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Disease-causing viruses, bacteria, fungi or protists are called pathogens. Sterilising water, preparing food hygienically, washing, vaccination and barrier contraception can reduce the spread of pathogens.

Pathogens are disease-causing viruses, bacteria, fungi or protists. Some pathogens infect plants and others infect animals. Plants have physical and chemical defences against pathogens.

The immune system defends humans from pathogens. Physical and chemical barriers prevent infection. White blood cells attack pathogens. Immunisations usually involve injecting inactive pathogens.

The development of drugs is a long, complicated and expensive process. Monoclonal antibodies are identical copies of an antibody. They are used in pregnancy tests and in cancer treatment.

Non-communicable diseases are not transferred between people, eg cancer, diabetes, genetic and neurological disorders and heart disease. Risk factors increase the chances of developing these diseases.

Understanding how to approach exam questions helps to boost exam performance. Question types will include multiple choice, structured, mathematical and practical questions.