Conditions for life on Earth

Why waters essential:

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

Temperature:

• 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.

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

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.