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A1.1 Water

A1.2 Nucleic acids

A2.1 Origins of cells (HL)

A2.2 Cell structure

A2.3 Viruses (HL)

A3.1 Diversity of organisms

A3.2 Classification and cladistics (HL)

A4.1 Evolution and speciation

A4.2 Conservation of biodiversity

B1.1 Carbohydrates and lipids

B1.2 Proteins

B2.1 Membranes and membrane transport

B2.2 Organelles and compartmentalization

B2.3 Cell specialization

B3.1 Gas exchange

B3.2 Transport

B3.3 Muscle and motility (HL)

B4.1 Adaptation to environment

B4.2 Ecological niches

C1.1 Enzymes and metabolism

C1.2 Cell respiration

C1.3 Photosynthesis

C2.1 Chemical signalling (HL)

C2.2 Neural signalling

C3.1 Integration of body systems

C3.2 Defense against disease

C4.1 Populations and communities

C4.2 Transfer of energy and matter

D1.1 DNA replication

D1.2 Protein synthesis

D1.3 Mutations and gene editing

D2.1 Cell and nuclear division

D2.2 Gene expression (HL)

D2.3 Water potential

D3.1 Reproduction

D3.2 Inheritance

D3.3 Homeostasis

D4.1 Natural selection

D4.2 Sustainability and change

D4.3 Climate change

IB Biology Topic C3.2: Defense Against Disease Lessons

Written by IB Experts

This lesson delivers structured, step-by-step lessons that guide students through every part of the IB Biology syllabus for C3.2 Defense against disease. These lessons simplify complex ideas like molecular biology, evolutionary mechanisms, and homeostasis, while worked examples show how to approach IB-style questions.

Designed for both HL and SL learners, RevisionDojo lessons ensure students not only understand the theory but also know how to apply it in IB Paper exam situations.

With clear explanations, active learning checks, and a syllabus-first design, RevisionDojo makes revision less overwhelming and more effective.

C3.2.1 Pathogens as the cause of infectious diseases

C3.2.2 Skin and mucous membranes as a primary defence

C3.2.3 Sealing of cuts in skin by blood clotting

C3.2.4 Differences between the innate immune system and the adaptive immune system

C3.2.5 Infection control by phagocytes

C3.2.6 Lymphocytes as cells in the adaptive immune system that cooperate to produce antibodies

C3.2.7 Antigens as recognition molecules that trigger antibody production

C3.2.8 Activation of B-lymphocytes by helper T-lymphocytes

C3.2.9 Multiplication of activated B-lymphocytes

C3.2.10 Immunity as a consequence of retaining memory cells

C3.2.11 Transmission of HIV in body fluids

C3.2.12 Infection of lymphocytes by HIV with AIDS as a consequence

C3.2.13 Antibiotics

C3.2.14 Evolution of resistance to several antibiotics

C3.2.15 Zoonoses

C3.2.16 Vaccines and immunization

C3.2.17 Herd immunity and the prevention of epidemics

C3.2.18 Evaluation of data related to the COVID-19 pandemic

IB Biology Topic C3.2: Defense Against Disease Lessons

A - Unity and Diversity

B - Form and Function

C - Interaction and Interdependence

D - Continuity and Change

A - Unity and Diversity

B - Form and Function

C - Interaction and Interdependence

D - Continuity and Change

IB Biology Topic C3.2: Defense Against Disease Lessons

Lessons for C3.2 Defense against disease - IB

IB Biology Topic C3.2: Defense Against Disease Lessons