Explains what groundwater is, how and where it occurs, how the quality of our groundwater is being affected by human activities, and the detrimental impact this has on plants and animals. (Updated: February 22, 2012)

Explains what carbon dioxide is, where it is found, sources of it, and describes human activities that contribute to carbon depletion and increased levels of carbon dioxide in the atmosphere. (Updated: February 22, 2013)