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The main way in which vaccinations prevent infection is by causing white blood cells to produce antibodies. These antibodies are produced rapidly upon re-infection and...

Definition: diffusion is the spreading out of particles from an area of high concentration to an area of low concentration

The theory:

Pathogens are microorganisms that can cause disease. Pathogenic bacteria make us ill in 2 way: 1) by damaging body cells 2) releasing toxins. Pathogenic viruses invade body cells where they use the cellul...

A reflex is an unconcious response to a potentially harmful stimulus, such as pulling a tray out of the oven without oven gloves on!

Reflexes bypass the brain an...

A population of one species is separated by a physical barrier, e.g a geographical barrier such as the movement of tectonic plates. There will then be 2 isolated groups of the same species unable to inter...