| Date | May 2014 | Marks available | 2 | 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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15M.2.SL.TZ0.2b.ii:
Explain how predation may lead to long-term population decrease or extinction of the prey species.
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15N.1.SL.TZ0.2b.i:
Identify one abiotic factor which may affect the population of insects in a forest.
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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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16M.1.SL.TZ0.1d:
Oystercatchers and avocets both feed on small animals in the mud of the wetlands. State the most likely relationship between these two species.
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19M.2.SL.TZ0.5a:
Identify four impacts on an ecosystem that may result from the introduction of an invasive species of herbivore.
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17M.2.SL.TZ0.1e.ii:
Outline how this relationship may be of benefit to the populations of both species.
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19N.1.SL.TZ0.2b:
Using Figure 7, state the St Lawrence beluga whale population in 1920 and 1940.
1920:
1940:
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15M.2.SL.TZ0.2a:
Outline the similarities and differences between predation and competition.
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18M.2.SL.TZ0.5a:
Distinguish between the terms niche and habitat with reference to a named species.
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14N.2.SL.TZ0.2a:
Distinguish between negative and positive feedback using examples from environmental systems.
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18N.1.SL.TZ0.10c:
With reference to Figure 10(b), explain the threats to the future existence of a small and sustainable population of wolves as a result of their protection in limited area.
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17N.2.SL.TZ0.1a.ii:
Identify three reasons why carrying capacity can be difficult to estimate.
- 17M.2.SL.TZ0.1e.i: State the relationship between large and small fish in Figure 1.
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18N.1.SL.TZ0.5:
With reference to Figures 9(a) and 9(b), describe one abiotic change and one biotic change in a beaver meadow community undergoing succession.
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19N.1.SL.TZ0.2c:
Calculate the percent decrease in beluga whale numbers from 1920 to 1940.
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19M.1.SL.TZ0.5:
With reference to Figure 4(d), suggest the impact on the marine food web if tuna numbers were to decline.
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19N.1.SL.TZ0.3c:
With reference to Figure 9(a), explain why the realized niche of the mottled sculpin has changed in recent years.
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16M.1.SL.TZ0.1a:
Define the term species.
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19M.2.SL.TZ0.5b:
Explain how both positive and negative feedback mechanisms may play a role in producing a typical S population growth curve for a species.
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15M.2.SL.TZ0.2b.i:
Explain how predation may lead to stability in a population of the prey species.
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15M.2.SL.TZ0.1d:
Evaluate the possible use of grass carp in controlling the growth of water hyacinth in Inle Lake.
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15N.1.SL.TZ0.2c:
Distinguish between a mutualistic relationship and a parasitic relationship.
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14N.1.SL.TZ0.2c:
Using Figure 1 below, calculate the annual rate of population increase for elephants in Zimbabwe from 1985 to 2005.
Figure 1 Elephant Population: Kenya compared to Zimbabwe, 1973 – 2011
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16M.2.SL.TZ0.3a:
Outline the role of limiting factors in S and J population curves.
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16N.2.SL.TZ0.1f:
Justify whether or not Mesquite should be cleared from the Swakop River Valley.
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16N.2.SL.TZ0.1e:
With reference to the data in Figure 4(b), suggest two conclusions which can be drawn from the camera trap data.
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15N.1.SL.TZ0.2a.ii:
Identify two possible reasons why species B and C were not present in the litter layer when it was resampled six months later.
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17N.2.SL.TZ0.1a.i:
Define the term carrying capacity.
