As we head into our Ecology Unit, I thought I would write a quick post about population growth. After we discuss the biological species concept, we move on to populations. I spend about 3 days going over different population models. I like to teach graphing and provide some hands on simulations for population growth models: exponential, logistic, and survivorship curves.
Logistic Growth Lab
I first spend a day going over the difference between exponential and logistic growth, where we cover vocabulary, parts of each graph, and how to graph. I use the Model 1 and Model 3 from the POGIL activity found here: https://drive.google.com/file/d/1ef-DqEx1DaPKqjyJ-InHSFus9j5h5Y2M/view?usp=sharing. Students also complete a graphing activity where they model exponential growth of bacteria from a lab and compare that to a scenario of rabbits exhibiting exponential growth in the wild.
Next, we move on to logistic growth, limiting factors, and carrying capacity. The goal of the lab is to simulate how limiting factors effect the growth of a population and determine the carrying capacity of an environment. The lab uses a grid (which we draw onto the lab tables), beans, and dice. It is such a low cost set-up, which is one reason I love this lab.
Students roll the dice and place beans into the grid. As the beans are placed into spaces where other beans are already inhabiting, those beans all die off. The beans that survive, reproduce. This continues over many generations. The students graph then graph the data and determine the carrying capacity.
Then they will graph an exponential line to show population growth if the environment could reach it's full biotic potential. This spirals back in the information about exponential growth from the day before. Then they use the data to answer analysis questions. You can find the full lab here: https://docs.google.com/document/d/1hbnsbtG8ngeNx8jl8qf2dWHNyfP-yKmGgH_8xaHj-EM/edit?usp=sharing
Survivorship Lab
I spend the first part of class going back over the POGIL (https://drive.google.com/file/d/1ef-DqEx1DaPKqjyJ-InHSFus9j5h5Y2M/view?usp=sharing) using Model 2. Then I introduce them to the Survivorship of Bubbles.
Essentially, the students are going to test the survivorship of two model organisms: Bubblia bubblias and Bubblia bubbobles. These two organism produce bubble offspring. One of the organism lets their bubbles fly without any parental contact, the other organism likes to nurture and provide parental care until the bubbles are 15 seconds old, then they let them go on their own.
Students record how long the bubbles survive in each population. Then using Google Sheets, they graph the survivorship for each population. Then they answer the question: Question: How does a life history that includes extended parental care affect the survivorship of a population of model “organisms?” using CER format.
Not only is this lab super fun, because who doesn't love bubbles?!?!?! but it also very easily shows how survivorship changes with prenatal care/nurturing. Here is the lab for you to give it a try with your kiddos: https://docs.google.com/document/d/1KDC_NhLFbPmUDbijvhqOyIMVsiK3Hk6Douj7yIXwXzk/edit?usp=sharing
Happy Teaching!
Mrs. Townsend