Water And Nitrogen Cycle

key notes :

Water Cycle (Hydrological Cycle)

  • The water cycle is a natural process through which water moves continuously between Earth’s surface and atmosphere, maintaining the planet’s water balance.
  • Key Processes in the Water Cycle:
    1. Evaporation: The heat from the sun causes water from oceans, rivers, and lakes to convert into water vapor and rise into the atmosphere.
    2. Condensation: As the water vapor rises, it cools and changes into tiny water droplets, forming clouds.
    3. Precipitation: When the water droplets in clouds combine and grow heavy, they fall to the ground as rain, snow, or hail.
    4. Infiltration: Some of the water from precipitation seeps into the ground, replenishing underground water sources or aquifers.
    5. Runoff: Water that does not seep into the ground flows over the surface into rivers, lakes, and eventually back to the oceans.
    6. Transpiration: Plants absorb water through their roots and release it as vapor into the atmosphere through their leaves.
  • Significance of the Water Cycle:
    • It ensures a consistent supply of fresh water for living organisms.
    • It regulates the Earth’s temperature and climate by influencing weather patterns.
    • It plays a vital role in supporting ecosystems and agricultural practices.

Nitrogen Cycle

  • The nitrogen cycle is a critical process that converts atmospheric nitrogen into forms usable by living organisms and returns nitrogen to the atmosphere to maintain balance.
  • Key Processes in the Nitrogen Cycle:
    1. Nitrogen Fixation: Atmospheric nitrogen gas (N₂), which cannot be used directly by plants, is converted into ammonia (NH₃) or other compounds by nitrogen-fixing bacteria in the soil or during lightning storms.
    2. Nitrification: Ammonia is further converted into nitrites (NO₂⁻) and then into nitrates (NO₃⁻) by nitrifying bacteria. Nitrates are absorbed by plants to create proteins and other compounds.
    3. Assimilation: Plants use the nitrates absorbed from the soil to synthesize proteins and nucleic acids. When animals consume plants, the nitrogen becomes part of their bodies.
    4. Ammonification: Decomposers break down organic matter like dead plants and animals, releasing ammonia back into the soil.
    5. Denitrification: Denitrifying bacteria convert nitrates in the soil back into nitrogen gas (N₂), which is released into the atmosphere, completing the cycle.
  • Significance of the Nitrogen Cycle:
    • It provides plants with essential nitrogen, a key component of proteins and DNA.
    • It ensures the recycling of nitrogen within ecosystems, supporting life processes.
    • It maintains the balance of nitrogen levels in the soil and atmosphere, preventing excess buildup or depletion.

Importance of Both Cycles

  • These cycles are interconnected and crucial for maintaining the balance of essential elements on Earth.
  • They support life by recycling water and nitrogen, ensuring the availability of these resources for plants, animals, and microorganisms.

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