A-level Biology: Diseases and Pathogens Lesson-by-Lesson Breakdown

This is a suggested lesson-by-lesson scheme of work for the A-level Biology diseases and pathogens topic, based on verified content from AQA, WJEC, and Pearson Edexcel Biology A specifications.

It is designed as a teachable sequence rather than an official board-issued order of lessons.

Lesson 1: Introduction to Pathogens and Infectious Disease

Lesson focus

Introduce the basic language and concepts needed for the topic.

Learning objectives

Define pathogen, infectious disease, antigen, antibody, vaccine, antibiotic, vector, and resistance.
Distinguish between communicable and non-communicable disease.
Recognise that disease-causing organisms include bacteria, viruses, and protoctists.

Core content

Meaning of key disease-related terms.
Overview of pathogens as disease-causing agents.
Examples of named diseases that appear across specifications.

Suggested activities

Keyword matching activity.
Starter quiz on disease vocabulary.
Sorting task: pathogen type vs disease example.

Sources: WJEC specification, AQA specification

Lesson 2: How Communicable Diseases Spread

Lesson focus

Understand how pathogens move between hosts and establish infection.

Learning objectives

Describe common routes of transmission.
Explain the role of vectors and sources of infection.
Relate transmission to disease control and prevention.

Core content

Spread of communicable pathogens between hosts.
Source of infection and mode of transmission.
How transmission affects public health response.

Suggested activities

Transmission pathway diagrams.
Case-study comparison of two named diseases.
Class discussion: why some diseases spread more rapidly than others.

Sources: WJEC specification, Pearson Edexcel Biology A specification

Lesson 3: Non-specific Defences of the Body

Lesson focus

Study the body’s first-line and general defence mechanisms.

Learning objectives

Describe physical and chemical barriers to infection.
Explain the roles of skin, mucus, cilia, tears, and other protective mechanisms.
Understand inflammation and clotting as part of defence.

Core content

Natural barriers in the body.
Protection provided by skin flora and gut flora.
Inflammation, mucus, ciliated epithelium, and clotting.

Suggested activities

Annotated diagram of the body’s non-specific defences.
Exam-style short-answer questions.
Compare first-line barriers with internal immune responses.

Sources: WJEC specification, Pearson Edexcel Biology A specification

Lesson 4: Phagocytosis and Destruction of Pathogens

Lesson focus

Examine phagocytosis as a major non-specific immune response.

Learning objectives

Describe the process of phagocytosis.
Explain how ingested pathogens are destroyed by lysozymes.
Link phagocytosis to the wider immune response.

Core content

Recognition and engulfment of pathogens by phagocytes.
Digestion of pathogens inside phagocytic cells.
Phagocytosis as part of the body’s defence against infection.

Suggested activities

Sequence-card activity on the stages of phagocytosis.
Labelled diagram practice.
Low-stakes retrieval quiz.

Sources: AQA specification, WJEC specification

Lesson 5: Specific Immune Response

Lesson focus

Move from general defence to targeted immune responses.

Learning objectives

Explain how foreign antigens trigger a specific response.
Describe the roles of B lymphocytes and T lymphocytes.
Distinguish between humoral and cell-mediated immunity.

Core content

Antigen recognition.
Antibody production and secretion.
Cell-mediated immunity and the role of T cells.
Formation of immunological memory.

Suggested activities

Flowchart of the specific immune response.
Compare B-cell and T-cell roles in a summary table.
Exam questions on humoral vs cell-mediated immunity.

Sources: WJEC specification, Pearson Edexcel Biology A specification, AQA specification

Lesson 6: Vaccination, Herd Immunity, and Types of Immunity

Lesson focus

Understand how immunity can be acquired and how vaccination works at individual and population level.

Learning objectives

Explain how vaccines protect against disease.
Define herd immunity.
Compare active and passive immunity.
Distinguish between natural and artificial immunity.

Core content

Use of vaccines to protect individuals and populations.
Concept of herd immunity.
Active vs passive immunity.
Natural vs artificial acquisition of immunity.

Suggested activities

Create a comparison table of the four types of immunity.
Interpret vaccination scenarios.
Short written explanation: why herd immunity matters.

Sources: AQA specification, WJEC specification, Pearson Edexcel Biology A specification

Lesson 7: Antibiotics and Antibiotic Resistance

Lesson focus

Explore bacterial treatment and the problem of resistance.

Learning objectives

Explain how antibiotics control bacterial infections.
State why antibiotics are ineffective against viruses.
Describe how overuse of antibiotics contributes to resistance.
Recognise the difference between bacteriostatic and bactericidal action where required.

Core content

Antibiotics as treatments for bacterial disease.
Limits of antibiotics in viral infection.
Antibiotic resistance and its spread.
Examples such as penicillin and tetracycline in some specifications.

Suggested activities

Data interpretation on resistance trends.
Class debate on antibiotic overuse.
Exam paragraph practice: explain why resistance develops.

Sources: AQA specification, WJEC specification, Pearson Edexcel Biology A specification

Lesson 8: Antigenic Variation and Difficulties in Disease Prevention

Lesson focus

Study why some pathogens are harder to control than others.

Learning objectives

Define antigenic variation.
Explain why changing antigens make disease prevention harder.
Link antigenic variation to vaccination challenges.

Core content

Variation in pathogen antigens.
Impact on immune recognition and vaccine effectiveness.
Role in continued disease transmission.

Suggested activities

Teacher-led explanation with diagram support.
Apply the idea to a named viral example.
Exam-question deconstruction.

Source: AQA specification

Lesson 9: Named Diseases Case Studies

Lesson focus

Apply the topic to specific diseases named in the specifications.

Learning objectives

Identify the type of pathogen involved in each named disease.
Describe source of infection, tissues affected, mode of transmission, prevention, and treatment.
Compare diseases caused by different pathogen groups.

Core content

HIV/AIDS.
Tuberculosis.
Cholera.
Influenza.
Smallpox.
Malaria.

Suggested activities

Complete a disease comparison grid.
Student presentations on one named disease each.
Practice exam questions based on case studies.

Sources: AQA specification, Pearson Edexcel Biology A specification, WJEC specification

Lesson 10: Review, Synoptic Links, and Exam Practice

Lesson focus

Bring the whole topic together and prepare for assessment.

Learning objectives

Link pathogens, transmission, immunity, vaccination, and treatment into one coherent topic.
Apply knowledge to unfamiliar scenarios.
Practise extended-response and data-based exam questions.

Core content

Review of the entire diseases and pathogens topic.
Connections between immune responses and disease control.
Common exam pitfalls and key terminology.

Suggested activities

Retrieval practice quiz.
Timed exam questions.
Whole-topic concept map.

Draws together content from: AQA specification, WJEC specification, Pearson Edexcel Biology A specification

Optional adjustment: if you want a shorter teaching sequence, this can be compressed into 6-8 lessons by combining Lessons 3 and 4, combining Lessons 5 and 6, and reducing the case-study section.