APES UNIT 1 - Phosphorus Cycle

• What is phosphorus needed for in cells?

  To make ATP (adenosine triphosphate)
• Why is phosphorus considered to have a slow cycle?

  Because there is no atmospheric cycle and the lithosphere is a slow cycle
• What makes phosphorus a limiting factor for plants?

  Its availability is restricted in the environment
• Which nutrient is a limiting factor for terrestrial producers?

  Nitrogen
• Which nutrient is a limiting factor for aquatic producers?

  Phosphorus
• Why do fertilizers contain both nitrogen and phosphorus?


  Because both are limiting factors for plant growth
• What is the sequence of human impact on the phosphorus cycle?

  Fertilizer run-off leads to eutrophication, which causes depletion of oxygen and creates dead zones
• What processes are involved in the abiotic cycle of phosphorus?

  • Weathering of rocks releasing phosphates into solution
  • Runoff into waterways
  • Precipitation of solid phosphates
  • Phosphates in soil
• What processes are involved in the biotic cycle of phosphorus?


  • Plants absorbing phosphates
  • Plants being eaten by herbivores (e.g., rabbits)
  • Decay of plants and herbivores releasing phosphates back into soil
• What is the currency for energy in all cells?

  ATP
• How does the phosphorus cycle differ from the nitrogen cycle in terms of atmospheric presence?

  The phosphorus cycle does not have an atmospheric cycle, while the nitrogen cycle does