Early conditions

• After the formation of earth 4.6 billion years ago, conditions changed, eventually becoming suitable for life to develop.
• Presence of water

  • all living organisms require water. It performs essential physiological functions.
  • Solvent water - chemical reactions involve reactants that are dissolved in water
  • Transport - water is the solvent in blood and sap where it transports dissolved gases, sugars etc.
  • Temp control - evaporation of water absorbs heat.
  • Aquatic habitats
  • Absorption of UV radiation - protected living organisms before the ozone layer devolved.
• Temp range

  • most areas of earth have temps between 0’C and 35’C so most areas are warm enough to have liquid water but not hot enough to denature proteins.
• Atmospheric gases

  • Carbon dioxide for photosynthesis and the synthesis of carbohydrates, proteins and lipids.
• solar insolation

  • sunlight provides energy for photosynthesis. Heat produced by absorption of sunlight provides the energy that drives the water cycle and warms the Earths surface and the oceans.
  • Amount of sunlight absorbed depends upon the albedo of the surface.