How materials are cycled

• describe how materials cycle through the living and non-living components of an ecosystem

  • organisms take in elements from their surroundings
  • elements converted to complex molecules which become biomass
  • elements transferred along food chains
  • elements returned to environment during excretion and decomposition of dead organisms
• give 3 molecules which are cycled through ecosystems

  • oxygen
  • carbon dioxide
  • water
• describe the carbon cycle

  • plants fix CO2 into organic molecules during photosynthesis
  • organic carbon-containing molecules are passed onto organisms that eat the plants
  • CO2 is released back into the atmosphere by respiration from animals and plants
  • burning fossil fuels also releases CO2
• why is the carbon cycle important?

  carbon-containing molecules such as glucose are important for living organisms to grow and provide energy for vital functions within cells
• describe the water cycle

  • water from lakes and oceans evaporates
  • evaporated water condenses into clouds and returns to earth as precipitation
  • water from precipitation is useful for life on land
  • water then returns to rivers and oceans through surface runoff
• why is the water cycle important?

  living organisms require water and the water cycle provides organisms on land with a continuous supply of water
• why are microorganisms important for the cycling of materials through an ecosystem?

  • return carbon to the environment by releasing CO2 through respiration while they decompose dead matter
  • decomposition of dead matter in soil returns mineral ions to the environment for other organisms to use