Nutrient Cycles Flashcards
Name molecules nitrogen is found in
Amino acids/proteins
Nucleic acids/DNA/RNA
ADP/ATP
NADP/NAD/FAD
What are key process in the nitrogen cycle?
Ammonification
Nitrification
Nitrogen fixation
Denitrification
What is nitrogen fixation in the nitrogen cycle?
Nitrogen fixing bacteria found in the soil and root nodules of some leguminous plants can reduce N2 gas to ammonia
What is nitrification in the nitrogen cycle?
Ammonia is oxidised to nitrites then nitrates by nitrifying bacteria (in soil)
What is ammonification in the nitrogen cycle?
Saprobiotic bacteria secrete extracellular enzymes to hydrolyse nitrogen containing polymers into monomers which can be absorbed and release ammonia into the soil
What is denitrification in the nitrogen cycle?
Nitrates converted to nitrogen gas by denitrifying bacteria (only occurs in waterlogged, anaerobic conditions - a natural way to prevent leaching)
Describe how the action of microorganisms in the soil produces a source of nitrates for crop plants (5)
Proteins/amino acids/DNA converted to ammonia
By saprobionts
Ammonia into nitrite
Then nitrite into nitrate
By nitrifying bacteria
Nitrogen gas to ammonia
By nitrogen-fixing bacteria
Name molecules phosphorus is found in
ATP
Phospholipids
Nucleic Acids
What is the phosphorus cycle?
Phospholipids, RNA and DNA from dead organisms into phosphate ions
Decomposed by saprobionts
Phosphate ions also found in waste and remains (e.g. guano, bones and shells)
Phosphate ions transported by streams, rivers, lakes and oceans
Form sedimentary rocks
Weathering and erosion of rocks helps phosphate ions dissolve in oceans, lakes and soils
Phosphate become available for absorption by plants to incorporate into biomass
What two types of fertilisers are there?
Organic/natural (waste material such as manure)
Inorganic/artificial (manufactured, man-made powders or pellets produced in factories containing nitrates, phosphates and potassium ions)
What are the environmental impacts of using fertilisers?
Reduced species diversity - plants adapted to soils with high in nitrate concentration outcompete other species
Leaching
Eutrophication
What is leaching?
Ions dissolve in soil water and are washed from the soil into streams, rivers and lakes
What is eutrophication?
Nitrates washed away into water courses (leaching) and build up
High concentration of ions causes rapid growth of algal bloom
Blocks out light
Plants cannot photosynthesis so die
Saprobionts break down dead organisms
Saprobionts use up oxygen so organisms that respire aerobically die
Increase in anaerobic respiration which releases toxins
What is the role of mycorrhizae on nutrient cycles?
Increase surface area for the plant to absorb water and minerals
Improves uptake of ions
Microorganisms make the carbon in polymers in a dead worm available to cells in a leaf. Describe how (5)
Microorganisms are saprobionts
Secrete enzymes/extracellular digestion
Absorb products of digestion/smaller molecules
Respiration by microorganisms produces carbon dioxide
Carbon dioxide taken into leaves
Through stomata
