Comprehensive Guide to the Nitrogen, Phosphorus, and Carbon Cycles

The Nitrogen Cycle

• Nitrogen Fixation:

  • The process by which bacteria located in the soil and within the root nodules of leguminous plants convert atmospheric nitrogen gas into ammonium ions.

• Nitrification:

  • The biochemical process that converts ammonium ions into nitrites and subsequently into nitrates.
  • This process is carried out by specialized groups of nitrifying bacteria.

• Assimilation:

  • The process involving the direct uptake and absorption of nitrates from the soil by the roots of plants.

• Ammonification:

  • The process in which decomposers, specifically fungi and bacteria, break down organic nitrogen compounds found in dead organisms and organic waste.
  • Converts these organic nitrogen compounds back into ammonium.

• Denitrification:

  • The process that turns nitrates back into atmospheric nitrogen gas.
  • Executed by denitrifying bacteria.

The Phosphorus Cycle

• Weathering:

  • The physical and chemical breakdown of rocks.
  • In the phosphorus cycle, weathering releases bound phosphate ions from geological formations into soil and aquatic environments.

• Surface Runoff & Fertilizer Runoff:

  • Phosphate ions readily dissolve in water and are carried via surface runoff into natural waterways.
  • Agricultural fertilizers spread on land contain high concentrations of phosphates that can similarly wash off into surrounding waterways.

• Decomposition:

  • Decomposers process dead organisms, extracting and releasing stored phosphates back into the environment.

• Sedimentation:

  • The process where the remains of dead marine organisms accumulate and undergo compaction by sediment over thousands of years.
  • Over time, this compaction forms sedimentary rocks.

• Uplift:

  • A major geological process that shifts sedimentary rocks from ocean floors onto terrestrial land environments, exposing them to renewed weathering.

The Carbon Cycle

• Photosynthesis:

  • The process by which autotrophic organisms, specifically plants and algae, take in atmospheric carbon dioxide ($CO_2$).
  • They convert carbon dioxide ($CO_2$) into glucose by utilizing energy from sunlight and water.

• Cellular Respiration:

  • The metabolic pathway used by both animals and plants to break down organic compounds and release energy essential for vital biological processes.
  • Cellular respiration releases carbon dioxide ($CO_2$) back into the atmosphere or water.

• Decomposition:

  • Fungi and bacteria act as decomposers to break down dead organisms and organic waste products.
  • This process breaks down organic matter, releasing organic compounds, inorganic compounds, and carbon dioxide ($CO_2$).

• Fossilization:

  • Occurs under specific environmental conditions when dead organisms are buried without fully decomposing.
  • Over timescales extending over thousands and millions of years, these remains undergo fossilization to form fossil fuels.

• Combustion:

  • The chemical burning of fossil fuels for energy.
  • Combustion releases vast amounts of carbon dioxide ($CO_2$) directly into the atmosphere.