Balance in the Environment and Food Web

• Role as producers in the food chain

  • Autotrophic bacteria and protists (algae) produce their own organic nutrients - photosynthesis and chemosynthesis (bacteria)
  • First link of the food chain
  • Energy stored in carbohydrates, available to next trophic level, the consumers
• Role as decomposers

  • Decomposition bacteria, saprophytic fungi and protists (e.g slime moulds)
  • Break down dead organic matter to their building blocks
  • Water, Carbon Dioxide, ammonia and heat energy released into soil, water and air during decomposition
  • Carbon, Nitrogen, Phosphorus and Sulphur recycled in environment, now available for the uptake by plants
• Role in the nitrogen cycle

  • Free-living soil bacteria and nodule bacteria convert free nitrogen into nitrates, accessible to plants
  • Ammonia released by decomposing bacteria is processed by nitrifying bacteria into nitrites then nitrates, absorbed by plants
  • Ammonia and nitrates converted into free nitrogen in the atmosphere by denitrifying bacteria
• The Nitrogen Cycle

  
• Plants need nitrogen to produce plant proteins. Plant cannot absorb free nitrogen, it must be in the form of nitrates
• Maintaining balance between O₂ and CO₂

  • Autotrophic bacteria and protists (algae) use carbon dioxide and release oxygen during photosynthesis
  • Algae are responsible for more than 50% of the O₂ produced by photosynthesising organisms
  • O₂ and CO₂ balance in maintained
• Phytoplankton produce their own food, Zooplankton include heterotrophic protozoa, which obtain nutrients from other organisms