Bio- Unit 1 Ch 3: Pathogens

Nature and Variety of Living Organisms Unit

pathogen

any micro-organism that causes disease in another organism such as

• bacteria

• fungi

• protoctists

• ciruses

  all viruses are pathogenic because they can only exist by living inside the living cells of other organisms

Pathogenic bacteria

They do not always infect the cells of hosts, they can remain within body cavities or spaces

• M. Tuberculosis causes tuberculosis in humans

• the bacteria infect the lungs, causing a chronic cough and bloody mucus

• it is a disease often associated with poor hygiene and sanitation

• M. bovine in cows can also transmit to humans to cause TB

Pathogenic fungi

Fungal diseases are much more common in plants than animals. Cattle ringworm and athletes foot are fungal diseases that exist on the surface of the skin. Fungal diseases in plants tend to be much more serious and can threaten entire crops

Pathogenic protoctists

Plasmodium falciparum is a protoctist that causes severe forms of malaria in humans and is spread by mosquitos.

Viruses

They are not usually included in the classification of living organisms as they are not considered to be alive because they don’t carry out Mrs C Gren.

• they are small particles

• they are parasitic and can only reproduce inside living cells

• they infect every type of living organism

• they have no cellular structure but have a protein coat and contain one type of nuclei acid, either DNA, or RNA