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Edexcel Biology Carbon & Nitrogen Cycles

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Why bother with a post grad course - waste of time? 17-10-2016
    • Thread Starter

    I know the basics of these cycles, but would someone be able to put it in the form of a 6 marker??

    Summarised version I made of the water cycle, (Working on the next two now, happy to share if you'd like.) :

    Driven by the Sun's thermal energy, water from lakes, streams and oceans evaporate and form gaseous water vapour in the atomosphere. Transpiration of plants and respiration of both plants and animals contribute to this water vapour in the atmosphere. When these clouds of water vapour pass over high ground they cool, condense and a precipitation of rain falls to the ground, rivers and oceans, and the process is reset.

    Atmospheric carbon dioxide is fixed by plants to form glucose via photosynthesis. Plants the respire to release carbon dioxide back into the atmosphere. Plants may also be eaten by animals transferring carbon compounds to animals , and animals too respire to release carbon dioxide into the atmosphere. When plants or animals die the are either decomposed by decomposers- a process that releases carbon dioxide- or when in anaerobic conditions, subject to high pressure and temperature they form fossil fuels. These are burnt and thus carbon dioxide is once again released to the atmosphere due to combustion.

    The N-N triple bond can be broken by lightening and then dissolves in water to form nitrate and nitrite ions which then reach the soil. These nitrate ions can be directly absorbed by plants (via active transport) and assimilated to form proteins and amino acids. The nitrite ions can be converted to the more usable nitrate form by nitrogen fixing bacteria present in the soil.

    Some leguminous plants have nitrogen fixing bacteria present in their root nodules which can convert atmospheric nitrogen to form nitrate and ammonium ions which can be assimilated by the plant.

    Detritus, dead and decaying matter are broken down by decomposers which break down the material to release ammonium ions into the soil. These are then converted by nitrifying bacteria to form nitrate ions which also assimilated.

    Denitrifying bacteria turns any nitrate ions present in the soil to nitrogen which is then evolved to the atmosphere.
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