Nutrient Cycles Flashcards
Name the stages of the phosphorus cycle
- weathering
- run off
- assimilation
- decomposition
- uplift
Why is the phosphorus cycle a slow process
- phosphorus has no gas phase so there is no atmospheric cycle
- most phosphorus is stored as PO3- 4 in rocks
What happens during weathering and run off
Phosphate compounds from sedimentary rocks leach into surface water and soil
Why is phosphorus important to living organisms
- Plants convert inorganic phosphate into biological molecules eg DNA, ATP, NADP
- is passed to consumers via feeding
What happens ruing uplift
Sedimentary layers from the ocean are brought up to land over many years
How does mining affect the phosphorus cycle
Speeds up uplift
Describe the phosphorus cycle
- physical process of the climate (weathering) release phosphate ions from rocks
- phosphate ions pass to the environment, soil and water
- producers absorb phosphate ions from the environment
- transfer to consumer through food chain
- when producers and consumer dies, decomposition as the result of decomposers release phosphate ions into the environment
- phosphate ions are recycled and available for absorption by new gen of producers an transfer from producer to consumers
4 main stages of nitrogen cycle
- nitrogen fixation
- ammonification
- nitrification
- denitrification
Why can’t organisms use nitrogen directly from the atmosphere
N2 is very stable due to strong covalent triple bonds
What happens during atmospheric fixation of nitrogen
- nitrogen gas (N2) converted to nitrogen containing compound (ammonia) by nitrogen fixing bacteria
Role of nitrogen fixing bacteria
- Mutualistic nitrogen-fixing bacteria in nodules of legumes and free living bacteria in soil
- using the enzyme nitrogenase to reduce gaseous nitrogen into ammonia
What is ammonification
- nitrogen containing compounds Brocken down
- converted to ammonia which form ammonium ions in the soil
- by saprobionts
What is nitrification
Ammonium ion in soil —> nitrites —> nitrates
- by nitrifying bacteria
- in aerobic conditions - need o2
What is denitrification
Anaerobic denitrifying bacteria convert soil nitrate back into gaseous nitrogen
What conditions does denitrification usually occur in
Waterlogged skills as there is no o2 an conditions are anaerobic
Significance of nitrogen to living organism
- plant roots Utah nitrates via active transport an use them to make biological compounds
- eg amino acid, NAD/NADP
- nucleic acid
Role of mycorrhizae
- Mutualistic relationship between plant and fungus increases SA of root system
- increase uptake of water and mineral ions
Benefits of planting a different crop on the same field each year
- nitrogen fixing crops eg legumes make soil more fertile by increasing soil nitrate content
- different crops have different pathogens
- different crops use different promotions of certain ions
Two types of fertilisers
- Organic
- Inorganic
Purpose of fertilisers
Increase gross productivity for higher yield
Organic fertilisers
Decaying organic matter and animal waste
Inorganic fertilisers
Minerals from rocks usually containing nitrogen, phosphorus, potassium
Why at a certain point do fertiliser no longer increase crop yield
Conc of mineral ions limits the rate of photosynthesis so rate o growth cannot increase any further
2 main environmental issues cause by fertilisers
Leaching and eutrophication
Leaving
Nitrates dissolve in rainwater and runoff into water sources
- can prevent efficient o2 transport in babies
What happens during eutrophication
- aquatic plants grow exponentially since nitrate level is no longer a lifting factor
- algal bloom on water surface preventing lit from reaching the bottom and plants die
- o2 levels decrease as population of aerobic saprobionts increase to decay dead matter so fish die
- anaerobic organisms reproduce exponentially and produce toxic waste making water putrid
How can the risk of eutrophication be reduced
- Sewage treatment marshes on farms
- pumping nutrient enriched sediment
- using phosphate free detergent
What are saprobionts (decomposers)
- release extracellur enzymes
- hydrolyse large complex materials in dead organisms into mall ones which they can absorb
- realises minerals in a form useable by plants
