IGCSE Biology 2026 -2028 Syllabus Checklist Topic 10 Diseases and Immunity

Describe a pathogen as a disease-causing organism.

Describe a transmissible disease as one in which the pathogen can be passed from one host to another.

State that a pathogen is transmitted: ▪ By direct contact , including through blood and other body fluids. ▪ Indirectly , including from contaminated surfaces, food, animals, and air.

Describe the body defences , limited to: skin, hairs in the nose, mucus, stomach acid, and white blood cells.

Explain the importance of the following in controlling the spread of disease: ▪ A clean water supply . ▪ Hygienic food preparation . ▪ Good personal hygiene . ▪ Waste disposal . ▪ Sewage treatment (details not required).

Describe active immunity as defence against a pathogen by antibody production in the body.

State that each pathogen has its own antigens , which have specific shapes.

Describe antibodies as proteins that bind to antigens, leading to direct destruction of pathogens or marking them for destruction by phagocytes .

State that specific antibodies have complementary shapes that fit specific antigens.

Explain that active immunity is gained after an infection by a pathogen or by vaccination .

Outline the process of vaccination : ▪ Weakened pathogens or their antigens are put into the body. ▪ The antigens stimulate an immune response by lymphocytes that produce antibodies. ▪ Memory cells are produced that give long-term immunity.

Explain the role of vaccination in controlling the spread of diseases.

Explain that passive immunity is a short-term defence against a pathogen by antibodies acquired from another individual, including across the placenta and in breast milk .

Explain the importance of breastfeeding for the development of passive immunity in infants.

State that memory cells are not produced in passive immunity.

Describe cholera as a disease caused by a bacterium transmitted in contaminated water.

Explain that the cholera bacterium produces a toxin that causes secretion of chloride ions into the small intestine, leading to osmotic movement of water into the gut, causing diarrhoea , dehydration , and loss of ions from the blood.