CourseCourse QuestionQuestion

IB Environmental Systems and Societies

Topic 1: Foundation

Topic 2: Ecology

Topic 3: Biodiversity and conservation

4.1 Water systems

4.2 Water access, use and security

4.3 Aquatic food production systems

4.4 Water pollution

4.4.1—Water pollution sources

4.4.2—Plastic debris accumulation

4.4.3—Water quality measurement

4.4.4—Biochemical oxygen demand (BOD)

4.4.5—Eutrophication

4.4.6—Eutrophication sequence

4.4.7—Eutrophication and ecosystem services

4.4.8—Eutrophication management levels

4.4.9 (HL)—Water pollutants

4.4.10 (HL)—Harmful algal blooms

4.4.11 (HL)—Anoxic and hypoxic waters

4.4.12 (HL)—Sewage treatment stages

4.4.13 (HL)—Indicator species

4.4.14 (HL)—Biotic index

4.4.15 (HL)—Water Quality Index (WQI)

4.4.16 (HL)—Water quality guidelines

4.4.17 (HL)—Citizen action

Topic 6: Atmosphere and climate change

Topic 7: Natural resources

Topic 8: Human populations and urban systems

IB/ESS/HL//Concept/Topic 4: Water/4.4 Water pollution/4.4.6—Eutrophication sequence

Topic 4: Water

Syllabus: First assessment 2026
Section: —
Level: HL

Exam analysis

Most tested topics

Water systems
Water access, use and security
Aquatic food production systems
Water pollution