## Zombie Attack and Exponential Growth (What to do after state testing…)

After the End of Course test I am always scrambling to find activities for my students. I did this zombie activity in my class last year, but this year several other teachers and I teamed up and collaborated to put together this very cool activity. (To be honest, my contribution was only the worksheet.)

On day one, we showed the movie Contagion. We discussed the r not value and how viruses spread.

We prepared small cups of water, numbering them on the bottom. We filled the cups half way with water and put a few lemon drops in one of the cups. Each student received a cup.

The students were then told to share water with one other student. This involved two students getting together and one of them emptying their content into the other cup. We asked them to transfer the water from one cup to another three times to make sure the liquids mixed. After this, the students equally distributed the water between the two cups. This constituted sharing with one other person. We repeated this two to three more times (depending on the size of the class). After this we added a few drops from this pH test kit.

If the water turned yellow, the student was infected. We then discussed what students shared water and who they shared with. In both classes the students were able to discover who initially had the virus (lemon juice). We confirmed this with the numbers on the bottom of the cups. Doing this part of the activity really helped students understand exponential growth and how viruses spread. We handed out the following zombie attacks packet and had the students work through the exponential growth using different scenarios.

Next year, the plan is to have the entire STEM academy join in the fun. We would like the STEM English teachers to have their students research creative stories that include exponential growth and decay or the spread of bacteria. The science teachers will add their expertise and critique the film from a scientific plausibility stand point. We asked the history teachers if they would have their students research past epidemics and the effects on society. As we collaborated as a STEM academy, the excitement grew and new ideas sprouted. I’m excited to see the great collaboration that will happen next year after the End of Course test. This is just evidence that learning doesn’t stop after state testing.

Shouldn’t that sharing method result in a logistic growth model rather than an exponential one? In a small class, sharing will pretty soon be highly probably with someone already “infected”, slowing the growth of the “infection”. You would need a huge class for random mixing to match the exponential model for more than a few rounds of sharing.

I agree it would, but my students have not been exposed to the logistic model so for our purposes, the exponential is the best fit. If you download the zombie packet, you will find the last question addresses the logistic function. I ask students to research it and create their own explanation. I then ask the students if the logistic or exponential is a better fit for our story and all my students concluded the logistic function was a better fit. It is a nice way for them to discover this new function on their own and remember the differences between the two. Several students did try to perform a logistic regression, but it failed due to our domain. Thanks for reading the blog!

When you complete the Tracking section, are you doubling for each day? Each zombie infects one person per day, right?

By ‘r not’ you mean ‘r naught’, right?

thanks

You are correct. Each zombie infects one person per day. Thank you for catching my typo on the r naught. I updated the file.

Amber