Great lesson on species diversity and adaptation as it relates to evolution measuring beaks with compasses and rulers on prints from the National Science Teacher Association here. It is based on the studies of scientists tracking medium-sized finches on the Galapagos Islands.
After finding the Galapagos Islands on the globe and reading the introduction to why this isolated, harsh environment makes it interesting to study, I divided 25 students into six groups, with each group responsible for measuring one finch beak. We then compared data, seeing the range in sizes and subtracting the difference between the largest and smallest beak in the same species of finch.
For the seed test, we used radish and pea seeds for small and large seeds. I told students to push the pennies toward the elastic if their beak stopped working. The three classes participating had varied results, but all came to the conclusion that big beaks were better adapted to getting seeds than small beaks. This was even more apparent during a "drought", when we removed most of the smaller seeds.
I divided the tasks within the group of four as well, assigning one child to use the compass, another the ruler, a third to record the data, and a fourth to report it to me. They then each got a turn with either the big beak or small beak as I timed them for one minute as they collected as many tools as they could.