AQA AS level biology unit 1- Disease

Infectious Disease

• Infectious diseases are caused by pathogens
• A pathogen is an organism that causes disease
• Pathogens include: Bacteria
•                              Certain Fungi
•                              All Viruses

Pathogens need to enter the body in order to cause Disease:

• They penertrate the organisms interface with the environment e.g. nose, cut , eyes
• An organism has three main interfaces with its environment the gas exchange system, the skin and the digestive system.

Gas Exchange System

Pathogens can be breathed in in the air, most of them will become trapped by the epithelium…