ecosystems

• ecosystem - interaction of a community of living organisms and abiotic parts of the environment
• habitat - where an organism lives
• population - all the organisms of one species living in a habitat
• community - all living organisms living in a habitat
• abiotic factors - non living parts of the environment eg. temperature, pH
• biotic factors - living factors of the environment
• interdependence - the species are dependant on each other
• the line between two animals shows the energy transferred on a food web
• interdependance - the species are dependant on each other
• The Carbon Cycle

  A) decomposition

  B) photosynthesis

  C) burning fossil fuels

  D) respiration

  
• biomass - mass of material in living organisms. made by plants, passed through food webs/eating
• the atmosphere contains 78% nitrogen gas, this is very unreactive and therefore can't be used directly by plants and animals. nitrogen is needed for making proteins
• plants get their nitrogen from the soil, so nitrogen in the air has to be turned into nitrates for plants. nitrogen compounds are then passed along food chains as animals eat plants and each other.
• decomposes [bacetria and fungi in the soil] break down proteins in rotting plants and animals. they also break down urea in animal waste into ammonia, which forms ammonium ions. this return the nitrogen compounds to the soil, meaning nitrogen is recycled [in these organisms].
• nitrogen fixation


  process of turning N2 from the air unto nitrogen compounds in the soil so plants can use it.
• nitrogen fixation


  1. lightning:

  there is so much in a bolt of lightning that it's enough to make

  nitrogen react with oxygen to give nitrate
• nitrogen fixation


  2. nitrogen fixing bacteria in the roots:

  turn atmospheric nitrogen into nitrogen compounds that plants can use
• types of bacteria used in the nitrogen cycle


  nitrogen fixing bacteria: turn atmospheric nitrogen into nitrogen compounds that plants can use
• types of bacteria used in the nitrogen cycle


  decomposers: decompose proteins and urea and turn them into ammonia, which form ammonium ions.
• types of bacteria used in the nitrogen cycle

  nitrifying bacteria: turn ammonium ions in decaying matter into nitrates
• types of bacteria used in the nitrogen cycle


  dentrifying bacteria: turns the nitrates back into N2 gas. dentrifying bacteria is usually found in waterlogged soils.
• factors affecting the rate of decomposition


  1. oxygen availability
  2. temperature
  3. water content
• factors affecting the rate of decomposition


  oxygen availability:

  many decomposers need oxygen for aerobic respiration so the rate of decomposition increases when there is plenty of oxygen available

  some decomposers can respire anaerobically but this transfers less energy, so these decomposers work less slowly.
• factors affecting the rate of decomposition


  temperature:

  • most decomposers work best in warm conditions
  • this is because decomposers contain enzymes which dugest dead/waste material
• factors affecting the rate of decomposition


  water content:

  • decomposers need water to survive, so the rate of decomposition increases in moist conditions.
  • however waterlogged soils don't contain much oxygen so the rate decreases if there is too much water
• calculating the rate of decomposition


  1. draw a line on your graph at the required number of days
  2. divide the amount of mould by the number of days
• examples of abiotic factors: temperature, moisture level, pH levels of the soil, light intensity
• examples of biotic factors: availability of food, competition [for shelter, space, food etc], number of predators
• the main types of biotic factor include predators, prey, competitors, mutualists and parasites
• biomass is lost from the food chain through egestion [faeces] and excretion [sweating, urinating, breathing out]
• animals use some of the biomass they consume for respiration to provide energy for movement, keeping warm etc
• effiency = biomass available to the next level / biomass that was available to the previos level x100