Upload
southernmiss
View
0
Download
0
Embed Size (px)
Citation preview
Running Head: UNDERSTANDING EVOLUTION AND EVIDENTIARY SUPPORT 1
Understanding Evolution and Evidentiary Support
Carrie Jo Boyce & Kristy Lynn Halverson
University of Southern Mississippi
Boyce, C.J. & Halverson, K.L. (2011, April). Understanding evolution and evidentiary support.
Paper presented at the annual meeting of the National Association for Research in
Science Teaching, Orlando, FL.
UNDERSTANDING EVOLUTION AND EVIDENTIARY SUPPORT 2
Abstract
Scientists are expected to provide evidentiary support to mold, strengthen, alter, and refute ideas.
Systematic biologists explore how organisms are related through their evolutionary histories by
collecting different types of informative evidence. However, students often struggle with
understanding science content and evidence selection when considering evolutionary relatedness.
The purpose of this study was to explore how upper-level biology students made sense of
evolution and used evidentiary support with their understandings. Using a mixed methods
approach, we gathered data from 120 upper-level life-science majors. We found a statistically
significant relationship between evidence used to support evolutionary relationships and the
accuracy of students’ understandings of evolution. However, we found that students who
provided scientific explanations of evolution did not always use informative evidence to support
their understandings; this suggests that these students did not recognize meaningful patterns that
highlight appropriate evidence. Findings from this study can be used by instructors to develop a
curriculum that helps explain the evolutionary theory and the evidence required for support.
Key Words: Evolution, Evidentiary Support, Evolutionary Understanding
UNDERSTANDING EVOLUTION AND EVIDENTIARY SUPPORT 3
Understanding Evolution and Evidentiary Support
Scientists are expected to provide evidentiary support to ground findings and claims they
make. Systematic biologists explore how organisms are related through their evolutionary
histories by collecting different types of informative evidence, such as: genetic, molecular,
developmental, functional morphological, fossil record, and possibly geological information
(Halverson, 2008; Cooper, 2002; Crisp & Cook, 2005). In systematics biology, biological
information is organized via phylogenetics; phylogenetic or evolutionary tree diagrams depicting
evolutionary relationships are interdisciplinary tools and frameworks for researchers to assess
evolutionary evidence (Baum, Smith & Donovan, 2005). Knowing what types of evidentiary
support are needed and which are biologically/evolutionarily relevant, influences how scientists
hypothesize evolutionary relatedness among organisms and impacts how scientists generate
phylogenetic trees (Crisp & Cook, 2005).
Unlike expert scientists, students are unable to chunk information into meaningful
patterns or even see patterns in information (Bransford, Brown, & Cocking, 2000). Thus, we
assume this is one reason why they may struggle with recognizing what constitutes informative
and uninformative evidence of evolutionary relationships. Additionally, students may incur
hardships due to a reduced ability to recall different facets of their knowledge base (Bransford et
al., 2000). This makes it harder for students to connect their knowledge of evidentiary support
from other aspects of science to evolution, potentially to the point where they cannot transfer the
information.
Furthermore, many students find difficulty in understanding how evolution occurs (Lord
& Marino, 1993). When asked to explain evolution, often students restate definitions provided
in textbooks or information shared by their teachers without processing the information to
UNDERSTANDING EVOLUTION AND EVIDENTIARY SUPPORT 4
develop a conceptual understanding of evolution (Enderle, Smith, & Southerland, 2009). By
doing this students are inhibiting their chances of true understanding and learning of
evolutionary history. Thus, the types of evidentiary support students then rely upon may also be
related to the understanding of evolution they have constructed. This could perpetuate students
deducing incorrect or incomplete evolutionary hypotheses because they rely upon uninformative
evidence.
Research Questions
The purpose of this study was to explore how upper-level biology students made sense of
evolution and used evidentiary support with their understandings. To address this idea we asked
the following three research questions:
1. How scientifically accurate are students’ understandings of evolution?
2. What are the types of evidence students utilize when determining evolutionary
relationships among taxa?
3. What is the relationship between students’ understandings and the types selected
evidence they use to support their perceptions of evolutionary relatedness?
Research Design/Methods
Participants included 120 life-science majors from two public universities enrolled in one
of three upper-level biology courses on evolution and systematics. Data included student
responses to open-ended and multiple choice questions on a pretest (Appendix) that assessed
students’ ideas of evolution, inheritance, relatedness and evolutionary evidence (Halverson,
2009). We tested for difference in the populations between universities using a one-way
ANOVA and across semesters using an independent t-test. There were no significant differences
UNDERSTANDING EVOLUTION AND EVIDENTIARY SUPPORT 5
between student responses from the two universities (t(61)=1.322, p=.191) nor across the
semesters (F(2, 117) = 2.273, p = .108). Therefore, we were able to combine our data for
analysis.
We used a mixed method approach to analyze findings from our data. For the qualitative
portion of the analysis, first, we used an inductive method to code student definitions and
understandings of evolution and inheritance. We grouped similar responses and developed
categories defining the scientific accuracy of students’ understandings. Second, we used a
deductive method to code the types of evidence students selected to support evolutionary
relationships. We then separated these selections into two categories: informative and
uninformative. We determined the frequency of students’ understanding and the frequency of
evidence types chosen.
Informative evidence included information that is relevant for indentifying evolutionary
relationships among taxa (Morphology, Genetic Data, and Fossil Data). Uninformative evidence
included information that is not traditionally used to determine evolutionary relationships
(Learned Behavior and Ecological Variables). To increase reliability of coding, we utilized
investigator triangulation (Patton, 2002). Each researcher coded all of the data. We compared
codes and had 100% inter-rater reliability.
For the quantitative portion of the analysis, we analyzed the data using a cross-tabulation
between students’ understanding of evolution and types of evidence selected. This provided a
Pearson’s Chi-square value in order to determine the relationship between these variables. For
this analysis we scored students’ accuracy of understandings (scientific=3, naïve=2, non-
scientific=1, None=0) and the types of evidence selected (informative=1, uninformative=0).
Statistical significance was assigned when p < 0.05.
UNDERSTANDING EVOLUTION AND EVIDENTIARY SUPPORT 6
Findings
We organize our findings in the following sections with respect to our research questions.
First, we describe the scientific accuracy of students’ understandings of evolution. Second, we
report the frequency of the types of evidence used by students to support evolutionary
relationships among taxa. Third, we found a statistically significant relationship between
evidence used to support evolutionary relationships and students’ understandings of evolution.
Finding 1- Students’ understanding of evolution
Prior to the course, most students (70%) did not have an accurate understanding of
evolution. We found four levels of scientific accuracy: Scientific, Naïve, Non-scientific or None
(Table 1).
Table 1. Frequency Distribution of Evolution Definitions
Accuracy of Understanding
Percentage
(n=120)
Scientific 30%
Naïve 40%
Non-Scientific 17%
None 13%
Total 100%
Scientific. Many students had a scientifically accurate understanding of evolution and
inheritance. Students with this understanding had a scientifically acceptable evolutionary
definition that contained responses such as: descent with genetic modification, genetic change
over time, or genetic change through generations. All of these definitions included three
elements: mention of change, time and genetic factors. For example, Ruth “changes in DNA that
is passed on from one generation to another.”
UNDERSTANDING EVOLUTION AND EVIDENTIARY SUPPORT 7
Some students also denoted mechanisms for evolution that contributed to their
understanding. For instance Sarah stated, “Evolution is change in genes over time. These
changes occur by either genetic drift or natural selection.”
For students to qualify for this category they also had to indicate they understood that
only genetically determined characteristics could be passed from parents to offspring; this was
assessed based on their response to the multiple choice question and subsequent explanation.
Naïve. The majority of students (40%) had an understanding of evolution that was based
in science. However this definition was incomplete or partially inaccurate. Definitions were
considered incomplete if part of the scientifically acceptable definition was missing. For
example, Latrice simply stated “changes over time.” This definition is considered Naïve because
it lacks the element of genetics. Latrice did not show if they understood that the changes were
happening in the gene frequency. However this student also understood that only genetics could
be passed on to offspring not learned behaviors; this was exhibited by later responses. Other
Naïve responses included mentioning a mechanism of evolution while neglecting to add the
genetic element. For example, Brett stated, “changes that organisms go through throughout time
via natural selection.”
Additionally, students were classified as having a naïve understanding if they mentioned
mutation without explaining how they played a role in evolution. For example, Jed stated,
“Evolution, is powered by mutations in DNA, which effect genotypes and phenotypes.” He did
not specify how the mutations powered evolution; however, he later explains that only “Genetics
are passed down biologically, learned behaviors aren’t.” Both of these responses working
together showed that Jed understood that genetics and mutations played a role, but he had a naïve
view of evolution because he did not state how these factors contributed to evolutionary theory.
UNDERSTANDING EVOLUTION AND EVIDENTIARY SUPPORT 8
Non-Scientific. The remaining students were split between this category (17%) and the
next. Students in this category have an understanding of evolution that is not accurately based in
science. Students in this category may have a definition that is used improperly. Such as Jose’s
statement, “changes needed for adaptation/survived over a long period of time.”
Likewise, student definitions may be missing two of the three elements, such as Wendy’s
response of “change in a species,” or where Sheldon states, “constant change or ‘evolving’ of
species, organism, and many other things into something different becoming better and some
even worse.” In these examples there is no mention of time or genetic factors, only change,
indicating that these students did not have a scientifically accurate understanding of evolution.
Also, Sheldon’s response indicated he believes other “things” can evolve and become
better or worse. This shows that Sheldon holds a view of evolution that is similar to the
Lamarckian view; that things evolve for the better, or in Sheldon’s explanation worse. Where
Lamarck’s view was based in science for his time period, Sheldon’s response does not make use
of today’s scientific data or processes.
Additionally, in this category only one student, Jethro, accurately understood that only
genetic material can be inherited. However, he also wrote that evolution was “changes for the
better in your environment” thus qualifying for the Non-scientific category. With this statement
Jethro is suggesting that organisms can choose to evolve based on environmental factors, when
in fact each individual is simply adapting to the environment. All of these understandings also
lacked the important aspect of time. Evolution does not occur in one generation, but over a
greatly extended period of time. Students in this category did not add this component to their
definitions or explanations.
UNDERSTANDING EVOLUTION AND EVIDENTIARY SUPPORT 9
None. Student responses are least frequently found in this category (13%). These students
did not have any understanding of evolution. To be considered part of this category, student
responses either: 1- did not give a definition of evolution; or 2- their definition lacked any of the
three elements. For example, Alton stated that evolution is “the beginning of all living
organisms” and Julio said evolution was “the history of existence.” These definitions had no
indication if scientific processes were involved and were lacking details. Where Joe said, “it is
what the world went through, and how it happened.”
Where the above mentioned students were vague some, like Stan, anthropomorphized the
organisms stating that evolution is “a point in line, for survival,” and later stated that organisms
evolved to help their species survive. These definitions indicated that students do not have an
evolutionary understanding due to the student’s failure to recognize that evolution is not a
process that an individual organism goes through, but one that populations undergo over
extended periods of time.
We were not able to accurately judge students that did not respond. A blank answer could
indicate that either: 1- the student did not have enough time to finish the pretest; or 2- the student
did not know/understand how to define evolution in the context of the pretest. Of the students
that did not generate a written definition of evolution 40% did not answer the multiple choice
question regarding inheritance properly. Many of the students that did answer the multiple choice
question properly did not provide a written explanation, leaving the researchers to wonder if they
had a correct understanding of inheritance or if they simply guessed the correct answer.
Finding 2- Evidentiary support for evolutionarily classifying organisms
Part of the two-tiered pretest, asked students: What information do scientists use when
categorizing organisms into evolutionary related groups (Appendix)? Student responses were
UNDERSTANDING EVOLUTION AND EVIDENTIARY SUPPORT 10
then categorized as either choosing informative or uninformative evidence based on the types of
information selected, or generated as part of the “Other” category.
Informative evidence included students who only selected morphology, genetic data,
and/or fossil data. Student responses were classified as uninformative evidence in one of two
ways: 1) if they only selected learned behaviors and/or ecological variables; or 2) if they chose
informative evidence in addition to selecting uninformative evidence (subcategory both).
The reasoning, if students chose both types of evidence they may not have a grasp of
what constitutes good evidentiary support for evolutionary relatedness. The majority of students
selected physical traits to classify organisms, then ecosystem factors, genetic data, fossil data and
behavior (Table 2).
Table 2. Frequency Distribution of Evidence Types
Evidence Type Number of Students Percentage
Informative
Physical Traits 97 81%
Genetic Data 33 27%
Fossil Data 7 6%
Uninformative
Behavior 4 3%
Ecosystem Factors 44 37%
*There are no totals because students could choose more than one type
of evidence.
Overall, there was little difference between the frequency of students choosing
Informative (49%) and Uninformative (51%) evidence (Table 3). Of the student responses that
were categorized as Uninformative, five chose only learned behaviors/ecological variables,
whereas the remainder (56) chose both evidence types.
UNDERSTANDING EVOLUTION AND EVIDENTIARY SUPPORT 11
Table 3. Frequency Distribution of Informative Only and
Uninformative Evidence Types
Evidence Type Number of Students Percentage
Informative 59 49%
Uninformative 61 51%
(Uninformative only) (5)
(Both) (56)
Total 120 100%
These trends could indicate that students largely do not think of genetic and fossil data as
readily available and therefore not usable as evidence for evolutionary relatedness. While other
data, such as behavior and ecosystem variables are readily available and thusly students may
believe these evidence types should be used. This could also indicate that while the majority of
students understand the concept of evolution, they do not understand the different data that play a
role in the evolutionary process.
Finding 3- Students’ understanding of evolution as related to types of evidentiary support
We conducted a Pearson’s Chi-Square test and found a statistically significant
relationship (χ2(4)=13.415, p<.01) between students’ accuracy of understanding evolution and
the use of informative evidence to support evolutionary relationships among taxa. Students with
a scientifically accurate understanding of evolution were more likely (42%) to rely on
informative evidence to support hypotheses about relatedness with a small percentage choosing
uninformative evidence (Table 4).
UNDERSTANDING EVOLUTION AND EVIDENTIARY SUPPORT 12
Table 4. Cross tabulation of Students Understanding of Evolution and Evidence Type Chosen
Evidence
Type
Understanding of Evolution
Total Scientific Naïve
Non-
Scientific None
Informative 25 24 5 5 59
Uninformative 11 24 15 11 61
Total 36 48 20 16 120
This shows that students with a scientifically accurate understanding of evolution also
understand evidence types that accurately inform evolutionary relationships. Students in this
category may also have the ability to store information in ways that allow for greater recall.
However, there is still a percentage (18%) of students with a scientifically accurate
understanding of evolution that still chose uninformative evidence.
This is interesting in that it suggests two things. That some of these students may be
unable to recall information they have learned in previous courses. Or, that students choosing
uninformative evidence, while having a scientifically accurate understanding of evolution, did
not recognize how information from different aspects of science could be applied to evolution
and thusly are not storing information in significant segments.
Students with a naïve understanding of evolution were equally likely (40%) to choose
informative and uninformative evidence. This could indicate that students in this category
understand the concept of evolution, but not the mechanisms by which systematic biologists
classify evolutionary relationships or what constitutes evidentiary support for evolution. These
students may have learned what constitutes appropriate evidence in science but may experience
the same problems as students with a scientifically accurate understanding; the inability to
transfer their knowledge between science disciplines.
UNDERSTANDING EVOLUTION AND EVIDENTIARY SUPPORT 13
The naïve category of student may be unable to transfer the knowledge gained about
appropriate evidence in science, to evolution. They simply may not understand the types of
evidentiary support needed for evolution. Alternatively, these students may have been unable to
accurately recall information regarding the required evidentiary support for evolution. This
suggests that students classified in the naïve category of understanding may have a decreased
ability to store information in pathways or patterns that allow for easy accessibility and retrieval
for application to new situations.
Of the students with a non-scientific understanding, the majority (25%) chose
uninformative evidence. The remaining students that were classified as no understanding of
evolution (none) also selected uninformative evidence (18%). This indicates that students with a
scientifically accurate or naïve understanding of evolution were more likely to choose
Informative evidence. Where students with an evolutionary understanding not based in science,
or with a lack of understanding chose uninformative evidence.
There are a variety of reasons that students classified as having non-scientific or no
understanding would choose uninformative evidence over informative evidence. These students
may have the inability to: properly store information, transfer information well, or recall
information they have already learned. Additionally, the uninformative evidence types may fit
into students’ current alternative conceptions regarding evolutionary theory.
Contribution & Implications
The use of evidence to support ideas is a necessity in science. Scientists use evidence to
mold, strengthen, alter, and refute ideas (Crisp & Cook, 2005). If the evidence a scientist uses is
weak or inappropriate, the subsequent ideas will not hold up to scrutiny by the scientific
community. Thus, it is a fair assumption that students with a scientific understanding of
UNDERSTANDING EVOLUTION AND EVIDENTIARY SUPPORT 14
evolution would choose informative types of evidentiary support. We did find that students with
scientific understandings of evolution more often chose informative evidence and students with
non-scientific understandings were more likely to choose uninformative evidence.
However, we found that students who provided scientific explanations of evolution did
not always use informative evidence to support their understandings; this suggests that these
students did not recognize meaningful patterns in previously learned information that highlight
appropriate evidence. This lack of appropriate evidentiary support could also be due to student’s
diminished ability to transfer information across disciplines in the same way as expert scientists
(Bransford et al., 2000). Although there is a significant relationship between students’ use of
informative evidence and the accuracy of their understandings about evolution, the use of
informative evidence cannot be used as a predictor of the scientific accuracy of students’ ideas.
Instructors can use this information to develop a curriculum that helps explain the evolutionary
theory and the evidence required for support. Instructors need to be explicit in their instruction
on why scientists use particular kinds of evidence to support hypotheses about evolutionary
relationships and why other data is uninformative (Halverson, 2009).
When instructors present the difference between informative and uninformative evidence
for evolution in a clear manner with a few examples, students will be able to store this
information in a way that allows for easier recall in the future. By providing examples of
evidence types and explaining how evidence relates to evolutionary theory, instructors will help
students create connections between the new information and knowledge from previous course
work.
Additionally, by helping students build pathways between old and new knowledge
instructors are enabling students to go forth and build additional meaningful patterns across their
UNDERSTANDING EVOLUTION AND EVIDENTIARY SUPPORT 15
scientific knowledge. This in turn will help students transition from novice to expert learners
(Bransford et al., 2000; Halverson, 2008). When students are able to think like experts they will
be better able to synthesize new knowledge from existing information, have greater recall of
information and will have the ability to apply concepts across scientific fields.
Future aspects of this project will be to assess if students’ accuracy of understanding
changes after instruction. It will also be important to determine if students change the type of
evidence they select, informative or uninformative, based on instruction as well. The types of
changes that occur, coupled with the instruction type, could provide valuable information
regarding how students learn, store and recall information regarding evolutionary understanding
and evidentiary support.
For instance, if more students have a scientifically accurate understanding of evolution,
but are still choosing uninformative evidence, this could indicate that the instructor is promoting
the conceptual understanding of evolution, but may need to try alternative teaching methods
regarding evidentiary support. Where if students have the same accuracy of understanding
evolution, but are choosing informative evidence, this could indicate that the instructor is being
explicit when teaching the differences between evidence types. In this case however, the
instructor may need to enhance instruction on the conceptual understanding of evolutionary
theory.
Acknowledgements
This work was supported by the Mississippi INBRE (P20RR016476) funded by the National
Center for Research Resources, National Institutes of Health.
UNDERSTANDING EVOLUTION AND EVIDENTIARY SUPPORT 16
References
Halverson, K.L. (2008, March). Paper presented at the annual meeting of the National
Association for Research in Science Teaching, Baltimore, MD.
Halverson, K.L. (2009, April). Paper presented at the annual meeting of the National Association
for Research in Science Teaching, Garden Grove, CA.
Baum, D. A., Smith, S. D., & Donovan, S. S. S. (2005). The tree-thinking challenge. Science,
310, 979-980.
Bransford, J.D., Brown, A.L., & Cocking, R.R. (2000). How people learn: Brain, mind,
experience, and school (Expanded ed.). Washington D.C.: National Academy Press.
Cooper, R.A. (2002). Scientific knowledge of the past is possible: Confronting myths about
evolution and scientific methods. American Biology Teacher, 64, 427-432.
Crisp, M.D., & Cook, L.G. (2005). Do early branching lineages signify ancestral traits? TRENDS
in Ecology and Evolution, 20, 122-128.
Enderle, P.J., Smith, M.U., & Southerland, S. (2009). Does prior knowledge matter? Do
Lamarckian misconceptions exist? A critique of Geraedts and Boersma (2006).
International Journal of Science Education, 31, 2527-2532.
Lord, T.R., & Marino, S. (1993). How university students view the theory of evolution. Journal
of College Science Teaching, 22, 353-357.