| Date | May 2014 | Marks available | 1 | Reference code | 14M.1.SL.TZ0.1 |
| Level | Standard Level | Paper | Paper 1 | Time zone | Time zone 0 |
| Command term | Identify | Question number | 1 | Adapted from | N/A |
Question
Figure 1 below shows an example of a lake ecosystem.
Figure 1
© International Baccalaureate Organization 2014
State the source of energy for this ecosystem.
Identify one way in which energy may leave this ecosystem.
Draw a food chain from the ecosystem in Figure 1 consisting of four trophic levels.
Identify two possible effects of removing trout on this ecosystem.
Predict how the introduction of a non-native species may affect this lake ecosystem.
Markscheme
sun/sunlight/solar radiation/insolation;
[1 max]
removal of organisms from the lake/removal of fish/fishing/removal of reeds/run-off/outfall/outflow/loss of heat (to environment);
Do not accept only ‘respiration/evaporation/transpiration’
Accept any other appropriate response.
[1 max]
Accept any appropriate food chain from figure 1 with four different trophic levels and correct direction of arrows indicating flow.
eg phytoplankton (diatoms) → zooplankton → small fish (perch) → bird (kingfisher);
[1 max]
increase in secondary consumers/organisms in trophic level below them (eg small fish);
reduction in primary consumers/zooplankton due to increase in secondary consumers population;
less competition for other tertiary consumers;
increase in bird population due to less competition;
loss of biodiversity;
[2 max]
out competes local species;
introduction of disease;
loss of biodiversity;
reduce/feed off other species;
provides an additional food source to native species leading to increase in native population;
may have little or no effect;
may not adapt to new environment and die out;
may breed with native species/interbreeding;
Accept any other appropriate response.
[2 max]
Examiners report
Most candidates correctly identified sunlight as the source of energy. A common mistake was to state producers/plants/phytoplankton.
Most candidates answered this question well. Common answers included ‘heat loss from respiration’ or ‘migration of kingfishers/birds’. Some answers were considered too vague such as just ‘respiration’ or ‘death of species’.
The majority of candidates were able to draw a food chain correctly. Common errors included incorrect direction for the flow of energy/arrows or drawings of foodwebs or pyramid of numbers.
This question was generally well answered. In some cases answers were too vague e.g. ‘changes would occur in food chain/some species would increase/decrease’ or ‘change in biodiversity’.
This question was slightly less well answered than 1aiv). Common errors included generalized statements e.g. ‘would disrupt the foodchain’ and ‘causes an imbalance in the food chain’.
Syllabus sections
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14N.1.SL.TZ0.5a:
Label the diagram above to complete the processes and flows in the nitrogen cycle.
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17N.2.SL.TZ0.4a:
Describe the role of primary producers in ecosystems.
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18M.2.SL.TZ0.2c.iii:
Identify one other output from the mineral storage in the “A” horizon in Figure 2(b).
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18N.2.SL.TZ0.5c:
Discuss strategies that can be used to improve the sustainability of food production systems.
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14M.2.SL.TZ0.2b:
Explain how the first and second laws of thermodynamics are demonstrated as energy from the sun flows through the primary producers in a food chain.
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16M.2.SL.TZ0.2b:
Describe the similarities and differences between the terms sustainable yield and sustainable development.
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16N.1.SL.TZ0.4a:
State the process represented in the box labelled X.
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18M.2.SL.TZ0.5c:
Quantitative models are frequently constructed to show the flow of energy and cycling of matter in natural systems.
To what extent can these models be useful in assessing the sustainability of named food production systems?
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14M.1.SL.TZ0.4b:
Overgrazing may lead to soil degradation. Identify one impact that overgrazing may have on a named flow and a named storage within the nitrogen cycle.
(i) Impact on flow:
(ii) Impact on storage:
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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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18M.2.SL.TZ0.4b:
Explain how a community of trees in a woodland may be considered a system.
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14N.1.SL.TZ0.5c:
Describe two ways in which humans may impact the nitrogen cycle.
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16M.1.SL.TZ0.1e.ii:
Describe its role in the carbon cycle of the system.
- 17M.2.SL.TZ0.1a: State the main source of energy for the food chain in Figure 1.
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14M.2.SL.TZ0.2a.i:
Define net secondary productivity.
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19N.1.SL.TZ0.1d:
Outline why estuaries are highly productive ecosystems.
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17M.2.SL.TZ0.4b:
Suggest a series of procedures that could be used to estimate the net productivity of an insect population in kg m–2 yr–1.
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19N.1.SL.TZ0.1a:
Using Figure 4(a), identify an ecosystem that has an average net primary productivity above 30 000 kJ m–2 a–1.
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14N.1.SL.TZ0.5b:
Distinguish between a transfer and a transformation in the nitrogen cycle.
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18M.2.SL.TZ0.2c.ii:
Identify one other input to the mineral storage in the “A” horizon in Figure 2(b).
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14M.1.SL.TZ0.4a:
Identify in the spaces provided the missing flows and storages labelled 1–4 within the diagram.
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15M.2.SL.TZ0.3b:
Construct a labelled flow diagram to show the processes that link soil with the following three storages:
The atmosphere
The lithosphere
Living organismsAnnotate each labelled flow with an example of the matter involved.
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16M.1.SL.TZ0.2a.iv:
With reference to the cattle in the area, explain how the maximum sustainable yield could be calculated.
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17M.2.SL.TZ0.4a:
Identify four ways in which solar energy reaching vegetation may be lost from an ecosystem before it contributes to the biomass of herbivores.
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14N.2.SL.TZ0.4b:
Explain the transfer of energy through an ecosystem. Support your explanation with a labelled diagram.
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17N.2.SL.TZ0.7b:
Compare and contrast the impact of humans on the carbon and nitrogen cycles.
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16N.1.SL.TZ0.4b:
Define net primary productivity.
