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Diseases are abnormal conditions that affect an organism’s body, organs, tissues or cells. Some are caused by pathogens, and organisms have defences to them.

There is a race between pathogens, which need to grow and reproduce in other organisms, and the organisms they infect. Humans use various ways to keep themselves and their crops free of disease.

There are many kinds of pathogens that cause infections. Scientists use a variety of tests to learn more about the pathogen causing an individual's disease in order to identify it.

Our genomes interact with our environment to create our phenotypes. While some aspects of our environment are beyond our control, scientists are realising that lifestyle interacts with the genome too.

Humans have used medicines for centuries. Most have come from plants and fungi, but increasingly they are being synthesised with chemical reactions.

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