4.1 how important are water and carbon to life on earth

Question 1

how is water essential for development and evolution of life on earth

Answer 1

1. essential for development + evolution on earth:
   - organic molecules mix + form complex structures
   - the large amount of water on earth due to its distance from sun - allowing it to exist in liquid form
2. comparison with mars
   - mars has very little water in liquid form - most frozen in vapour
   - water increases potential for life

Question 2

what is waters environmental and climate role

Answer 2

• waters cover 71% of earths surface
• water regulates earths temps by absorbing, storing and releasing heat
• clouds reflecting incoming sunlight which lowers surface temps
• water vapour absorbs outgoing long-wave radiation, keeping global temps approaching 15 degrees warmer than without it

Question 3

what are the 5 key uses of water - plants, humans

Answer 3

1. BIOLOGICALLY: makes 65-95% of living organisms, vital for photosynthesis, respiration and transpiration plants, circulation, temp reg + nutrient tranpsort humans/ animals
2. PHOTOSYNTHESIS: in leaves producing biomass
   water + co2 + sun –> glucose + oxygen
3. RESPIRATION
   glucose + oxygen –> co2 + energy + water
4. TRANSPIRATION: water evaporates from leaf surfaces –> cools plants
5. OTHER: irrigation, hydroelectric power, drinking, sewage, industiral

Question 4

what is the importance of carbon to life on earth

Answer 4

• carbon - chemical element
  1. BIOLOGICAL –> found in large complex molecules eg carbs, proteins, lipids, DNA, RNA. essential in photosynthesis and respiration

2. STORAGE –> found in: carbonate rocks (eg limestone), ocean (dissolved), atmosphere (gas), biosphere (living organisms)
3. ECONOMIC –> carbon based fuels (coal, oli, gas) power global economy. manufacturing plastics, textiles, paints etc

Question 5

how are the water and carbon cycles open and closed systems

Answer 5

1. CLOSED
   - global scale
   - energy enters and leaves (from sun) but matter does not
   - but the speed of this cycle gets affected by the energy of the sun eg the high intensity of sunlight - the higher rate of photosynthesis
2. OPEN
   - local scale
   - energy and matter cross system boundaries between atmosphere, oceans and land

Question 6

main water stores and their % of global water

Answer 6

• oceans 97%
• glaciers 2%
• groundwater (aquifers) 0.7%
• lakes 0.01%
• soils 0.005%
• atmosphere 0.001%
• rivers 0.0001%
• biosphere 0.00004%

Question 7

inputs and outputs of water

Answer 7

1. INPUTS INTO THE ATMOSPHERE:
   - evaporation from oceans, lakes, soils
   - transpiration from plannts
   - = evapotranspiration
2. OUTPUTS
   - precipitation: rain, snow, hail etc
   - condensation: forms clouds
   - ablation and sublimation from glaciers and ice sheets
3. OUTPUTS - RUN-OFF
   - precipitation that doesn’t infiltrate contributes to run-off - flows to rivers/oceans
   - dry areas –> water flows into inland basins
4. OUTPUT INFILTRATION
   - water entering soil
   - may percolate to groundwater and return via springs

Question 8

whats the average residence time of a water molecule in the atmosphere

Answer 8

9 days

Question 9

main stores in the carbon cycle and how much carbon is in these stores per billion tonnes

Answer 9

• sedimentary rock 100,000,000
• oceans 40,000
• sea floor sediment 6000
• fossil fuels 4000
• soils/peat 2500
• atmosphere 600
• land plants 550

Question 10

the slow carbon cycle - inputs and outputs

Answer 10

INPUTS
- operates over millions of years
- co2 diffuses from atmosphere to oceans, marine organisms (clams, corals) combine dissolved carbon and calcium to form calcium carbonate shells
- these shells sink to sea floor and accumulate over millions of years –> sedimentary rock (99.9%)
OUTPUTS
- these sedimentary rocks r subducted and re-emitted via volcanic eruptions, or exposed to chemical weathering
- co2 in rainwater forms carbonic acids, which dissolves carbonate rocks, releasing co2 into rivers, oceans and atmosphere
- on land, dead organic matter gets buried and converted into fossil fuels like coal, oil and natural gas

Question 11

the fast carbon cycle - inputs and outputs

Answer 11

• rapid transfer of carbon between atmosphere, biosphere, oceans and soils
• 10 to 1000 times fast than the slow cycle
• key components:
  BIOSPHERE –> ATMOPSHERE
  1. phytoplankton (ocean algae) and land plants uses photosynthesis converting co2 –> glucose. respiration opposite reaction and releases co2 to atmosphere
  2. decomposition of organic matter releases co2

ATMOSPHERE –> HYDROSPHERE
1. c02 dissolves from atmosphere into ocean surfaces
2. upwelling and downwelling circulates this water and releases co2 back into atmosphere

Question 12

the main processes in the carbon cycle

Answer 12

• photosynthesis: atmosphere –> biosphere
• respiration: biosphere –> atmosphere
• oxidation: reaction of rocks with the air which then releases carbon
• decomposition: biosphere –> atmosphere
• weathering: biosphere –> atmosphere/ hydrosphere (leaching of carbonated top soil into air/ lakes, rivers)