Brett Couch and Angie O’Neill recently teamed up to create an activity to help students develop an intuitive understanding of scale and size of microscopic objects in their separate eukaryotic microbiology and neuroscience courses.
Below, they describe the activity they developed, the changes they’ve made based on the assessment and student feedback they received, and what they learned along the way.
What was your motivation for developing this activity?
The motivation was trying to get students to have a better understanding of scale when they’re looking at things under the microscope. We both have experienced that students often have misconceptions about the sizes of microscopic things they view in class based on what they see in textbooks. For example, textbook figures will have a figure of a cell that shows the nucleus, mitochondria, chloroplasts, ribosomes, and proteins all within the same figure, and this type of diagram can lead students to think that they should be able to see all of this stuff when they look at a cell under a light microscope, when in reality, individual ribosomes and proteins are much too small to be seen at this magnification. So, we wanted to help them develop a better intuitive sense of scale. What are the things they’re likely to see with a light microscope? What are the things they’re likely not going to be able to see? How big are cells? Imagining things that are outside of our experience, for example, things that are really, really small or really, really large, is hard for people. We wanted to help students with this, so that was the initial motivation.
How did you do it?
We both saw a need for this type of activity in our courses, so we worked on this together as a first draft and then implemented different flavours of it in our specific course; Angie used examples that were appropriate to a neuroscience course and Brett used examples that were focused on eukaryotic microbes in his course. The activity was essentially identical, except for specific examples, between the courses. It was really productive to work together on it as we had lots of informal discussions as we developed the activity, then we tried it out in our different courses and assessed it using a pre- and post-survey to determine what students were learning and how they were experiencing the activity. This assessment was helpful in determining what revisions to make for the second iteration.
What changes did you made to the activity in the second iteration?
We have used this activity over two terms in our courses. In the first iteration of the activity, we tried to do too much (a common problem with new activities). We had students come up with a formula for calculating scale and perform a number of calculations. We found that this was confusing for students and it seemed to detract from the main purpose of the activity. We revised the activity to simplify it and make sure it really focused on our specific learning outcomes of getting students to understand scale and recognize the things that they can and can’t see with a light microscope.
Another change was to allow some ambiguity in answers to questions that we asked. The purpose here was to promote discussion and introduce some more nuanced thinking about microscopy. In the first iteration we asked questions that had definitive ‘yes’ or ‘no’ answers. What we realized is that students got very hung up on knowing the “right” answer. This approach did not really capture the reality of viewing some types of samples with lab microscopes. For example, we asked students if they could see an E. coli cell when viewed with the 40X objective (400x magnification). E. coli cells are on this boundary of what can be viewed with this magnification with lab microscopes. So, in the second iteration we added ‘maybe’ as another possible answer, which allowed us to get students to consider some additional microscopy concepts of contrast and optical systems that that influence whether something can be seen or not. We found that making this little change of adding ambiguity allowed us to incorporate discussion of other microscopy concepts.
What did you learn or find surprising?
We found that students were better at some of the skills than expected, based on their answers in the pre-survey. Students actually started off with a reasonable ability to estimate the size of things using the scale bar as a reference, using a field-of-view as a reference, and using other things of known size as a reference. So that was surprising.
Also, more of the students seemed to have had some experience with microscopes than we expected. We often have trouble getting students comfortable using their microscopes in the lab, so our impression has been that students didn’t have a lot of experience with microscopy. Students seem to have more experience than we expected, but that experience may not exactly translate into being able to use the microscopes effectively in the lab, so students still need training and work to improve their skills.
What advice would you give someone who wanted to do something similar in their course?
Talk to us! We’re happy to share the activity with you, and you can find both the eukaryotic microbiology and neuroscience course versions at the links below. This activity is organism agnostic and could apply to any course that involves using microscopes or microscopic images. It can also be modified to meet the needs of your course context. For example, it could be adapted to online, you could have students work through it in groups or individually, or you could use a shortened version of the activity (it takes about an hour to complete in its current form). You also don’t need physical microscopes to do the activity, so it could be done in a classroom or lab. Angie’s implementation of the activity was in lecture, Brett’s version was done in lab.
Word document versions of the activity: Eukaryotyic microbiology course & Neuroscience course