other cells, such as muscle cells or nerve cells can only serve that one purpose. Stem
cells are able to develop into any type of cell." One student used "evolve" to describe the
change ("They're cells in the bone marrow that can evolve into any other type of cell
throughout the body. It's the most basic cell able to do so").
While most students believed stem cells became other cells, there were a variety
of less frequent responses. Some students felt stem cells had more functions or more
special characteristics than other cells, such as "stem cells are cells that can develop into
any kind of cell ... they contain all of the organism's DNA so, they can develop into any
kind of cell" (implying that "specialized" cells only have DNA coding for their function).
Conversely, another class of student responses indicated that stem cells had fewer
functions than other cells, perhaps due to being "immature." There were a few isolated
responses, such as one student believing that stem cells "are different from other cells
because they can tell genetic tendencies of a person."
Question 2. According to student responses to Q2, most students (28) cited
fetuses, embryos, or umbilical cord fluid as the primary source of stem cells. Another
commonly cited source of stem cells (12 students) was from a certain part of the body,
42
such as bone marrow, the spine, or nerve cells. Few students explicitly mentioned how
the source of stem cells might be controversial, although many students suggested that
pregnancies were aborted in order to obtain stem cells. Interestingly, two students
suggested that obtaining stem cells from embryos or fetuses doesn't destroy or harm the
developing organism.
Question 3. Responses to Q3 focused primarily on the hopes that byproducts of
stem cell research could be used to treat illness; many of the applications suggested by
students are those proposed by experts in the field, suggesting that students have had
some previous exposure. Many students (15) indicated that potential applications of stem
cell research would be particularly effective at treating diseases with a neurological
component, such as regrowing nerves, curing paralysis, or treating Alzheimer's disease.
Two students believed stem cell research was related to cloning. A few students (4)
suggested that stem cells could be used to regrow organs and lost tissue.
5.2.3. JBHS06 Pre-test Responses
Much like JBHS05, many JBHS06 students exhibited some understanding of stem
cells. A summary of responses to JBHS06 pre-test questions follows.
Question 1. As in JBHS05, virtually all students responded that stem cells were
cells that could become other cells. Words such as "reproduce," "develop," and
"specialize" were used to describe this process in a manner similar to JBHS05.
Question 2. According to students, the most common sources of stem cells were
from bone marrow, embryos, and umbilical cord fluid. In contrast to JBHS05 students,
43
who tended to list a single source of stem cells, most JBHS06 students listed more than
one sources in their answer (such as "bone marrow or fetuses").
Question 3. Results for Q3 in JBHS06 were generally the same as in JBHS05 most students focused on proposed medical applications. Six students felt stem cells
could be used to re-grow or regenerate damaged tissue, while two believed stem cells
were linked with cloning. Two students focused on behavioral or research applications,
saying stem cells could be used to understand an organism's behavior or could be used to
research tissues and organism development.
Question 4. Over half of the students (18) believed stem cell research is
controversial because obtaining stem cells involves an abortion or killing an unborn
chjld. Several students (6) suggested that research oti an embryo or fetus or taking a cell
from a fetus is controversial but didn't explicitly say the embryo was destroyed. An
example of this is the response "Because it deals with the harvesting of cells from a
fetus." Other students (6) had a variety of answers that focused less on the death of an
embryo and more on general social, philosophical, or health concerns. For example, one
student wrote "It is an outline to cloning - like pre-cloning. It can bring on situations ...
without laws to restrict it." Another student in this group said "It is controversial because
it is not a normal/natural way to repair the body." One student suggested that research on
stem cells is "highly controversial because it is removing identity."
44
5.2.4. Post-test Responses
The post-test responses for JBHS05 Q4 and Q5 and JBHS06 Q6 and Q7 focused
the impact instruction may have on student opinions of stem cell research and on student
perceptions of their own learning.
The average for JBHS05 Q4 (1.795) indicates that students felt they learned a lot
about stem cells. The average for JBHS05 Q5 (2.667) suggests that students had no
strong opinion as to whether or not instruction changed their views on stem cell research.
In JBHS06 Q6, most students indicated that the unit has not changed the way they
think about stem cell research. If instruction did change the way they think, it usually
reinforced their preexisting belief. For example, one student wrote "I used to think it was
a good thing to research, and I do even more now that I really know what they can do."
Table 6 lists answers to JBHS06 Q7. One of the lecture students didn't answer
the question. All students who answered indicated that they agreed or strongly agreed
with that statement.
Table 6 - Answers to JBHS06 Q7 "I feel I learned a lot about stem cells.
Response
Strongly Agree
Agree
Disagree
Strongly Disagree
Inquiry
5
10
0
0
Lecture
5
9
0
0
5.3. Interview Results
Pre-instruction interviews were conducted in JBHS06. Six students volunteered
to participate in the interviews. Unfortunately, the first and fourth interviews (the
participating students being designated Si and S4) have no sound and could not be
45
transcribed or analyzed in greater detail. However, they still shed some light on how
students understand stem cells. SI believed that stem cells are found only in the embryo,
and that adults don't have them, holding onto this belief with conviction. S4 was
strongly supportive of stem cell research and advocated increased funding, but she didn't
know why it was controversial or what stem cell research entailed.
5.3.1. Interview 2
In the second interview, S2 indicated that she did a project on stem cell research
in 8th grade, and as such she had a reasonably good idea that stem cells can become other
cells and that they are found in bone marrow, the spinal cord, and early in an organism's
development. In addition to potentially harming the fetus, she believed stem cell research
was also controversial because "it's just kind of impersonal, and, some people might
view it as inhumane, you know, if you're using it for its cells rather than its person."
According to S2, an organism starts "with a big amount" of stem cells that are
"differentiated and used ... as somatic cells." When asked a follow-up question about
what, exactly, is used, S2 felt it was that "they're just not susceptible to change
anymore." Later on in the interview, the student was asked at what stage of life stem
cells are finally "used up" and she responded:
I don't know, I'd say when, like, after babies, like, [are] done getting all of
[their] ... more mature characteristics. But I thought adults had them too,
so that doesn't make sense.
46
From this response it appears the student found it difficult to reconcile her belief that
stem cell differentiation potential is depleted early in life with her belief that adults
possess stem cells as well.
The interview touched on other topics such as the politics of stem cell research,
the genetic content of stem cell information versus other cells, and the relationship
between stem cell research and cloning. S2 hadn't yet formed an opinion on stem cell
research, nor did she know the current US policy toward stem cell research. She was
unsure on a question regarding the amount of genetic information present in stem cells
but felt they contained less information than other cells, saying "I'm guessing less [than
somatic cells]. Cause they're immature maybe." Finally, S2 saw stem cell research and
cloning as two distinct issues, believing that "stem cells are being used to help someone.
I think that's different from just therapeutic cloning." S2 believed that applications of
cloning would be more selfish in nature, focusing on restoring a favored pet or cloning a
child in order to harvest the clone's body parts for the original, while she considered the
applications of stem cell research to be inherently positive.
5.3.2. Interview 3
Like S2, S3 had previous experience with stem cells because he did a project on
them in 9th grade, and he had a reasonably good idea of what stem cells are and where
they come from. In addition, S3 believed stem cells are used up as an organism grows
(the interviewer is abbreviated with an "I"):
S3: Yeah I believe they are used up, I'm not really sure about this. But
because I know as adults we have a lot less than, like, as a small child, and
47
I'm not sure what they're used for, but I just know they do get used up
along the lines.
I: And I guess by used up - when I say "used up," how do you interpret that?
Like, is it like gasoline is used up, the tank is empty after a while, or
something else, just to give you an idea.
S3: Yeah, yeah ... Like used up, like some of them are used. Say you're
lacking muscle cells and, the stem cells, because they're that neutral cell
that can adapt to another cell, will go and help out the muscle cells and
generate more muscle cells, if you need them. So I believe as you become
and adult that would happen more and more.
I: Okay, so eventually you would lose your store?
S3: Yeah.
Later on in the interview, the student qualified his response, saying that an
organism's initial allotment of stem cells is "not really used up, but kind of used, not
completely used up." The exchange continued in the following manner:
I: Gotcha. You always have some in reserve?
S3: Yeah.
I: Okay. Do you think there's a particular time in an organism's life where
there's a particular small amount, maybe not zero but real low levels?
S3:1 would say, like, after the age of 21 because puberty's over and your body
kinda stays in a certain shape. And as you're developing you're going to
need those things.
48
When asked to compare the process of cell differentiation with adaptation, S3
replied:
S3:1 would say it's a lot like adaptation because the cells are able to adapt to
other cells lifestyles, like humans were able to adapt to their environment
so these cells are able to adapt to any environment, which makes them
really cool.
I: Okay, so it's kind of- is there like a selection process in the sense that
there are various stem cells competing to become the muscle cell, say?
S3: This I don't know about...
I: Do you have an intuition or gut feeling?
i S3: Um, there's probably, there's natural selection in everything I'd say, so
probably the best for that certain job would take over, I guess ...
In another exchange, the student was asked if a stem cell contains all of an
organism's DNA. Initially, the student said "they would have to, because of the jobs that
they can take." However, when asked if a muscle cell has all of an organism's DNA, the
student retracted his statement, saying:
No, no, no ... Yeah, so I would say no - I'm going to take back - so I'd
say no to the stem cells. Because I believe what would happen was they
would copy themselves off of a template of another cell and if that cell had
the DNA the stem cells would get the DNA from the copy of the template.
The student appears to be working from a model where stem cells are cells that adapt to
their environment. During this process of adaptation, the stem cell acquires the DNA of
the cell it is trying to emulate.
49
5.3.3. Interview 5
Much like S2 and S3, S5 had some previous knowledge of stem cells while doing
a controversial topics project. As such, she also seemed to have a reasonably good idea
of what stem cells are and where they come from. She seemed to exhibit a reasonably
good understanding of the politics of stem cell research in the US and had at least some
idea that other nations take different approaches. For example, when asked if she knew
of any policies other governments have toward stem cell research, she said "I think it's
more in, uh, Europe, over in the UK and everything, they're more actively [pursuing stem
cell research] than we are."
S5 felt that the most desirable stem cells were found shortly after fertilization,
saying:
... the zygote develops over the weeks that I know, um, when they do
abortions usually it's in those first few month, not more than the first
trimester usually. And that's when the stem cells are the most, that's
when they like to get them, because, I guess, that's when they have the
most potential. Um, because that tissue is very you, it's still developing.
When the S5 student was asked if the zygote would be considered a stem cell, she was
unsure. Wondering aloud if the zygote is "made up of more than one cell," she went on
to say:
I just know when that when the sperm and egg form it just forms that
zygote - it replicates, the cells replicate over time ... I guess I don't know
if you really could call [the zygote] a stem cell or not. It doesn't seem like
there's that much more to work with.
50
It isn't clear when the cells resulting from zygote cleavage become stem cells from this
student's model - her response "It doesn't seem like there's that much more to work
with" may indicate that the zygote itself is too generalized and needs to divide before
forming "actual" stem cells.
5.3.4. Interview 6
This interview was the shortest in duration, and as such few new insights on how
students understand stem cells could be gleaned from it. Like the preceding interview
subjects, S6 did a project on stem cell research in 10th grade and therefore had some
experience with the subject. She displayed a similar level of proficiency as the preceding
students regarding what stem cells are, where they came from, and why research on them
is so controversial.
When asked if stem cells contain more or less DNA than other cells, the student
said, "More," but her follow-up statement was ambiguous:
Well I guess that they're so useful and helping with different diseases,
because you can't just pick any cell and help with like any sort of disease,
in a human.
While the student wasn't asked exactly what role the larger amount of DNA in stem cells
plays, statements she makes later on in the interview indicate that an organism's DNA is
"split up" amongst all of its cells:
S6: Well, each cell has to be like, contain a certain amount of DNA. I don't
know, like the proportion, how much DNA, or if it's all the same.
51
I: Do - and, you know, just, if this sounds off base, say no, you don't agree
with it - but do you think maybe red blood cells contain information
specific to just what they do? You know what I mean? As opposed toS6: Yeah, I think they have a more specific function, [whereas] stem cells can
kind of have different functions or like mold to different functions in a
way.
I: Okay. And do they have, do red blood cells have genes just specific to
their function? Basically is what I'm saying.
S6: Yeah, I think.
It is worth noting that red blood cells have no nucleus and therefore have no nuclear
genes. However, this mistake on the part of the interviewer did not appear to affect the
student's response. According to her, an organism's DNA split up amongst it cells and
cells contain DNA specific to their function.
5.4. Discussion
5.4.1. Inquiry Versus Lecture
The work of Wynne et al. (2001) and Knight and Wood (2005) shows that
injecting even a small of degree inquiry into a traditional curriculum can be beneficial to
students. However, according to the results in table 5, students in the lecture unit of this
study exhibited greater learning gains than the inquiry students. In light of this result, the
inquiry-based unit needs to be reevaluated to determine how much genuine inquiry it
actually allows. While students in the inquiry section were able to discover various
52
aspects of stem cell research in a manner of their own choosing, most inquiry students
needed only to consult various websites and incorporate the content into their research
essays. So instead of truly building a deep understanding of the material, the inquiry
students may have been relegated to the role of passive receivers of information in a
manner similar to lecture students. The only difference was that, in the lectures, the
instructor transmitted the information instead of a computer.
Furthermore, the pre-/post-test questions, being primarily lower-order content
questions, are inherently biased toward lecture-based learning. Lecture students had the
advantage of the instructor telling them what they needed to know for the post-test in a
highly focused manner. However, inquiry students acquired the information for the posttests with less direct guidance from the instructor. Thus the lecture students could have
simply been better prepared for the post-test. Other assessments, such as the policy
activity, may have been a better indicator of inquiry student understanding.
Unfortunately, copies of the inquiry student policy activity papers weren't kept by the
instructor and weren't available for further analysis.
While students in the lecture section had a more focused delivery of the material,
students in all implementations of the stem cell unit appeared interested and engaged with
their activities. In one case, student curiosity was tinged with apprehension. During the
presentation on ES cells, lecture-section students were told that a potential consequence
of simply injecting ES cells is the formation of a teratorcarcinoma, a bizarre form of
tumor composed of a variety of tissue types such as rudimentary eye structures or bones.
One student asked if the teratocarcinoma was trying to form a new organism. The answer
is no, it is essentially an uncontrolled expression of genes coding for certain
53
morphologies. However, it illustrates how developments in stem cell research may
induce some level of anxiety in students, an observation that echoes the findings of Bryce
and Gray (2004).
One aspect unique to the inquiry unit was that it facilitated a discussion conducted
in large part by the students. After the groups presented their statements for permissive,
flexible, and restricted policies, the follow-up conversation drifted to the topic of the
products of stem cell research. The students who gave the restricted policy presentation
said they would ban stem cell research but allow for the importation of stem cell products
produced in more permissive countries. The instructor asked the group if this might be
seen as hypocritical, but after some discussion the entire class came to the conclusion that
it was okay for a country to ban stem cell research but reap the benefits of other
countries' research. After a prodding question, students took a lead role in the
conversation similar to the student-initiated discussions also seen by Bryce and Gray.
5.4.2. DNA Content of Stem Cells
A common theme of student responses concerns the DNA content of stem cells,
which students seemed to think can be greater than or less than the amount of DNA in a
differentiated cell. In the first case, student logic suggests that stem cells may have more
DNA than differentiated cells because somatic cells only contain DNA specific to their
function. Therefore, since stem cells have high potencies, they must possess a greater
amount of genetic material in order for the DNA to be "split up" or "divided" into the
differentiated cell. The interview of S6 and the JBHS05 pre-test response stating that
stem cells "contain all of the organism's DNA" are examples of this misconception. This
54
may be a logical outgrowth of the observations of Lewis and Wood-Robinson (2000),
whose work suggests that most students believe cells only contain the information they
need to perform their function.
In the second case, students appear to think stem cells may have less DNA than
differentiated cells. The reason for this, as explained by S2 in her interview and some
JBHS05 pre-test responses, is that stem cells are "immature" cells. Exactly what these
students meant by "immature" is unclear. It may be that these students view them as
undeveloped "infant" cells that grow up and acquire the characteristics of adult cells. In
this case, students may be relying on their observations of human growth from infancy to
adulthood to help explain how a stem cell can become other cells. This is similar to
anthropomorphic views of the cell as seen by Flores et al. (2003). However, further
interview questions that explicitly ask what is meant by "immature" are necessary to
confirm that this is what students believe. It also remains uncertain what these students
think the DNA content of differentiated cells actually is. That is, while students may
believe a stem cell has less DNA than a differentiated cell, these students may still
believe that differentiated cells still do not possess an organism's entire DNA.
Related to the idea of immaturity, another rationale given for why stem cells have
less DNA than differentiated cells is that stem cells are "blank slates" that acquire the
DNA or characteristics of the other cells. An example is the interview of S3, who
suggests that stem cells copy the DNA of cells in order to assume their functions. While
he didn't explicitly state this, S3's response also suggests that differentiated cells have
DNA specific to their function.
55
Whatever the case, it is clear that misconceptions about the DNA content of
somatic cells play a role in student understanding of stem cells. Future work in this area
should almost certainly return to this issue. A good question for future work focusing on
this issue might ask "Do stem cells contain more, less, or the same amount of DNA than
other cells?" In addition, in order to firmly establish student understanding of cellular
DNA content in general, another question might ask students how the DNA of
differentiated cells compares to other differentiated cells. Is it more, less, or the same
amount? Do cells only have DNA specific to their function? How does the genetic
information of sex cells (eggs and sperm) compare to that of somatic cells? These
questions would be followed by requests for an explanation, allowing a researcher or
educator to more explicitly focus on the issue.
5.4.3. Stem Cells as a Finite Resource
A broad class of student responses indicates that stem cells are "used up" as an
organism ages. To some extent this is correct, as the toti- and pluritpotent ES cells
present in the early stages of development are not found in adult bodies and AS cells are
generally more difficult to isolate. However, "used up" may imply that the cells vanish
after use, which is rather different than a cell differentiating into another. Some students,
such as S2, seem aware of this distinction. Others, such as SI and S3, indicate that adult
bodies have no stem cells or far fewer stem cells than an embryo.
More work needs to be done to see exactly what students mean by the phrase
"used up." For example, S3 was aware that stem cells can become other cells, but he also
believed stem cells were used up as an organism develops (although he stated he didn't
56
know what they were used for). Additionally, while S2 indicated that stem cells use up
their ability to change, she also said that an organism starts out with "a big amount" of
stem cells. This is as much of a development question as a stem cell question, as a "big
amount" could be interpreted to mean that an organism begins its development as a large
mass of stem cells that differentiates and coalesces into a many-celled embryo. While S2
probably didn't think this happened, no follow-up question was asked in order to clarify
what she meant. It seems that students are aware of a connection between stem cells, the
early stages of development, and the perceived utility of stem cells, but rather than
thinking in terms of differentiation potential students seem to assume that there are
simply more stem cells present early in life and they are depleted as an organism ages.
5.4.4. Student Understanding of Cell Differentiation
As shown in the results for Ql in JBHS05 and JBHS06, students may use a
variety of terms as proxies for "differentiate" when describing a stem cell's transition
from undifferentiated to differentiated states. Examples include "reproduce,"
"regenerate," "develop," "specialize," and "evolve." These terms suggest transformation,
indicating that students have at least some idea of the concept of cell differentiation if not
the precise terminology. For example, the words "develop" or "specialize" imply
movement from a general to more specific state, which is a fair approximation of what
differentiation is. However, because follow-up interviews weren't conducted for JBHS05
pre-tests, it's unclear if students were simply using these terms as substitutes for the more
technical "differentiate" term or if they believed these were the actual processes.
57
The interview with S3 offers deeper insight into how students might interpret the
process of differentiation. After being asked for his "intuition or gut feeling," S3
indicates that the transformation from undifferentiated to differentiated state is similar to
adaptation. Notably, S3 initially stated he didn't know if several stem cells "competed"
in order to become a particular differentiated cell, indicating that he does not know the
details of differentiation. While he shouldn't be faulted for this (even biologists have an
incomplete understanding of the mechanisms of differentiation), it shows that S3 falls
back on the more familiar idea of adaptation when confronted with an unfamiliar
problem. Interestingly, S3's idea that stem cells "copy themselves off of a template of
another cell" bears a resemblance to cell induction. It may be that S3 possesses
independent models for adaptation and cell induction and is combining those ide"as when
describing differentiation.
The ideas used by S3 - and other students - could be thought of as resources, as
defined by Hammer (2000). Resources are general, commonly used ideas that are
applicable in many different contexts, such as "used up" to describe food in a refrigerator,
fuel in a fire, and so on. Some contexts of "used up" are inappropriate. For example,
information does not get used up, but spreads from person to person. Students might be
thought of as using resources in their responses, but as of this writing no resource-based
studies in this particular area of biology education research have been published.
5.4.5. Sources of Stem Cells
Many students indicated that a major source of stem cells was from aborted
fetuses, perhaps because the ES cell research debate is often framed that way in the media
58
or in public forums. While developing fetuses do possess stem cells and ES cell research
does destroy embryos, the most acceptable source of stem cells in the US would be
supernumerary embryos from fertility clinics - the embryos would ordinarily be disposed
of. Grappling with whether or not this constitutes abortion may be a useful exercise for
biology classes when setting parameters for class discussion or debate activities in the
manner suggested by Cannard (2005).
59
Chapter 6
CONCLUSIONS
6.1. Future Work
The abundance of ideas found in student responses and interviews suggests that
there is great potential for future work in determining what students understand about
stem cells. Of particular interest is what students perceive the DNA content of stem cells
to be, because it appears to be a natural extension of widespread misconceptions of cell
DNA content found by Lewis and Wood-Robinson (2005). When students are asked to
compare the DNA content of a stem cell with a differentiated cell they may say one has
more DNA than the other. Sometimes-the stem cell has more DNA, because as it
assumes a differentiated form the stem cell discards "unnecessary" DNA and keeps the
DNA required for cell function. Alternatively, a stem cell can have less DNA because it
is something like a blank slate, somehow acquiring the DNA it needs in order to become
a particular kind of differentiated cell.
In order to more fully understand why students believe stem cells have the DNA
content that they do, future studies should include some kind of investigation into how
students understand the DNA content of cells in general. This may include asking
students how the DNA content of one differentiated cell compares to another, what the
DNA content of sex cells might be, and if cells have DNA specific to their function. This
kind of investigation would allow researchers to see what beliefs students bring to class.
Stem cells may then serve as a context to elicit misconceptions of cell DNA content
60
similar to how the inclined-plane problem in physics is used to elicit student
misconceptions of force.
Another avenue for future research may focus less on student misconceptions and
more on how students apply the intuitions, concepts, or models from other contexts to the
context of stem cells. For example, asking students to describe the process of cell
differentiation may result in students applying a variety of models, theories, and ideas in
incomplete or incorrect manners, such as how S3 may have been applying adaptation and
cell induction models. Another possibility may be asking students to resolve their idea of
having a "big amount" of stem cells early in life with the idea of development from a
single-cell zygote to multi-celled embryo.
6.2. Implications for Teaching
Instructors should be aware that students come to class with a variety of ideas
about stem cells. This includes the belief of more or less DNA content as discussed
above, in addition to other beliefs such as abortions being the main source of stem cells.
Most students are aware that stem cells can become other cells and stem cell research
may lead to valuable medical treatments, but their understanding is generally vague or
very limited. However, even this rudimentary understanding can be a useful hook for
students, and the controversy surrounding stem cell research is a valuable feature for
motivating study.
Post-test responses indicate that most students did not change their previous
opinion of stem cell research. If change did occur, it mostly served to amplify their preexisting beliefs. Thus while educators will still want to approach the controversial topic
61
of stem cells with respect and civility, they may not need to be so concerned that simply
exposing students to the topic will offend or radically change student opinions. It is
likely that this is also the case with controversial subjects in other areas of science.
While the lecture students may have performed better on the post-tests, we have
no evidence that those students gained a deep understanding of the material. Lecture
students indeed achieved some level of success on the tests, but this may be due to
focused, direct exposure to the material. In essence, they may have been taught to take
the test. Another reason is that the pre-/post-tests themselves prioritized lower-order, rote
knowledge answers. In this era of standardized testing, there is a real danger that
students are simply parroting back what the teacher told them or that test questions may
not be designed in order to showcase deep understanding. Lecture-based teaching can
easily be made to seem more effective than inquiry-based methods, so, as discussed by
Wiggins and McTighe (2005), the only way teachers can reliably evaluate student
understanding is to use a variety of assessment tools.
The results for the inquiry unit compared to the lecture unit suggest that a
combination of lecture and inquiry may be a better way to teach stem cells. The
combined unit could be developed as a form of guided inquiry, where the instructor gives
a small series of initial lectures before assigning students a more genuine inquiry activity
such as a stem cell policy construction activity. Such an approach allows the instructor to
deliver important content information to students quickly and efficiently while allowing
students to explore the implications of stem cell research in a meaningful way.
62
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Appendix A
LEARNING STANDARDS
U.S. National Content Standard C: Life Science
As a result of their activities in grades 9-12, all students should develop
understanding of:
The Cell
•
Cells have particular structures that underlie their functions. Every cell is
surrounded by a membrane that separates it from the outside world. Inside
the cell is a concentrated mixture of thousands of different molecules
which form a variety of specialized structures that carry out such cell
functions as energy production, transport of molecules, waste disposal,
synthesis of new molecules, and the storage of genetic material.
•
Most cell functions involve chemical reactions. Food molecules taken
into cells react to provide the chemical constituents needed to synthesize
other molecules. Both breakdown and synthesis are made possible by a
large set of protein catalysts, called enzymes. The breakdown of some of
the food molecules enables the cell to store energy in specific chemicals
that are used to carry out the many functions of the cell.
65
•
Cells store and use information to guide their functions. The genetic
information stored in DNA is used to direct the synthesis of the thousands
of proteins that each cell requires.
•
Cell functions are regulated. Regulation occurs both through changes in
the activity of the functions performed by proteins and through the
selective expression of individual genes. This regulation allows cells to
respond to their environment and to control and coordinate cell growth
and division.
,•
Plant cells contain chloroplasts, the site of photosynthesis. Plants and
many microorganisms use solar energy to combine molecules of carbon
dioxide and water into complex, energy rich organic compounds and
release oxygen to the environment. This process of photosynthesis
provides a vital connection between the sun and the energy needs of living
systems.
•
Cells can differentiate, and complex multicellular organisms are formed as
a highly organized arrangement of differentiated cells. In the development
of these multicellular organisms, the progeny from a single cell form an
embryo in which the cells multiply and differentiate to form the many
specialized cells, tissues and organs that comprise the final organism.
This differentiation is regulated through the expression of different genes.
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U.S. National Contest Standard F: Science in Personal and Social Perspectives
As a result of activities in grades 9-12, all students should develop
understanding of:
Science and Technology in Local, National, and Global Challenges
•
Science and technology are essential social enterprises, but alone they can
only indicate what can happen, not what should happen. The latter
involves human decisions about the use of knowledge.
•
Understanding basic concepts and principles of science and technology
should precede active debate about the economics, policies, politics, and
ethics of various science- and technology-related challenges. However,
understanding science alone will not resolve local, national, or global
challenges.
•
Progress in science and technology can be affected by social issues and
challenges. Funding priorities for specific health problems serve as
examples of ways that social issues influence science and technology.
•
Individuals and society must decide on proposals involving new research
and the introduction of new technologies into society. Decisions involve
assessment of alternatives, risks, costs, and benefits and consideration of
who benefits and who suffers, who pays and gains, and what the risks are
and who bears them. Students should understand the appropriateness and
value of basic questions - "What can happen?" - "What are the odds?" and "How do scientists and engineers know what will happen?"
67
Humans have a major effect on other species. For example, the influence
of humans on other organisms occurs through land use - which decreases
space available to other species - and pollution - which changes the
chemical composition of air, soil, and water.
68
State of Maine Standard L: Communication
Students will communicate effectively in the application of science and
technology. Students will be able to:
1. Analyze research or other literature for accuracy in the design and findings
of experiments.
2. Use journals and self-assessment to describe and analyze scientific and
technological experiences and to reflect on problem-solving processes.
3. Make and use appropriate symbols, pictures, diagrams, scale drawings, and
models to represent and simplify real-life situations and to solve problems.
4. Employ graphs, tables, and maps in making arguments and drawing
conclusions.
5. Critique models, stating how they do and do not effectively represent the
real phenomenon.
6. Evaluate the communication capabilities of new kinds of media (e.g.,
cameras with computer disks instead of film).
7. Use computers to organize data, generate models, and do research for
problem solving.
8. Engage in a debate, on a scientific issue, where both points of view are
based on the same set of information.
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Appendix 8
RUBRIC
" 1 . " Exhibits no understanding or an obviously wrong or extremely vague answer.
Responses that were graded as a " 1 " include "I don't know," obviously wrong or
inappropriate answers (such as this actual answer from JBHS05 Ql: "Stem cells are cells
from bone marrow - they are different from other cells because they are fighting cells"),
or an extremely vague answer (such as this actual answer from CHS05 Q3: "stem cell
research can be used to help people").
"2." Exhibits some understanding, but is too broad or unclear.
Ql: Noting that "stem cells are cells that can become other cells"
Q2: Noting that stem cells came from a single source, such as bone marrow, the embryo,
or aborted fetuses (indicating the student had some idea of where stem cells are from).
Q3: Noting that stem cells could be used to regrow certain parts of the body without
mentioning why.
Q4: Suggesting that stem cell research has something to do with the fetus or embryo.
"3." Exhibits a good understanding, noting key distinctions but not going into depth.
Ql: Noting that stem cells vary in their potencies.
Q2: Describing the two main sources of stem cell - embryonic and adult
Q3: Mentioning hopes that stem cells could be directed to become specific cells, organs,
or tissues but not mentioning particular diseases.
Q4: Noting that embryonic stem cell research involves the destruction of an embryo.
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"4." Exhibits excellent understanding, noting key distinctions and possessing more
thoughtful, comprehensive answers.
Ql: Describing what the various stem cell potencies actually mean.
Q2: Describing alternative sources of stem cells such as those from fertility clinics or
oocyte donations.
Q3: Mentioning a particular disease and how stem cell-based treatments might help treat
that disease.
Q4: Mentioning other sources of controversy (exploitation of poor women, safety
concerns, ownership issues, etc.).
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BIOGRAPHY OF THE AUTHOR
Jonathan Christian Rabe Moyer was born Columbus, Ohio on November 12,
1978. Not long after his birth, his family moved to various places in the Northeast United
States before finally settling in Maine. He graduated from Machias Memorial High
School in Machias, Maine in 1997. In 2003, he graduated from the University of Maine
with a Bachelor of Science degree in Physics and with High Honors.
Over the years Jonathan has worked as a library clerk, tutor, teaching assistant,
and bookseller. In addition, he has interned at the Laboratory for Surface Science and
Technology in Orono, Maine and at the Jackson Laboratory in Bar Harbor, Maine.
Jonathan plans to work on a Ph.D. in Physics or Biology sometime in the future.
Until that time comes, he wants to bring his appreciation for science and mathematics to
secondary school students and to inspire them to pursue scientific careers of their own.
Jonathan is a candidate for the Master of Science in Teaching degree from The University
ofMaineinMay, 2007.
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