Phosphorus Cycle – Class 12 | Chapter – 14| Biology Short Notes Series PDF

Phosphorus Cycle: The phosphorus cycle is a biogeochemical cycle that describes the movement of phosphorus through the biosphere, lithosphere, hydrosphere, and atmosphere. Phosphorus is an essential element for all living organisms and is a key component of DNA, RNA, ATP, and cell membranes.

In the natural cycle, phosphorus moves through different forms, including rock minerals, soil, water, and organisms. The main processes involved in the cycle are weathering, which releases phosphorus from rocks into the soil, uptake by plants, transfer from soil to water, sedimentation and incorporation into sedimentary rock, and volcanic activity. Human activities, such as agriculture, mining, and wastewater disposal, can greatly impact the natural cycle by altering the levels of phosphorus in different parts of the cycle, leading to environmental problems such as eutrophication and algal blooms.

Steps of Phosphorus Cycle

The Steps of Phosphorus Cycle are:

  • Phosphorus in rocks: Phosphorus is found in rocks, primarily in the form of phosphate minerals.

  • Weathering: Weathering of rocks releases phosphorus into the soil in the form of inorganic phosphate.
  • Uptake by plants: Plants absorb phosphorus from the soil in the form of inorganic phosphate and incorporate it into their tissues.
  • Transfer from soil to water: Some of the phosphorus in soil is transported into nearby waterways through runoff or leaching.
  • Phosphorus in water: In water, phosphorus is taken up by algae and other aquatic organisms, which use it for growth and reproduction.
  • Sedimentation: Dead plant and animal matter containing phosphorus settles to the bottom of waterways and accumulates as sediment.
  • Incorporation into sedimentary rock: Over time, the sediment containing phosphorus becomes compacted and incorporated into sedimentary rock.
  • Volcanic activity: Volcanic activity can release phosphorus from the lithosphere and return it to the soil or water.
  • Decomposition and mineralization: Decomposition of organic matter by bacteria releases phosphorus back into the soil, where it can be taken up by plants again or enter the water cycle.
  • Human activities: Human activities such as mining, agriculture, and wastewater disposal can greatly impact the natural phosphorus cycle by altering its levels and distribution.

Importance of Phosphorus Cycle

Importance of Phosphorus Cycle are:

  • Energy storage: Phosphorus is a key component of ATP (adenosine triphosphate), the molecule that stores and releases energy in cells.
  • DNA and RNA: Phosphorus is a critical component of DNA and RNA, the genetic material that controls the expression of genes and the transmission of genetic information from one generation to the next.
  • Cell membrane structure: Phosphorus is a component of phospholipids, the main building blocks of cell membranes.
  • Bone and teeth formation: Phosphorus is an important component of bones and teeth, providing structural support and helping to maintain their strength and stability.
  • Plant growth: Phosphorus is a key nutrient for plant growth, helping to regulate root development, flowering, and seed production.
  • Soil fertility: Phosphorus is an essential component of fertilizers, helping to maintain soil fertility and improve crop yields.
  • Environmental balance: Phosphorus plays a critical role in maintaining the balance of aquatic ecosystems, by influencing the growth and reproduction of aquatic plants and animals.


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By Team Learning Mantras