Ecosystems

• The water cycle describes how water moves between different locations, eg. rivers, oceans, atmosphere.
• The carbon cycle shows how carbon is recycled throughout the atmosphere.
• The nitrogen cycle shows how nitrogen moves throughout an ecosystem before being recycled back to the atmosphere.
• Carbon is present in all living organisms.
• Carbon cycle

  • Carbon is removed from the atmosphere by producers (such as algae) who use it in photosynthesis.
  • Animals gain carbon via feeding (eating) these producers.
  • Animals respire, returning carbon to the atmosphere as Carbon dioxide (CO2).
  • When animals and plants die, decomposers return the carbon back to the atmosphere via decay.
  • Other forms of returning Carbon to the atmosphere is via burning fossil fuels and/or factory emissions.

  
• Nitrogen cycle

  • Nitrogen -> Soil (Nitrogen fixing bacteria)
  • Leads to nitrates in soil.
  • Uptaken by plants.
  • Nitrifying bacteria turns these nitrates in the soil to ammonia (NH3) /ammonium (NH4).
  • Denitrifying bacteria takes nitrates from soil and recycles it in the atmosphere.
  • Animals feed on plants.
  • Animal waste decays via death or excretion (by decomposers).

  
• Water cycle

  • Water evaporates from the Earths surface into the atmosphere.
  • Once in the atmosphere, the water vapour cools and condenses into either rain or snow.
  • Rainfall causes this water to go back to the Earths surface.
  • Plants take up water through their roots.
  • Transpiration recycles the water into the atmosphere.

  
• Aerobic Decay

  Depends on:

  • Oxygen availability (High best).
  • Moisture availability (High best).
  • Temperature (High best).
• Anaerobic Decay

  • Occurs in areas that lack Oxygen.
  • Produces biogas (eg. Methane).
  • Crucial that temperatures are maintained and that Oxygen cannot enter the site of fermentation.
• Biotic = living organisms.
• Abiotic = non-living organisms.
• Levels of a ecosystem

  King = Kingdom

  Prawn = Phylum

  Curry = Class

  Over = Order

  Fat = Family

  Greasy = Genus

  Sausage = Species
• Species may be interdependent on eachother. This means that they rely on other species for their survival.
• An Apex Predator is at the top of the food chain.
• A predator-prey graph should have oscillating curves, there should always be more prey than predator and it should have a cylic structure.
• Parasite


  • One organism benefits, other organism harmed.
  • eg. mosquito + human
• Mutualism


  • Both species benefit.
  • eg. Lichen (moss + algae).
• Pyramid of biomass

  • Biomass is the total mass of living material in an organism multiplied by the number of organisms.
  • Pyramid shaped.
  • Shows each trophic level.
• Pyramid of number

  • Shows how many of each organism is at each level.
• Around 10% of energy is passed between the trophic levels.
• Why is energy lost/wasted between each trophic level?

  • Excretion
  • Movement
  • Body temperature
  • Digestion
• transfer efficiency = (energy transferred / total energy of that trophic level) x 100