Understanding how to read and interpret phylogenetic trees is an essential skill for biology students. We tested an alternative approach in which students draw trees showing the evolution of familiar nonliving objects, such as cell phones and vehicles, rather than unfamiliar species. We surveyed students in a two-semester biology sequence for majors to determine whether this approach increased engagement, and we found that they preferred the alternative approach. Another group of students performing the activity with nonliving objects showed that performance on a content assessment was not changed before and after the activity. A final group showed that students who had drawn trees of nonliving objects beforehand were able to draw phylogenetic trees of living species more accurately than classmates who did not draw them previously. Although drawing trees of nonliving objects rather than living species did not affect students’ content-learning outcomes, it did improve their ability to draw phylogenetic trees accurately, and they preferred it. These pieces of evidence suggest that drawing trees showing the evolution of nonliving objects is an engaging and beneficial addition to evolution lesson plans.

Introduction

Educating high school and undergraduate students in the processes of evolution and confronting their misconceptions is one of the greatest challenges in American science education. Students often enter biology courses with deeply held misconceptions about mechanisms of evolution such as natural selection, as well as misconceptions about how species and other taxa change and arise over long periods. Misconceptions about natural selection have traditionally received substantially more attention (Meir et al., 2007) than those about speciation and evolutionary relationships, although understanding how groups of species are related is arguably as important, and more lacking in the American public (Pew Research Center, 2013). Such relationships among groups of organisms have been depicted visually using phylogenetic trees since Origin of Species, and understanding these trees has become essential to biology and biology education (Baum et al., 2005; Gregory, 2008).

Alternative methods for engaging students, such as modeling with household objects (e.g., Byrd, 2000) or connecting concepts with pop culture or fictional characters (e.g., Pryor, 2008; Cruz, 2013), are common in biology education literature. Since these engaging methods have been widely explored previously to use common materials to teach “abstract” biological concepts such as genetics and natural selection, we saw a need to create more engaging activities to teach students how to read and infer phylogenetic trees. Approaches that have been used include inventing organisms to classify (such as “Caminalcules”; see Gendron, 2000) and making phylogenies of chocolate bars (Burks & Boles, 2007). In the latter example, the authors explained that students are more familiar with chocolate than with model organisms like finches (and enjoy it more). We agree with these authors that common, familiar objects may engage students more than organisms they are not familiar with.

Here, we question whether an alternative approach, creating phylogenetic trees of familiar objects rather than of living taxa, would engage students and improve functional learning of phylogenetic trees. The concept of using trees to display relationships among members of a group is broadly applicable and has been used in fields outside of biology to show how groups have changed over time (e.g., Kraaijeveld, 2000). We hypothesized that students developing phylogenetic trees of familiar objects would be effectively engaged and would still successfully learn how to draw phylogenetic trees of living species. We also predicted that (1) given a choice, students would prefer phylogenies of familiar objects over those of unfamiliar biological groups; and (2) because of this familiarity, they'd be able to accurately draw trees depicting the relationships and “evolution” of common objects with little training.

Context & Student Participants

Our measurements of student engagement and learning gains were collected from four cohorts (see Table 1) taking a two-semester sequence of introductory biology for biology majors at a 4-year public undergraduate institution. The first course focuses on concepts that unify life – molecules of life, cell structure and function, genes and gene expression, and heredity. It is a prerequisite for the second course, which focuses on concepts that differentiate life: evolution and diversity of microbes, plants, fungi, and animals; ecology; and environmental biology. Although the courses do not need to be taken consecutively, students routinely do so.

Table 1.
Student cohorts that participated in this project.
CohortIIIIIIIV
Semester Summer 2013 Fall 2013 Fall 2013 Spring 2014 
Instructor Lampert Lampert Mook Lampert 
Number of Student Participants 27 37 42 Subgroup A: previous members of Cohort III
(18, 19)* 
Subgroup B: not members of Cohort III
(57, 61)* 
Biology Course Sequence Second course Second course First course Second course 
Tree Type Used Choice of living or nonliving Choice of living or nonliving Nonliving Living 
Activity Engagement survey Engagement survey Pre- and post- test with testbank questions Pre- and post-test with phylogenetic-tree handout 
CohortIIIIIIIV
Semester Summer 2013 Fall 2013 Fall 2013 Spring 2014 
Instructor Lampert Lampert Mook Lampert 
Number of Student Participants 27 37 42 Subgroup A: previous members of Cohort III
(18, 19)* 
Subgroup B: not members of Cohort III
(57, 61)* 
Biology Course Sequence Second course Second course First course Second course 
Tree Type Used Choice of living or nonliving Choice of living or nonliving Nonliving Living 
Activity Engagement survey Engagement survey Pre- and post- test with testbank questions Pre- and post-test with phylogenetic-tree handout 

*Numbers in parentheses indicate different numbers of students taking the pre- and post-assessments.

Cohorts I and II participated in this study by responding to surveys after completing an active-learning-based systematics and diversity module at the start of the second course. Cohort III participated in this study by completing assessments of concept-learning gains before and after an activity drawing nonliving trees in the first course of the sequence. Cohort IV, which included several students who had participated in Cohort III (see Table 1), participated in this study by completing assessments of skill-learning gains (drawing trees) at the beginning and end of the systematics module in the second course of the sequence.

The systematics module used in the second course includes both guided- and open-inquiry approaches and features collaborative learning. Students complete this module, which lasts four weeks, in teams of three to five. In the first two weeks, the guided-inquiry portion of the module consists of teams developing two phylogenetic trees of beetles, using morphological characteristics and amino acid sequence data of five beetle species that they select (for a full description of this activity, see http://www.beanbeetles.org/protocols/bioinformatics/synopsis.html). The open-inquiry portion of the module that follows consists of student teams developing and contrasting two phylogenetic trees of the same group of organisms from two different types of data. Upon instructor approval, students are allowed to select any group of eight organisms they can find sufficient characteristic data for, and they are encouraged to obtain a variety of types of characteristic data, including but not limited to morphological, chemical, behavioral, physiological, and nucleic acid base or amino acid sequences. Students may collect data from online sources, including a required number of peer-reviewed publications, and from their own observations. At the end of the module, students are assessed by presenting posters of their projects.

Student Engagement & Attitudes

Engagement and attitudes were measured in Cohorts I and II. During the summer and fall 2013 semesters, students completing the systematics and diversity module were given the option to modify their open-inquiry exercise by replacing living species with nonliving objects.

Combining both cohorts, 13 of 16 student teams chose nonliving objects over living species, although groups such as “Bug-type Pokémon” (considered nonliving) and “football team mascots” (considered living) fell somewhat between categories. The overwhelming choice to select nonliving objects can be explained in part by the novelty of being allowed to choose, as well as by their unfamiliarity with enough species to infer quality trees. Students tended to be more innovative in devising different types of characteristic data for nonliving “trees”; an example submission from summer 2013 showing how car motor technology and physical form changed in the past century is provided in Figure 1.

Figure 1

Reproduction of two trees of automobiles created by Cohort I (summer 2013) students, showing (A) design changes over time (analogous to morphology) and (B) engine changes over time (analogous to physiological innovations). Students obtained all information from common online image searches. These two trees differed substantially because the students selected number of wheels (three versus four) and roof (convertible) characteristics for tree A, which were design characters that did not match propulsion systems (analogous to convergent characteristics).

Figure 1

Reproduction of two trees of automobiles created by Cohort I (summer 2013) students, showing (A) design changes over time (analogous to morphology) and (B) engine changes over time (analogous to physiological innovations). Students obtained all information from common online image searches. These two trees differed substantially because the students selected number of wheels (three versus four) and roof (convertible) characteristics for tree A, which were design characters that did not match propulsion systems (analogous to convergent characteristics).

Surveys given to students in Cohorts I and II also included three items related to engagement (see Table 2). Responses showed that students believed that drawing trees of nonliving objects improved, rather than hindered, their ability to infer phylogenetic trees (Figure 2). Sample student responses are provided in Box 1. Actual content knowledge and skills were tested more explicitly in Cohorts III and IV.

Table 2.
Transcribed responses of surveys given to Cohorts I & II. Each item was answered only by students who selected nonliving objects to draw a tree (n = 37).
Item 1. Did developing this tree enhance your knowledge of phylogenies? (See Figure 2 for data.) 
  • “By using more familiar, common objects this process came with more ease.”

 
  • “Being able to classify nonliving objects ensured that we could do this with living organisms.”

 
  • “The concept of phylogenies was easier to understand with making a phylogenetic tree of nonliving things.”

 
  • “The nonliving objects tree was a more tangible, relatable version of a complex live species tree that acted well as an intermediate step toward understanding a real, live species tree. It was a great idea!!!!”

 
  • “Helped us identify similarities and differences between two objects/organisms. Showed us the concept can be applied to even nonliving things.”

 
  • “I can now create more trees from both living and nonliving things. If I can do something abstract, then normally will be easy.”

 
Item 2. Did developing this tree hinder your knowledge of phylogenies? (See Figure 2 for data.) 
  • “It actually furthered my knowledge b/c prior to the assignment, I was pretty confused as to how to construct a tree, so making a tree with the nonliving things gave me a better understanding of the concept.”

 
  • “It was simpler to relate the phylogeny to a real-world example. It helped me better understand the basics.”

 
  • “Trees of nonliving objects could simplify the concept too much and important details could be overlooked”

 
  • “It helped more than hinder if hindered at all”

 
Item 3. Did developing this tree engage you more or less than a phylogenetic tree of living species? (77% answered more) 
  • “More because I felt like I actually understood what I was doing.”

 
  • “Phylogenetic trees of nonliving species are more interesting and fun.”

 
  • “Because it made it easier for me to create a mental picture of where each species went in the phylogenetic tree/structures, I could easy put the phylogenetic tree or living species more easily.”

 
  • “Not all phylogenetic trees have to be constructed with living organisms, so using objects (such as clothes or cell phones) that I am familiar with helped me understand for future reference.”

 
  • “I feel like I would have learned more if I had done something living since they have many traits that can be differentiated easily.”

 
  • “In order to make a phylogenetic tree of a living species, we would have only had to click a few links online. For a nonliving object, we had to do the work ourselves. Also, we were more interested in our nonliving objects than living species.”

 
  • “Relating to something I understood more helped me to become more invested in the project.”

 
Item 1. Did developing this tree enhance your knowledge of phylogenies? (See Figure 2 for data.) 
  • “By using more familiar, common objects this process came with more ease.”

 
  • “Being able to classify nonliving objects ensured that we could do this with living organisms.”

 
  • “The concept of phylogenies was easier to understand with making a phylogenetic tree of nonliving things.”

 
  • “The nonliving objects tree was a more tangible, relatable version of a complex live species tree that acted well as an intermediate step toward understanding a real, live species tree. It was a great idea!!!!”

 
  • “Helped us identify similarities and differences between two objects/organisms. Showed us the concept can be applied to even nonliving things.”

 
  • “I can now create more trees from both living and nonliving things. If I can do something abstract, then normally will be easy.”

 
Item 2. Did developing this tree hinder your knowledge of phylogenies? (See Figure 2 for data.) 
  • “It actually furthered my knowledge b/c prior to the assignment, I was pretty confused as to how to construct a tree, so making a tree with the nonliving things gave me a better understanding of the concept.”

 
  • “It was simpler to relate the phylogeny to a real-world example. It helped me better understand the basics.”

 
  • “Trees of nonliving objects could simplify the concept too much and important details could be overlooked”

 
  • “It helped more than hinder if hindered at all”

 
Item 3. Did developing this tree engage you more or less than a phylogenetic tree of living species? (77% answered more) 
  • “More because I felt like I actually understood what I was doing.”

 
  • “Phylogenetic trees of nonliving species are more interesting and fun.”

 
  • “Because it made it easier for me to create a mental picture of where each species went in the phylogenetic tree/structures, I could easy put the phylogenetic tree or living species more easily.”

 
  • “Not all phylogenetic trees have to be constructed with living organisms, so using objects (such as clothes or cell phones) that I am familiar with helped me understand for future reference.”

 
  • “I feel like I would have learned more if I had done something living since they have many traits that can be differentiated easily.”

 
  • “In order to make a phylogenetic tree of a living species, we would have only had to click a few links online. For a nonliving object, we had to do the work ourselves. Also, we were more interested in our nonliving objects than living species.”

 
  • “Relating to something I understood more helped me to become more invested in the project.”

 
Figure 2

Student-engagement survey responses from Cohorts I and II (summer and fall 2013). More students believed that inferring phylogenies of nonliving objects was more a benefit than a hindrance in learning biological phylogenetic trees (Fisher's exact test, P < 0.0001, n = 37).

Figure 2

Student-engagement survey responses from Cohorts I and II (summer and fall 2013). More students believed that inferring phylogenies of nonliving objects was more a benefit than a hindrance in learning biological phylogenetic trees (Fisher's exact test, P < 0.0001, n = 37).

Student Learning Gains

We used Cohorts III and IV to see whether content knowledge and skills were affected by the activity. Only Cohort III participated in the alternative approach to drawing phylogenetic trees in the first course. Because several students from Cohort III continued into Cohort IV the next semester (see Table 1), we were able to compare, within Cohort IV, the learning gains of students who had drawn trees of nonliving objects with those of students who had not.

Cohort III. Cohort III members, which presumably had no prior college education about phylogenetic trees, were assigned an activity of drawing a phylogenetic tree based on nonliving objects (computers, cell phones, automobiles, video games, writing utensil) of their choice (for an example, see Figure 3) in the last three weeks of the first course. An assessment created using the testbank from Reese et al. (2012) was given to students before the activity as an in-class assignment and was also incorporated into the course's comprehensive final exam ( Appendix 1).

Figure 3

Scan of student-drawn phylogenetic tree of toys from Cohort III (fall 2013). This team of students had no prior training about how to draw phylogenetic trees. While the structure of the tree is generally correct, this tree has two representative errors. First, there is no information explaining how lineages differentiate after nodes N1, N2, N3, and N4 (added by authors in red). Second, “plastic” and “furry” are emergent characteristics, and the tree as drawn suggests instead that “plastic toys” and “furry toys” are ancestors of all of the other toys.

Figure 3

Scan of student-drawn phylogenetic tree of toys from Cohort III (fall 2013). This team of students had no prior training about how to draw phylogenetic trees. While the structure of the tree is generally correct, this tree has two representative errors. First, there is no information explaining how lineages differentiate after nodes N1, N2, N3, and N4 (added by authors in red). Second, “plastic” and “furry” are emergent characteristics, and the tree as drawn suggests instead that “plastic toys” and “furry toys” are ancestors of all of the other toys.

Overall, J.M. received paired pre- and post-assessment scores from 42 students in Cohort III. Pre- and post-assessment scores did not differ (paired t-test: t42 = −0.102, P = 0.92); however, 19 students showed a higher score (mean = 1.3 more correct answers) while 15 students showed a lower score (mean = 1.56 more incorrect answers) on the post-assessment.

Cohort IV. Cohort IV students participated in the systematics module of the second course. These students completed handouts twice as pre- and post-assessments of their ability to draw phylogenetic trees. The handout, which was given to students during the first lab of the semester and at the conclusion of the systematics module, instructed students to create a table of characteristics using photographs of moths and butterflies (Junonia coenia, Trichoplusia ni, Helicoverpa zea, Manduca sexta, and Spilosoma virginica) and then draw a tree based on those characteristics (Figure 4). Errors made by the students in filling out tables and drawing trees were recorded and split into 22 types of errors in three categories (see  Appendix 2).

Figure 4

Representative phylogenetic trees of five moths and butterflies (students were not told the identities of species A–E) from the pre-assessment given to Cohort IV (spring 2014). These trees compare (A) students in Subgroup A (who had drawn phylogenetic trees of nonliving objects in the previous semester) and (B) students in Subgroup B (who had not).

Figure 4

Representative phylogenetic trees of five moths and butterflies (students were not told the identities of species A–E) from the pre-assessment given to Cohort IV (spring 2014). These trees compare (A) students in Subgroup A (who had drawn phylogenetic trees of nonliving objects in the previous semester) and (B) students in Subgroup B (who had not).

Cohort IV assessments were analyzed by splitting the cohort into two subgroups, those who had been members of Cohort III the previous semester (Subgroup A) and those who had not (Subgroup B). For the pre-assessment, there were 18 students in Subgroup A and 57 students in Subgroup B. We compared how many in these two subgroups made each type of error using Fisher's exact tests.

The most frequent error students made was to not label the emergence of characteristics on the trees (so that branches at nodes were not explained), and this did not differ between the two subgroups (P = 0.60); in fact, the two subgroups did not differ in rates of making any of the errors. Students in Subgroup A had a slightly higher tendency (not significant; P = 0.053) to make errors in how they drew roots and branches. These tests were mostly not significant because there were too few different outcomes to compare with the tests (i.e., too few Subgroup A members made errors). Subgroup A members had a tendency to make fewer errors in selecting appropriate physical characteristics from observations. Specifically, all 18 Subgroup A members clearly described the type of characteristics selected (e.g., “elongated body”) while seven members of Subgroup B listed vague characteristics (e.g., “body”). Only one member of Subgroup A repeated traits of a single characteristic several times in a table (e.g., “brown wings,” “gray wings,” “yellow wings”), while 11 members of Subgroup B made this error.

The post-assessment was completed by 80 members of Cohort IV, 19 of whom were in Subgroup A and 61 of whom were in Subgroup B (six students didn't draw trees on the first assessment). We compared student performance between the two assessments by counting the numbers of different errors ( Appendix 2) made when drawing trees. On the pre-assessment, every student made at least one error, with a range of 1–8 errors. On the post-assessment, 23 of 80 students made no errors, with a range of 0–3 errors (Figure 5). We used repeated-measures analysis of variance (ANOVA), treating subgroup (A vs. B) as the independent variable and pre- and post-assessment scores as within-subject factors. Overall, pre- and post-assessment scores were significantly different (F1,68 = 124.37), indicating that students made fewer errors on the post-assessment than on the pre-assessment (Figure 5). Because the factor*subgroup interaction was not significant (F1,68 = 0.98, P = 0.33), the amount of improvement did not differ between the two subgroups (Figure 5). Subgroup A members had an average of 2.71 fewer errors in the post-assessment, while Subgroup B members had an average of 2.27 fewer errors.

Figure 5

Comparison of numbers of different errors made by students in Cohort IV in a tree-drawing assessment. Pre-assessments were completed before a systematics teaching module, and post-assessments were completed after it. Subgroup A had drawn phylogenetic trees of nonliving objects in the first semester, whereas Subgroup B had not. Box points represent the 25th, median, and 75th percentiles; whiskers represent the 10th and 90th percentiles. Means are represented by symbols (●).

Figure 5

Comparison of numbers of different errors made by students in Cohort IV in a tree-drawing assessment. Pre-assessments were completed before a systematics teaching module, and post-assessments were completed after it. Subgroup A had drawn phylogenetic trees of nonliving objects in the first semester, whereas Subgroup B had not. Box points represent the 25th, median, and 75th percentiles; whiskers represent the 10th and 90th percentiles. Means are represented by symbols (●).

The post-assessment data also revealed several emergent trends. The most common error made during the post-assessment, made by 14 of 19 (74%) Subgroup A members and 26 of 57 (46%) Subgroup B members, was not matching emergence of characteristics to nodes and branches. We considered the number of characteristics not matched correctly, out of five possible, to be the main quantitative indicator of student proficiency. Subgroup A members, on average, mismatched 1.86 ± 0.25 (mean ± SE) characteristics to nodes; whereas Subgroup B members, on average, mismatched 2.50 ± 0.21 possible characteristics to nodes (unpaired t-tests showed that Subgroup A means were lower; P = 0.03). Subgroup A members had a tendency, though not significant (P = 0.06), to not label emergent characteristics on the tree (the most common error from the pre-assessment).

Linking Engagement to Assessment of Learning Outcomes

Our hypotheses were mostly supported. First, our survey results showed that students in Cohorts I and II were engaged by the option to draw trees of familiar objects, even if they were not living species, and preferred that over the option of drawing trees of unfamiliar living species. Research has shown that engaging students is an important part of education that significantly promotes critical thinking and improves performance (Kuh, 2001; Carini et al., 2006). Our results support those findings, as we found no negative effect of drawing trees of nonliving objects on learning gains and that students who drew trees of nonliving objects (Subgroup A of Cohort IV) were able to more accurately draw phylogenetic trees of living organisms than their counterparts in Cohort IV who had not. Specifically, these students were more able to correctly draw nodes and branches that matched their observations. We were not able to directly correlate engagement and assessment results, however, as a result of using separate cohorts.

Surprisingly, Cohort III did not show improvement in their post-assessment survey. Because we were interested in students’ existing skills in drawing trees showing relationships, students who drew trees of nonliving objects received no instruction and had no stake in performing well (the activity was not graded for accuracy, only completion). Thus, student misconceptions about how to draw phylogenetic trees potentially continued uncorrected until the post-assessment. Demographics may also explain the lack of improvement between the two assessments; J.M.'s courses were added to the registration schedule in the summer, and the class roster was made up primarily of students who either chose not to register during earlier registration periods or couldn't register previously because of academic holds due to their incoming-freshman status. However, even if students did not appear to have improved their assessment scores substantially by drawing trees of nonliving objects, the extra experience of drawing trees was shown to be beneficial, in that those students were able to draw trees more accurately following the initial exercise.

Suggestions for Teacher Implementation

Drawing phylogenetic trees of nonliving objects is a fun and engaging activity for both students and instructors, and we have shown that it is beneficial in learning about phylogenetic trees of living species. Although biodiversity and biological evolution are essential and irreplaceable concepts in science education, we believe that adding an activity in which students draw trees of nonliving objects can be an effective supplement. Such an activity can be implemented in a variety of settings, although we consider an active, collaborative learning environment essential.

Developing an Activity

An activity that tasks students with drawing trees of familiar nonliving objects can be added at the beginning of a systematics unit or chapter to engage students in the concept. We suggest a collaborative activity in class (rather than homework) in which students work in pairs or small groups; this activity can be completed in lab (as E.L. did) or in class to replace a day of lecturing (which students may likely appreciate). Students at a level similar to those we've worked with (freshmen/sophomores in introductory courses) should be able to draw a tree within a single 1-hour class period. An activity to draw phylogenetic trees of familiar objects may be graded or ungraded, depending on desired outcomes. If trees are graded, we recommend that the first tree be for practice and turned in only for feedback, with a subsequent tree graded by the instructor.

An activity in which students draw trees of nonliving objects can be implemented with different levels of rigor to fit a variety of course contexts. A smaller number of objects, such as four, to classify should be an appropriate modification for high school students. Students in introductory college courses should be able to draw trees with five or more items. Students in upper-level college courses would enjoy such an activity as a low-stakes “refresher” before rigorous activities for inferring phylogenies start. Increasing the number of objects that need to be in a tree to 8–10 can increase the rigor. Presenting phylogenies in a poster or oral presentation to classmates will also increase the rigor of the activity. Cohorts I and II were also required to find primary publications to support their trees; since these students barely knew how to find and read research articles, finding sources outside of biology significantly increased the rigor of the project.

The objects selected are very important. We allowed teams considerable freedom in selecting what objects (e.g., cars, cell phones, clothing) they grouped in trees. Students mostly enjoyed selecting objects themselves, despite a few challenges (e.g., one team in Cohort I had a difficult time organizing two different types of phone characteristics). Allowing teams to select their own objects to group is also more stimulating to the instructor. Because students may choose objects that are difficult to group in a tree, in most cases the instructor will need to briefly meet with each team to ensure that they are selecting objects that can be grouped easily and are selecting usable characteristics. Some objects can be difficult to find good photographs of; so, when possible, we suggest that the students try to find the physical objects themselves (e.g., compare each other's phones or the clothing of nearby students). The activity may be easier or more difficult if the instructor selects the objects, depending on whether the students are very familiar with the objects the instructor selects.

Addressing Student Errors

This activity was a low-stakes opportunity to discover and then address the most common errors students made when drawing phylogenetic trees. We were able to show students that nodes that split branches were associated with the emergence of new characteristics, and that it was necessary to label the emergence of characteristics on the tree to understand why lineages branch. Allowing students to review and correct their submissions is a useful way to reinforce knowledge about inferring trees. If time permits, it is also useful to discuss the errors the class has made, and discuss how those errors lead to inaccurate phylogenies.

Benefits & Drawbacks

There are numerous considerations when designing a new activity. Students can be more engaged when selecting their own objects. In addition, they will be more knowledgeable about features of these objects than about characteristics of unfamiliar species. This activity can also provide numerous analogies for discussion about how living and nonliving things change. Conversely, nonliving objects may not show transitional forms as logically or accurately as living species. Also, the modifications in these objects are driven by human wants and economic gain rather than natural selection. Finally, these student-selected lineages may be more open to interpretation than actual lineages of living species.

This project was supported through an Innovative Teaching Award from the University of North Georgia (UNG) Center for Teaching, Learning, and Leadership. Ashley Lafoy, UNG undergraduate student, assisted with data collection from student surveys. Students in Biology 1107 and Biology 1108 created and provided phylogenetic trees during the summer 2013, fall 2013, and spring 2014 semesters. Nancy Dalman, Frank Corotto, and anonymous reviewers provided helpful comments on the manuscript.

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Appendix 1. Pre-assessment questions provided to Cohort III, as selected from a published testbank (Reese et al., 2012).

  1. Which of the following pairs are the best examples of homologous structures?

    • (A)

      porcupine quill and cactus spine

    • (B)

      bat forelimb and bird wing

    • (C)

      Australian mole and North American mole

    • (D)

      bat wing and human hand

    • (E)

      owl wing and hornet wing

    Use Figure A1 to answer the following questions.
  2. A common ancestor for both species C and E could be at position number

    • (A)

      1.

    • (B)

      2.

    • (C)

      3.

    • (D)

      4.

    • (E)

      5.

  3. The four-chambered hearts of birds and the four-chambered hearts of mammals evolved independently of each other. If one were unaware of this independence, then one might logically conclude that

    • (A)

      the common ancestor of birds and mammals had a four-chambered heart.

    • (B)

      birds and mammals should be placed in the same family.

    • (C)

      the birds were the first to evolve a four-chambered heart.

    • (D)

      birds and mammals are more distantly related than is actually the case.

    • (E)

      early mammals possessed feathers.

  4. The similarity of the embryos of fish, frogs, birds, and humans is evidence of ______.

    • (A)

      analogy

    • (B)

      genetic drift

    • (C)

      convergent evolution

    • (D)

      common ancestry

    • (E)

      diversifying selection

    The following questions refer to the hypothetical patterns of taxonomic hierarchy shown in Figure A.2 .
  5. If this figure is an accurate depiction of relatedness, then which taxon is unacceptable, based on cladistics?

    • (A)

      1

    • (B)

      2

    • (C)

      3

    • (D)

      4

    • (E)

      5

  6. According to this phylogenetic tree, chordates are most closely related to _____.
    • (A)

      Molluscs

    • (B)

      Arthropods

    • (C)

      Poriferans

    • (D)

      Echinoderms

    • (E)

      Platyhelminthes

  7. Which of the five marks in the tree below corresponds to the most recent common ancestor of a mushroom and a sponge?
    • (A)

      a

    • (B)

      c

    • (C)

      e

    • (D)

      b

    • (E)

      d

  8. If you were to add a trout to the phylogeny shown below, where would its lineage attach to the rest of the tree?
    • (A)

      d

    • (B)

      c

    • (C)

      a

    • (D)

      c

    • (E)

      b

  9. Cladograms (a type of phylogenetic tree) constructed from evidence from molecular systematics are based on similarities in ______.

    • (A)

      biochemical pathways

    • (B)

      morphology

    • (C)

      habitat and lifestyle choices

    • (D)

      mutations to homologous genes

    • (E)

      the pattern of embryological development

  10. When using a cladistic approach to systematics, which of the following is considered most important for classification?

    • (A)

      analogous primitive characters

    • (B)

      shared primitive characters

    • (C)

      the number of homoplasies

    • (D)

      overall phenotypic similarity

    • (E)

      shared derived characters

  11. Which of the four trees below depicts a different pattern of relationships than the others?
    • (A)

      d

    • (B)

      a

    • (C)

      c

    • (D)

      b

  12. In the tree below, assume that the ancestor had a long tail, ear flaps, external testes, and fixed claws. Based on the tree and assuming that all evolutionary changes in these traits are shown, what traits does a sea lion have?
    • (A)

      long tail, ear flaps, abdominal testes, and retractable claws

    • (B)

      short tail, ear flaps, abdominal testes, and fixed claws

    • (C)

      short tail, no ear flaps, abdominal testes, and fixed claws

    • (D)

      long tail, ear flaps, external testes, and fixed claws

    • (E)

      short tail, no ear flaps, external testes, and fixed claws

  13. Phylogenetic hypotheses (such as those represented by phylogenetic trees) are strongest when ______.

    • (A)

      they are supported by more than one kind of evidence, such as when fossil evidence corroborates molecular evidence.

    • (B)

      they are based on amino acid sequences from homologous proteins, as long as the genes that code for such proteins contain no introns.

    • (C)

      they are based on a single DNA sequence that seems to be a shared derived sequence.

    • (D)

      each clade is defined by a single derived character.

    • (E)

      they are accepted by the foremost authorities in the field, especially if they have won Nobel Prizes.

Appendix 2. List of different types of errors made by members of Cohort IV during the tree-drawing pre-assessment. Errors were split into five categories.

Character Table Errors

  • Students listed characters too vague to be of use (e.g., “body”) (Subgroup A students tended to make this error less often)

  • Table was incomplete (e.g., only two or three characters observed rather than five)

  • Several states of one character were used as several characters (e.g., brown body, gray body, dark body) (Subgroup A students tended to make this error less often)

  • Several character states shared by all members of group (e.g., six legs, has wings) (these do nothing to separate members of group)

  • Characters inaccurately match observations (e.g., moth is said to have concealed head when head is prominently visible)

Characters & Trees

  • Same characters show up on multiple branches (OK if convergent evolution occurs, but most instances were instead erroneous)

  • Characters aren't labeled anywhere on the tree

  • Derived characters are shown on tree as ancestral

  • Characters are at branch tips, rather than species

Roots, Nodes, & Branches

  • No root

  • No branches

  • Branches reconnect (this would be OK if the group shows horizontal gene transfer)

  • Branches have nothing at the tip

  • Nodes are not explained with any labeled emergent character (no way to determine why specific branches and nodes were drawn)

  • Nodes and branches are different than observations (most common error in how tree was drawn; this was quantified in the post-assessment to determine accuracy, but not in pre-assessment because so few nodes and branches were labeled)

Species Out of Place

  • One species shows up on several branches

  • Several species are at tip of same branch

  • Some species are not included on trees

  • Coexisting species are in parts of tree other than branch tips (inaccurately portrays one species as another's ancestor, as if chimpanzees were our ancestors – very important misconception!)

Outgroup

  • Outgroup not included on tree

  • Outgroup shares several characters with rest of group