Earth life support systems


KQ1 how important are water and carbon to life

The uses of water for flora, fauna and the people 

  • water makes up 65-95% of all living organisms. 
  • plants need water; photosynthesis, repiration and transpiration.

photsynthesis takes place in the leaves of plants - it combines; 

  • carbon dioxide, sunligtht and water to produce glucose and starches. 
  • respiration in plants and animals converts glucose to energy throughts its reaction wiht oxygen, releasing water and CO2 in the process. 
  • transpiration of leaf surfaces cools leaves by evaporation.
  • plants also need water to transfer minerals to the soil and atmosphere. 

in people and animals

  • use water for all chemical reactions in the body - including oxygen circulation. 
  • sweating also cools down animlas by realising water. 

water is also economically essential - electricity, irrigation, food and sewage disposable. 

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KQ1 importance of carbon to life on earth

carbon is stored in; carbonate rocks (limestone), seafloor sediments, ocean water, the atmosphere and the biosphere. 

life is carbon based - built on large molecules of carbon atoms such as; proteins, carbs and nucleic acids. 

Carbon as an economic resource

  • fossil fuels such as; coal, oil and natural gas power the global economy. 
  • oil - used as a raw material to manufacture products e.g. plastic, synthetic paints. 

agricultural crops and forest trees store large amounts of carbon which are available for human use as; 

  • food
  • timber 
  • paper 
  • textiles 
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KQ1 The water and carbon cycles

both water and carbon flow in a closed system between the atmosphere, oceans and biosphere.

water and carbon cycles are closed systems on a global scale driven by the suns energy. But on a small scale are opened systems comprised of stores and flows. 

water cycle

  • at macro scale - the global water cycle consists of three main stores; the atmosphere, ocean and lands. 
  • water moves between stores through - precipitation, evapotranspiration, run off and groundwater flow. 

carbon cycle 

  • is also made up of stores and flows. 
  • longterm storage in sedimentary accounts for 99.9% of all carbon. 
  • carbon rapidly moves between the atmosphere, the oceans, soil and biosphere. 
  • main pathways of carbon flows are; photosynthesis, respiration, oxidation (decomposition & combustion) and weathering. 
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KQ1 Global water cycle - reservoirs and stores

resevoirs - places where water is stored for a length of time. 

  • 97% of water is stored in the worlds oceans 
  • 2% is stored in polar ice caps and glaciers. (hold 3/4 of fresh water in the world in Antarctica and greenland) 
  • 0.7% is stored as groundwater. (1/5 of fresh water is stored in permeable rocks) 
  • 0.01% is stored in Lakes 
  • 0.005% is stored in soils 
  • 0.001% is stored in the atmosphere 
  • 0.0001% is stored in rivers 
  • 0.00004% is stored in the biosphere. 

only a small proportion of the earths water is stored in the atmosphere - due to the rapid movement of water in and out of the stores. 

The average water molecule remains in the atmosphere for maximum time of 9 days. 

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KQ1 Inputs and outputs of water

1) inputs to the atmosphere; 

  • water vapour evaporated from oceans, soils, lakes and rivers, vapour transpired through leaves of plants. - all of these processes are known as evapotranspiration. 

2) moisture leaving the atmosphere; 

  • as precipitation and condensation. Ice sheets, glaciers and snowfields release water by ablation (melting and sublimation) 

3) precipitation and meltwater; 

  • drain from the surface as run-off into rivers, rivers flow to oceans or inland basins (in continental drylands). water sometimes only reaches rivers through infiltration from precipitation. 

4) water may percolate into permeable rocks

  • gravity can cause water to percolate into groundwater. 
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KQ1 The global carbon cycle

consists of a number of flows and stores (sinks) connected by flows of carbon. 

Principle stores are; 

  • atmosphere - 600 billion tonnes 
  • oceans - 38,700 billion tonnes
  • sedimentary rock - 60,000 - 100,000,000 billion tonnes 
  • seafloor sediment - 6,000 billion tonnes 
  • fossil fuels - 4,130 billion tonnes 
  • land plants - 560 billion tonnes 
  • soils/peat - 2,300 billion tonnes 

carbonate rocks e.g. limestone, chalk and deep ocean sediments are largest stores of carbon. 

Most of carbon not found in rocks is dissolved as CO2 in the oceans. 

atmospheric, plant and soil carbon soils are relatively small.

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KQ1 inputs and outputs in the carbon cycle

The slow carbon cycle 

  • carbon which is stored in rocks, seafloor sediments and fossil fuels is locked away for millions of years. - carbon circulated in these stores is between 10 and 100 million tonnes ayear. 
  • Carbon dioxide diffuses from the atmosphere into oceans - marine organisms such as clams and corals make their shells by fixing carbon and calcium to form calcium carbonate - when animals die, the bodies sink to the oceanfloor, accumulaet and heat and pressure converts them into carbon rich sedimentary rocks. - residence time of 150 million years.
  • some sedimentary rocks are subduceed into upper mantle at tectonic plate boundaries and later get released into the atmosphere through volcanic eruptions. 
  • others are exposed to chemical weathering by being close to the surface. 
  • chemical weathering e.g. carbonation occur when precipitation gets charged with CO2 particles - forming a weak acid. - acid attacks carbonate minerals in rocks - causing carbon to be released into the atmosphere. - then gets dissolved in streams, rivers and oceans. 
  • on land - partly decomposed material can be buried underneath younger sediments, forming; carbonaceous rocks e.g. coal, lignite, oil. - these act as carbon sinks for millions of years. 
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KQ1 inputs and outputs in the carbon cycle

The fast carbon cycle

  • carbon circulation is most rapid between the atmosphere, oceans, living organisms and soils.  - transfers are between 10 and 1,000 times faster than the slow carbon cycle. 
  • land plants and microscopic phytoplankton in the oceans are key components of the fast carbon cycle. 
  • they absorb CO2 from the atmosphere and combine it with water to make carbohydrates (sugar/glucose) through photosynthesis. 
  • respiration by plants and animals is the opposite process to photosynthesis and is a process in which animals and plants release CO2 .
  • decomposition of dead organisms by microbial activity also causes CO2 to be released into the atmosphere. 

carbon exchange between the atmosphere and the oceans 

  • atmospheric CO2 dissolves in ocean surface waters, whilst the oceans ventilate CO2 back into the atmosphere
  • individual caarbon atoms are stored in oceans by natural sequestration for 350 years. 
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