Understanding Evolution and Evidentiary Support

Running Head: UNDERSTANDING EVOLUTION AND EVIDENTIARY SUPPORT 1

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

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

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

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.

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.”

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.

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.

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

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.

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).

Table 4. Cross tabulation of Students Understanding of Evolution and Evidence Type Chosen

Evidence

Understanding of Evolution

Total Scientific Naïve

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.

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

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

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

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.

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

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Baum, D. A., Smith, S. D., & Donovan, S. S. S. (2005). The tree-thinking challenge. Science,

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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

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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.

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