Topic 1: Foundation

1.1 Perspectives

1.2 Systems

1.3 Sustainability

Topic 2: Ecology

2.1 Individuals, populations, communities, and ecosystems

2.2 Energy and biomass in ecosystems

2.3 Biogeochemical cycles

2.3.1—Biogeochemical cycles purpose

2.3.2—Cycle components

2.3.3—Carbon stores

2.3.4—Carbon flows

2.3.5—Carbon sequestration

2.3.6—Ecosystems as carbon stores/sinks/sources

2.3.7—Fossil fuels as carbon stores

2.3.8—Agriculture as carbon store/source/sink

2.3.9—Ocean carbon exchange

2.3.10—Ocean acidification

2.3.11—Alleviating carbon cycle impacts

2.3.12 (HL)—Lithosphere carbon stores

2.3.13 (HL)—Carbonate fossilization

2.3.14 (HL)—Fossil fuel formation

2.3.15 (HL)—Methane production

2.3.16 (HL)—Methane cycle

2.3.17 (HL)—Nitrogen cycle stores

2.3.18 (HL)—Bacterial roles in nitrogen cycle

2.3.19 (HL)—Denitrification conditions

2.3.20 (HL)—Plant nitrogen fixation

2.3.21 (HL)—Nitrogen cycle flows

2.3.22 (HL)—Human impacts on nitrogen cycle

2.3.23 (HL)—Haber process

2.3.24 (HL)—Nitrogen planetary boundary

2.3.25 (HL)—Global collaboration needed

2.4 Climate and biomes

2.5 Zonation, succession and change

Topic 3: Biodiversity and conservation

3.1 Biodiversity and evolution

3.2 Human impact on biodiversity

3.3 Conservation and regeneration

Topic 4: Water

4.1 Water systems

4.2 Water access, use and security

4.3 Aquatic food production systems

4.4 Water pollution

Topic 5: Land

5.1 Soil

5.2 Agriculture and food

Topic 6: Atmosphere and climate change

6.1 Introduction to the atmosphere

6.2 Climate change—causes and impacts

6.3 Climate change—mitigation and adaptation

6.4 Stratospheric ozone

Topic 7: Natural resources

7.1 Natural resources—uses and management

7.2 Energy sources—uses and management

7.3 Solid waste

Topic 8: Human populations and urban systems

8.1 Human populations

8.2 Urban systems and urban planning

8.3 Urban air pollution

HL.a Environmental law

HL.b Environmental economics

HL.c Environmental ethics

IB ESS HL 2.3.18 (HL)—Bacterial roles in nitrogen cycle Question Bank

• Nitrogen fixation: N₂ → ammonia

• Nitrification: ammonia → nitrates

• Denitrification: nitrates → N₂

• Decomposition: amino acids → ammonium

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