One of the important topics we cover in my BI111 (Biological Diversity & Evolution) class is the idea that Natural Selection leads to adaptive evolution. One way in which I teach this us this class (total enrolment ~800), is by a role-playing game I call the "Battle of the Beaks"
The exercise is based specifically around the drought-related events described in of Boag & Grant (1984) Ecological Monographs 54:463-489. For this exercise I have purchased a number of pliers of various sizes from needle-nose through to pipe-wrenches (mostly from garage sales and/or dollar stores), as well as peanuts and walnuts* I start off by creating two teams of students with different sized-pliers. Typically each team is made up of 3 individuals (1 to be the "baby finch", who is to be "fed" by the "adult finches").
There are buckets of peanuts* at each of the classroom, and students have to run to the buckets, pick up peanuts, race back to the starting point, crush the shells to release the contents (one team member (the "baby") counts the number of nuts cracked). This is a race, to see how different beak teams perform in 2 minutes. This is meant to simulate a good year in the Galapagos.
Next, to simulate what happens during a drought (when there is less food available, and what is left are primarily harder nuts), I break out the walnuts, and we re-do the competition between the teams. Now, the larger beaks have the advantage**. I then use this to talk about adaptive evolution, and specialization. Overall it is a fun and easy exercise that I highly recommend.
**Sometimes the results are not what you expect if you get a particularly competitive (or the opposite) team, so be prepared if the results are not what you might have been expecting!