Living world

• What are the 5 main conditions for life on earth?

  • position in the solar system

  • magnetosphere

  • atmosphere

  • insolation

  • orbital behaviour
• What 3 conditions allowed life on earth to develop?

  • liquid water

  • temperature range

  • atmospheric gases
• How did Earths position in the solar system allow life on earth?

  liquid water and suitable temperatures maintained by earths distance from the sun
• How did earths magnetosphere allow life on earth?

  Deflects solar wind which prevents atmosphere being blown away and harmful solar radiation hitting Earth
• what allowed the Earths magnetic field to form?

  molten layers beneath the crust
• How did Earths atmosphere allow life on Earth?

  • provides gaseous resources (C, H2, O2, N2) present in compounds (CO2, ammonia, methane) • atmospheric pressure and temperature prevented liquid water from boiling
• How did the Earths atmosphere form?

  The mass of Earth and force of gravity retained an atmosphere and was great enough to prevent most gases escaping
• What controls the suitable temperature range on Earth?

  • incoming insolation (from the sun) and its behaviour in the atmosphere
• How does insolation allow life on Earth?

  Heat energy from the sun drives the water cycle and warms earths surface/ oceans
• What controls the amount of sunlight absorbed by the Earths surface?

  The albedo of the surface
• What controls how much IR energy is absorbed and converted to heat?

  the atmospheres composition
• What does the atmospheres composition control?

  The amount of IR energy that is absorbed and converted into heat
• What does the albedo of the surface control?

  The amount of sunlight absorbed by the Earths surface
• How does Earths axis of rotation allow life on Earth?

  The angle produces seasonal variations in conditions which are niches for life
• How does Earths speed of rotation allow life on Earth?

  The temperature of Earths surface rises when exposed to sunlight. The 24 hour period of rotation around its axis reduces temperature extremes
• How does Earths orbital behaviour allow life on Earth?

  Helps to regulate temperature and light, creating seasons and days/ nights
• How did the presence of liquid water allow life to develop? (7 reasons)

  • solvent

  • transport in organisms

  • temperature control

  • aquatic habitats

  • absorption of UV

  • high specific heat capacity

  • Anomalous expansion on freezing
• Why does water need to be a good solvent for life on earth?

  most chemical reactions in living organisms involve reactants dissolved in water
• How does water used in transport in organisms help life on Earth?

  It’s a solvent in blood and sap - transports dissolved gases, sugars, amino acids, mineral nutrients and waste products
• How is water used in temperature control useful for life on earth?

  The evaporation of water absorbs heat so temperatures decline
• How does water expanding when freezing allow life on Earth?

  Water is most dense at 4°C so water that is cooler floats stopping the convection currents that may have cooled the water body
• How does waters high specific heat capacity allow life on Earth?

  Water warms and cools slowly which helps to moderate the rate and size of temperature changes
• What habitats does water create?

  Rivers, sea, oceans, marshes and lakes
• How does water help absorb UV radiation on Earth?

  Protected living organisms in the sea before the ozone layer developed
• What is the temperature range in most areas of the world?

  Between 0°C and 35°C
• How does Earths temperature range allow life to develop?

  Most areas are warm enough to have liquid water but not hot enough to denature proteins
• How do the Earths atmospheric gases allow life to develop?

  • CO2 for photosynthesis and the synthesis of lipids, proteins and carbohydrates

  • Nitrogen for protein synthesis
• What 5 environmental changes did life cause on Earth?

  • Atmospheric oxygen production

  • ozone layer

  • carbon sequestration

  • biochemical cycles

  • transpiration
• What is carbon sequestration?

  The absorption of CO2
• How does carbon sequestration work/ where does the carbon go?

  • Photosynthetic organisms absorb CO2 which helps to retain heat • some storage of carbon in geological sediment
• What does carbon sequestration do?

  Reduces atmospheric CO2 to help prevent long term temperature rise
• How does transpiration cause environmental change?

  Plants on land = water vapour back into the atmosphere faster. This increases the spread of rainfall and allowed life to colonise further around earth
• How do biogeochemical cycles cause environmental change?

  Wider range of organisms = inter - connected biological processes develop. Allowed recycling of elements which supports life for longer periods and preventing the build up of waste products or resource shortages/ depletion
• How was oxygen produced?

  2.7 billion years ago: archea and Cyanobacteria in oceans able to photosynthesise and release O2
• What did oxygen react with?

  Iron in the oceans forming rust
• What happened after iron reacted with oxygen in the oceans?

  The surplus dissolved oxygen built up in the oceans. Much of this was released into the atmosphere where concentrations rose
• How did the ozone layer form?

  • Cyanobacteria released O2

  • UV from the sun catalysed reaction of 2O2 to form 2O3 (ozone)

  • the ozone built up to form the ozone layer
• What does the ozone layer do?

  Absorbs harmful UV radiation from the sun. It still allows some UV to reach earth
• What is insolation?

  The energy released by nuclear fusion from the sun. It is released as electromagnetic radiation
• What does electromagnetic radiation include?

  • visible light

  • near infrared (shortwave)

  • UV