As the students enter class, they take out their journals and respond to the prompt:
Is mitosis important? Why or why not? Write your answer in Claims-Evidence-Reasoning format.
While the students work on the prompt, I circulate through the room reading their responses and asking them probing questions. For instance, if a student writes that mitosis is important because it is the process through which new cells are created, as is seen in this student journal sample, I ask them to explain what types of cells are created.
Once the students have finished up their writing, I lead a whole class discussion on the topic. I begin by asking for a show of hands for which students think mitosis is important and then a show of hands by the students who think mitosis is not important. There are a couple of students in each class that thought mitosis was not important, so I asked students to explain their positions using the evidence they had written in their CER. By the end of the discussion, the students come to consensus that mitosis is important for replicating somatic cells.
This is the video that students are expected to view and take notes from prior to this lesson.
The students take out their mitosis notes and notes review, so they may add information as necessary. We review the notes as a class, paying close attention to the stages of mitosis. We carefully review the various diagrams and pictures of the steps, and I share reminders with the students as to how they can remember some of the items that are occurring during each phase. For instance, I explain that in metaphase, the chromosomes are meeting in the middle, and I emphasize that the primary words in the descriptor begin with the letter "m". I also describe anaphase with the phrase - A A Anaphase Away, as a reminder that in anaphase the chromatids are moving away from each other.
After we have reviewed the phases of mitosis by looking at pictures, I lead the students in a model sorting activity. I have a model set that shows a cell going through the various phases of mitosis. I randomly hand out the models and ask the students holding the models to stand in a line at the back of the room. It is then the job of the students who are not holding models to correctly line up the students who are holding the models. I facilitate this discussion by first asking the students if they think the models are all in the correct order; I make sure that they never are. I then call on a volunteer to suggest where one of the models should be moved. I require that the volunteer provide an explanation as to why he/she has moved the model to a different place in the line. This then opens up class discussion as I ask the rest of the class if they agree or disagree with the placement. We continue this process until the students are satisfied with the order of the models. I then ask the students holding the models to look for the number written on the model. I begin with the first student in line and have the students read off their numbers. If the sequence is correct, all of the numbers will be in the correct order. If the sequence is not correct, which is what occurred in this organizing mitosis models video, we discuss the errors and take a closer look at the models, so the students understand the correct placement.
Once we have practiced with the models, I explain to the students that they will be working in groups to create their own models of the phases of mitosis. I hand out the Mitosis Model Activity sheet and explain the expectations for completion. The students must begin by writing in the information and selecting a group member to create a model for each specific phase. Their finished worksheet (student work) serves as their entrance ticket into the lab, where they are able to collect supplies for the activity. The students then begin making mitosis models. The students are told that they will share their models with the class in an upcoming lesson. By making the models and reviewing the function of cells, students are addressing NGSS SP2 and MS-LS1-2. I have found that having students make models of the various phases of mitosis helps them to better understand which cellular structures are changing during the phase and how they are changing. Working in groups on this process also encourages a dialogue centered around how the cellular components change throughout the entire process of mitosis. Finally, as we review the students' finished models as a class, the students are able to identify which phase is being modeled, even though the students used different materials, showing that they have an understanding of the concept being modeled.
I used to use paper plates as the cell templates for this activity, but now I use coffee filters, since we usually have some left over after our DNA extraction. I also provide students with various colors of string, beads, toothpicks and other items. This year I added a variety of uncooked pastas for possible use during model creation. I have found that my students are much more creative and willing to think creatively if I provide a supply table for them to choose from, rather than giving them all the same item to work with. This is a video review of student work.
Near the end of the class period, I have the students clean up their area and then we discuss any difficulty they may be having in the creation of their models. Some of the students have difficulty manipulating the materials in a way that they feel best represents what is occurring the phase they are attempting to model, so we discuss possible alternatives as a class. This discussion allows them to brainstorm with their peers, but more importantly, it provides me with insights into how well the students understand what is occurring during the phases of mitosis. This discussion also addresses NGSS Cross Cutting Concept Systems and System Models as we discuss not only the limitations of the materials for the models but also the limitations of the models themselves.