The organisms which cause diseases in plants and animals are called:

The organisms which cause diseases in plants and animals are called pathogens . Various types of pathogens are:

1.Viruses: These are segments of either DNA or RNA and are not cells. They cause viral infection. Example: Retro virus, Human Immuno Deficiency Virus etc.

2.Bacteria: These are uni-cellular microorganisms which cause bacterial infections. For example: Streptococcus pneumoniae

3.Fungi: These are eukaryotic organisms like molds and yeast. They cause fungal infections. For example Tricophyton, Asperigillus

4.Protozoa: These are unicellular organisms like algae, amoeba & Euglena etc. These are from the family of protists.

5.Worms: Also known as Helminths. They are of many types like hookworm, thread worm, pin worm, flatworm & Roundworm etc.