"When we try to pick out anything by itself,
we find it hitched to everything else in the Universe."
Earth is virtually a closed system; with little matter being added from meteorites that survive their passage through the mesosphere. Given this fact, the matter that does exist on Earth must perpetually cycle. The general view of cycling on Earth, is of inorganic substances moving. We often refer to the rock cycle and the water cycle, with both examples devoid of biological intervention. Every level of all matter cycling involves interaction with the biotic world, however unseen. Microbes may not be large enough to see with the unaided eye, but they are there assisting in every aspect of the dynamic Earth. This unit will cover the basics of biogeochemical cycling, its importance, an explanation of microbes and their influence on nutrient cycling, followed by a more detailed description of the most referenced cycles; the carbon, nitrogen, phosphorus, and sulfur cycles.