Nutrient cycles (13) Flashcards
What are the 5 stages of the phosphorus cycle?
1) weathering
2) runoff
3) assimilation
4) decomposition
5) uplift
What are the 2 reasons why the phosphorus cycle is a slow process?
- phosphorus has no gas phase so there is no atmospheric cycle
- most phosphorus is stored as phosphate (Po43-) in rocks
What happens in weathering and runoff?
phosphate compounds from sedimentary rocks leach into surface water and soil
What are 2 reasons why phosphorus is significant in organisms?
- plants convert inorganic phosphate into biological molecules
- phosphorus is passed to consumers via feeding
What are 3 biological molecules that phosphate can be converted into?
DNA
ATP
NADP
What happens in the uplift stage?
sedimentary layers from oceans are brought up to land over many years
What is sedimentary layers from oceans formed from?
the bodies of aquatic organisms
What speeds up uplift?
mining
Why can’t organisms used nitrogen directly from the atmosphere?
very stable due to strong covalent triple bond
What are the 4 stages of the nitrogen cycle?
1) nitrogen fixation
2) nitrification
3) ammonification
4) dentrification
What is the purpose of using fertilisers?
to increase gross productivity for higher yield
What are 2 advantages of aerobic conditions?
- uses oxygen so nitrogenase works
- provides ATP for reaction
What happens during nitrogen fixation?
mutualistic nitrogen-fixing bacteria in modules of legumes use nitrogenase to reduce nitrogen into ammonia
What are 3 ways to reduce the risk of eutrophication?
- sewage treatment marshes on farms
- pumping nutrient-enriched sediment out of water
- using phosphate-free detergent
What happens during ammonification?
saprobionts break down proteins by feeding on and decomposing waste, this causes ammonia to be released and dissolve in water in the soil to form ammonium ions
What happens during nitrification?
saprobionts convert ammonium ions into nitrite using oxygen, and then nitrite into nitrate using oxygen
What is the equation for the conversion of ammonium ions into nitrite?
2NH4- + 3O2 > 2NO2- + 2H2O + 4H+
What is the equation for the conversion of nitrite into nitrate?
2NO2- + O2 > 2NO3-
What is the significance of nitrogen to living organisms?
plant roots uptake nitrates via active transport and use them to make biological molecules
What are 3 biological molecules that nitrogen can be converted into?
amino acids
NAD/NADP
nucleic acids
What happens during dentrification?
anaerobic denitrifying bacteria convert nitrate back into nitrogen
What is the relationship between plant and fungus called?
symbiotic relationship
What type of fungus is associated with plants?
mycorrhizae
How do plants benefit from a relationship with fungus?
fungus increases surface area of root system and increases uptake of water and mineral ions
How does fungus benefit from a relationship with plants?
provides access to sucrose
What are 3 advantages of planting different crops on the same field each year?
+ nitrogen-fixing crops make soil more fertile by increasing soil nitrate content
+ different crops have different pathogens
+ different crops use different proportions of certain ions
What are the 2 types of fertiliser?
organic
inorganic
What is an organic fertiliser made from?
decaying organic matter and animal waste
What is an inorganic fertiliser made from?
minerals from rocks usually containing nitrogen, phosphorus and potassium
What are 2 issues that fertilisers can cause?
leaching
eutrophication
What happens during leaching?
nitrates dissolve in rainwater and runoff into water sources
What is meant by eutrophication?
when a water source becomes putrid as a result of algal bloom
What are the 4 stages of eutrophication?
1) aquatic plants grow exponentially as nitrate level isn’t a limiting factor
2) algal bloom on water surface prevents light from reaching bottom and plants die
3) oxygen levels decrease as aerobic saprobionts increase to decay dead matter, so fish die
4) anaerobic organisms reproduce exponentially and produce toxic waste, making water putrid
