| Date | May 2018 | Marks available | 1 | Reference code | 18M.2.SL.TZ0.3 |
| Level | Standard Level | Paper | Paper 2 | Time zone | Time zone 0 |
| Command term | Identify | Question number | 3 | Adapted from | N/A |
Question
Figure 3 represents a system of aquaculture with four groups of harvestable species.
Figure 3: Integrated aquaculture
[Source: Adapted from and reprinted with permission from Ocean Conservancy]
Identify one producer in the system illustrated in Figure 3.
Outline one reason why aquaculture production has increased globally.
Describe two negative environmental impacts that may arise from integrated aquaculture.
Explain why this system may cause fewer environmental impacts than systems that farm only fish.
Markscheme
algae/seaweed/sea grass
increased food demand from increasing population/affluence;
health benefits / change of diet preferences;
depletion of marine fisheries / considered more sustainable;
limited arable land for food production;
more economically efficient/profitable;
requires less resources/expertise (boats, fishermen, etc) than wild fisheries;
technology/technological methods have improved.
Award [1 max].
escaped fish impact wild stocks through genetic degradation/disease/competition;
high density populations lead to more disease;
farmed species may consume/displace food species for local populations;
loss/degradation of habitat due to clearance for aquaculture / nets/cages may trap/endanger local species;
introduction of non-native species;
pollution due to use of medication/growth hormones/pesticides.
NB do not credit high nutrients/eutrophication/low diversity/high BOD or any other impacts that integrated agriculture actually limits or reduces (as indicated in responses to question 3(d)).
Award [1] for each correct answer identified, up to [2 max].
polyculture helps maintain biodiversity/complexity/resilience in the environment;
(polyculture) allows for species to recycle wastes of other species;
lobsters/mussels will reduce particles of organic waste/faecal matter/excess feed;
(reduction of particles will) reduce BOD/decomposition and oxygen consumption;
filtration by the mussels will improve water clarity/photosynthesis;
cropping/harvesting algae will prevent build-up of nutrients/eutrophication;
algae will absorb excess CO2 reducing acidification of water;
algae will release oxygen limiting anaerobic conditions;
food is provided naturally from within system/feeds made up from wild populations are not required.
Award [1] for each correct answer identified, up to [4 max].
Examiners report
The vast majority of candidates identified a “producer” in the system.
The great majority identified a valid reason for rise in aquaculture
A good proportion of candidates identified at least one potentially negative impact of aquaculture.
Surprisingly few candidates could suggest more than one (occasionally two) advantages of integrated culture. It was as if they had not registered the 4 marks available and were satisfied once they had given just one possible reason.
Syllabus sections
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19N.1.SL.TZ0.2a:
Using Figure 6(c), identify a food chain in the St Lawrence River ecosystem that has five trophic levels.
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18N.1.SL.TZ0.3a:
With reference to Figure 6, draw a food chain that includes four trophic levels.
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18N.1.SL.TZ0.3b:
Identify two ways that human activity in Algonquin Provincial Park may affect the food web.
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17N.1.SL.TZ0.7:
To what extent might Iceland be viewed as a role model for sustainability by other countries?
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17N.1.SL.TZ0.5b:
With reference to Figure 8(c) state the impact that an increase in the mackerel population might have on the Atlantic puffin population.
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18M.2.SL.TZ0.5b:
Suggest the procedures needed to collect data for the construction of a pyramid of numbers for the following food chain:
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16N.2.SL.TZ0.4a:
Outline why top carnivores are vulnerable to non-biodegradable toxins.
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19M.2.SL.TZ0.1d:
Outline two ways in which the food web is likely to change as a result of succession.
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19M.1.SL.TZ0.8:
With reference to Figure 5, describe how loss of a coral reef ecosystem could impact a neighbouring seagrass community.
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17N.2.SL.TZ0.4a:
Describe the role of primary producers in ecosystems.
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17N.2.SL.TZ0.7a:
Outline how soil can be viewed as an ecosystem.
- 18N.2.SL.TZ0.4c: Using examples, discuss whether habitat conservation is more successful than a species-based...
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18N.1.SL.TZ0.10a:
With reference to Figure 7(a), outline one reason why there are more beaver remains in wolf faeces during summer.
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19N.1.SL.TZ0.3b:
With reference to Figure 9(a), outline how the round goby both positively and negatively affects the St Lawrence River ecosystem.
- 18N.1.SL.TZ0.1: Identify one ecosystem in Algonquin Provincial Park.
- 17N.1.SL.TZ0.5a.ii: Identify one argument against humans hunting puffins.
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19N.1.SL.TZ0.2e:
Suggest why the St Lawrence River beluga whale population has not recovered despite being given protected status in 1983.
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18M.2.SL.TZ0.4b:
Explain how a community of trees in a woodland may be considered a system.
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17M.2.SL.TZ0.1d:
With reference to the concepts of bioaccumulation and biomagnification, outline how the concentration of DDT has changed along the food chain.
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19N.1.SL.TZ0.1d:
Outline why estuaries are highly productive ecosystems.
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19N.1.SL.TZ0.2d:
With reference to Figure 8, explain why the beluga whale is more at risk from toxic pollutants, such as heavy metals and persistent organic pollutants (POPs), than most other organisms in its food web.
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17M.2.SL.TZ0.1b:
State the trophic level labelled X in Figure 1.
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19M.1.SL.TZ0.7:
Explain two ways in which mangroves improve the water quality for primary producers within marine ecosystems.
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16N.1.SL.TZ0.4c:
Describe how the second law of thermodynamics operates in relation to the transfer of energy within the Silver Springs ecosystem.
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16N.1.SL.TZ0.4d:
Distinguish between a pyramid of numbers and a pyramid of productivity.
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17N.1.SL.TZ0.5c:
Identify two reasons why the future size of the Atlantic puffin population is difficult to predict.
- 21N.2.SL.TZ0.1a.iii: Explain how the second law of thermodynamics applies to this food chain.
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21M.1.SL.TZ0.7a:
Outline the impact that a reduction in the tiger population may have on other populations in the food web shown in Figure 8(c).
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20N.1.SL.TZ0.2e:
With reference to Figures 2(a) and 2(b), suggest two reasons why the red-necked amazon population has recovered more quickly than the imperial amazon population following Hurricane David in 1979.
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20N.1.SL.TZ0.1a:
Using Figure 1(c), state one ecosystem found at sea level in Dominica.
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21N.1.SL.TZ0.1a:
With reference to Figures 2(b) and 3, identify an ecosystem found in London.
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21N.2.SL.TZ0.5b:
Explain how models of ecosystems might be used in species conservation.
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22M.2.SL.TZ0.7b:
Explain how negative and positive feedback mechanisms may influence the growth of decomposer populations in the soil.
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21N.2.SL.TZ0.4a:
Identify four factors that make the use of the insecticide DDT controversial.
- 21N.2.SL.TZ0.1a.i: State the trophic level of the zebra.
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21N.1.SL.TZ0.1b:
Outline one factor which limits the primary productivity of an ecosystem in London.
