Nitrogen Cycle

The nitrogen cycle is the process by which nitrogen is converted between its various chemical forms. This transformation is essential for life as it makes nitrogen available to living organisms for the synthesis of vital compounds such as amino acids and nucleic acids. Key steps include:

1. Nitrogen Fixation: Conversion of atmospheric nitrogen (N2) into ammonia (NH3) by bacteria (e.g.,Rhizobium in root nodules) or by industrial processes.
2. Nitrification: Conversion of ammonia into nitrites (NO2-) and then into nitrates (NO3-) by nitrifying bacteria (e.g., Nitrosomonas and Nitrobacter).
3. Assimilation: Uptake of nitrates by plants to form organic molecules like proteins and nucleic acids.
4. Ammonification: Decomposition of organic nitrogen back into ammonia by decomposer organisms.
5. Denitrification: Conversion of nitrates back into nitrogen gas (N2) by denitrifying bacteria (e.g., Pseudomonas), releasing it into the atmosphere.

Phosphorus Cycle

The phosphorus cycle describes the movement of phosphorus through the lithosphere, hydrosphere, and biosphere. Phosphorus is a crucial element for biological molecules like DNA, RNA, and ATP. Key steps include:

1. Weathering: Phosphate ions (PO4^3-) are released from rocks through weathering and erosion.
2. Absorption: Plants absorb inorganic phosphate from the soil.
3. Assimilation: Phosphates are incorporated into organic molecules by plants and then passed through the food chain.
4. Decomposition: Organic phosphate is returned to the soil by decomposers when plants and animals die.
5. Sedimentation: Phosphates can end up in water bodies, where they may eventually form sedimentary rock, continuing the cycle.

Water Cycle

The water cycle, or hydrological cycle, describes the continuous movement of water on, above, and below the surface of the Earth. Key processes include: