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.

Green food coloring with Trustex condoms

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

Green food coloring with Skyn condoms

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

Green food coloring with Naturalamb condoms

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!

Posted in Experimental design, Laboratory activities | Tagged , , , , , , , , , , , | 1 Comment

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.

Tortoise on Galapagos with open mouth

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.

Illustrates genes and alleles controlling neck length

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:

Graph of neck length

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.

Posted in Active learning, Evolution | Tagged , , , , , , , , , , , | 3 Comments

“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.

Four gymnasts

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.

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The Laptop Ban: New Research

Group of students in a classroom with phones raised.

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.

Posted in Instructional technology, Teaching | Tagged , , , , , , , | 2 Comments

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.

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.

2019-01-18 12.46.13 pm

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.

Posted in Engaging students, fungi, Laboratory activities, Microbiology | Tagged , , , , , , , , , | 2 Comments

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.

Student Raising Hand

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.

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Another Way to Connect Selection, Phenotype, and Genotype

Now that it’s summer, I’m catching up on my American Biology Teacher backlog. I found this interesting-looking activity by Janina Jördens and three coauthors in the February 2018 issue. The title of the article says it all: “Interrelating Concepts from Genetics and Evolution: Why Are Cod Shrinking?” I haven’t tried it — it is summer, after all — but it looks like it addresses some of the learning objectives that I have previously outlined in the oft-requested reptilobird and antibiotic resistance activities.

The authors point out that traditional activities illustrating natural selection — like picking scattered colored dots off a piece of patterned fabric — emphasize phenotypes while ignoring genotypes. But if evolution means changes in allele frequencies over multiple generations, we should not let students focus purely on changes in phenotypic frequencies. Jördens and her coauthors developed a simulation that could help students understand the connection between phenotype and genotype in the context of cod overfishing.

All of the materials needed for the simulation are described at the evolution-of-life website. As I discovered in writing this blog post, the site is not easy to navigate. Thank goodness for the site map, which led me to all of the site’s teaching materials, which led me to the teaching resources for this activity. Here they are. They include handouts with background information and instructions, the playing board, and teaching advice.

The lesson begins with an 8-minute video explaining how the average body size of cod has declined over time, thanks to decades of selectively harvesting the biggest fish. Students also read about the situation on handouts. Each group of five students then receives a playing board depicting 10 cod fish. They also get a non-transparent bag containing 60 colored plastic disks: 15 red, 15 yellow, 15 black, and 15 blue (or, less durably but more deliciously, chocolate candies with different colored wrappers). Separately, they also receive enough “spare” disks to make up a total of 60 of each color.

Each of the 10 fish on the playing board has room for six alleles, two for each of three genes (labeled as A1, A2, B1, B2, C1, and C2) that control the individual’s body size. The students begin by randomly drawing 6 disks from the bag (no peeking!) and placing them on the first fish on the playing board. They repeat that process for each of the remaining nine fish — if they have done it right, they should have used up all of the disks in the bag.

Screenshot of cod fish game board

The upper third of the game board, showing where to put two alleles for each of the three genes (A, B, and C) conferring fish size. Screenshot taken from game board at

The colors represent different numbers of “size units,” with red conferring the largest size (4 units), followed by yellow (3 units), black (2 units), and blue (1 unit). With this information, students can calculate the size of each fish and compute the average size for the entire population of 10 fish. At this point, the largest five individuals are “caught” and their alleles are removed from the board before they have a chance to “reproduce.” The alleles from the surviving individuals are duplicated (to simulate reproduction) and the surviving alleles plus the duplicates are returned to the bag. At this point, the number of alleles in the bag should be back to 60.

Students are now ready to produce the second generation. They randomly assign each fish on the playing board its 6 alleles, measure the size of each fish, compute the average population size, and tally the frequency of each allele. Then the five largest individuals are caught, and the entire process is repeated to produce and measure generations 3 and 4. Afterward, students graph the individual and/or average body sizes for each generation; given the strong selection pressure against large body size, the trend should point downward. Likewise, the frequency of the red and yellow alleles should decline. The authors suggest several thought questions and followup activities that could be useful, depending on the instructor’s priorities.

For my part, I am happy to see more ways to connect selection, phenotypes, and genotypes. This simulation appears to be well-thought out, and the materials are freely available on the evolution-of-life website. By the way, I encourage you to explore the entire site. The “Teach” page has links to materials for the shrinking cod activity described here, as well as the origin of life, Darwin, evolution in fast motion, and coevolution. If I find other gems, I will certainly let you know; if you do, please leave a comment and let me know!


JördensJanina, Roman Asshoff, Harald Kullmann, and Marcus Hammann. 2018. The American Biology Teacher 80(2):132-138.
Posted in Evolution, Laboratory activities, Teaching | Tagged , , , , , , , , , , , | 3 Comments

So many learning resources … so little time

Contributed by Matt Taylor

Suppose you are searching for that great new activity, assignment, or video for your class. Do you ever feel overwhelmed by the never-ending list of resources that you can find? Your students might feel the same way about the abundance of learning resources available to them. The good news is that we can help students take control in the chaos.

Many teachers and educational developers want students to have a variety of resources to help them master concepts. Since student learning styles or preferences vary, it is useful to provide different tools for a diverse body of learners.

But more is not necessarily better if students don’t know how to use the resources available to them. To overcome this gap in understanding, teachers could tell their students how each learning resource might be useful. Or better yet, teachers could encourage students to develop their own strategies. It turns out that the latter—asking students to make deliberate study plans—has a small but significant impact on class performance, according to Patricia Chen and her coauthors in a 2017 Psychological Science article. The research team set up an experimental group of students who developed specific strategies to use learning resources and compared the performance and psychology of those students to others who made no deliberate study plans.

Students who made deliberate study plans improved their course grade by about 4%.

Chen and the other researchers conducted their experiment in two introductory statistics classes. All students in these classes received weekly reminders of what resources were available to them. Also, in return for extra credit points, students were given the option to take surveys before and after two midterm exams. Participation in all four surveys was around 60%. Upon starting the first survey, students were randomly assigned to the control group or the experimental group (the class instructor was blind to this assignment). Post hoc analysis of these groups revealed that their members were not significantly different in terms of past performance, motivation, or confidence.

Pre-survey: Students in both the experimental and control group were asked questions targeting four areas: what grade they wanted to receive on the exam, how motivated they were to receive that grade, how important it was to receive that grade, and how confident they were in success.

Then, only the students in the experimental group went on to answer questions about their study plans. The first question asked them to select which resources from a list would be likely to help them study for the exam. For example, in an introductory biology course using a McGraw-Hill book, the list might look like this:

  • Textbook readings
  • Connect questions
  • LearnSmart questions
  • Smartbook learning resources
  • Tutorial animations
  • Office hours
  • Lecture notes
  • Previous exams
  • Lab materials

After making their selections, students described in essay format how each chosen learning resource would help them. Then, they were asked to describe in detail when, where, and how they would use each resource to study in the week before the exam (e.g., “on Monday morning I will go to the library to rewrite my lecture notes”).

Post-survey: All students received the same post-survey. It asked questions about what resources students had used and how useful they thought each resource was to their learning. They were also asked about how much control they thought they had over their own grades, how much they plan for an exam, and how well they follow through with their plans.

Results: Students in the experimental group who participated in at least one pre-survey scored approximately 4% higher than their classmates who did not make deliberate study plans. Students who made study plans before both tests got an even higher boost in overall course performance. (Importantly, the treatment effect remains statistically significant even when the researchers removed the extra credit points that students received for participating in the surveys.)

Finally, the researchers also found that students who participated in strategic study planning on a previous exam felt more confident, less anxious, and more in control of their grades on an upcoming exam.

The research article has many other details that I did not explain here, and I encourage you to read it for yourself. But the major takeaway is this:

If you encourage strategic planning of learning resource use, then your students will be more confident and successful.

Do you encourage students to plan and self-reflect on their learning? How does it work in your classroom?


Patricia Chen, Omar Chavez, Desmond C. Ong, and Brenda Gunderson. 2017. Strategic Resource Use for Learning: A Self-Administered Intervention That Guides Self-Reflection on Effective Resource Use Enhances Academic Performance. Psychological Science, Vol 28, Issue 6, pp. 774 – 785.

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Antibiotic resistance in the lab … with actual bacteria!

Apparently my post on the antibiotic resistance activity using green, yellow, and red beads was a big hit with instructors, because lots of people want a copy of the worksheet. I have been happy to oblige, and now I want to follow up by calling your attention to a potential companion activity in the March 2018 edition of The American Biology Teacher.

I hasten to add the disclaimer that I have not tried this lab in my own class; I only just read about it this week. But the title certainly seems promising: Modeling the Emergence of Antibiotic Resistance in Bacterial Populations.

The authors outline a 5-day procedure in which students expose a bacterial population to antibiotics at two different times. On day 1, students select a single colony of bacteria from an agar plate and suspend the cells in a nutrient broth. The bacteria-laden broth is then swabbed across the surface of an agar plate. Students then place paper disks with and without antibiotics on the plate. The bacteria on the plate are allowed to grow overnight in an incubator and are then placed in the refrigerator until day 5. Meanwhile, the original broth also incubates overnight. On day 2, the instructor transfers bacteria from the broth into fresh broth and again allows the cells to multiply overnight in the incubator. On day 3, each student group swabs the resulting inoculum onto a fresh agar plate and adds disks with and without antibiotics. Like the plate from day 1, this plate is allowed to incubate overnight and is subsequently stored in the fridge until day 5.

On day 5, it’s time to collect the data. Students examine their plates, measuring the zone of inhibition around each antibiotic-infused paper disk. They use the data they collect to test two models of antibiotic resistance. According to the article, “Model 1 illustrates need-based acquisition of antibiotic resistance. Here, the bacteria rapidly gain antibiotic resistance only when exposed to the antibiotic.” If model 1 is correct, then the number of resistant colonies arising from the “day 1” swab should be equal to the number of resistant colonies arising from the “day 3” swab. In contrast, “Model 2 illustrates acquisition of antibiotic resistance through mutation. Here, the bacteria acquire mutations over time that increase their level of resistance to the antibiotic independent of antibiotic exposure.” If model 2 is correct, then the bacteria plated on day 3 should have more mutations — and more resistance — than those plated on day 1.

The article contains great illustrations, explores the molecular mechanisms of antibiotic resistance, introduces the idea of intermediate resistance, and has lots more information about how to implement this activity. The authors also offer student handouts and even a PowerPoint presentation. I can’t endorse it because I haven’t tried it, but heck, if you’re looking for antibiotic resistance activities that actually involve growing bacteria, you might want to check it out.


Michelle A. Williams, Patricia J. Friedrichsen, Troy D. Sadler, Pamela J. B. Brown. Modeling the Emergence of Antibiotic Resistance in Bacterial Populations.
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Attend the best conference for people who teach biology labs … for free!

This is a good time to direct your attention to my favorite professional organization: The Association for Biology Laboratory Education, or ABLE.

I raved about ABLE in a previous post, and I won’t repeat my praise here. I just wanted to let you know that the 2018 conference will be at The Ohio State University from June 19-22. Registration isn’t open yet, so I can’t tell you the cost … but it’s typically in the $300 range and includes quite a few meals.

Are you thinking to yourself, “I can’t afford that!”? If so, I have good news for you. ABLE grants a limited number of registration waivers for graduate students, post-doctoral fellows, new academic faculty/staff, and faculty/staff from community colleges. You don’t even need to be an ABLE member to apply. (If you feel inspired to join, it is a real bargain at $15 for students/post-docs and $35 for everyone else.)

Now you are probably thinking to yourself, “That sounds great!” If you are, then hightail it over to the registration waivers website and apply by March 5. The application is simple. It collects basic information, asks you to describe “how attendance at this conference would be of benefit to you personally and/or your institution as a whole,” and then requires you to upload a CV and a letter of support from your chair. It’s that easy!

If you are awarded a grant, you can enjoy a meeting full of hands-on activities and wonderful, collegial colleagues on ABLE’s dime. (Note that travel and lodging expenses are not included.) I urge you to give it a try; you won’t regret it.

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