Biogeochemical Cycles

• Biogeochemical cycles


  The flow of materials in the ecosystem
• Law of Conservation of Matter: "matter cannot be created nor destroyed in any chemical reaction. It can only be changed from one form to another."
• As energy flows through the food chain


  Nutrients also flow within the food chain
• Nutrients


  Chemical elements and compounds that are crucial to the growth of living organisms
• Oxygen-carbon dioxide cycle


  1. Organisms use and produce gases in photosynthesis and respiration

  2. Gases flow through organisms and the environment in a cyclic process

  3. Plants produce oxygen and use carbon dioxide in photosynthesis

  4. Animals produce carbon dioxide and use oxygen in respiration

  5. Plants use oxygen and produce carbon dioxide in respiration at night

  
• Water cycle


  1. Evaporation

  2. Transpiration

  3. Condensation

  4. Precipitation

  5. Absorption by plant roots

  6. Seepage into groundwater

  7. Overflow into oceans

  
• Nitrogen cycle


  1. Fixation

  2. Atmospheric fixation

  3. Biological fixation

  4. Industrial fixation
• About 79 percent of the gases in the atmosphere is made up of nitrogen gas
• Organisms use nitrogen to build proteins and nucleic acids
• Some bacteria convert nitrogen to ammonia through nitrogen fixation
• Nitrogen-fixing bacteria live in soil and are abundant in the nodules of legumes such as mung beans
• Nitrogen cycle


  1. Fixation

  2. Conversion to ammonia

  3. Other stages
• Monoculture


  • Cultivation of a single crop in large areas
• Herbicides and insecticides


  • Destroy insect pests and weeds, but also beneficial organisms
• Chemical fertilizers


  • Increase soil acidity and destroy soil structure over time
• Deforestation


  • Non-selective cutting of trees from a large tract of a forest
• Pollution


  • Addition of harmful substances to the environment in a concentration that damages the health of organisms
• Introduction of non-native or exotic species

  • Organisms introduced by humans that become invasive and outcompete native species
• Desirable practices to conserve the environment

  • Growing a variety of crops
  • Biological control of insect pests
  • Organic farming using natural fertilizers