This module provides students with opportunities to explore/test the impact of different components of natural selection. Students may also explore the concept of fitness in this model.
Grades: 9-12, College Introductory Biology;
NGSS standards: HS-LS4-2
A population of mice will be generated when you start the model. Before pressing on the "start" button, you may adjust the "color-variation" slider to decrease or increase the mouse color variation of the starting population. The "color-variation" slider also determines the possible range of progeny coloration. Use the "environment-color" slider to adjust the environment color to be lighter or darker.
Every mouse carries 20 units of energy. They randomly move in the environment and loses 1 unit of energy per move. If the environment patch color is not black (0), it gains an amount of energy determined by the "energy-gained" slider. If the net of the energy of a mouse is 0, it dies. The carrying capacity of the habitat ranges from 500 to 600.
If a mouse cumulates 40 units of energy, it reproduces one offspring. If the "color-heritable?" switch is on, the offspring inherits the parent color or mutates to any color ranging from 31 (dark brown) to 38.5 (light brown) based on the chance determined by the color-variation slider. If the color-heritable? is off, the offspring can be any color ranging from 31 (dark brown) to 38.5 (light brown).
Due to the predation, the more similar is the mouse color to the environment color, the more likely the mouse survives. The "Number-of-visual-predators" slider allows you to adjust the intensity of the predation. When selection pressure is 0, there is no predation
Users may input the number of years to control the years to run the simulation. It is particularly useful for testing ideas systematically.
When assigning tasks to students, we suggest you define the controlled variable value so students can get the desired results. One set of option is:
color-heritable? ON
Color-variation 15
Energy-gained 1.5
Number-of-visual-predators 15
Environment-color 37
Years 1000
Then, students may change one of the variables to explore its effect on the population.
Students may label any of two mice in the simulation to compare their fitness in a certain environment (a certain background color)
This module is made by Dr. Lin Xiang at University of Kentucky, Lexington, KY. If you mention this model in a publication, we ask that you include the citations below.
Xiang, L. (2019). Pocket Mouse Module-Fitness. Department of STEM Education, University of Kentucky, Lexington, KY.
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