conditions for life

• life first appeared on earth 3.8 billion years ago
• earths mass is great enough for the effect of gravity to hold gasses close to earth
• the earths distance from the sun is what gave the earth a molten core
• carbon dioxide, dinitrogen gas, methane, ammonia and water vapour are gases released by volcanoes
• N2 is essential for protien synthesis
• CO2 is essential for photosynthesis
• greenhouse gases help regulate global temps
• carbon fixed in plants is essential for organic molecule synthesis. (carbohydrase, protiens and fats)
• earth gets enough uv to provide a warm climate and enables water to be found in liquid form
• water is a solvent (allows biochemical reactions)
• water is a fluid (moves and transports nutrients around the planet and into organisms)
• water has a high heat capacity (heats and cools slowly to maintain stable temps)
• water expands when it freezes (most dence at 4dc meaning ice floats. this stops convection currents in the sea releasing heat) ice also protects organisms under the sea from the surface
• earths magnosphere (created by the molten iron core and convection currents) deflects solar winds. the winds cause molecular damadge (dna mutations) and strip atmospheres
• insolation is a measure of solar energy concentrated on a specific area over time
• solar insolation is needed for photosynthesis
• conditions for life:

  liquid water

  temp range

  atmospheric gases

  insolation
• 5 characteristics of planet earth;

  mass of earth

  axis of rotation

  speed of rotation

  distance from sun

  magnetosphere
• the speed of rotation means that earth takes 24 hours to complete one rotation. this gives a day and night. which means that insolation is evenly distributed
• the distance from the sun puts earth in the habitable zone (goldilocks). it keeps temps between 0-100 degrees, this allows liquid water to be found
• water:

  is a solvent

  transports nutrients around organisms and the planet

  high specific heat capacity

  expands when frozen
• the orbit and rotation of earth creates the seasonal and daily variations in insolation and temp