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: