Final answer:
Organisms contribute to putting phosphorus back into the atmosphere through volcanic activity, where phosphorus is released into the atmosphere in the form of ash.
Step-by-step explanation:
Organisms contribute to putting phosphorus back into the atmosphere through the process of volcanic activity. During volcanic eruptions, phosphorus is released into the atmosphere in the form of ash, which contains phosphorus compounds. This ash can then be deposited over land and water, and can eventually be weathered and recycled into the ecosystem.