Cycles in ecosystems

• Ecosystem -  is a community of organisms living in an area, as well as all the non-living (abiotic) conditions, e.g. soil quality, availability of water, temperature.

  Materials organisms need to survive, such as carbon and water are recycled through both the biotic and abiotic components of ecosystems.

  • This means they pass through both living organisms (the biotic components of an ecosystem) and things like the air, rocks and soil (abiotic components of an ecosystem) in a continuous cycle.
• The carbon cycle shows how carbon is recycled:

  Carbon is an important element in the materials that living things are made from.

  But there's only a fixed amount of carbon in the world. This means it's constantly recycled:
• Carbon cycle


  1. CO2 in the air

  2. Green plants use carbon from CO2 to make carbohydrates, lipids and proteins

  3. Eating passes carbon compounds in the plant along to animals in a food chain or web

  4. Plant and animal respiration releases CO2 back into the air

  5. Plants and animals decompose

  6. Decomposers release CO2 back into the air

  7. Combustion of plant and animal products releases CO2 back into the air

  8. Decomposition maintains habitats by returning nutrients to the soil and preventing waste buildup
• Water cycle


  Water is endlessly recycled
• Water cycle


  1. Water evaporates from land and sea due to energy from the Sun

  2. Water vapour is carried upwards

  3. Water vapour cools and condenses to form clouds

  4. Water falls from clouds as precipitation

  5. Some water is absorbed by soil and taken up by plant roots

  6. Some water becomes part of plant tissues and is passed to animals

  7. Animals return water to soil and atmosphere through excretion and condensation

  8. Water that doesn't get absorbed runs off into streams and rivers

  9. Water drains back into the sea, before evaporating again
• Transpiration


  Water evaporating from plants
• Like carbon, water on planet Earth is constantly recycled