Biology 120: creating a modeling lab

1. Biology 120:creating a modeling lab Nathaniel Meyer, Louis Weiss, Lauren Shuler

2. Background • Target Audience • Genetics, Evolution, & Ecology Students and teachers (Biology 120) • Teaching Objectives • Provide an introduction to modeling and the systems perspective • Reinforce Understanding of population dynamics & the Lotka-Volterra predator-prey model • r- & k-selected species • Build the associated model and draw conclusions based on findings • Lotka-Volterra (predator-prey) oscillations • Given a model and an interface, allow the students to explore system dynamics by systematically changing coefficients

3. Pedagogy • Thought process • How can we best create a lab exercise that provides enough information to give students a basis for exploring the concepts on their own? • Is building or exploring more effective at first? • How do we avoid a recipe book lab? • What questions do we ask to stimulate the students? • Which concepts in the Biology 120 curriculum would be most appropriate for a modeling lesson? • Which can be most effectively taught using modeling? • Which is the best vehicle to teach modeling?

4. Structure • Presented background on modeling including STELLA software • Introduced the systems perspective i.e. stocks, flows, and feedback • Guiding steps through the exponential (r-selected species) model • Expand the exponential model to include a carrying capacity (k-selected) • Provide an interface for the Lotka-Volterra model

5. r-selected Species • Purpose of this model • Introduce the students to the STELLA software and modeling • Create a simple model of exponential growth without a limiting resource • Help them understand what ‘r’ means in “r-selected” • Formulation: Exponential Growth • dN/dt = R*N • N=P*e^rt

6. Adding k (carrying capacity) to the model • Purpose of this model • Expand the student’s knowledge of STELLA by creating a more complicated model • Help students understand what ‘k’ means in “k-selected” • Allow them to play with coefficients to see what factors most heavily affect the system • Formulation: Logistic Growth • dN/dt = r*N*(K-N) = r*N*K – C*N^2 (second order loss, first order growth)

7. r- & k-selected species Interface

8. Exploring Lotka-Volterra • Purpose of this model • Allow the students to explore predator-prey population dynamics using a previously created model • Systematically change coefficients to examine the effect of each on system dynamics • Address feedback loops and explore their implications in this model Feedback Loop (-) Predator Prey

11. Calibration • We roughly calibrated the model to Hudson Bay pelt data to find the correct coefficient values. • We then reset the values and challenged the students to calibrate the model as well.

12. Current Bio120 Student Reactions • Fit the lab to the current Bio 120 lab structure (break down into separate parts) • More explicit directions • Cover more of the material discussed in lecture • It would have been nice to see a simple ecological model prior to constructing their own (phytoplankton + nutrients) • Allow for more hypothetical thinking: maybe tell us to conceptualize a food web model • We thought we could apply what we learned more extensively (i.e. analogies)

13. Conclusions • We need to spend more time working directly with students who are unfamiliar with systems modeling. • The balance between too much and too little information is difficult to achieve. • This project and its integration into the biology program is entirely feasible.

14. In the Future • Meet with the three BIO 120 lab instructors and John (during commencement, John?) to review our exercise and discuss improvements. • Explore other possible biology topics to be used in this exercise. • Give the lab to more biology students (without modeling background).