In My Classroom: Going Bananas for Phenomenon Based Teaching

I originally drafted this “In my classroom” as a way to talk about this cool lab that I used to begin talking about the role of biological molecules in living things.  I originally intended to end this with talk of how it was a great lab experience for my students and made for a good model to explain how living things utilize biological molecules.  This was all before the recent NABT conference when I learned about the work being done by teachers in Illinois to create phenomenon based storylines as a way to teach concepts and practices from the NGSS.  I still intend to say all of those things, but the ending has really just sparked a thousand new fires in my head.  Brad’s use of the lighting of the beacons from The Return of the King is in full effect, and I am seemingly humming the score as I type away.

A few years ago, an inquiry idea got posted in the October 2015 ABT about utilizing bananas as a model for learning about biochemistry.  This year, I decided to utilize the model in my classroom as a way to introduce biological molecules and begin talking about cells and cellular processes.  I started with the bananas in class, giving groups of my students (both AP and General) very ripe, somewhat ripe, and unripe bananas.  I asked them to use their chalk markers and record as many observations as they could, comparing and contrasting the bananas.  I got some predictable responses like their coloration was different, but most made great observations about the texture, mass, and taste of the bananas.  My favorite interaction was when one adventurous student informed the class of the taste and consistency of all the banana peels, pointing out that the unripe banana appeared to have a higher water content in the peel compared to the riper specimens.

So after all these observations and in class discussion, I directed students to use the two chemicals I had provided them (iodine and Benedict’s solution) and create an assay to observe how they affected the various bananas.  We made some observations, and recorded our qualitative data from what we saw.  This lead to me revealing that Iodine serves as an indicator for starches and Benedict’s for sugars.  At this point we talked about carbohydrates and their overall structure, pointing out that polysaccharides like starches are formed from sugar monomers like glucose.  We could see clearly that one banana was strongly positive for the presence of starches while the other was more strongly positive for sugars.  This lead to me posing a question.  How did all those starches seemingly disappear, and the sugars replace them?  

My students sat on this for a second.  I had to prove that I had not injected them with sugar.  Students teetered around an answer, but I eventually had a student in each class suggest that the starches are being digested.  I had one student go so far as to name drop amylase.  This lead to us talking about chemical reaction that are occurring to break these polymers up into simpler pieces.  We modeled what they looked like and investigated the role and structure of proteins, particularly amylase.  With the last few minutes of class, we broke out the microscopes and identified cells that had been stained with iodine to indicate the location of starches in the cells.  My students were super engaged with the whole process.  We had a small writeup to summarize and model the processes we had observed.  But that was kind of the end. We still talked about these things in class, but I left a pretty cool phenomenon just hanging there.

A student slide of unripe banana stained with iodine to highlight the presence of starch (in this case amylose).

As previously stated, I got to see some awesome phenomenon based teaching from my experiences at NABT, and am looking at next steps with my students.  Jason Crean from the Illinois Association of Biology Teachers has formulated these NGSS storylines in his class following specific organisms and phenomena.  His phenomena are very heavily focused on real data from collaborations with zoologists and some of his work can be found at   His focus is on how all of the content standards in the NGSS connect to each other in an engaging and coherent storyline, all sparked by an investigation into a particular phenomenon.  

While thinking about writing this post, it occurred to me that the banana lab seems like a great piece in the puzzle to start my own conceptual storyline unit on how “We are what we eat.” In my head, this will be something that delves into why some people have trouble processing certain foods and how malnutrition affects us.  I have shared a little bit about this idea already on a Facebook post, and am now looking into a collaboration to produce some conceptual storylines that follow phenomenon, not just the order the standards are packaged and delivered to us.  I realize there is safety there, but safety has never been fun.

In My Classroom # 9: I’ve Come to Have An Argument

Welcome to the KABT new blog segment, “In My Classroom”. This is a segment that will post about every two weeks from a different member. In 250 words or less, share one thing that you are currently doing in your classroom. That’s it.

The idea is that we all do cool stuff in our rooms, and to some people there have been cool things so long that it feels like they are old news. In this segment, if you are tagged all you need to do is share something you’ve done in your classroom in the last two weeks. It must be recent, but that’s it. If you are tagged, you’ve got two weeks to post your entry. Who knows… your supposedly mundane idea, lesson, or lab might be exactly what someone else really needs. Keep it brief, keep it honest about the time window, and share it out! Here we go:


This year, I am working on what kind of labs my students are conducting, and building my students skills in inquiry.  We have spent the first weeks focused on questioning and the inquiry process.  My students have already conducted a guided inquiry on Drosophila behavior in choice chambers where they came up with their own testable and measurable conditions, and followed through the scientific method. It was a great learning experience for all of us, but I want to find ways to make these labs a richer experience for the students.

Students are investigating Drosophila behavior in their choice chambers.
Students are investigating Drosophila behavior in their choice chambers.

In a process to embed the Scientific Practices and Cross-Cutting Concepts into my labs, I am starting to follow the model for Argument Driven Inquiry in my classes.  I have so far been very pleased in how my students have engaged in the experiences, and it’s exciting to see my students have a chance to engage in planning investigations and leading their own learning.  They also get a chance to share their ideas and understanding with the class when they defend their claims in an argument session.

My students are currently working on their second argument.  In our first argument, students worked on making and defending a claim to answer the question “Should Viruses be considered a living or non-living thing?” We talked briefly about the problem, and the data they had access too, but I did not explicitly teach them much of the characteristics of life before jumping in.  I simply helped model the process and what are final product could look like.  I was blown away by the results.

One group of students begins defending their claim to whether viruses are living or non-living. Their evidence and justification were a key part of their boards that they were assessed for.
One group of students begins defending their claim to whether viruses are living or non-living. Their evidence and justification were a key part of their boards that they were assessed for.

Most of my students were digging much deeper into the content then I had ever planned on assessing them for.  I had many groups looking into how viruses replicate and asking questions about why some viruses had DNA and others RNA. Students were going as far to research and describe plasmid structure, and how that may affect their claim. I did not ask for a specific amount of evidence, but only that it be sufficient to defend their answers to the guiding question.

Argument Boards

Once the evidence and justification was gathered, we all had a round-robin where we went around and critiqued other groups arguments and evidence.  Many of my students sided with the camp that viruses are non-living, but I had a couple groups that defended their status as living things.  This made are initial argumentation session somewhat one-sided, but the conversations we had were excellent.  After students recieved critiques, they went back and reformed their arguments if needed, and turned in final written arguments as groups.

A student in my class defends his group’s divided claim on virus’ living status. Some groups found evidence to support both sides, and were a little divided on whether viruses fit the model for life.

Having this experience made teaching the characteristics of life much easier. I am now having my students forming arguments on “Why do Great White Sharks travel such long distances” as a way to study animal behavior and ecology. We are using real shark tracking data from a group called OCEARCH , and going deeper into the process by having students formulate their own methodology for collecting data.  My advanced bio classes will also be doing a peer-review of final argument papers to help improve their content writing. So far, my students seem to really enjoy the process of argumentation and I hope to post more on this topic in the future.

For now, I am passing the torch on to our Kansas Teacher of the Year, Shannon Ralph, to see what’s going on in her classroom.