Lesson 4. Evaluating the Model

Sugat Dabholkar, Philip Woods, Connor Bain, Golnaz Arastoopour Irgens, Kevin Hall
Biology, Self-directed
45-50 min
Introductory High School Biology
v3

Overview

In previous lessons in this unit, students have built up a model of a simple ecosystem based mainly on their intuitions about how individual animals would behave.  In this lesson they will use this model in several ways.  First, they will look at how that model is able to produce interesting patterns at the population level, even though this was not an intentional part of the process of building the model.  Second, they will think about what it means for a model to be good, and see how they can evaluate their model by comparing its results to real data from Isle Royale.

Standards

Next Generation Science Standards
  • Life Science
    • [HS-LS2] Ecosystems: Interactions, Energy, and Dynamics
    • [HS-LS4] Biological Evolution: Unity and Diversity
  • NGSS Crosscutting Concept
    • Patterns
    • Systems
    • Stability and Change
  • NGSS Practice
    • Analyzing Data
    • Using Models
    • Conducting Investigations
Computational Thinking in STEM
  • Data Practices
    • Analyzing Data
    • Manipulating Data
    • Visualizing Data
  • Modeling and Simulation Practices
    • Using Computational Models to Find and Test Solutions
    • Using Computational Models to Understand a Concept
  • Computational Problem Solving Practices
    • Troubleshooting and Debugging
  • Systems Thinking Practices
    • Investigating a Complex System as a Whole
    • Thinking in Levels
    • Understanding the Relationships within a System

Credits

Unit designed/developed by Dabholkar, S., Hall K., Woods P., & Bain C.

Acknowledgement

This work is supported by the National Science Foundation (grants CNS-1138461, CNS-1441041 and DRL-1020101) and the Spencer Foundation (grant 201600069). Any opinions, findings, conclusions, and/or recommendations are those of the investigators and do not necessarily reflect the views of the funding organizations.

Activities

  • 1. Updating our Isle Royale Predictions
  • 2. Isle Royale Model
  • 3. Comparing With Real Data

Student Directions and Resources


In this lesson, you will look at a version of the model you have been building in the earlier lessons. You will evaluate the accuracy of the model based on data from the real world. 

1. Updating our Isle Royale Predictions


In this lesson we will look at the wolf and moose ecosystem on Isle Royale again. In an earlier lesson, you thought about why the numbers of wolves and moose might change over time. Now, we will make more predictions about this ecosystem.

Look at this table showing the wolf and moose population sizes in 2011 and answer the questions below.

  Population Size
Wolves 16
Moose 515

 


Question 1.1

Do you think the number of wolves will increase, decrease, or stay the same in the future?

  Increase
  Decrease
  Stay the same


Question 1.2

Do you think the number of moose will increase, decrease, or stay the same in the future?

  Increase
  Decrease
  Stay the same


Question 1.3

Are you confident in your predictions? Why or why not?



Question 1.4

How do you think we could test predictions like these?

2. Isle Royale Model


In earlier lessons, we tried to think about how a wolf or a moose might behave in the wild. We also thought about how the populations of wolves and moose might change on Isle Royale. You have used this to build a model ecosystem, but we don't know how good of a model it is yet. In this activity we will try to figure that out.

The model below is very similar to the model you have been working with in earlier lessons. The wolves and moose follow all of the same rules as before, except that now there are plants for the moose to eat. If the wolves or moose don't eat enough food, they will die. Look at how the size of the populations changes over time.

We have also added sliders to the model that allow you to change parts of the code without having to go back into the code tab.


Question 2.1

Run the model and look at the graph.  What do the different parts of the graph represent?



Question 2.2

What do you notice about how the number of wolves and the number of moose compare? For example, when one group is large, how big is the other one? When the size of one group changes, how does the other one change?



Question 2.3

How do these patterns in the graph change when you change the inputs on different sliders?



Question 2.4

Do you think the size of the wolf and moose populations on Isle Royale would actually increase and decrease like they do in this model? Why or why not?

3. Comparing With Real Data


Scientists have studied the wolf and moose populations on Isle Royale for decades. This means we have detailed data on how these populations have changed over time. We can see how good our model is by comparing it with these data.  When a scientist ran the model from the last activity with the default settings, they got the graph on the left.  The data from Isle Royale is on the right.
 


Question 3.1

How is the graph from the model similar to the graph of real population sizes?



Question 3.2

How is the graph from the model different from the graph of real population sizes?



Question 3.3

Based on this comparison, how good do you think our model is?

  Very good
  OK
  Not good


Question 3.4

Explain your answer.