International A Level Biology / Immunity

The evolutionary race between pathogens and hosts revision notes

Edexcel International A Level Biology (YBI11), chapter 18: Immunity, specification point 6.12. Part of the full course.

Watch the video lesson · International A Level Biology past papers

An evolutionary race happens as pathogens evolve ways to evade the immune system and hosts evolve better defences in response. Evasion mechanisms in influenza, HIV and TB show how each side acts as a selection pressure on the other.

More lessons in Immunity

• Non-specific responses: inflammation, lysozyme and interferon
• Phagocytosis
• Antigens, antibodies and antigen-presenting cells
• The specific response: B cells and antibodies
• The specific response: T helper, T killer and T memory cells
• Natural, artificial, active and passive immunity
• Antibiotics: bacteriostatic and bactericidal
• Core practical 14: the effect of antibiotics on bacteria
• Antibiotic resistance and hospital-acquired infections