Howard Hughes Medical Institute
Hhmi: Biointeractive: The Geologic Carbon Cycle
A college-level video lecture explaining and discussing the carbon cycle. Gives an interesting perspective on the chemistry of the carbon cycle and how essential it is to the survival of life on Earth. [6:20]
Crash Course
Crash Course Ecology #9: Nitrogen & Phosphorus Cycles: Always Recycle Part 2
Hank describes the desperate need many organisms have for nutrients (specifically nitrogen and phosphorus) and how they go about getting them via the nitrogen and phosphorus cycles. [9:23]