Lesson 5. Natural Selection: Part 1

Sugat Dabholkar, Connor Bain, Philip Woods, Kevin Hall
Biology, Self-directed
40-50 min
High School Advanced Biology (AP)


In this lesson, students explore the computational model of a population pocket mice further. Specifically, they investigate how inheritance works in this model.  


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


Unit co-designed by Sugat Dabholkar in consultation with teachers at Schurz High School


CODAP is a computational tool for data analysis and representation developed and built by The Concord Consortium at https://codap.concord.org/  

The first four lessons are based on a Howard Hughes Medical Institute (HHMI) Biointeractive (https://www.hhmi.org/biointeractive/pocket-mouse-evolution)

Lesson 5 is based on the lesson Evolution in Action: The Galápagos Finches Authored by Paul Strode for Howard Hughes Medical Institute based on data collected by Peter and Rosemary Grant, Princeton University.

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.


  • 1. Understanding the Mechanism of Inheritance
  • 2. Exploring the model

Student Directions and Resources

In this lesson, you will continue to explore our computational model of pocket mice further. Today, you'll be investigating the concept of inheritance of a trait across generation and how it affects evolution of a population in the model.

1. Understanding the Mechanism of Inheritance

Remember that in this model, there are mice with two types of fur coat colors: light and dark. Observable characteristics (also called as traits) like fur color, eye color, or blood type are referred to as phenotypes. These phenotypes, including the color of fur coats is determined by the genes that a mouse has. 

There are two kinds of genes in this models that affect the fur coat color of mice. 

While answering the following questions, make sure that the "PREDATION?" box is unchecked

Question 1.1

Change the sliders under the "Initial Settings" in the model. Make sure every time you change the sliders that you press SETUP afterwards so that you can actually see the effects of your new settings. Try to change the settings such that all the mice have light-colored fur. Once you get all mice with light fur, describe the initial settings you used.  

Question 1.2

What will happen after lots of generations if the initial population of mice all have light-colored fur?

Question 1.3

Run an experiment to prove or disprove your answer to the previous question and explain your observations.

Question 1.4

What will happen after lots of generations if the initial population of mice all have dark-colored fur?

Question 1.5

Run an experiment to prove or disprove your answer to the previous question and explain your observations.

Question 1.6

In this model, "AA", "Aa", and "aa" are genotypes of mice. As we saw earlier, the fur coat color of a mouse is dependent on its genotype. Based on your investigations so far, can you say which of the three genotypes applies to each of our two fur-colors (light and dark)? 

2. Exploring the model

Question 2.1

Explain how the value set by the 'chance-of-predation' slider affects the population size.

(Try setting at least five different values and observing how it affects the model before explaining the effects.)

Question 2.2

Start a new experiment with a mixed population: some mice with dark fur and some mice with light fur.

Let the model run for at least 100 generations ("ticks"). Now change the background and let it run for 100 generations again. 

Repeat the experiment a few times with different backgrounds. 

What sorts of things did you observe in your experiments?

Question 2.3

What might explain the observations that you wrote down in the previous question?