IB ESS HL 2 Ecology Questions

Analyse ecology data, evaluate energy and matter pathways, and connect climate, succession and human impacts across ecosystems.

Exam points

identify and explain how species, populations and communities are defined and linked, using habitat, niche, interactions, limiting factors, carrying capacity and ecosystem structure
design and interpret ecological sampling and fieldwork methods, including quadrats, transects, capture-mark-release-recapture, climate or biomass figures and repeated measurements, while judging reliability and units
trace energy and matter through food webs and biogeochemical pathways, identifying trophic levels, stores, flows, productivity, respiration, decomposition, nutrient cycling and pollutant transfer
calculate or interpret ecological quantities such as population abundance, productivity, biomass, storage change, concentration and diversity, then explain what the data show about ecosystem structure or function
explain how abiotic conditions, species interactions, feedbacks, climate circulation, ocean heat, biome conditions and succession alter distribution, productivity, diversity, stability and resilience
evaluate how human population growth, resource use, land disturbance, pollution, climate change and management alter populations, energy and matter pathways, biomes and successional recovery using evidence
complete and analyse nitrogen-cycle transformations and human nitrogen stores and flows, and compare them with carbon-cycle changes
calculate and evaluate trophic efficiency, sustainable yields and entropy or respiratory losses rather than assuming a fixed transfer percentage
analyse ENSO and tropical-cyclone data, including frequency, intensity, vulnerability, sea-surface-temperature relationships and exceptions in climate evidence
explain how bedrock, soils, geomorphology, disturbances, productivity, r/K strategies and human activity shape succession, climax-community uncertainty and plagioclimax

Covered syllabus points

2.1 Individuals, populations, communities, and ecosystems 2.2 Energy and biomass in ecosystems 2.3 Biogeochemical cycles 2.4 Climate and biomes 2.5 Zonation, succession and change

[Maximum number: 5]

Figure:Example of a lake ecosystem

Figure: Example of a lake ecosystem below shows an example of a lake ecosystem.

Rooting flowering plants: producers

(a)

State the source of energy for this ecosystem.
(a) (i) State the source of energy for this ecosystem.

[ 1 ]

(b)

Identify one way in which energy may leave this ecosystem.

Birds: secondary and tertiary consumer eg kingfisher

Floating plants: producers eg lilies, water fern

Frog: secondary consumer

[ 1 ]

(c)

Draw a food chain from the ecosystem in Figure: Example of a lake ecosystem consisting of four trophic levels.

[ 1 ]

(d)

Identify two possible effects of removing trout on this ecosystem.

[ 2 ]

[Maximum number: 11]

(a)

Identify four characteristic features of the tropical rainforest biome.

[ 4 ]

(b)

Explain how a community of decomposers contributes to the stability of the whole ecosystem.

[ 7 ]

a. Decomposers will feed on dead organic matter/detritus (like dead leaves, wood, carcasses, feces)...;
b. ... reducing their accumulation / cleaning up Earth;
c. They will break down organic matter into inorganic matter…;
d. ...enhancing soil fertility / increasing nutrient availability;
e. The inorganic minerals (nitrates, phosphates, metals) will then feed plant communities / will be absorbed by plant roots...;
f. ...supporting high vegetation/plant abundance;
g. ...and may support high habitat/niche diversity;
h. Decomposers are responsible for nutrient cycling / e.g. nitrogen cycling (nitrogen fixation/ammonification/nitrification/denitrification/phosphorus cycling/carbon cycle;
i. ...high flow of matter may support complex food webs;
j. Decomposers are the basis of a detritus-based food web / important part of ecosystem flow of energy / may be eaten/pass biomass on to carnivore community...;
k. ...supporting/stabilizing carnivore abundance;
I. As decomposer numbers decrease due to predation, so do carnivores;
m. ... thereby contribute to regulation of the carnivore community / which is an example of negative feedback (leading to stability);
n. Decomposer will release organic matter through their own death/defecation...;
o. ... which would provide food for other decomposers;
p. Decomposers participate in humus formation...;
q. ...increasing water holding capacity of soil (and soil fertility = MPd);
r. Decomposers may compete with one another regulating their populations (another example of negative feedback = MPm);
s. Decomposers, like earthworms, loosen soil / disperse nutrients / create space for air and water circulation...;
t. ...helping root growth / improving soil structure;
u. Fragmentation: larger invertebrates initially fragment larger chunks of organic matter (then bacteria and fungi complete decomposition into nutrients = MPc);
v. After a disturbance, decomposers will increase their metabolic/respiration rate/feeding on detritus...;
w. ...contributing to a faster return to original state (resilience entailing stability);

[Maximum number: 3]

(a)

Figures:Fact file on Hokkaido and Climate graph for Sapporo, Hokkaido

Using the climate graph for Sapporo, state the annual temperature range for Sapporo.

[ 1 ]

$27^{\circ} \mathrm{C} /$ from -4 to $(+) 23^{\circ} \mathrm{C}$ ;

Marking guidance:

Accept use of dash to indicate 'to'. Units are not required for credit.

(b)

Figure:World map showing location of Japan

Figures:Fact file on Hokkaido and Climate graph for Sapporo, Hokkaido

Figure:Elevation map of Hokkaido

Using Figures: World map showing location of Japan, Climate graph for Sapporo, Hokkaido and Elevation map of Hokkaido, identify one terrestrial biome found on Hokkaido.

[ 1 ]

(c)

Figure:Hokkaido's national parks and airports

Using Figures: Elevation map of Hokkaido and Hokkaido's national parks and airports, outline one relationship between the location of Hokkaido's national parks and their elevation.

[ 1 ]

a. national parks are mainly found in areas above $500 \mathrm{~m} / 1000 \mathrm{~m}$ in elevation / found mainly in the areas of highest/high elevations;
b. (there is no relationship, as) the national parks are found at all elevations (i.e. Kushiro Marshlands);

Note: Must give a reason if they say there is no relationship.

[Maximum number: 6]

(a)

Figure:Average net primary productivity of ecosystems

Figure:Mudflats along the St Lawrence River estuary at low tide

Figure:Fact file on the St Lawrence River estuary and Gulf of St Lawrence

- Figure: Fact file on the St Lawrence River estuary and Gulf of St Lawrence
- The St Lawrence River estuary and Gulf of St Lawrence are recognized as a Large Ocean Management Area by the Canadian government.
- The area is an important shipping route, highly productive, provides habitat for birds, whales and crabs, and provides nursery grounds for commercial fish species.
- Management is challenging because stakeholder interests may conflict or be environmentally damaging.

Using Figure: Average net primary productivity of ecosystems, identify an ecosystem that has an average net primary productivity above $30000 \mathrm{~kJ} \mathrm{~m}^{-2} \mathrm{a}^{-1}$ .

[ 1 ]

(b)

Figure:Salinity variation in the Large Ocean Management Area

Figure:Water-surface temperature variation across the LOMA

Figure:temperature scale

Suggest one reason for the zonation seen in Figure: Water-surface temperature variation across the LOMA.

[ 1 ]

(c)

Estuaries are one of the most productive ecosystems in the world, but only account for 3 % of global productivity.

State one reason why this occurs.

[ 1 ]

(d)

Outline why estuaries are highly productive ecosystems.

[ 3 ]

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