nutrient cycles Flashcards
Nutrient Cycles [2]
- Energy flow is linear as the Sun continually provides a supply of energy
- Elements must be recycled: Water, Carbon, Nitrogen, Phosphorus, Magnesium, Potassium
Why is Nitrogen Cycle important?
Organisms need protein, nucleic acids
Nitrogen Cycle [8]
- Plants are consumed by animals
- Both of these organisms eventually die and are hydrolysed by decomposers
- The process of ammonification takes place by saprobionts, converting protein into Ammonium ions in the soil
- These are converted to Nitrites via nitrification by nitrifying bacteria
- These are then converted to Nitrates via nitrification by nitrifying bacteria
- Some Nitrates are absorbed by plants from the soil
- Some Nitrites are converted to Nitrogen Gas in the atmosphere via denirtification by denitrifying bacteria in anaerobic conditions
- The Nitrogen Gas can then be converted to nitrogen containing compounds via nitrogen fixation by nitrogen fixing bacteria, which can be absorbed by plants
Nitrogen Fixation [2]
- Nitrogen gas converted to nitrogen containing compounds
- Carried out by nitrogen fixing bacteria
Ammonification [2]
- Production of ammonia from organic nitrogen containing substances (urea, faeces)
- Carried out by saprobionts
Nitrification [2]
- Conversion of ammonium to nitrites and then to nitrates
- Carried out by nitrifying bacteria
Denitrification [3]
- Conversion of nitrates to nitrogen
- Occurs in water logged soils in anaerobic conditions by denitrifying bacteria
- This is not a useful process
Where can Nitrogen Fixing bacteria be found?
Can be free living in soils or live in root
e.g. nodules of leguminous plants
Fertilisers [3]
- Fertilisers improve productivity of plants
- Natural ecosystems ensure soils are fertile through decomposition of dead organisms
- Intensive farming means mineral ions are regularly depleted and need replacing for the next crop, fertilisers can be used
Natural Fertilisers
manure, slurry, bone meal
Artificial Fertilisers [2]
Mined from rocks and blended depending on minerals needed
Nitrogen, Phosphorous and Potassium are usually present
Problems with Fertilisers [3]
Reduced species diversity - some plants are better at absorbing minerals compared to others and out-compete
them
Leaching - rainwater dissolves nutrients and washes them away
Eutrophication - fertilisers are washed or leaching occurs into bodies of water
Eutrophication [9]
- Fertilisers wash into lake
- Fertilisers cause algae to grow at the surface (algal bloom)
- The algal bloom blocks light to plants and algae lower in the water
- These plants and algae die
- Decomposers break them down, carrying out respiration as they do so
- Water become oxygen-depleted (anoxic)
- Other aerobic organisms e.g. fish will die due to lack of oxygen
- Anaerobic organisms now have no competition for space so will reproduce
- Anaerobic organisms produce toxic waste, creating putrid water
Why is the Phosphorus Cycle important?
Organisms need nucleic acids, proteins, ATP
Phosphorus Cycle [9]
- Decomposers (saprobionts) cause formation of sediment and rocks containing phosphate
- Decomposers also cause phosphate ions to be released into soil / water
- This also occurs by weathering of rocks containing phosphate
- Uptake of phosphate ions by plants and algae
- Phosphorus in biological molecules in primary producers
- Feeding means phosphorus is present in biological molecules in primary consumers
- Feeding means phosphorus is present in biological molecules in secondary consumers
- Death of primary producers
- Death and excretion of primary and secondary consumers
- Decomposers
