1. Conditions for Life on Earth

• Mass 


  Prevents gases escaping into space and creates enough atmospheric pressure that prevents boiling
• Distance from the sun 


  Suitable to produce temperatures appropriate for life (Goldilocks Zone)
• Speed of Rotation 


  The 24 hour period of rotation that reduces temperature extremes
• Axis of Rotation 


  Produces seasonal variation
• Magnetic Field 


  The molten layers beneath the crust produce the earths magnetic field. This deflects 'solar winds', Preventing biologically damaging radiation reaching the earths surface.
• Liquid water 


  Water is essential to all living organisms, both in terms of their physiology and their environment. e.g. universal solvent, internal transport, temperature control in the body, aquatic habitats, absorption of UV rays, anomalous expansion on freezing.
• Atmospheric gases

  Carbon Dioxide - used in Photosynthesis and the synthesis of carbohydrates, proteins and lipids

  Nitrogen - protein synthesis
• Solar energy

  • Sunlight provides energy for photosynthesis
  • Most areas on earth are between 0 - 35 degrees Celsius, allowing liquid water, but not denaturing proteins
  • Energy from sunlight drives the hydrological cycle
• Atmospheric Oxygen 


  Archaea evolved to photosynthesize 2.7 billion years ago, the oxygen released reacted with iron. Once all the iron reacted, the surplus dissolved in the oceans, until it was released in the atmosphere 2.4 bya.

  Atmospheric oxygen formed ozone, which absorbed harmful UV rays.
• Carbon Sequestration


  Photosynthetic organisms absorb atmospheric carbon dioxide, of which some of the carbon ends up in geological sediments (carbonated rocks and fossil fuels)

  This reduction in carbon dioxide helps reduce long-term temperature rise
• Transpiration 


  Once plants had colonised land, transpiration returned water vapour to the atmosphere and increase the amount of precipitation, making the growth of even more plant life possible