1.3 recall the term ‘pathogen’ and know that pathogens may be fungi, bacteria, protoctists or viruses.

Any micro-organism that causes disease is pathogenic, it is known as a pathogen. Therefore, pathogens are simply micro-organisms that cause disease.

Fungi, bacteria, protoctists and viruses are all micro-organisms, and some cause disease. Therefore, some fungi, bacteria, protoctists and viruses are pathogens (or are pathogenic). 

It is importants to remember that not ALL fungi, bacteria and protoctists are pathogens, as not all of them cause disease but all viruses are, as they all cause disease.