3.4.6 Nutrient Cycles (AQA A2 Biology)

Overview of nutrient cycles for A2 biology. Includes the carbon cycle, greenhouse gases, global warming, nitrogen cycle (ammonification, nitrification, nitrogen fixation and denitrification and the bacterias involved in each process), fertilisers, leaching and eutrophication.

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  • Created on: 01-05-14 18:07
Preview of 3.4.6 Nutrient Cycles (AQA A2 Biology)

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3.4.6 Chemical elements are recycled in ecosystems. Microorganisms play a
key role in recycling these elements.
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.
1

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Chemical elements are recycled in ecosystems. Microorganisms play a
key role in recycling these elements.
THE CARBON CYCLE
The importance of respiration, photosynthesis and human activity in
giving rise to short-term fluctuations and long-term change in global
carbon dioxide concentration.
The roles of carbon dioxide and methane in enhancing the greenhouse
effect and bringing about global warming.
Plants absorb CO2 in the atmosphere and convert it to useful
macromolecules. All organisms return CO2 into the air through
respiration.…read more

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Chemical elements are recycled in ecosystems. Microorganisms play a
key role in recycling these elements.
GLOBAL WARMING and DEFORESTATION
Reasons for deforestation:
Mining
Agriculture
Fuel demand
Raw materials
Transport routes
Impact on ecosystem
Reduced species diversity: Many species live in forests, they will die.
Water cycle: Trees keep water grounded through the roots.
Soil erosion: Tree roots won't keep soil anchored so it will erode away.
Life quality: Silt from soil erosion enters lakes and water systems, decreasing
water quality.…read more

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Chemical elements are recycled in ecosystems. Microorganisms play a
key role in recycling these elements.
The environmental issues arising from the use of fertilisers.
Leaching and eutrophication.
Plants need nitrogen to grow but must get this through nitrate ions in
the soil which are taken in by root hair cells via active transport. Nitrate
ions enter the soil through decomposition of other organisms.
STAGE OVERVIEW BACTERIA CONVERSION
Ammonification Produces ammonia
from organic Ammonium
ammonium found in Saprobiotic molecules
dead things.…read more

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Chemical elements are recycled in ecosystems. Microorganisms play a
key role in recycling these elements.
In intensively farmed areas of land, natural minerals and ions are in constant demand
due to farmers wanting to gain maximum yield from their crops. However, very few
ions are recycled back into the land because of farming transportation that takes crops
to different places. Productivity would consequently be reduced due to few ions in the
soil which is why fertilisers are added.…read more

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Chemical elements are recycled in ecosystems. Microorganisms play a
key role in recycling these elements.
1. Nitrates are a limiting factor for the growth of plants in water.
2. Nitrates leach into the water, plants and algae grow quickly.
3. Algal bloom appears.
4. Light can't penetrate past the algal bloom so plants at lower depths die.
5. Saprobiotic bacteria feed off the dead plants.
6. Oxygen becomes a limiting factor as the bacteria respire.
7. High demand for oxygen means aerobic organisms (fish) die.…read more

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