Quick Takes: Fill-in-the-blank review races

I love a good Kahoot as much as the next teacher, but they do have their limitations. Sometimes I want a review activity that has a little more conceptual heft. And sometimes I need to mix things up so it’s not “all Kahoots all day”. I’ve used cloze reading activities in the past, so it was an easy pivot to make them into a review activity.

A good starting place to make a cloze reading activity is the supplemental materials that are commonly published with textbooks.* The book we use, Biology by Miller and Levine, includes summaries of each textbook section. I adapt those by using the parts of the section we covered, and then add information from other activities (including labs or class notes). Once you have the basic text, you strategically replace words or phrases with blanks. Many times, I will remove a vocabulary word but also add some context clues so students have to understand the meaning of the vocabulary word to correctly fill in the blank.

You can use a cloze reading activity at any point in an instructional unit, but I like to save them for review days. By that time, we’ve covered the content through reading, note-taking, labs, and formative assessments. Using the cloze reading is a form of retrieval practice. As I tell my students, “The information is in your brain already, you just have to teach your brain how to find it.”

And of course, kids love review games. I pair students, usually with their table partner, and have them set their notebooks on the table for easy access. I set this review up as a race – partners work together to fill in the blanks, and the first group to correctly complete the reading gets a prize. (I usually give prizes to second place winners as well.) By working with a partner, students who are less confident in their knowledge still have a good shot at winning.

I hand out the reading by placing it face-down in front of each group, telling students to leave the paper face down until I get all of them handed out. And then it’s “Ready . . . Set . . . GO!” While they’re furiously working, I am at my desk with the answer key. As a group finishes, they come up and I mark any blanks that are incorrect and send them back to keep working. If multiple groups are finished, they form a line at my desk so I can check their papers in order.

Once winners are declared, I project the answer key – all students are expected to complete a reading worksheet and glue it in their notebook. I also ask students to reflect on how well they knew the answers and use that reflection to plan their study time. I can also take questions to clarify any knowledge gaps or misunderstandings.

In my experience with this review activity, all students are engaged to the very end. And it only takes ten minutes, so I can do other review activities during the same class period. I also send a blank copy (and the answer key) to our Center for Student Success so the teachers there can use it to review with students who have a CSS period (supported study hall).

*I can’t include a sample, since the worksheets I make are derived in large part from copyrighted textbook materials.

A follow-up to the Agar Cell Size lab

In my recent post, “A new spin on the agar cell size lab”, I outlined my take on a common surface-area-to-volume-ratio activity. Since then, my students have turned in their lab assignments, so I wanted to follow up with how they did. Students were very successful at collecting raw data, but struggled with some of the calculations. I am going to make some modifications to my instructions to clarify a couple of things.

Recorded data – both BTB agar spheres were submerged in vinegar for 15 minutes
Each student group had a small sphere; I had the large sphere and shared that photo with students

One benefit of having a 1:1 device school is that I could easily share my photo of the large sphere with students. I wanted students to insert photos of both spheres into their document so they could complete the calculations at home without having to figure out where their photos were. I also had several students absent for this lab, so I could email them both photos – no need to have them come in later for a make-up lab because the only data they needed were the photographs.

Calculating the rate of diffusion

I had students calculate the rate of diffusion only for the large sphere. In a later question, students used that rate of diffusion to calculate how long it would take a molecule to completely diffuse into the center of each sphere (assuming the rate of diffusion to be constant for both spheres).

Once they made that comparative calculation, the final question asked them to summarize their findings, CER style. One of the main foci this year has been analyzing labs using the claim-evidence-reasoning practices. Students used their calculations to explain how changing the SA/V ratio affects a cell’s efficiency.

Evidence-based conclusion, CER style

By focusing on one small aspect of cell size, students were able to more clearly articulate why cells tend to be small. In addition, since the agar was pre-formed, there wasn’t the margin of error that results from students cutting their own agar shapes.

How does meiosis produce genetic diversity? A hands-on but simple modeling activity

It’s easy to say, but hard to visualize – “Meiosis produces genetic diversity through crossing over and independent assortment.” NGSS Standard HS-LS3-2 says (in relevant part), “Make and defend a claim based on evidence that inheritable genetic variations may result from new genetic combinations through meiosis.” Last week I went over this with my classes a couple of times – I gave a mini-lecture and had students take notes that included a description of crossing over and independent assortment. I provided them with a blank diagram that I drew with two pairs of homologous chromosomes, and had them illustrate crossing over first, and then independent assortment into gametes. We did the Build-a-Bird activity from the Genetic Science Learning Center with paper chromosomes. But after completing both those activities, students couldn’t quite make the jump from modeling the processes with just one or two chromosomes to understanding how this process happens with a larger number of chromosomes.

The word I kept repeating was “random”, and pointed out where we saw randomness in each of the activities. In the Build-a-Bird activity, after each student had completed crossing over, I had them look at other students’ chromosomes and notice that everyone had “crossed over” at different places. And I pointed out that it was random which of the four gametes they chose for their offspring. Still, based on the questions they were asking me, I felt like they weren’t quite getting it. I think part of the difficulty was because the activities we used had such a small number of chromosomes and genes.

I struggled to find something online that could show the concept, especially independent assortment, but without taking up another whole class period. I didn’t find anything, so I decided to put together something on my own. One of the things I especially liked about the Build-a-Bird activity was that students were physically modeling concepts on paper chromosomes, so that was my starting point. I created 12 chromosomes (because my largest class has 12 students ) of varying sizes, and spread 26 different “genes” over those chromosomes, with a variety of homozygous and heterozygous alleles. I printed them on colored paper so students could see the paternal and maternal chromosomes, and also so that when they modeled crossing over, it would be visually clear where it happened.

Replicated chromosomes prior to crossing over

Each student got one chromosome – I explained that the chromosomes had already been replicated, so each student got one tetrad. I instructed students to perform crossing over either one or two times, at anyplace on the chromosomes, as long as the crossing over was between non-sister chromatids. To “cross over”, students cut the non-sister chromatids at the same place, switched the cut pieces, then taped the chromosome back together. (To be honest, this activity doesn’t really show the randomness of crossing over since each student has a different chromosome. The Build-a-Bird activity is much better for this.) After they completed crossing over, I had students separate their tetrad into four separate chromatids, turn over their papers, and mix them up.

To demonstrate independent assortment, I set four large beakers on a table and told students that each beaker was going to represent one gamete. I instructed them to bring their chromatids and drop each one into a different beaker, in whatever order they wanted.

Four separate gametes, each containing twelve chromatids

Each table group got one beaker – I instructed them to place the chromosomes in order and tape them onto a piece of construction paper. They could then easily see that each of the gametes had a unique combination of alleles and of paternal and maternal chromosomes.

The final gametes

I had students write down the alleles in each gamete, then work with their table groups to discuss how this activity showed the randomness of crossing over, and the randomness of independent assortment. They wrote a brief reflection on their understanding of genetic diversity. As I circulated and listened to students discussing the prompts, they seemed to have a deeper understanding of how these two events worked together to create diversity in gametes.

About halfway through the first class, a lightbulb went off – if I have each of my classes do this activity, I can then create a display showing that one individual can create many unique gametes because of the huge number of possible crossing over events and the huge number of possible ways to sort chromatids into gametes. I ended up with 16 gametes, so I made the display below and hung it in the hallway outside my classrooms. (I float between two classrooms, so I wanted all of my classes to be able to see the display.)

One individual, many unique gametes

I think that the kinesthetic activity of putting each of the four chromatids into a separate “bucket” helped students understand the role of independent assortment in creating genetic diversity. The benefit of this activity (compared to Chromaseratops or similar activities) is that it was very quick – the whole activity took 15 minutes at most, and that it isolates one of the more confusing concepts. By demonstrating independent assortment with 12 chromosomes (and 26 genes), it’s not a great leap from there to understand why siblings are so different from each other.

4/22 edit: Here are the documents I created for this activity. Feel free to use them – they are set to “View only”, so you will need to download them. Modeling Meiosis and Gametogenesis worksheet; Chromosomes/tetrads; Chromosomes/parent.