Paper 2 - Nutrient Cyles And Eutrophication Flashcards
What is nitrogen mostly used for ?
To manufacture proteins, nuclei acids and other nitrogen-containing compounds.
Nitrogen Cycle - Nitrogen fixation
Nitrogen is converted into ammonia by nitrogen fixing bacteria via a reduction reaction, catalysed by nitrogenase. This dissolves to form ammonium ions.
What is a symbiotic relationship ?
When 2 species live very closely together and one or both species depend on each other for survival
Nitrogen Cycle - Ammonification
Saproboints ( e.g. dead organisms and waste products) convert the nitrogen into ammonia and is then converted into ammonium ions in the soil. They do this by secreting enzymes and via extra cellular digestion.
Nitrogen Cycle - Nitrification
Nitrifying bacteria transforms ammonium ions into nitrate ions and then these are oxidised into nitrate ions. Plants take these up through their roots by active transport.
Nitrogen Cycle - Denitrification
Using anaerobic respiration, denitrifying bacteria converts soil nitrates into gaseous nitrogen through reduction reactions. This is prominent in waterlogged soils.
What is a detritivore ?
An organism that feeds on organic waste and helps to increase the decompositions by saproboints.
Explain how crop rotation involving legumes can improve crop yield
The clover uses the nitrogen in ammonia to make proteins. For example when left to decay the saprobiontic bacteria will convert the proteins in the dead clover to ammonia, and nitrifying bacteria will convert it to nitrates.
The Phosphorus Cycle
1- P ions in the rocks are released into the soil by weathering
2- P ions are taken into the plants through the roots. Mycorrhizae increases the rate at which the phosphorus can be assimilated.
3- P ions are transferred through the food chain
4- P ions are lost from animals in excretory products.
5- When plants and animals die saproboints break down the organic compounds releasing P ions into the soil for assimilation. These microorganisms also release the P ions from urine and faeces.
6- Leaching of rocks releases P ions into seas/lakes/rivers and are taken up by aquatic producers such as algae.
7- Guano contains a high proportion of P ions. They return a sig amount of phosphate to soils and can be used as a natural fertiliser.
Give two ways in which the phosphate ions are returned from living organisms to the soil.
Decomposition — transported by streams and rivers into lakes and oceans.
Excretion — waste
How do farmers increase the productivity of crops?
By using fertilisers:
Natural (organic) — dead and decaying remains of plants and animals, animal waste e.g. manure
Artificial (inorganic) — nitrogen which increases the rate of photosynthesis, phosphorus and potassium from rocks.
Describe the main issues surrounding agricultural practices on terms of nutrient cycles
- Leaching, from the phosphorus cycle, may lead to pollution of watercourses.
- Eutrophication from the fertiliser into watercourses — increase of nitrates in water = algae so anything underneath us blocked from sunlight - can’t photosynthesise fully = death and decay = increase in respiration for microorganisms
- Removing the crop to use so animals cannot habitat there — not going to decompose in the same area
- Reduces species diversity
Process of eutrophication
- Nitrates (fertilisers) are washed into the sea/river due to rain — leaching
- This leads to the increase of nitrates in water — forms algae bloom
- Organisms in water will be blocked from sunlight so cannot photosynthesise
- Organisms will die, microorganisms will respire more so dead will decay
- Not enough oxygen for anything else alive e.g. invertebrates, fish
How can eutrophication be prevented ?
By using more natural fertilisers than artificial fertilisers
Avoiding the use of soluble fertilisers
Rotating drips permitting the soil to recover from nitrogen hungry crops e.g. wheat
Adding a nitrogen fixing crop into the rotation cycle
