Lesson 2. Introduction to the case of rock pocket mice

Sugat Dabholkar, Teresa Granito, Kevin Hall
Biology, Self-directed
40-50 min
High School Advanced Biology (AP)
v2

Overview

In this lesson, students will be introduced to the 'anchoring phenomenon' of rock pocket mice, specifically how the color of the fur coat changed because of the change in the environment where the live. They will explore a computational model of a population of rock pocket mice and observe changes in the population over time. 

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 co-designed by Sugat Dabholkar in consultation with Teresa Granito of Evanston Township High School

Acknowledgement

This lesson is based on a curricular unit developed by HHMI (https://www.hhmi.org/biointeractive/making-fittest-natural-selection-and-adaptation).

Activities

  • 1. The curious case of Rock Pocket Mice
  • 2. Introduction to the Computational Model
  • 3. Further investigations into the computational model
  • 4. Can you use such model to investigate what might have happened in American Southwest?

Student Directions and Resources


In this lesson, you will study a phenomenon about a population of rock pocket mice. You will explore a computational model of a population of rock pocket mice and observe changes in the population over time. You will be able to explain how the color of fur coat of mice changed because of a change in the environment where they lived. 

1. The curious case of Rock Pocket Mice


The American Southwest is a fantastic place to study rock pocket mice with different fur coat colors. Ancestral pocket mice had light-colored fur coats that blended in with the rocks and sandy soil that was prevalent in the region. This kept the mice hidden from their predators (mainly owls).  Then, a series of volcanic eruptions spewed a river of black lava more than 40 miles long that wove right through the middle of pocket-mouse territory. Lava flows created huge patches of dark rock among the surrounding light-colored sand.

Today there are now two forms of pocket mice:

  • light-colored mice that live on sandy soil
  • dark-colored mice that live on black lava rock

Researchers noticed that rock pocket mice with a dark fur coat were more common on the dark lava flows, whereas the mice with light colored fur coat were more common on the light-colored sand. How might this have happened? 

In the next few lessons we will investigate this case of pocket mice evolution using computational models.

Let's start by watching a video developed by HHMI Biointeractive about this phenomenon.


Question 1.1

Mention at least two things that you found interesting in the video.



Question 1.2

Mention at least two questions that you would like to investigate about the pocket mice in the desert of New Mexico. 

2. Introduction to the Computational Model


Here is a computational model of a population of pocket mice. 

The rules of interactions between the pocket mice are similar to the Hardy-Weinberg activity that you must have already done in class. 

Each clock tick in the model is a mouse-generation. In each generation, male and female mice move around randomly, search for a partner, and reproduce if they find a partner. The heritable trait that is modeled here is fur-coat-color of the mice. 

Explore the model and answer the questions below.

 


Question 2.1

There are two fur coat colors, light and dark. Which of these is a homozygous recessive condition?  



Question 2.2

Explain how you figured out the answer the the previous question.



Question 2.3

There are two alleles A (dominant) and a (recessive). What would the phenotype be of the genotype 'Aa'?  



Question 2.4

Explain how you arrived at the answer to the previous question.

3. Further investigations into the computational model


Let's investigate how genotype frequencies change over time in this population.

The five conditions for Hardy-Weinberg law of genetic equilibrium are:

1. The breeding population is large.

2. Mating is random.

3. There is no mutation of the alleles. 

4. No differential migration occurs.

5. There is no selection.


Question 3.1

Do you think all the conditions of Hardy-Weinberg law of genetic equilibrium are satisfied in this model? Explain your answer.



Question 3.2

Set the initial population such that it is not at Hardy-Weinberg genetic equilibrium. Write down your initial settings.



Question 3.3

Write your initial allele frequency and phenotype frequency values.



Question 3.4

Run your model for 15 generations (ticks). Note the Hardy-Weinberg equation values and genotype frequency values in the table below,



Question 3.5

Explain your observations.

4. Can you use such model to investigate what might have happened in American Southwest?



Question 4.1

Based on your investigation using this model, modify your research questions that you wrote before.

Make the modifications such that you could investigate the new questions using a computational model such as the one you explored in this lesson.