Chapter 1 - Conditions for life on Earth

• Why did carbon dioxide change?

  Its stored in oceans and used in photosynthesis
• Why did water vapour change?

  It condenses into oceans
• Why did nitrogen change?

  Its ureactive and so it stays
• Why did hydrogen change?

  It reacted with oxygen to make water.
• Why did Oxygen change?

  Photosynthesis
• Water importance - Enzymes

  at high temperatures enzymes denature and at low temperatures, they work slowly
• Water importance - Transport

  solvent in blood, allows carbon dioxide, oxygen and sugar to be transported around plants and animals
• Water importance - Temperature control


  The evaporation of water from the body cools it down
• Water importance - absorbs UV radiation


  provides protection to organisms
• How did carbon reduce?

  Carbon sequestration in forests stores a large amount of carbon,
• How do we know early conditions? Data gaps:

  • lack of ancient historical data
  • limited co-ordination between researchers
  • lack of data collection in many areas
• How do we know early conditions? Proxy data:

  Dendrochronology

  Warm - thicker tree rings Cold - thinner tree rings

  Ice cores

  Carbon dating

  Limited reliability for ancient conditions
• What is the albedo effect?

  Light surfaces reflect more heat than dark surfaces
• What factors might increase the albedo effect?

  Positive feedback -

  Earth's temperature dropped because of its position in orbit.

  The ice sheets grew.
• Orbital behaviour

  Axis - produces seasonal variation

  Rotation - causes daily variations
• Magnetosphere

  • caused by molten iron core
  • deflects solar flare
  • prevent biological damaging radiation
• What is proxy data?

  Data that has preserved physical characteristics
• Gas analysis of ice cores

  Encloses small bubbles of air (sample)

  measures the concentration of atmospheric gases
• O16 and O18 isotope analysis

  Determine past temperatures

  Ocean floor sediments, reflect the oxygen isotope of the ocean floor

  Warmer climate = more O18 Colder climate = more O16
• Mg:Ca in calcite

  More magnesium is linked with higher temperatures.
• Earth - Mass

  Helps create gravitational field which prevents gases escaping

  Allows for right temperatures and pressures for water to exist
• Earth - Magnetic field

  To deflect solar winds
• Earth - Speed and axis of rotation

  Linked to temperature regulation and seasons
• Name the 4 essential elements for life

  Carbon

  Nitrogen

  Oxygen

  Hydrogen
• How long ago was the Earth "formed"

  4.5 billion years ago
• What is meant by the goldilocks zone ?

  Not too hot, or not too cold for human life
• Why do we have seasons?

  The Earth spins on an axis at an angle
• What do the Earth's magnetic field deflect?

  Harmful solar flares
• What is solar insolation

  Incoming solar radiation
• Name an atmospheric reason why we need water?

  Water absorbs UV radiation which regulates temperatures
• At what temperature is water most dense?

  4 degrees
• Name one reason the level of oxygen increased in the Earth's atmosphere

  Photosynthetic organisms
• Name one analytical technique that can be used to estimate past climates

  Ice cores