But what bothers me about this exercise is that it's all pretty abstract. We can talk about resources and even think of examples. But it remains a kind of thought exercise without a compelling hook into the reality of biological systems.
So the other day I picked up some Legos and started to model a termite mound, which incidentally is my favorite example for discussing environmental constraints with students. What looked like thousands of blocks began to appear quite inadequate by the time I had started an outer chamber to surround the inner chamber of my termite mound. I realized I would have to build more efficiently or much, much smaller as my supply of lego bricks dwindled. What would a termite colony do?
Aha! A way to teach about how constraints limit biological processes! Maybe I shouldn't order all those extra bricks after all.