Lesson Summary

P mining
Phosphate mining is one way humans alter the phosphorous cycle. Photo courtesy of Susan Drackett/Flickr.

  • The circulation of important materials through Earth's spheres are known as biogeochemical cycles
  • There are 4 major biogeochemical cycles of particular importance to planet Earth: the water, nitrogen, phosphorous, and carbon cycles
  • Despite the fact that most of our atmosphere is composed of nitrogen, it is not in a form usable by organisms
  • Nitrogen needs to be "fixed" in order to be used by plants and animals; this is done mainly by bacteria, but lightning and forest fires can fix nitrogen too
  • Humans alter the nitrogen cycle mainly through the addition of fertilizers to agricultural fields
  • Nutrient pollution, the addition of too much nitrogen and/or phosphorous to the environment, causes eutrophication
  • Humans alter the phosphorous cycle mainly through phosphate mining. Phosphorous is mined for use in detergents and fertilizers
Last modified: Thursday, 7 October 2010, 9:03 AM