L27

Question 1

Geological carbon cycle

Answer 1

• Begins with CO2 in rain that reacts with rocks and soil
• Ions form and carbonic acid eventually gets transported in the ocean
• Forms calcium carbonate in the ocean which enters the lithosphere

Question 2

Biological weathering- Biological Pump

Answer 2

exudation
respiration
litter decomposition
evaporation
root stabilisation

Question 3

Plant fungal soil biophysical effects on weathering

Answer 3

Hyphae Eg symbiosis with fungi

* Products of respiration are released to the atmosphere
* Long-term carbon sequestration can take place in organic substrates and secondary minerals

Question 4

Great oxidation event

Answer 4

• Ocean was initially very high iron content
  Today it is now high o2

Question 5

Key processes in the great oxidation event

Answer 5

• Oxidation of iron forming iron oxide
  
  • Oxygen depleted methane which reduces global temperature
  • Oxygen also reacted with UV to form separate O2 molecules which then helped form ozone (the ozone layer)
  • Ozone is phytotoxic

Question 6

Evolution of leaf size - coping with heat

Answer 6

• High CO2 and low leaf size means plants overheat
  • Cannot transpire
  • High CO2 and larger leaves with few stomata were most susceptible

Question 7

Feedbacks on the carbon cycle

Answer 7

• Leaf evolution had huge effects on the long term carbon cycle
  • Increased photosynthesis
  • Root and shoot co-evolution