Cycles and decomposition: 2. The
Doc Brown's GCSE level Biology exam study revision notes
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INDEX of notes on natural cycles, their importance, decay
Carbon Cycle and its
important role in the Earth's biosphere
FOSSIL FUELS, coal, oil & natural gas and the Carbon Cycle
(gcse chemistry revision)
Limestone and lime
- their chemistry and uses (gcse chemistry revision notes)
Summary of learning objectives and key words or phrases
Be able to construct a simple diagram of the carbon cycle
and be able to interpret and explain a more complex diagram of the carbon
cycle described above.
Be able to show an understanding of how carbon is recycled
(CARBON CYCLE diagram above):
photosynthesis plants remove carbon dioxide from the atmosphere
carbon dioxide + water ==
energy/chlorophyll ==> glucose + oxygen
is the process by which plants make food, for themselves, and for most
animal life, including us too!
Note that the only way carbon
dioxide is removed from the air is photosynthesis in green land based plants
or marine organisms like phytoplankton (this point ignores long term
formation of carbonate rocks like limestone).
b) carbon compounds pass along a food chain
All food chains involve the passing of
carbon compounds e.g. sugars, carbohydrates, fats and proteins up to the
next trophic level i.e. the consecutive eating along a food chain (and waste
produced on the way).
c) during plant or animal aerobic respiration organisms release carbon dioxide into the
d) decomposers release carbon dioxide into the atmosphere
- slow aerobic respiration
Microorganisms like bacteria and fungi in
the soil feed off decaying plant material and animal droppings or remains.
Most dead plant matter consists of cellulose
which most animals can't digest, but bacteria and fungi, do have the enzymes
to break it down and without their help there would be no carbon cycle.
Most of these bacteria and fungi respire
aerobically so they need a good supply of oxygen to produce the carbon
dioxide essential to keeping the carbon cycle going.
e) combustion of fossil fuels releases carbon dioxide into the
millions of years from the remains of tropical plant material, mainly
consists of carbon, Burning coal produces a lot of pollution as
the greenhouse gas carbon dioxide.
Natural gas (mainly
methane) and petrol molecules like octane (and lots of other
molecules) from oil and gas reserves.
methane + oxygen ===> water
+ carbon dioxide
+ oxygen ===> water + carbon dioxide
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