Food web simulator
http://www.learner.org/courses/envsci/interactives/ecology/food_web.php
Darwin simulator
http://darwinproject.mit.edu/research/
geochemical cycles
http://www.learningscience.org/esc3bgeochemicalcycles.htm
water cycle
https://www.youtube.com/watch?v=al-do-HGuIk&feature=youtu.be
acid rain on national monuments