(2) Biogeochemical Cycles

• Carbon Cycle

  • nature's way of reusing carbon atoms, which travel from the atmosphere into organisms in the Earth and then back into the atmosphere over and over again
• Six main processes of the carbon cycle

  • photosynthesis
  • respiration
  • exchange
  • sedimentation
  • extraction
  • combustion
• Photosynthesis

  • plants absorb carbon dioxide and sunlight to create fuel--glucose and other sugars--for building plant structures
• Respiration

  • chemical process organisms use to release the energy from food, which typically involves the consumption of oxygen and release of carbon dioxide
• Exchange

  • plants constantly exchange carbon dioxide with the atmosphere
• Sedimentation

  • organic or inorganic carbon will settle to the bottom of the ocean or a freshwater system, creating sediments that are rich in carbon
  • cna be a short-term or long-term term deposit or sink for carbon
• Extraction

  • CO2 is removed after burning the fossil fuel
  • CO2 is captured from the exhaust (or 'flue') gases
• Combustion

  • occurs when any organic material is reacted (burned) in the presence of oxygen to give off the products of carbon dioxide and water and ENERGY
• Nitrogen Cycle

  • biogeochemical process which transforms the inert nitrogen present in the atmosphere to a more usable form for living organisms
• Nitrogen

  • key nutrient element for plants
• Stages of Nitrogen Cycle

  • Nitrogen Fixation
  • Nitrification
  • Assimilation
  • Ammonification
  • Denitrification
• Nitrogen Fixation

  • the inert form of nitrogen gas is deposited into soils from the atmosphere and surface waters, mainly through precipitation
  • completed by symbiotic bacteria, which are known as diazotrophs
  • can occur either by atmospheric fixation - which involves lightning or industrial fixation by manufacturing ammonia under high temperature and pressure conditions
  • can also be fixed through man-made processes
• Atmospheric Fixation

  • natural phenomenon where the energy of lightning breaks the nitrogen into nitrogen oxides, which are then used by plants
• Industrial Nitrogen Fixation

  • man-made alternative that aids in nitrogen fixation by the use of ammonia
• Biological Nitrogen Fixation

  • bacteria like rhizobium and blue-green algae transform the unusable form of nitrogen into other compounds that are more readily usable
• Nitrification

  • AMMONIA is converted into NITRITE by the presence of bacteria in the soil
  • NITRITES are formed by the oxidation of ammonia with the help of NITROSOMONAS BACTERIA species
  • nitrites are then converted into NITRATES by NITROBACTER
• Reaction involved in Nitrification

  
• Assimilation

  • plants take in the nitrogen compounds from the soil with the help of their roots, which are available in the form of ammonia, nitrite ions or ammonium ions and are used in the formation of the plant and animal proteins
• Ammonification

  • when plants or animals die, the nitrogen present in the organic matter is released back into the soil
  • decomposers convert the organic matter back into ammonium
• Denitrification

  • process in which the nitrogen compounds make their way back into the atmosphere by converting nitrate (NO3-) into gaseous nitrogen
  • final stage and occurs in the absence of oxygen
  • carried out by clostridium and pseudomonas, which will process nitrate to gain oxygen and gives out free nitrogen gas as a byproduct
• Why is most of the nitrogen in the atmosphere unavailable for use by organisms?

  Because the strong triple bond between the N atoms in N2 molecules makes it relatively inert
• Rhizobium

  • symbiotic
  • found on legumes (beans, peas, and clover)
• Azotobacter

  • free-living
  • found in the soil
• Blue-green Algae

  • aka cyanobacteria
  • important free-living nitrogen-fixing bacteria in aquatic environments
• Phosphorus Cycle

  • describes the transformation and translocation of phosphorus in soil, water, and living and dead organic material
• Phosphorus

  • essential nutrient for animals and plants
  • plays a critical role in cell development and is a key component of molecules that store energy, such as ATP, DNA and lipids
• Weathering

  • cause rocks to release the phosphate ions and other minerals into the soil and bodies of water
  • plants can assimilate phosphates in the soil and incorporate it into organic molecules, making phosphorus available to consumers in terrestrial food webs
• Absorption by Plants

  • phosphate salts dissolved in water are absorbed by the plants
  • inorganic phosphorus is absorbed by aquatic plants from lower layers of water bodies
• Absorption by Animals

  • animals absorb phosphates by eating plants or plant-eating animals
• Return of Phosphorus Back to the Ecosystem

  • when the plants and animals die, they are decomposed by microorganisms; during this, the organic form of phosphorus is converted into the inorganic form, which is recycled to soil and water
• Sulfur Cycle

  • the movement of sulfur through the geosphere and biosphere.
• Sulfur

  • primarily found in sedimentary rocks or sea water
  • important to living things because it is a component of many proteins
• What is the first step in the sulfur cycle?

  Sulfur is released by the weathering of rocks.
• How is sulfur converted into sulfates in the sulfur cycle?

  Sulfur comes in contact with air and is converted into sulfates.
• What happens to sulfates in the sulfur cycle?

  Sulfates are taken up by plants and microbes and are converted into organic forms.
• How does sulfur move through the food chain?

  The organic form of sulfur is consumed by animals through their food.
• What happens to sulfur when animals die in the sulfur cycle?

  Some of the sulfur is released by decomposition while some enters the tissues of microbes.
• What are some natural sources that release sulfur into the atmosphere?

  • Volcanic eruptions
  • Evaporation of water
  • Breakdown of organic matter in swamps
• How does sulfur fall back to Earth after being released into the atmosphere?

  This sulfur falls on Earth with rainfall.