| Date | November 2019 | Marks available | 3 | Reference code | 19N.1.SL.TZ0.3 |
| Level | Standard Level | Paper | Paper 1 | Time zone | Time zone 0 |
| Command term | Outline | Question number | 3 | Adapted from | N/A |
Question
Figure 9(a): Fact file on the round goby (Neogobius melanostomus)
- An invasive species from Asia.
- First discovered in the St Lawrence River in 1990.
- Females lay eggs three times a year; up to 5000 eggs at a time.
- Young fish mature quickly.
- Can eat up to 4000 eggs of other fish in 15 minutes.
- Aggressively defend the best egg-laying sites, out-competing the native mottled sculpin (Cottus bairdii).
- Eat invasive zebra mussels.
- Eaten by native fish, such as lake trout and yellow perch.
Figure 9(b): Pictures of the round goby and mottled sculpin
Using Figures 9(a) and 9(b), identify one feature of the round goby that shows it is an r-selected species.
With reference to Figure 9(a), outline how the round goby both positively and negatively affects the St Lawrence River ecosystem.
With reference to Figure 9(a), explain why the realized niche of the mottled sculpin has changed in recent years.
Markscheme
frequent egg laying (3 times per year);
many eggs laid at one time (5000);
young fish grow quickly / early maturity.
Positive [2 max]:
provide additional food source for native fish (e.g. yellow perch);
eat other invasive species, such as the zebra mussel.
Negative [2 max]:
increased competition for food, outcompeting native fish;
outcompetes the native mottle sculpin for the best egg-laying sites;
outcompetes native species which may become extinct;
eat other fish eggs, reducing populations/biodiversity;
introduce disease, reducing populations/biodiversity.
Accept any other reasonable response.
Do not accept only ‘outcompetes native species’, for credit must be linked to competition for food, egg laying sites or species extinction.
Do not accept ‘aggressively takes the habitat of native species’.
resources declined due to competition with round goby;
competition for/loss of nesting sites;
loss of food resources due to additional competition;
realized niche has changed because of impacts of climate change affecting temperature.
Examiners report
Syllabus sections
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14N.2.SL.TZ0.3a:
Distinguish between a pyramid of numbers and a pyramid of productivity.
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17N.2.SL.TZ0.7a:
Outline how soil can be viewed as an ecosystem.
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17N.2.SL.TZ0.4a:
Describe the role of primary producers in ecosystems.
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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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14M.1.SL.TZ0.1a.i:
State the source of energy for this ecosystem.
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16M.1.SL.TZ0.1e.i:
State its trophic level in the ecosystem.
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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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18N.1.SL.TZ0.3a:
With reference to Figure 6, draw a food chain that includes four trophic levels.
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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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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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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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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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16M.2.SL.TZ0.1c.iii:
Identify four factors that would affect the primary productivity of forest plantations in the Copperbelt Province.
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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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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.TZ0.5c:
Identify two reasons why the future size of the Atlantic puffin population is difficult to predict.
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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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19N.1.SL.TZ0.2a:
Using Figure 6(c), identify a food chain in the St Lawrence River ecosystem that has five trophic levels.
- 17N.1.SL.TZ0.5a.ii: Identify one argument against humans hunting puffins.
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14M.1.SL.TZ0.4d:
Explain how the use of non-biodegradable pesticides on farmland may affect the human food chain.
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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.
- 18N.2.SL.TZ0.4c: Using examples, discuss whether habitat conservation is more successful than a species-based...
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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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16M.2.SL.TZ0.1d.i:
With reference to Figure 7, state the most common ecosystem in Zambia.
- 18N.1.SL.TZ0.1: Identify one ecosystem in Algonquin Provincial Park.
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17M.2.SL.TZ0.1b:
State the trophic level labelled X in Figure 1.
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19N.1.SL.TZ0.1d:
Outline why estuaries are highly productive ecosystems.
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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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14N.1.SL.TZ0.2b:
Elephants eat a variety of vegetation: grasses, shrubs, leaves and small tree seedlings. Describe the impact on a grassland ecosystem of the main large herbivore being removed.
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16N.2.SL.TZ0.4a:
Outline why top carnivores are vulnerable to non-biodegradable toxins.
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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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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.
- 18M.2.SL.TZ0.3a: Identify one producer in the system illustrated in Figure 3.
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16N.1.SL.TZ0.4d:
Distinguish between a pyramid of numbers and a pyramid of productivity.
