Bean Counters: A Rabbit Breeding Simulation

To simulate genetic shift in a population, we'll be breeding rabbits.  But, because the gestation period for a rabbit spans longer than the two 57-minute periods allotted for this lab, we had to settle for a simulation to squeeze in 10 generations.  Instead of rabbits, we'll be using red and white beans to simulate dominant and recessive alleles.

W. E. Castle discovered an English breed of rabbits that sometimes produce furless offspring.  England is cold.  Not having fur is usually a death sentence for our hoppy friends.  But it does give us a good model for testing out genetic shift over generations.

The lab setup:

1. In a cup (our Gene Pool), there are 100 beans.  50 are red, representing the dominant allele (normal fur - H) and 50 that are white, representing the recessive allele (furless rabbit - h).
2. Students will randomly pull two beans from our gene pool.
3. HH combinations and Hh combinations will "survive" and be placed back in a cup for the next generation.
4. hh combinations will be eliminated from the gene pool.
5. Students will record the number of remaining H and h beans in the gene pool and move on to the next generation.

Over the 10 generations, the white beans should be quickly reduced but not eliminated.  This lab has a bunch of moving parts and will require some clear instruction, but it should go well.

Here's a shot of the whiteboard.

Crabby Graphs

A lot has happened since my days in science class.  Even in college, we used peppered moths as the example of natural selection.  Peppered moths have been hammered into our minds.  I rather like our peppered moth friends, but it's also nice to mix things up.

Enter pocket mice and freshwater crabs.  Like the peppered moths, both pocket mice and freshwater crabs demonstrate natural selection in their coloration.  Last week, we used pocket mice as the last activity to solidify the concepts of natural selection; this week we will add data to the concept of natural selection as we look at populations of freshwater crabs.

Today's activity will revolve around specific types of selection in relation to environmental changes of freshwater crabs.  We will cover directional selection, disruptive selection, and stabilizing selection.  Towards the end of the period the students will be looking at data and will be graphing  phenotype frequencies (light to dark coloration) to determine the type of selection in a specific scenario.

Today's Goal:  Students will understand the concepts of directional selection, disruptive selection, and stabilizing selection.  Given phenotype frequency over time, students will be able to graph data and determine the type of selection for a given scenario.

Here's a shot of the whiteboard: