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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 State 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.

[1]
a.i.

Identify one way in which energy may leave this ecosystem.

[1]
a.ii.

Draw a food chain from the ecosystem in Figure 1 consisting of four trophic levels.

[1]
a.iii.

Identify two possible effects of removing trout on this ecosystem.

[2]
a.iv.

Predict how the introduction of a non-native species may affect this lake ecosystem.

[2]
a.v.

Markscheme

sun/sunlight/solar radiation/insolation;

 

[1 max]

a.i.

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]

a.ii.

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]

a.iii.

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]

a.iv.

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]

a.v.

Examiners report

Most candidates correctly identified sunlight as the source of energy. A common mistake was to state producers/plants/phytoplankton.

a.i.

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’.

a.ii.

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.

a.iii.

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’.

a.iv.

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’.

a.v.

Syllabus sections

Topic 2: Ecosystems and ecology » 2.2 Communities and ecosystems
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Topic 2: Ecosystems and ecology

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