This simulation shows the spread of a favorable mutation through a population of pocket mice. Even a small selective advantage can lead to a rapid evolution of the population.
Pocket Mouse Evolution Background
The pocket mice that evolved on dark lava rock had a selective pressure associated with being light or dark—owls and other predators could more easily see the light pocket mice than the dark pocket mice (see "Pocket Mouse and Predation" animation). By using a mathematical formula from population genetics called the Hardy-Weinberg equation, we can calculate how quickly a given advantageous trait will spread through a population. The main variable we will consider is called s (selection coefficient). It is a measure of how much of an advantage is given to the individual with that trait. An s equal to 0.01 is a very modest 1% selective advantage—for every 100 light-morph offspring that survive, 101 dark morphs survive. In this case, the dark variation will make up 95% of the population in about 1,000 generations. With s equal to 0.1—a more significant but still moderately modest 10% advantage—the population becomes almost all dark colored in only 100 generations, illustrating how a rapid evolutionary change can occur even when the selective advantage is relatively low.
From Lecture Two of the 2005 Holiday Lectures Series "Evolution: Constant Change and Common Threads"
Pocket Mouse Evolution Teaching Tips
The animations in this section have a wide variety of classroom applications. Use the tips below to get started but look for more specific teaching tips in the near future. Please tell us how you are using the animations in your classroom by sending e-mail to firstname.lastname@example.org.
Use the animations to make abstract scientific ideas visible and concrete.
Explain important scientific principles through the animations. For example, the biological clocks animations can be used to demonstrate the fundamentals of transcription and translation.
Make sure that students learn the material by repeating sections of the animations as often as you think necessary to reinforce underlying scientific principles. You can start, restart, and play back sections of the animations.
Urge students to use the animations in accordance with their own learning styles. Students who are more visually oriented can watch the animations first and read the text later, while others might prefer to read the explanations first and then view the graphics.
Incorporate the animations into Web-based learning modules that you create to supplement your classroom curricula.
Encourage students to incorporate the animations into their own Web-based projects.
The 2005 Holiday Lectures Series "Evolution: Constant Change and Common Threads"