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IB ESS HL 2 Ecology Questions

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

Syllabus
First assessment 2026
Course
ESS HL
Level
HL

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 ecosystems2.2 Energy and biomass in ecosystems2.3 Biogeochemical cycles2.4 Climate and biomes2.5 Zonation, succession and change

Question 1

[Maximum number: 5]
Figure: Example of a lake ecosystem

Figure:Example of a lake ecosystem

Figure 1 shows an example of a lake ecosystem.

Rooting flowering plants: producers
Birds: secondary and tertiary consumer eg kingfisher
Floating plants: producers eg lilies, water fern
Frog: secondary consumer

Question (a)

(a)

State the source of energy for this ecosystem.

[ 1 ]

Question (b)

(b)

Identify one way in which energy may leave this ecosystem.

[ 1 ]

Question (c)

(c)

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

[ 1 ]

Question (d)

(d)

Identify two possible effects of removing trout on this ecosystem.

[ 2 ]

Question 2

[Maximum number: 11]

Question (a)

(a)

Identify four characteristic features of the tropical rainforest biome.

[ 4 ]

Question (b)

(b)

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

[ 7 ]

Question 3

[Maximum number: 3]

Question (a)

(a)
Fact file on Hokkaido

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 ]

Question (b)

(b)
World map showing location of Japan

Figure:World map showing location of Japan

Fact file on Hokkaido

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

Elevation map of 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 ]

Question (c)

(c)
Hokkaido's national parks and airports

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 ]

Question 4

[Maximum number: 6]

Question (a)

(a)
Average net primary productivity of ecosystems

Figure:Average net primary productivity of ecosystems

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

The St Lawrence River estuary and the Gulf of St Lawrence are recognized as a Large Ocean Management Area by the Canadian government (Figure 2(b)).

• It is an important shipping route from the Atlantic Ocean to eastern Canada.
• The area is highly productive (Figure 4(a)).
• It provides habitat for wildlife, including resident and migratory birds, whales and crabs.
• It provides nursery grounds for commercial fish species (cod, halibut).
• Management of the area is challenging because the interests of different stakeholders may be in conflict or environmentally damaging.

Using Figure 4(a), identify an ecosystem that has an average net primary productivity above 30 000 kJ m⁻² a⁻¹.

[ 1 ]

Question (b)

(b)
Salinity variation in the Large Ocean Management Area

Figure:Salinity variation in the Large Ocean Management Area

Water-surface temperature variation across the LOMA

Figure:Water-surface temperature variation across the LOMA

temperature scale

Figure:temperature scale

Suggest one reason for the zonation seen in Figure 5(b).

[ 1 ]

Question (c)

(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 ]

Question (d)

(d)
Mudflats along the St Lawrence River estuary at low tide

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

Outline why estuaries are highly productive ecosystems.

[ 3 ]
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