What Does a STEM Professional Look Like? One Graduate Student’s Perspective

Photo courtesy of Montrai Spikes

I encourage you to visit today’s Science Careers website and read the moving commentary entitled Why I’ve struggled with the pressure to assimilate when teaching. The author is Montrai Spikes, a graduate student in Biology at the University of Oklahoma (where I teach).

Trai writes that as a teaching assistant, “the mask [that he] crafted” to appear “professional” to his white students had the unintended effect of “alienating students of color.” He ends by inviting us to discard our preconceptions about what it means to be a professional. His observations were enlightening to me, and I think they deserve to be widely shared; I hope you will read his commentary and distribute the link to your colleagues.

Calling on students at random: What are the keys to success?

Photo credit: Wikipedia

Lofty principles of equal opportunity guide our country and our schools, but the truth is that not everyone is treated fairly, and not everyone’s voice has an equal chance of being heard. As instructors, we must confront the painful idea that our own teaching practices can unintentionally reinforce inequality. I am therefore attracted to people who approach this problem thoughtfully and offer constructive suggestions for improvement.

A while ago, I wrote a blog post about an excellent and still-timely article that lists an impressive variety of ways to promote engagement and equity in the classroom (Structure Matters: Twenty-One Teaching Strategies to Promote Student Engagement and Cultivate Classroom Equity, by Kimberly D. Tanner).

One of my favorite strategies from that article was to call on students randomly instead of waiting for volunteers to answer questions directed to the class. Since I read that simple tip for boosting participation and encouraging diverse voices, I have used it in both my medium-to-large nonmajors biology class and in my small science writing class aimed at graduate students. In short, I like it.

Recently, I was interested to read a new article from CBE–Life Sciences Education devoted entirely to random calling. The authors, Alex H. Waugh and Tessa C. Andrews, recognize that random calling has benefits and costs. Even among instructors for whom the benefits outweigh the costs, they don’t necessarily agree on how best to implement random calling. So Waugh and Andrews interviewed 12 instructors who use this technique in an effort to find the “critical components” that are essential to success. If you want all the gory details, I urge you to read the full article. But for those of you who just want the take-home message, here you go.

According to Waugh and Andrews, the critical components of random calling are:

• Explaining to students why you are using this technique in your class, emphasizing the benefits and detailing how you are minimizing the potential costs;
• Allowing students to discuss a question among themselves before randomly calling for an answer;
• Calling on a group, as opposed to an individual student;
• Allowing a student to report the group’s collective ideas rather than their personal thoughts;
• Being “respectful and polite” (I might add here, editorially, an enthusiastic thumbs-up for this piece of advice).

The 12 instructors were divided on the finer details of implementation, including whether each group should assign a reporter role ahead of time vs. allowing an outspoken group member to volunteer information on behalf of the group. Another area of controversy was whether random selection should be with or without replacement – that is, once a student or group has been called on, is that student exempt for the day/week/rest of the semester, or might that same name be called again? In addition, a few instructors allow students to “pass” on a question; a few others allow students to put themselves on a “do-not-call” list. The article explores all of these issues in detail.

The article does not touch on random calling in online classes, but I am writing this blog post in the midst of the COVID-19 pandemic, so I have been thinking about which of my favorite teaching techniques lend themselves to teaching online. In a synchronous online class, e.g. on Zoom, I don’t see any reason why an instructor couldn’t call on an individual student at random. If the Zoom class uses breakout rooms, the instructor could also call out groups randomly when the class as a whole reconvenes. I would love to hear (in the comments section) from instructors who have relevant experiences to share.

If you have not yet tried random calling, I encourage you to do so. If you have tried it but want to know more, take a look at the Waugh and Andrews article. Either way, keep an open mind about your longstanding practices as you think about how you can be part of the solution.

Reference:

Alex H. Waugh and Tessa C. Andrews. 2020. Diving into the Details: Constructing a Framework of Random Call Components. CBE–Life Sciences Education, vol. 19, no. 2. https://www.lifescied.org/doi/full/10.1187/cbe.19-07-0130

Instructors: Be kind to your future self

I’ve posted a few times on helping your students cultivate a growth mindset. But I think its also important to think about our own mindsets as instructors. How can we cultivate a growth mindset about teaching, learn from our mistakes, and make our courses better each semester? I have a couple of suggestions.

Read my previous posts about the growth mindset: At the End, I’m Looking to the Start and Cultivating a Growth Mindset in Your Students.

My first suggestion for instructors is to pay attention to what works and what doesn’t during each class session. Then, right after class is over, put a note to future self in your PowerPoint presentation. The note should be obvious, so you don’t miss it, and it should include the date you wrote it. Something like the PowerPoint slide below:

 

A second idea is to ask your students two questions during a class leading up to an exam. One is “What is the most interesting thing you have learned during this portion of the semester?” That question is a favor to your present self because it helps reassure you that at least something was interesting, despite the sea of expressionless faces that greets you each day. The second question is, “What is something you still don’t understand?” You can sort the answers by frequency and use them to formulate a review session before the exam. But they are also a favor to your future self because those answers can reveal where you can improve your teaching. For me, bond polarity and hydrogen bonds frequently top the list of topics students don’t understand before exam 1. I have therefore worked very hard to improve my approach to those topics.

I have one more suggestion for a way to be kind to your future self, and it pertains mostly to instructors who teach classes that meet once a week for several hours. My writing class fits that format, and it’s a challenge to plan out the three hours such that the pace is not too rushed and not too slow. One suggestion is to make a plan on paper for each class, e.g., from 4:30-5:15 we’ll recap their homework, readings, and other assignments for the past week, from 5:15-6:00 we’ll do peer review, at 6:00 we’ll take a 10-minute break, and so on until class ends at 7:20. During class, note right on the paper how long everything actually took, along with observations about what worked and what didn’t. After class, take a picture of the paper and insert the photo into your class PowerPoint. Next time you teach the class, you’ll have a better idea of how to adjust your strategy. Trust me when I tell you that your future self will thank your past self for taking a few minutes after class for this task.

Instructors, in what other ways are you doing favors for your future self? Leave a comment to let us know.

My Students Need Help Asking for Help; Do Yours?

We finished exam 2 in my nonmajors biology class last week, and after the exam was over, I had an epiphany: Very few students asked me for help.

For context, I’ve been doing this job for more than 20 years. Years ago, on the night before an exam, I would have to warn students to email me questions before 10 pm because after that I’d be in bed. I’d host popular online chat sessions near exam times, and my Action Centers would see a lot of (ahem) action. Students would ask me to recommend tutors. On exam days, my office would be crammed with students asking for last-minute help. Now: crickets. No student ever emails me a question about course content or asks about tutors. A handful of students come to Action Center, and my office hours remain empty, even on the morning before an exam.

The Internet is full of articles about why students don’t use office hours. The reasons are interesting, but they’re missing information about trends. Why did students ask for help in the past, and now they don’t? Let’s rule out a couple of possibilities right off the bat. First, have I become such a fantastic teacher that none of my students need help? Nope, it’s not that, as the range on exam 2 was 39.5 to 97.5, with an average of 71. That adds up to a lot of students with sub-par performances. Second, am I meaner and more intimidating now than I was when I was much younger? Sure, that’s possible, but I certainly bend over backwards to be approachable and to remind students of how to get help.

It’s hard to test hypotheses about how students have changed over the years without hard data, so I decided to ask my students why they don’t seek help. I used a not-for-points clicker question:

If you were struggling in a class (any class, not this one in particular), what would be most likely to keep you from seeking the professor’s help? Mark all that apply.
Feel free to switch clickers if you don’t want me to connect you with your answer.

A. I don’t have time to get help.

B. I get help from my friends; I don’t need the professor’s help.

C. I’m afraid I’ll look stupid if I ask for help.

D. I’m too intimidated by my professors to ask for help.

E. I’m so overwhelmed that I’m not even sure where to begin asking for help.

F. If I’m not naturally good at the subject, then seeking help wouldn’t do any good anyway.

G. It’s stressful to confront failure, so I procrastinate.

H. Other

Students could choose as many options as they wanted. Have you already predicted which choices received the most votes? Go on, do it now. I know what I thought they’d say: They don’t have time (choice A), they’re too intimidated (choice D), and it wouldn’t do any good anyway (choice F). Well, I’m glad I asked instead of making assumptions. The graph below shows the number of votes that each choice got:

What really hit me hard about the results is that students admitted to the pain of confronting failure (choice G), to being overwhelmed by the challenge of seeking help (choice E), and to being afraid of looking stupid (choice C). I am no psychologist, but I feel sure there must be tools that can help students overcome these challenges, and I plan to look for ways to identify and recommend such tools in the future.

Choice H, “Other,” bears special mention as well because it was tied for third in the voting. I emailed the students who had selected it to find out what I had missed in crafting my question. Each of those who replied had a different reason for choosing H. One prefers to go to a tutor before bothering a professor. Another battles anxiety and depression and would find it difficult to approach a professor for help. Another isn’t sure what kinds of questions (content or policies?) one is supposed to ask in office hours. Another has had professors in the past who seemed annoyed when students came to office hours. Yet another likes to do things alone and therefore prefers not to ask for help.

My big takeaway from this question is that I need to help struggling students to be brave about asking for help. But am I offering the right formats? My followup question, in the next day’s class, aimed at that issue:

If you were to seek a professor’s help, how would you prefer to get that help? Mark all that apply.

A.One-on-one in professor’s office (in-person office hours or by special appointment)

B.Come-and-go “study time” with professor at a location outside professor’s office (without prepared activities)

C.Come-and-go Action Center (with prepared activities)

D.Email questions to professor

E.Online chat (virtual office hours or appointment)

F.Post questions to professor on Canvas discussion board

G.Informal group discussion with professor present at a neutral location, like a coffee shop

H.Other

Take a moment to predict what you think students said. I predicted a strong preference for virtual office hours (choice E) and perhaps the Canvas discussion board (choice F). This graph shows what they actually said they preferred:

When I saw the results, I thought to myself: “Wait, what!?” In-person office hours (choice A) and Action Center (choice C) are the two main types of help I’m already offering, and few students take advantage of them. Having group discussions and study groups at a neutral location also got a lot of votes, and those are two things I might consider in the future. Bringing up the rear were the options I thought students might like because they don’t require face-to-face conversations, such as emailing questions (choice D), the Canvas discussion board (choice F), and online chats (choice E).

According to these graphs, if I want my students to get the help they need, then I need to find ways to help them overcome the psychological barriers that keep them away from office hours and Action Center—both of which many say they want yet few are using. This predicament raises interesting side questions: How much of this is on me to solve, versus the students learning for themselves to be brave and conquer their fears? Stated another way, do changing student habits reflect a cultural shift that I need to adapt to, or should I tell my students to pull on their big kid pants and get over it?

I haven’t had time to think these issues through, but I will be ruminating on them in the coming weeks. In the meantime, I welcome your comments, especially if you have noticed this phenomenon too and have found new ways to help your students get the help they need.

The Incredibly Stretchy Condom, Revisited

It has been about 6 years since I wrote about the “Process and Tools of Science” lab in which students learn metric units of measure while they experiment with condoms. I still love this activity and use it every semester, but recently I heard of two possible enhancements, and I pondered how to elicit improved experiments from our students. Perhaps some of my readers will benefit from my recent experiences.

The enhancements come from Dr. Sehoya Cotner, an energetic and fearless professor at the University of Minnesota. In the summer of 2019, she led a workshop for the Association for Biology Laboratory Education, my favorite professional organization. (I cannot recommend it enough; check it out if you teach biology labs at any level.) The workshop covered several labs from her Evolution and Biology of Sex class, and I was thrilled to see the condom experimentation lab among them.

I was even more thrilled when I was randomly assigned to the condom experiment during the workshop. I was excited because she added two twists that I hadn’t thought of. One was to add condoms made of “natural membranes” (intestines) to the usual mix of latex and polyisoprene condoms. The natural ones are super expensive, and while they prevent pregnancy, they don’t protect against sexually transmitted infections (STI). Cotner taught us that green food coloring particles are larger than HIV and other viruses but smaller than bacteria and sperm. So our group designed an experiment in which we dispensed a known volume of green food coloring into natural condoms, latex condoms, and polyisoprene condoms, then dunked all of the condoms in a known volume of water. The idea was to time how long it took for green food coloring to become visible in the water. It worked fabulously well.

Trustex (latex) condoms are impermeable to green food coloring. (Photo by M. Hoefnagels)

Skyn (polyisoprene) condoms are impermeable to green food coloring. (Photo by M. Hoefnagels)

Naturalamb condoms are permeable to green food coloring. (Photo by M. Hoefnagels)

The other twist that Cotner added was the potential for the use of calipers as tools for measuring sensitivity. Specifically, calipers are a perfect tool for conducting two-point discrimination tests on bare skin and through a variety of materials, enabling students to stretch a condom over a hand and test whether condoms reduce sensitivity and by how much.

I couldn’t wait until that lab came up in my class this semester, which it finally did last week. I thought students would gallop to try those new tools, but alas, they did not. In our Tuesday section, they did the same old experiments–see how far the condoms can stretch, see how much fluid they can hold, or see how much weight they can bear. The end-of-class presentations were well done but somewhat redundant to each other. For Thursday lab, I thought it might help if we assigned a specific tool to each group. One group was assigned calipers as a tool, and another was assigned time. I hoped they would design the experiments as I would have, but alas, they did not. The team using calipers used them to figure out how far the condoms stretched widthwise; the team assigned to measure time didn’t end up doing that at all, despite the TA pointing out natural vs. latex condoms and explaining the significance of the green food coloring. Well, at least the presentations at the end of class had more variety, so that was a win, but I still didn’t see the creativity I had hoped for.

I thought a lot more about this after Thursday’s lab and it occurred to me that we may be asking too much from our students. We simply give them a list of materials and a limited amount of time, so it’s no wonder they ignore all the information available to them about condom construction and permeability and instead gravitate toward the simplest, quickest experiments. Next time I teach the class, I’m going to add two tables to the lab manual. One table will list all of the brands and styles of condoms available, along with the material they’re made of and whether they protect against STIs. The other table will list all of the other materials, what they’re for, and what sorts of questions they might be used to answer. I still want them to design their own experiments, and I think we will continue to assign at least one tool to each group so we keep getting a good variety of presentations. I’m hoping that with more information they can arrive at more interesting questions and better-designed experiments. Watch this space for updates; I’ll let you know what happens!

Natural Selection in Tortoises: A (Homemade) Video

[Doug Gaffin and Marielle Hoefnagels worked together to develop the materials used in this post.]

A while back, I wrote a post on an activity that connects genotype, phenotype, and natural selection. In a nutshell, the activity uses colored chips to represent alleles in cod. Students selectively “harvest” the largest fish over multiple generations and observe what happens to allele frequencies in the population.

What’s so funny about natural selection? (Galapagos tortoise photo by M. Hoefnagels)

This activity leaped to our minds when my husband and I were invited to give a lecture about natural selection to a group of non-biologists as we were all visiting the Galapagos Islands. We decided to adapt the cod activity to illustrate how natural selection could select for long necks in tortoises—we were particularly interested in driving home the point that tortoises didn’t “decide” or “try” to evolve in response to their environment. Our original intention was to have the group actually do the activity, but in practicing it before the lecture, we quickly realized that the activity involves quite a bit of counting and other tedious tasks that would use up our entire lecture time.

So we decided to do the activity in our hotel room, film it, and turn it into a video that we could show to our companions; you can see it here. The video, which is 2 minutes and 45 seconds long, requires a bit of explanation. It begins with a founding population of 10 tortoises, each of which inherits a total of six alleles for neck length. The alleles are represented by puzzle pieces of different colors: pink = 4 “length units,” yellow = 3 units, blue = 2 units, and purple = 1 unit. To assign genotypes to each tortoise in the founding population, equal numbers of alleles of each color are placed in a bag and shaken. Each tortoise receives a random assortment of six alleles. In the first 25 seconds of the video, we randomly select alleles from the bag to assemble the tortoise genotypes.

A tortoise from the “game board,” annotated to show the three genes and four possible alleles controlling neck length.

Next, the number of alleles of each color is tallied for each tortoise. The number of pink alleles is multiplied by 4, the number of yellow alleles is multiplied by 3, the number of blue alleles is multiplied by 2, and the number of purple alleles is multiplied by 1. These numbers are added to calculate the neck length of each tortoise. The five tortoises with the shortest necks do not survive (their totals are circled in the video), and the average neck length for the founding population is calculated. We are now through the first minute of the video.

For the next 27 seconds, the alleles for the shortest-necked tortoises are wiped off the board, the five survivors have their alleles doubled, and all of the alleles are swept into the bag and scrambled. At 1:27, we are ready to begin Generation 2. Each of 10 tortoises again gets a random assortment of six alleles, the numbers are tallied, the unfortunate ones with the shortest necks are identified for elimination, and the generation’s average neck length is calculated. We’re now about 2 minutes into the video. Then the survivors of Generation 2 have their alleles doubled and swept into the bag, and the start of Generation 3 is signaled at the 2:22 mark. By 2:45, the Generation 3 numbers are tallied.

The selection pressure against short necks in this simulation is very strong, so it’s not surprising that three generations is enough to produce a prominent trend toward long necks:

Whether using cod or tortoises, this activity is really good, and we are indebted to the inventors of the cod activity. If you want the tortoise version of the worksheet and student instructions, please leave a comment and we’ll send them your way. Or, if you simply want to show the video and explain it to students as you go along, feel free to do that as well.

“Practice Perfection”: It’s Not Just for Gymnasts

In case you are not focused on the world of college gymnastics, the University of Oklahoma’s men’s and women’s teams are second to none. I am not exaggerating: You can see the 2019 NCAA men’s rankings here and the women’s rankings here. We really are #1. Hey, it ain’t bragging if it’s true.

This isn’t a sports blog though; it’s a blog about teaching nonmajors biology. Where’s the connection? Well, I’ll get to that. But first, some back story.

Four of OU’s gymnasts recently spoke at an OU Honors College Q&A session for students. Among the questions was, “How do you do it?”  That is, when competing in a meet, how do these athletes put aside the distractions and the pressure, focus inward, and put together a perfect routine? The answer was shockingly simple: “We practice perfection.” That is, they do the routine so many times that they can execute it flawlessly during practice. Then, they said, the competition is easy. All they need to do is complete the same routine in the meet that they have done over and over in practice.

These four OU gymnasts talked about “practicing perfection” at a recent OU Honors College event. [Photo courtesy of Lisa J. Tucker]

The connection to teaching biology is that simple piece of advice: practice perfection. If students studied course material until they knew it perfectly, every time, then tests would be easy. (Teachers aren’t exempt, of course. If we practiced our presentations until we could do them flawlessly, our classes would probably go more smoothly too! But let’s focus on our students.)

How many of your students hold themselves to the “practice perfection” standard? Some do, but many don’t. Instead, many students study just enough to get the gist of the material, then simply hope the exam is easy. If that hope is dashed, it’s easy to blame the teacher for writing “tricky questions” or to blame an innate flaw, like “I’m terrible at science” or “I have really bad test anxiety.” Can you imagine an elite athlete using that strategy? The athlete would practice enough to gain a passing familiarity with the routine, perform during the competition, and blame the judge (or an inability to compete) if the score is low. Such a gymnast wouldn’t last very long.

So, how can teachers help our students to see the value in practicing perfection? If a student professes to be “terrible at science,” we can help by encouraging a growth mindset. If the student has test anxiety, point out resources that can help — and if you click on the link to those resources, notice how many of them connect good study skills (i.e., practice) with confidence, relaxation, and the ability to perform well on tests. If the student grumbles about tricky questions, ask for specific examples, then have an open mind. Your questions really might be ambiguous or unfair. But if a supposedly tricky question is actually difficult but fair, turn the problem back on the student: “Where can you find the material needed to answer that question, and how might you study next time to be able to answer a question like that?”

One additional concrete step we can take is to give students plenty of help finding ways to practice. Give them old exams and answer keys — not all of them, but a couple. Show them how to use the end-of-section and end-of-chapter questions published in textbooks. (If you want to see the practice materials that I provide for my own students, head for my teaching website.) Use class time and office hours to reinforce concept mapping and other skills that help students get away from rote memorization and work toward a deeper understanding of the material.  Let’s do what we can to help our students do what the gymnasts do: practice perfection.

The Laptop Ban: New Research

Students taking photos in class instead of taking notes. Source: Flickr

Faithful readers may remember that a couple of years ago I banned the use of laptops in my nonmajors biology classroom. You can read about the rationale in a previous blog post that summarizes the Mueller and Oppenheimer study, which found that students performed best on conceptual questions when they took notes by hand. And you can see how I implement the ban and sell the idea to my class during week 1.

In course evaluations, surprisingly few students complain about the ban, perhaps because my class proceeds at a pace for which it is possible for most students to take notes by hand. One student last fall did gripe about it; his main argument was that he’s a grownup, he’s paying for class, and he should be able to use his class time however he sees fit. I am sympathetic to that argument, as students need to learn to manage their own time and resources at some point. However, that point of view focuses only on the would-be laptop user and not on the neighboring students who would be constantly distracted by whatever is happening on someone else’s glowing screen. Moreover, the desire to look at screens of all sizes seem to be contagious. That is, it’s easy enough to ignore your phone if no one is using one (e.g., during an exam), but it’s a lot harder when others around you are enjoying the dopamine rush that accompanies incoming notifications and social media posts.

Why am I bringing this up again? It’s because the Chronicle of Higher Education just did. They recently noted that researchers tried to repeat the Mueller and Oppenheimer study that you can read about in my previous blog posts. In the Chronicle’s words, “The new paper … couldn’t completely replicate those findings.” The Chronicle also points out what’s wrong with both studies, namely that taking a test 30 minutes after taking notes (as they did in both studies) is a whole lot different from taking a test 4 weeks after taking notes (as often happens in the college classes). It also makes sense that student study habits during the exam-free interval might be more important than how they took notes in the first place.

The article began by mentioning the problem of distracting the neighbors, but only briefly returned to that point at the end. For me, that will remain one of the primary reasons to carry on with the ban. Most students aren’t complaining, so I’ll stay the course.

Moldy bread, experimental design, and you

For many semesters, my nonmajors biology lab did a lab called chicken wing microbiology. You can download it here, from the wonderful Association for Biology Laboratory Education website (Walvoord and Hoefnagels, 2006). In the lab, students devised a method to kill the bacteria on chicken wings, carried out an experiment (including serial dilutions) to test their proposed method, collected plate count data the following week, and wrote a short lab report on their results.

One semester, a vegetarian student notified me that he would refuse to work with chicken, so we agreed that he could try the same lab with potatoes in place of chicken wings. It worked, and what was once a lab that consumed dozens upon dozens of chicken wings, plus nearly 1000 test tubes and petri dishes, became a lab that consumed a lot of small potatoes — but still used the same number of test tubes and petri dishes. It was still very resource- and labor-intensive to set up. Plus, if you have ever tried incubating 1000 petri dishes containing wild bacteria for a week, you know they stink.

So last summer, I was looking around for a substitute that would be cheaper and easier to set up and that would use less space to complete than 1000 petri dishes. I happened upon a lab in Biology Brought to Life by Handelsman, Houser, and Kriegel. If you are not familiar with that book, it’s a unique product that focuses on active learning. The book has a lab called “Bread, mold, and environment: a lesson in biology and the environment.” Its focus is the Host – Pathogen – Environment disease triangle, with bread standing in for the host and bread mold standing in for the pathogen (while acknowledging that bread isn’t alive and that bread mold doesn’t cause disease). The lab challenges students to “develop a hypothesis about the environmental factors that might affect the ability of Penicillium to grow on bread and design an experiment to test your hypothesis.”

That turned out to be the inspiration I needed for our new lab. Sarah (my capable undergraduate assistant) and I unleashed the Summer of Mold to figure out whether we could have students test predictions about mold growth by spraying spore suspensions or sterile water control solutions on various baked goods. The first step was to figure out what type of baked goods would work the best. Sarah scoured the stores and came back to the lab with a huge variety of treats, including cookies, Twinkies, muffins, sweet breads, sandwich breads, garlic breads, and more. We sprayed, and then we waited. As you can see in the photos below, some baked goods got moldy. A lot of them did not.

Mini-blueberry muffins and cinnamon swirl bread. No mold! Photo by M. Hoefnagels.

Garlic bread slices and Twinkies. The Twinkies are pristine (and remain so to this day). Photo by M. hoefnagels.

One major finding was that the easiest baked goods to interpret were plain slices of sandwich bread, and further pilot testing revealed that quarter slices of bread would work just fine.

Fresh bread from a bakery got moldy, even after being sprayed with sterile water. Photo by M. Hoefnagels.

So for week 1 of the final lab, we decided to have students pretend they were opening a bakery but unable to decide whether or not their bakery’s bread should contain artificial preservatives. We let them think about how they might test the effect of preservatives on mold growth if they were given a squirt bottle containing mold spores and bread slices of two types: store-bought whole wheat bread with artificial preservatives, and fresh, bakery-bought bread without artificial preservatives. Once a TA approved their methods, they went at it. We had plenty of space in the back of the classroom to incubate all of the ziploc baggies at room temperature.

During week 2, each group had to figure out how to quantify the mold growth on their bread slices. We gave them plastic transparencies marked with 1-cm2 grids and asked them to figure out how to use the grids to generate their data (without opening their baggies). Once a TA approved their proposed methods, they collected their data, produced their graphs, and wrote their reports.

Good news: It worked! Freshly baked bread without preservatives typically got very moldy indeed, whereas store-bought bread with preservatives hardly had any mold spores at all. Below is an example of a graph submitted with a student’s report.

Sample graph; used with permission. In the color key, “Mold” refers to the mold spore suspension; “Water” refers to sterile water. No mold grew on store-bought bread sprayed with sterile water.

If you’re thinking of doing a lab like this, it does take some planning. A couple of weeks before the lab, you’ll need to sterilize several liters of water (and quite a few squirt bottles). You’ll also need to buy a Penicillium culture and some extra plates of potato dextrose agar, inoculate the plates with your Penicillium, and let the plates grow for a week or two — long enough to generate the spores you’ll wash into the squirt bottles as you prepare for the lab. You’ll also need to teach students about aseptic technique and make sure they know to spray INSIDE the plastic bags, not outside — this is an important precaution that maximizes safety and minimizes cross-contamination.

Once it’s time for week 1, the materials needed are simple: bread, Lysol, plastic knives (for cutting bread into four pieces), cutting boards, squirt bottles containing sterile water, squirt bottles containing Penicillium spores, ziploc baggies (for incubating the slices for a week), and Sharpies. During week 2, you’ll need transparencies pre-printed with a 1-cm2 grid and water-soluble marking pens. For safety’s sake, you’ll also need to remind students never to open ziploc baggies containing moldy bread.

What did the students think? They liked it! It was not overly complicated, but it was reasonably challenging. The TAs told me that students would have liked more freedom to test different types of natural preservatives, but I confess that I am not sure how to do that without introducing confounding variables. However, it would not be difficult to add refrigeration as a treatment to substitute for (or add to) store-bought bread with artificial preservatives. In our July pilot studies, refrigeration substantially inhibited mold growth.

Anyway, it’s an open-source lab so if you want a copy of the lab and prep notes, leave a comment below and I’ll send them to you.

Raise Your Hand: How Do You Start the Semester on the Right Foot?

Years ago, I published my best idea for semester prep, a checklist that has proved to be an audience favorite. Over the past 5 years, many readers have asked for my checklist, which I have freely shared.

I was knee-deep in my checklist a few weeks ago as I was prepping for this fall semester. While I was checking off tasks, a colleague shared a really useful article about starting the semester with a culture of student participation: Structure Matters: Twenty-One Teaching Strategies to Promote Student Engagement and Cultivate Classroom Equity, by Kimberly D. Tanner. I like articles with the word “Strategies” in the title because that means I won’t have to plow through a lot of edu-speak to get to the practical suggestions. Tanner’s article doesn’t disappoint, and I wanted to share with you a couple of the ideas that I tried in the first two weeks.

A student raises his hand in class. Image Credit: UC Davis College of Engineering Photostream.

Under the category “Giving students opportunities to think and talk about biology” is a tip titled “Wait Time.” Tanner suggests that when you pose a question to the class, count to yourself “one thousand one … one thousand two … one thousand three … one thousand four … one thousand five” before acknowledging any answers. Remarkably, according to Tanner, instructors wait an average of only 1.5 seconds before filling the empty air with a student response or with their own. The extra time gives students who are not lightning-quick a chance to think about the question.

A related tip, in the category called “Encouraging, demanding, and actively managing the participation of all students,” is “Hand raising.” According to Tanner, “Novice instructors, sometimes awash in silence and desperate for any student participation, can allow the classroom to become an open forum.” That might not sound like a bad thing, but it could also exclude students who aren’t brave enough to shout out their answers. Combining wait time with hand-raising has two benefits: It gives students time to think and it gives the instructor a chance to choose who will speak. Both outcomes reduce the chance that the class will be dominated by a few outspoken students.

Speaking of hand-raising, Tanner suggests that instructors ask for at least three volunteers to raise their hands before acknowledging anyone. In her words, this strategy “allows instructors to selectively call on those students who may generally participate less frequently or who may have never previously shared aloud in class.”

Out of the 21 strategies, I’ll just choose one more to share: “Random calling using popsicle sticks/index cards.” For smaller classes, Tanner suggests filling a cup with popsicle sticks, each with a student’s name on it. When you want to call on a student, you simply pick one randomly out of the cup. For larger classes, shuffle those index cards you collect from students on the first day of class, and pick one.

So, how have I done with these strategies in my first two weeks? I guess I’d give myself a C. In some cases, I have encouraged students to raise their hands instead of calling out answers, and that has given me a chance to say, “Let’s hear from someone we haven’t heard from yet” or “Let’s see if someone on this side of the room wants to contribute.” I also tried the index card strategy during a lesson on experimental design. I pulled a card and called out the student’s name, only to find she was absent. I muttered “Well, this is going well,” the students tittered, and I tried again. That student answered the question I had offered — and probably would never have done so if I hadn’t gently forced his hand by calling on him. That was a win.

In other cases, though, I’ve succumbed to the satisfaction of listening to a whole class shout out the answer to a question they couldn’t answer the day before. However, Tanner’s article has made me realize something: When I say the “whole class,” I might not be including everyone; most likely, a few students remain silent. Breaking old teaching habits is hard, and sometimes I forget the tricks I told myself I’d try, but I will work to get better.

If your student engagement could use a boost, scan through the article and see which strategies speak to you. (In particular, check out “Do not judge responses” and “Use praise with caution,” both of which I also found especially enlightening.) I think you’ll be pleased with the scope and practicality of Tanner’s suggestions. If you end up trying some, please feel free to share your experience as a comment to this post.