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z College

Nutrient Cycles
AQA Unit 4 Biology

Frihah Parvaiz

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Basic Sequence of all nutrient cycles

Nutrient cycles
The role of microorganisms in the carbon and nitrogen cycles in sufficient detail to illustrate the processes
of saprobiotic nutrition, ammonification, nitrification, nitrogen fixation and denitrification.
(The names of individual species are not required.)


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Nitrogen Fixation

Its when N2 gas in the air is converted into
ammonia by bacteria
The ammonia is used by plants
The relationship is mutualistic- they give the
plants nitrogen compounds and the plants
give them carbohydrates

Nitrogen compounds from
dead organisms (faeces) are
turned into ammonium
compounds by…

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The importance of respiration, photosynthesis and human activity in giving rise to
short term fluctuations and long term change in global carbon dioxide concentration

CO2 is absorbed by plants
during photosynthesis

Carbon is passed onto primary
consumers and along the food

When organisms die the
carbon in them is…

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The roles of carbon dioxide and methane in enhancing the greenhouse effect and bringing about global warming.

CO2 is a greenhouse gas and may be contributing
to global warming. However the evidence is
correlational, so no definite link can be proven.

The methane concentration has increased
rapidly over the past…

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Candidates should be able to analyse, interpret and evaluate
data relating to evidence of global warming and its effects on
· the yield of crop plants

· the life-cycles and numbers of insect pests

· the distribution and numbers of wild animals and plants. Some species such as boarfish are…

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Nitrogen The environmental issues arising from the use of fertilisers.

Leaching and eutrophication.

Leaching is the process where nutrients are removed from the soil. When inorganic fertilisers are
used, minerals are added directly to the soil and are available instantly. As these ions are soluble
they can be carried into…

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Nutrient Cycles

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Nutrient Cycles


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