nutrient cycles exam questions Flashcards
describe the role of saprobionts in the nitrogen cycle (2 marks)
M1: they use enzymes to decompose proteins
M2: to release ammonium
one environmental issue arising from the use of fertilisers is eutrophication. Eutrophication can cause water to become cloudy.
You are given samples of water from three different rivers.
describe how you would obtain a quantitative measurement of their cloudiness (3 marks)
M1: use of calorimeter
M2: measure the absorbance of light
M3: to standardise zero the calorimeter
The scientists used units of ug g-1 for the concentration of ammonia in soil.
suggest why, in this investigation, the scientists used these units (2 marks)
M1: ug because very little ammonia in soil
M2: g-1 to allow comparisons between samples
The scientists concluded that the soil mixture experiment showed there were different communities of bacteria in soils A and B
what evidence from figure 1 supports their conclusions? give reasons for your answer. (3 marks)
M1: B has fastest rate of breakdown of ammonia at pH 4.3
M2: A and B at pH 6.9 is slowest
M3: suggests community of ph 4.2 doesnt work well at 6.9
In which species was the number of copies of mRNA more affected by changes in soil pH from 4.9 to 5.7? use a calculation to support your answer (2 marks)
M1: species S change of 990,000 per gram of soil
M2: species T change of 9,900 per gram of soil
This method allowed the scientists to estimate the expression of the amoA gene in each culture but not the growth of the bacterial population in each culture.
Explain why. (4 marks)
M1: they didn’t count bacteria
M2: number of mRNA related to amount of enzyme produced
M3: don’t know how much mRNA produced by each cell
M4: don’t know if enzyme is linked to cell division
the scientists set up their cultures in sterile glass bottles.
suggest one suitable method for sterilising the bottles and explain why it was necessary to sterilise them. (2 marks)
M1: wash in disinfectant
M2: to kill other bacteria
use the data in the graph above to evaluate the use of artiticial fertilisers on grain producing crops in India (2 marks)
M1: using more but getting less response over time
M2: the graph shows correlation but doesnt prove changes in yield due to fertiliser
which one of the processes, P, Q and R involves nitrification
R
describe another process carried out by microorganisms which adds ammonium ions to soil (2 marks)
M1: proteins broken down to ammonium ions
M2: by saprobionts
denitrification requires anaerobic conditions. Ploughing aerates the soil. Explain how ploughing would affect the fertility of the soil. (2 marks)
M1: fertility increased as more nitrate formed
M2: less denitrification
one farming practice used to maintain high crop yields is crop rotation. This involves growing a different crop each year in the same field.
Suggest two ways in which crop rotation may lead to high crop yields ( 2 marks)
M1: grow plants with nitrogen fixing bacteria
M2: different crops use different minerals
During the light independent reaction of photosynthesis, carbon dioxide is converted into organic substances. Describe how (6 marks)
M1: carbon dioxide combines with ruBP
M2: produces 2 glycerate 3 phosphate
M3: GP reduced to triose phosphate
M4: using reduced NADP
M5: using energy from ATP
M6: triose phosphate converted into glucose
Nitrate from fertiliser applied to crops may enter ponds and lakes. Explain how nitrate may cause the death of fish in fresh water. (5 marks)
M1: growth of algae blocks light
M2: no photosynthesis so plants die
M3: saprobiotic microoganisms
M4: use oxygen in respiration
M5: meaning less oxygen for fish to respire
name process P
nitrification
