Conditions for life on Earth

First topic which explains what is essential in order to sustain the Earth and organisms living upon it.

This has all been taken from the AQA environmental studies AS/A2 textbook.

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Water and temperature range.

Why waters essential:

  • Physiological Solvent
  • Transport of water
  • Temperature control
  • Anomolous expansion on freezing
  • High specific heat capacity
  • Provision of aqauatic habitats


  • Most areas upon earth are over 0 degrees C which means it can support liquid water .
  • Enzymes need water as a solvent as at higher tempratures they can denature.
  • Some organisms can survive tempretures higher than this an example of these are thermophilic bacteria.
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Gases and the Sun.

Suitable ambient gases:

  • Carbon Dioxide (Photosynthesis and climate control)
  • Nitrogen (Protein synthesis)

Light and radiation from the sun:

  • Sunlight-Energy for photosynthesis
  • Heat production when absorbed-The source of energy for the water cycle and climate.
  • UV and Ionising radiation.

This can be caused by the earth itself or its posiion:

  • Distance from Sun
  • Daily Rotation
  • Tiltled Axis
  • Molten layers beneath the crust
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Environmental Change through the presence of life:

Atmospheric oxygen:

  • Oxygen is very reactive and due to this its abundance has declined in the atmosphere.
  • Photolysis of water releases oxygen and photosynthesis.
  • Oxygen absorbed UV light from the sun.

Atmospheric Carbon Dioxide:

  • Essential green house gas-without this the earth would be to cold to support life.
  • Excess levels of carbon dioxide can also cause the decline in life due to the high temperature levels.
  • Carbon dioxide gets reduced by photosynthesis, absorbed by fossil fuels,carbonate rocks, organisms and the sea.
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