1, Rain and weathering cause rocks to release phosphate ions into soils and water as inorganic phosphate
2. Plants take up the inorganic phosphate from the soil. the plants are eaten by animals and the inorganic phosphate is incorporated into organic molecules such as DNA.
3. Animals die and decay and the (organic) phosphate is returned into the soil.
4. Organic phosphate in soil is broken down into inorganic phosphates by bacteria, and some of the phosphate enters water ways and the ocean where with time it can be incorporated into sediments such as rock.