IB ESS HL · Unit 2 of 8

IB ESS HL Unit 2: Ecology

Unit 2 of IB Environmental Systems and Societies covers Ecology. This unit contains 6 topics and 31 sub-topics. Below you'll find free study notes, flashcards, and exam preparation resources for every topic in this unit.

Higher Level students should treat this unit page as a route map: revise the shared core, then use the HL notes and topic links to reach the extra depth and evaluation expected at HL.

6 topics31 sub-topics

ESS Flashcards Exam technique guide

What Unit 2 covers

HL Unit 2 extends ecological principles with more detailed quantitative analysis of energy flows, productivity calculations, complex nutrient cycling models, and deeper evaluation of human impacts. Students must interpret larger datasets and demonstrate more sophisticated ecological reasoning.

Topics in Unit 2

2.1

Individuals, populations, communities and ecosystems

8 sub-topics

2.2

Energy and biomass in ecosystems

6 sub-topics

2.3

Biogeochemical cycles

6 sub-topics

2.4

Climate and biomes

1 sub-topics

2.5

Zonation, succession and change in ecosystems

2 sub-topics

2.6

Human impact on ecosystems (to redistribute to Topics 3 & 6)

8 sub-topics

Study tip: Work through the topics in order — each builds on concepts from the one before. Start with notes, then reinforce with flashcards and practice questions.

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Unit 1 Unit 3