If you have some time, this ESRI Storymap of Alexander von Humboldt is a good reading assignment or a down-time article if they finish an in-class activty early. And though von Humboldt was an environmental determinist in his ideas of human culture, it is good to remember his contributions to the subject during his time, and their lasting legacies. If anything, any map or botanist lover will appreciate his detailed illustrated works, which in my opinion, are art.