Ecosystems and the environment

• Producer


  An organism that makes its own food
• Primary producers


  • Photosynthetic organisms like green plants and algae that trap energy from the sun
• Primary consumer


  An organism that feeds on producers
• Secondary consumer


  An organism that feeds on primary consumers
• Tertiary consumer


  An organism that feeds on secondary consumers
• Herbivores


  Animals that only eat plants
• Carnivores


  Organisms that mainly eat animals
• Decomposers


  Organisms that break down dead matter
• Food chains


  • Show the feeding relationships of different organisms and the flow of energy between the organisms
• Food web


  Shows the interactions of multiple different food chains
• Food chain


  Shows one path of food dependencies
• Biomass transfers are not 100% efficient
• Reasons for biomass transfers not being 100% efficient

  • Egestion (removal of faeces)
  • Excretion (removal of waste products e.g. urine)
  • Respiration
  • The production of inedible bones and shells
• Biomass


  The dry mass of all of the living organisms in an area
• Dry mass is used for biomass because the wet mass varies as the volume of water in the organism varies
• Biomass pyramid


  A pyramid that shows the total dry mass of organisms at each trophic level
• Pyramid of numbers


  A pyramid that shows the number of organisms at each trophic level
• This pyramid of numbers is not pyramid shaped because it doesn't take size and mass of organisms into account
• Calculating the efficiency of biomass transfer

  efficiency = (energy transferred / total energy available) × 100
• The efficiency of biomass transfers from the flowers to the caterpillar is 16.67%

  
• The efficiency of biomass transfers

  Affects the number of trophic levels in a biomass pyramid
• Types of decomposer


  • Bacteria
  • Fungi
• Nutrient cycles


  Processes by which molecules and ions are transferred between dead and living organisms
• Examples of nutrient cycles

  • Carbon cycle
  • Nitrogen cycle
  • Phosphorus cycle
  • Water cycle
• Carbon cycle


  1. Plants fix carbon dioxide into organic molecules during photosynthesis

  2. The organic carbon-containing molecules are passed onto organisms that eat the plants

  3. Carbon dioxide is released back into the atmosphere by respiration from animals and plants

  4. Burning fossil fuels also releases carbon dioxide into the atmosphere
• Water cycle


  1. Water from lakes and oceans evaporates

  2. The evaporated water condenses into clouds and returns to earth as precipitation

  3. The water from precipitation is useful for life on land

  4. The water then returns to rivers and oceans through surface runoff
• The water cycle is important because living organisms require water and it provides a continuous supply of water to organisms on land
• Types of decomposition


  • Aerobic decomposition (with oxygen)
  • Anaerobic decomposition (without oxygen)
• Aerobic decomposition is faster than anaerobic decomposition
• A decrease in water availability


  Affects the rate of decomposition
• Water cycle


  Provides organisms on land with a continuous supply of water
• Types of decomposition


  • Aerobic decomposition (with oxygen)
  • Anaerobic decomposition (without oxygen)
• Aerobic decomposition


  Faster than anaerobic decomposition
• Decrease in water availability

  Slows the rate of decomposition processes
• Presence of too much water

  Causes anaerobic decomposition which is slower
• Decrease in temperature


  Slows the rate of decomposition reactions
• Large increase in temperature

  Denatures enzymes, slowing or stopping decomposition
• Mummification


  Happens instead of decomposition in places with harsh climate (too dry or too hot)
• Nitrogen cycling in an ecosystem


  1. Nitrogen fixed by lightning, Haber process and bacteria

  2. Decomposers break down dead matter into ammonia

  3. Nitrifying bacteria convert ammonia into nitrites and nitrates

  4. Denitrifying bacteria release nitrogen back to the atmosphere
• Rising human population


  Leads to destruction of habitats which can threaten organisms