Final answer:
Phosphorus from rocks enters the human body through a cycle starting with weathering, which releases phosphate ions into soil and water. These are absorbed by plants, consumed by humans, and used for critical functions like forming bones and teeth.
Step-by-step explanation:
Phosphorus in rocks can become components of the human body through a natural process that includes the dissolution of phosphorus in water, absorption by plants, and then consumption by humans. This process begins with phosphate ions (PO4³-) being released into the soil, water, and air due to weathering of rocks and volcanic activity. From there, phosphorus enters terrestrial and marine food webs, eventually coming to rest on the ocean floor as sediment. Over geological time, uplifting of Earth's crust can return this sediment to land, where it can be absorbed by plants. Humans and other animals then consume these plants, and in this way, phosphorus becomes incorporated into our bodies, playing vital roles in our bones, teeth, and living cells.