Infection & response

• Pathogen is a microorganism that can cause disease
• The four main types of pathogen

  • virus
  • bacteria
  • fungi
  • protist
• Examples of transmitting pathogens

  • direct contact
  • water
  • air
  • unhygienic food preparation
  • vector
• Measles

  • viral communicable disease
  • symptoms: fever and red skin rash
  • spread: inhalation of saliva or mucus
  • treatment: vaccination
• HIV (Human Immunodeficiency Virus)

  • viral communicable disease
  • symptom: initial flu-like symptoms, can develop into AIDS
  • spread: unprotected sexual intercourse and shared needles
  • treatment: take antiretroviral drugs to slow down the development of AIDS
• Tobacco mosaic virus

  • viral disease in plants
  • symptom: causing 'mosaic' pattern of discolouration, curled or crinkled leaves
  • spread: direct contact between plants
  • treatment: no cure so just burn infected parts to minimise its impact
• Virus use biochemistry to make lots of copies of itself inside the host cell to make the cell burst and release the virus into the bloodstream, this damage and destruction of cells cause the host feel ill
• The three types of plant defences:

  • Physical
  • Chemical
  • Meachanical