Where does the phosphorus cycle start and end?
1 Answer
All of the biogeochemical cycles, like phosphorous, don't really have a 'start" and "end" - the term "cycle" can be a bit misleading.
Explanation:
All of the biogeochemical cycles on Earth have been operating for about 4 billion years - essentially when the Earth cooled. They haven't stopped since that time, although there are times when some of these cycles may have slowed down considerably (e.g. during the Snowball Earth episode 750 million years ago, the phosphorus cycle may have slowed down). Additionally, the phosphorous cycle may have been slower to get going than, say the water cycle, as life took awhile to evolve and become a major part of this particular cycle.
The phosphorous cycle, like all the other cycles does not consist of a step 1, step 2, kind of processes. Its more like trillions of components acting within the cycle on a continuous basis. Our own bodies are utilizing phosphorus right now on a continuous basis, so we are part of the phosphorous cycle.
