Research and Teaching
By Megan Nieberding, Sanlyn Buxner, Lisa Elfring, and Christopher Impey
If the 20th century was the century of physics, the 21st century has been touted as the century of biology (Venter & Cohen, 2004). It has been over 60 years since the molecular structure and the biological function of deoxyribonucleic acid (DNA) was discovered. Since then, understanding of DNA has driven enormous growth in genetics and biomedical science. Biology is underpinned by the coding and transmission of life’s information by DNA at the molecular level, and the evolution of organisms by natural selection at the species level. A case can be made that understanding DNA is as foundational for science literacy as understanding Darwin’s theory of evolution.
Biology is taught to almost every student in the United States during their K–12 schooling: 96% of students in the United States take basic biology at the secondary levels (Kena et al., 2015). DNA is the molecule at the heart of coding function and form in living organisms. Understanding DNA and concepts associated with it (e.g., genetic information, heredity) is necessary to understand media reports of biology, make health-care decisions, and to understand the spread and treatment of diseases in the world. An understanding of DNA is not only central to science education, but also for informed participation of college-educated adults in popular culture, modern health, and hygiene. Additionally, for college students in life-science majors, understanding DNA is crucial for them to build more complex understandings relevant to their coursework and future careers. Biology is the focus of this work because it constitutes a large and growing segment of the science, technology, engineering, or mathematics (STEM) major population. Biology also features prominently in societal debates over evolution, genetic engineering, and gene therapy in medicine. Ideally, we want the public to gain a well-rounded, accurate idea of how biology impacts our world, and ensuring this requires effective instruction for both science and nonscience majors.
In this study, we compared the knowledge of general-education students, both STEM and non-STEM majors, to students who were enrolled in a required introductory biology course for life-science majors at the same institution. The goal was to compare the biological and general science knowledge of our general-education students to that of students who had selected a biology-related major and were working toward careers in the life sciences. We additionally wanted to compare the science knowledge of students attending college compared to the general public. Overall, we were interested in whether students who were on paths to become future scientists and health-care professionals had greater scientific knowledge than the future lawyers, artists, and government officials (and others) in our non-STEM cohort. We also hoped to understand the topics students are struggling to understand, to be able to adapt science courses for both groups to focus on the areas of greatest difficulty.
We have been investigating students’ knowledge and attitudes about science, and our prior work has examined undergraduate students’ knowledge of basic science facts, beliefs in nonscientific phenomena (including astrology), and how students describe what it means to study something scientifically (Impey et al., 2011; Impey et al., 2012). We have collected data since 1989 from over 12,000 students enrolled in introductory astronomy courses, often used to fulfill a general education requirement. These students (henceforth called GenEd students) are primarily early-career college students who have completed from zero to the required two college-level science classes. The great majority of the students are nonscience majors. As documented elsewhere (Impey et al., 2011), these students are representative of the general (college-educated) public. The sample is approximately gender balanced. Our previous analyses have shown that these students outperform the general public on basic science questions, as measured by a survey administered by the National Science Foundation (NSF) and published in the biennial Science and Engineering Indicators (NSB, 2014). We have seen no overall change in students’ science knowledge over the 27 years of the survey, with a consistent average score of around 75% each year (Impey et al., 2012). Students who self-reported as STEM majors outperformed non-STEM majors in terms of science knowledge by only 5%. Based on these findings, we decided to take a closer look at STEM and non-STEM majors in the GenEd course and compare their answers to science majors taking an introductory biology course.
This study was conducted during the 2013–2014 academic year. We have collected data from our GenEd population since 1989, but started data collection from the students taking an introductory-biology course in 2013. Thus, we restricted our GenEd survey data for this study to that same year. We collected data from a total 397 GenEd students and 187 early-biology students. The survey includes both forced-choice and open-ended items in both physical and biological science (see Online Supplemental Materials). Physical science questions test basic facts such as knowing that light travels faster than sound and recognizing that the Earth goes around the Sun. Biological science questions test the knowledge that viruses cannot be killed by antibiotics, that humans and dinosaurs did not coexist, and that the inheritance of some diseases is governed by probability.
Early-biology students were students who committed to major in the life-sciences and were taking their first biology class in the Molecular and Cellular Biology Department at the University. This course highlighted DNA’s physical and chemical properties as well as its role in cells. The early-biology student sample represented future scientists, health-care practitioners, engineers, and chemists; we hypothesized that they would outperform students who were on a trajectory toward nonscientific professions.
To further test our prediction, we gathered additional data from a biological-research group at our university who assessed students with a survey containing overlapping questions with our survey. These students were selected to work in biology labs through the Undergraduate Biology Research Program (henceforth called advanced-biology students). To study the spectrum of students’ knowledge, we looked at similar questions answered by our GenEd students broken down by STEM and non-STEM majors, by early-biology students beginning their college career, and by advanced-biology students working in research labs between their second and final years in college. Because our questions overlapped with those used in a survey of the general public conducted by the National Science Board and published by the NSF in the Science and Engineering Indicators series (NSB, 2014), we were also able to compare the student responses to those of the general public.
For the analysis, GenEd students were separated into two main categories corresponding to students’ self-reported majors: those who had declared a major in the STEM majors and those who had not (non-STEM majors). All the early-biology students in the study were self-reported STEM majors.
The advanced-biology students participated in a highly selective research experience. These students had already completed their introductory science courses and all of whom were self-reported STEM majors. Data were collected from 127 students as part of an ongoing program evaluation of the research experience.
Finally, the NSF has commissioned a biannual survey of the general public since 1993 that addresses the public’s attitudes toward, and their perceptions of, science and society. These data are made publicly available for analysis. We used all the data (n = 2,256) but broke down results by individuals who did not go to college, those who had some college (most comparable to our sample), and those who had a college or post-Bachelor’s degree. Respondents answered questions during 2012, which were then published in the Science and Engineering Indicators 2014 report (NSB, 2014).
Most of the GenEd students were in their first two years of college (Table 1), and the majority had taken one or no college science classes (Table 2). Ten percent of the GenEd students reported being a STEM major, typically engineering, physics, biology, chemistry, and health science. Four students in the GenEd astronomy class were biology majors. The non-STEM majors included a large proportion of business or social and behavioral science (Table 3). In terms of gender, 57% of the GenEd students were male and 43% were female.
Most early-biology students were in their first two years of college. Over half (53%) had taken four or more college science classes before the introductory biology class, 27% took two or three science classes, and for 19% this introductory-biology course was their first or second science class in college (Table 2). The majority of the introductory biology students were majoring in health sciences (further breakdown of the majors is included in Table 3).
Most of the advanced-biology students were juniors or seniors in college (82%) and none were freshman. Almost all had taken four or more college science courses. These students were mostly life-science majors, including molecular and cellular biology, biochemistry, general biology, chemistry, bioengineering, and evolutionary biology majors. The rest majored in speech, psychology, engineering and other non-life-science majors.
The initial analysis of students’ survey responses included open-ended descriptions of DNA and descriptive statistics of the science knowledge scores. Analysis for the DNA free-response item (see Q13 in the Online Supplemental Materials) was based on our coding scheme for this question (Impey et al., 2012). The codebook originally derived was revised in collaboration with the instructor of the early-biology students’ course, an experienced biologist and science educator. Initial coding involved reading responses and binning it based on the categories in the codebook. For example, a statement stating DNA is “from your parents,” would be coded for heredity. Each response was read by 3 coders and intercompared. Each of the codes was grouped into a larger theme: incorrect ideas about DNA, physical characteristics of DNA, chemical characteristics of DNA, location of DNA in the cell, functions of DNA, how DNA is used in real-life situations, metaphors to describe DNA, and media references and trivial descriptions of DNA. To further our analysis, we looked for trends between students who mentioned specific DNA themes and popular phrases and their science knowledge scores or demographics. Finally, we compared the coded responses of the GenEd students and the early-biology students. The coding scheme was applied consistently across the different student groups.
To quantify students’ basic knowledge, we created a biological science–knowledge score and an overall science-knowledge score based on the forced-choice, science-knowledge items on the survey (see Online Supplemental Materials). The biological science–knowledge score included the nine life-science questions from the survey and was scored out of nine points (see Q3, Q8 and 9, Q16, Q17, and Q19A–D in the Online Supplemental Materials). The overall science-knowledge score included all the force-choice items answered and had a maximum score of 17 points.
The GenEd students had an average science-knowledge score of 13.7 points out of 17 (81%) and an average biological science–knowledge score of 7.1 out of 9 (79%) points (Table 4). Although the STEM majors in the GenEd class scored slightly higher than the non-STEM majors, these differences were not statistically significant, (t = 1.76 p > .05; t = 1.31, p > .05). The STEM majors had an average science-knowledge score of 14.4 points (84%), and an average biological science–knowledge score of 7.4 points (83%). Among the GenEd students, science majors had the highest scores and education majors had the lowest scores for both science-knowledge measures.
The early-biology students had an average overall science score of 14.4 points (85%) and a biological science score of 7.6 points (84%). The GenEd STEM students and the early-biology students had statistically indistinguishable scores (p > .05). This suggests that students on a STEM major path enter college having learned the same information in high school and in other nonschool settings prior to college.
Additionally, we compared the GenEd and early-biology students to both the advanced-biology students and the general public (NSF sample) for three of the five biological questions that overlapped on all four surveys. These three true/false items are questions 8, 16, and 17 in the Online Supplemental Materials. This was to assess the difference in biology knowledge between students who chose to go to college, students who chose a STEM major, and the general public (separated into those who did not go to college, those who had some college, and those who had a Bachelor’s or more advanced degree).
Figure 1 shows that the advanced-biology students outperformed every other group on the question regarding antibiotics. On the other hand, the early-biology students outperformed every other group on the item regarding radioactive milk, whereas the percentage of STEM and non-STEM students that answered that question correctly was similar. Additionally, only 51% of the general public answered the evolution question correctly, compared to 91% of the GenEd STEM students. This presumably reflects the fact that STEM majors have more classroom exposure to evolution than the average member of the public. Interestingly, the GenEd STEM students out-performed the early-biology students on this item; this may indicate a gap in the biology education of the majors, who are largely working on cellular and molecular biology in their coursework and research. The evolutionary-biology classes that cover evolution generally are taken after the introductory-biology course described in this study. However, 100% of the advanced students majoring in evolutionary biology answered this question correctly. The lowest scores among the general public on the antibiotics and evolution questions were from individuals who do not have any college education.
We note the following surprising or unanticipated results from Figure 1. Over a third of early-biology students thought that antibiotics kill viruses, which is a basic error in biology and health medicine. Early-biology students do not do better than non-STEM students in knowing that humans evolved from earlier species of animals. Even more surprisingly, advanced-biology students do slightly worse than early-biology students in recognizing the fact of human evolution and the fact that radioactive milk cannot be rendered safe by boiling it. These are substantial holes in the basic biological knowledge of students who have chosen life sciences as their field of study.
In Figure 2 we present results about two other biology-related questions in our survey, questions 3 and 5. The early-biology students scored significantly higher than the GenEd non-STEM students, but had comparable scores to the GenEd STEM majors on these questions. We also looked at questions 19A to 19D individually because they provide an extra metric for knowledge by combining biology with probability and statistics. In Figure 3, the early-biology students significantly (p < .05) outperformed the other students on just one of the questions (Illness 3); for all other questions, students performed basically the same (p > .05). Early-biology students are still somewhat confused about the independence of outcomes in different offspring (Illness 2 and Illness 4). This agrees with findings from other studies (Lewis & Wood-Robinson, 2000; Stewart et al., 1990). The use of probability as applied to independent events is core to the understanding of genetics and health science.
Next, we looked at the differences between the early-biology and GenEd student responses to the open-ended question in the survey asking “What is DNA?” (Q13 in Online Supplemental Materials). We were curious if students studying biology, as well as other STEM majors, would give more descriptive, accurate responses with fewer incorrect or trivial answers. We found that 43% of early-biology students mentioned that DNA contains information, compared to 20% of the non-STEM majors. Additionally, 56% of the early-biology students related DNA to genetics, compared to 42% of the non-STEM majors. On the other hand, only 2% of the early-biology students described DNA as being unique to each person or living thing, compared to a much larger 22% of the non-STEM majors. We postulate that early-biology students’ responses may reflect instruction about how similar DNA sequences are within a species (or between closely related species) over the smaller differences in sequences between individuals. Surprisingly, early-biology students used trivial or uninformative descriptions of DNA as often as the GenEd students (43% of the time) and they mentioned incorrect ideas as frequently as non-STEM majors (25% of the time). Apparently, early-biology students maintain some of the same misconceptions and simplistic ideas they had in high school or even earlier.
In their written responses, early-biology students mentioned specific topics that are relevant to DNA more often than nonscience majors (Figure 4). For example, 56% of early-biology students said that DNA is related to genetics or that it stores information, but only 4% said that the DNA is hereditary or heritable. This is a surprising omission. Students using the word “genetic” typically failed to qualify their statements, whereas students using the word “hereditary” often continued, for example stating that “it is passed on from generation to generation.” The fact that early-biology students describe DNA as something “genetic,” as opposed to mentioning that DNA that contains “heritable information” is similar to what is reported in other studies (Lewis, 2004; Duncan et al., 2009).
Figure 5 shows that students from all groups offered trivial or uninformative descriptions of DNA. These responses included spelling out DNA as deoxyribonucleic acid and stating that DNA is “what makes us up.” Early-biology students spelled out deoxyribonucleic acid more often than the GenEd non-STEM students. Only 7% of the early-biology students indicated DNA is “what makes us up,” compared with 20% of the GenEd, non-STEM students. Spelling out DNA is formally correct, but does not indicate understanding. There are many biological components in humans, of which DNA is just one. Figure 6 shows that GenEd STEM students used metaphorical statements more often than the early-biology and non-STEM students. For all three groups, the most popular metaphor is that DNA contains a code. A typical statement is “The unique genetic code that exists in our bodies.” Students using these metaphorical statements may be in the preliminary stages of being science literate, because these expressions build the foundation for sophisticated stages of comprehension (Koballa et al., 1997).
Next, we considered the incidence of erroneous answers and misconceptions in the open-ended responses. Figure 7 shows that the most common incorrect ideas among all the student groups examined corresponded to students noting that DNA relates to only humans, that it relates only to complex life, and it is “what we are made of.” Non-STEM majors related DNA to being a feature unique to humans 10% more frequently than STEM and biology students, whereas the early-biology and STEM students related DNA to complex life more frequently. As seen in other studies, students frequently recognized genetic variation in humans rather than plants, complex life, and mammals (Duncan et al., 2009). A substantial fraction of early-biology students, just over a quarter, invoked these various errors, not much less than the third of non-STEM majors that invoked them. This is a disconcerting outcome for students who have chosen life science as their field of study.
This exploratory study gives us insight into what our students come to college knowing about science, and specifically about biology. STEM and non-STEM majors enter college at essentially the same understanding level. Not surprisingly, students not inclined toward science did not score as highly as science-oriented students, but they had higher science literacy than people who decided not to attend college. On the other hand, it is surprising that science-oriented students display substantial holes in their core science knowledge and fundamental misconceptions about biology and DNA.
The good news is that lower-division undergraduate students in general scored 81% on a set of 17 basic science knowledge questions, substantially higher than the general public. However, STEM majors only scored 10% higher than non-STEM majors, and on life-science questions, biology majors only scored 10% higher than non-STEM majors. Elsewhere, we have shown that the gain in science knowledge of non-STEM majors between entering college and graduating after taking three general-education science classes is less than 10% (Impey et al., 2012). These well-educated young adults do not have substantially improved knowledge after what is likely to be their last formal exposure to science.
At the same time, the NSF released updated results for their survey in 2018, and after briefly analyzing their results, we noticed that the public’s science knowledge remained nearly the same as in 2014 (NSB, 2018). This means that college-educated students have a more solid foundation in understanding science and biology than the general public. In the end, all these students will be participating in a highly technological society in which knowledge of biology is essential.
In detail, by using true-false questions that address core life science facts and applying consistent coding schemes for a free-response description of DNA, we have uncovered substantial and surprising gaps in the knowledge of biology-tracked students. Advanced-biology students knew better than all other students that antibiotics cannot kill viruses, but they scored worse than non-STEM majors in knowing that humans evolved from other species (although all of the evolutionary-biology students answered this correctly). This result likely reflects the societal resistance to the acceptance and teaching of evolution in our schools. On the central question of their understanding of DNA, early-career biology majors related DNA to information and to genetics more often than non-STEM majors; both groups mentioned incorrect ideas at the same rate, and few biology majors said that DNA was hereditary. Regardless of major, students who reported that DNA connected to genetics and heredity also had higher overall scores of science knowledge.
Early-career STEM majors were less likely to use some incorrect or uninformative descriptions to discuss DNA than non-STEM majors. Non-STEM GenEd students tended to use language that was human-centric in describing the role of DNA. On the other hand, GenEd STEM majors and early-biology students were much more likely to indicate that DNA is characteristic of higher organisms, which is incorrect. Very few students in science majors seem to be aware that DNA stores heritable information. Instructors working with science students need to stress that all life relies on DNA as hereditary material.
Gaps in students’ biological knowledge are present throughout their time in college, even among the students who choose biology or medicine as a career or who are actively doing biological research. That result is the most significant outcome of this study. College instructors need to re-double their efforts to expose all students to the important “big ideas” of science. Biology instructors need to ensure that both nonmajors and STEM-focused students have opportunities to develop a nuanced and accurate understanding of the foundations of biology. What can biology and general-education instructors do, in designing interventions, to alter this persistent problem? Evidence-based teaching strategies can go a long way toward helping students to improve their conceptual understanding. Active-learning strategies that include tasks where students grapple with the key ideas in real-world contexts, such as problem-based learning or scenarios, are one place to start. Another strategy is to use problems that require students to “zoom in” to focus on details and mechanisms, and then to “zoom out” to relate the topic to phenomena such as health or disease, ecosystem diversity, or population size, that students experience in their everyday experiences. Approaching biology through a systems lens spurs understanding at a variety of levels. More focus on the core ideas of biology and how these ideas and processes impact us in our daily lives has been recommended by a variety of sources (NRC, 2003; AAAS, 2010). Finally, our work shows that we cannot assume that biology majors have all the answers—it is important for instructors to recognize that majors also need opportunities to explore topics throughout the hierarchy of scales in life science. For example, the micro-scale mechanism of information storage in DNA maps to the macro-scale mechanism of evolution by natural selection. In some ways, it is easier to maintain a big-picture focus when teaching nonmajor students. Communication between those who teach majors and those who teach general-education students might allow for a more consistent and evidence-based approach to teaching these key ideas. ■
This material is based on work supported by the National Science Foundation under award number 1244799. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation. We thank the hundreds of students who took the time to complete surveys.
Megan Nieberding (Nieberding.email@example.com) is a graduate student in the Department of Physics at Ohio State University in Columbus, Ohio. Sanlyn Buxner is an associate research professor of science education in the Department of Teaching, Learning, and Sociocultural Studies, Lisa Elfring is associate vice provost for instruction and assessment and associate specialist in molecular and cellular biology, and Christopher Impey is a university distinguished professor in the Department of Astronomy, all at the University of Arizona in Tucson, Arizona.
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