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C4.1 Populations and communities

Populations and communities describe abundance, sampling, growth limits, species interactions and trophic controls that shape ecological patterns across habitats and ecosystems.

Syllabus
First assessment 2025
Topic
C4.1
Level
SL

What you’ll learn

18 learning objectives

Choose one objective for a focused lesson, or study the complete topic.

Exam analysis

An aggregate view of how the complete C4.1 Populations and communities appears across past papers.

Chance of appearing47%of analysed past papers
Latest appearanceNovember 2025
Most common paperPaper3

Most tested objectives

  1. C4.1.13—Endemic vs. invasive species25 questions
  2. C4.1.10—Community13 questions
  3. C4.1.11—Interspecific relationships11 questions

Common question formats

  • Definition or recall
  • Structured response
  • Data analysis
  • Experimental design
  • Evaluation
  • Diagram interpretation
  • Calculation
  • Process explanation
  • Comparison

Exam question appearances

November 2025Paper1A ["SL"] · TZ327[ 1 ]C4.1.12—Mutualism as interspecific relationship
November 2025Paper1A ["SL"] · TZ126[ 1 ]C4.1.11—Interspecific relationships
November 2025Paper1B ["SL"] · TZ12(c)[ 3 ]C4.1.2—Population size estimation
November 2025Paper1B ["SL"] · TZ32(a)[ 1 ]C4.1.2—Population size estimation
May 2025Paper1B ["SL"] · TZ33(a)[ 3 ]C4.1.4—Capture-mark-release-recapture

Coverage 2010–2025 · Updated 16 Jul 2026

Study checklistC4.1 Populations and communities