Question

The movement of elements or compounds through living beings and across the ecosystem in form of characteristic pathways is known as what?

• A. Energy Flow
• B. Decomposition
• C. Nutrient Cycling
• D. Succession

Answer 1

Answer:

C. Nutrient Cycling

Understanding Nutrient Cycling (Biogeochemical Cycles)

• Nutrient cycling, also known as biogeochemical cycles, refers to the natural pathways by which chemical elements or compounds are transferred through the biotic (living organisms) and abiotic (non-living components like atmosphere, soil, water) parts of the Earth.
• These cycles ensure the continuous availability of essential elements required for life, as Earth is a closed system with respect to matter. Energy, however, flows through and is lost.

• Key Elements Involved:

  • The most important biogeochemical cycles include the Carbon Cycle, Nitrogen Cycle, Phosphorus Cycle, and Water Cycle (Hydrologic Cycle).
  • These elements are vital for the growth and sustenance of all living organisms.

• Components and Processes:

  • Each cycle involves specific reservoirs (places where elements are stored, e.g., atmosphere, oceans, rocks, biomass) and various fluxes (the movement of elements between reservoirs).
  • Carbon Cycle: Involves processes like photosynthesis (uptake by plants), respiration (release by organisms), decomposition, and the burning of fossil fuels. The atmosphere is a key reservoir for carbon dioxide (CO2).
  • Nitrogen Cycle: Crucial for protein and nucleic acid formation. It involves nitrogen fixation (converting atmospheric N2 to usable forms, mainly by bacteria), nitrification, assimilation, ammonification, and denitrification (returning N2 to the atmosphere).
  • Phosphorus Cycle: Unique as it does not have a significant gaseous phase. It primarily cycles through rocks, soil, water, and living organisms. Weathering of rocks releases phosphorus into the ecosystem.
  • Water Cycle: Involves evaporation, condensation, precipitation, transpiration (from plants), and runoff.

• Significance for Ecosystems:

  • Nutrient cycles regulate the availability of essential elements, supporting biodiversity and ecosystem stability.
  • Disruptions to these cycles due to human activities can lead to significant environmental problems, such as climate change (carbon cycle), eutrophication (nitrogen and phosphorus cycles), and acid rain.

• Competitive Exam Facts:

  • The term 'biogeochemical' highlights the involvement of biological, geological, and chemical processes.
  • Atmospheric nitrogen (N2) cannot be directly used by most organisms; it must be 'fixed' by bacteria like Rhizobium (symbiotic in legumes) or Azotobacter (free-living).
  • The primary source of phosphorus is rocks (e.g., apatite), making it a limiting nutrient in many ecosystems.
  • Deforestation and burning of fossil fuels are major human impacts on the carbon cycle, leading to increased atmospheric CO2.
  • Excessive use of nitrogen and phosphorus fertilizers in agriculture contributes to eutrophication of water bodies.