Download A2 Chapter 6 Common Exam Qs

A2 Chapter 6 Nutrient Cycles – Common Exam Questions
Carbon cycle:
Question
Substances found in dead
leaves contain carbon.
Describe how microorganisms
make this carbon available to
plants
How have human activities
lead to global warming
Why does growing crops for
biofuel lead to decease in
biodiversity?
Why do biofuels lead to a net
reduction in carbon dioxide
production
Perfect answer
1) Saprobiotic bacteria do extracellular digestion (secrete enzymes)
2) Starch converted to glucose by amylase enzyme
3) Glucose absorbed
4) Glucose used in aerobic respiration
5) Carbon dioxide released
6) Carbon dioxide taken in by plants for photosynthesis
1) Carbon dioxide is a greenhouse gas
2) Deforestation leads to reduced photosynthesis, so reduced
carbon dioxide uptake from atmosphere
3) Combustion of fossil fuels leads to carbon dioxide production
4) Methane is a greenhouse gas
5) Methane is produced from cattle or rice growing
6) Increased levels of greenhouse gases lead to global warming
1) Crop is a monoculture, so lowers biodiversity
2) Reduced variety of habitats for animals
3) Reduced variety of food for animals
1) Crops take in carbon dioxide when they photosynthesise
2) More carbon dioxide is taken in than produced when the crops
are burnt
Nitrogen cycle:
Make sure you know the names of processes and bacteria
Reaction
Type of bacteria
1) Proteins to amino acids
Saprobiotic
2) Amino acids to ammonia
Ammonifying
3) Ammonium to nitrites
Nitrifying
4) Nitrites to nitrates
Nitrifying
Nitrogen to ammonia 
Nitrogen fixing (in root
nodules or free living
in soil)
Nitrates to nitrogen 
Denitrifying
Question
Describe the role of
microorganisms in
producing nitrates for
plants (from the
remains of dead
organisms)
Explain how an
increase in nitrate ions
in ponds / rivers could
affect fish
Name of process
Digestion (Hydrolysis reaction)
Ammonification
Nitrification (oxidisation reaction)
Nitrification (oxidisation reaction)
Nitrogen fixing
Denitrification
Perfect Answer
1) Protein converted into amino acids by saprobiotic bacteria
2) Amino acids converted to ammonia by saprobiotic bacteria
3) Ammonium ions into nitrites by nitrifying bacteria
4) Nitrites into nitrates by nitrifying bacteria
If ‘from dead organisms’ is not mentioned in the question then you can add:
5) Nitrogen fixing bacteria convert nitrogen to ammonia
1) Increased growth of algae leading to algal bloom
2) Algae blocks light leading to lack of photosynthesis of plants and plant
death
3) Saprobiotic bacteria break down dead plants
4) Bacteria use up oxygen in aerobic respiration
5) Fish die due to lack of oxygen