Infectious diseases

• • Pathogens are microorganisms that enter body and cause disease
  • Pathogens cause communicable diseases
  • Plants and animals can be infcted by pathogens
• Bacteria:

  • Pathogen
  • Small cells
  • Reproduce rapidly inside body
  • Produce toxins that damage cells and tissues
• Viruses:

  • Not cells
  • Reproduce rapidly inside body
  • Live and reproduce inside cells - cells will burst and release new viruses
  • Cell damage
• Protists:

  • Eukaryotes
  • Parasites - live on or inside organisms and cause damage
  • Parasite transferred to organism by vector
• Fungi:

  • Can be single celled
  • Can be made of hyphae ( thread like structures)
  • Hyphae can grow and penetrate human skin and surface of plants, causing disease
  • Hyphae can produce spores which can spread
• Pathogens can be spread by:

  • Water - e.g cholera
  • Air - e.g influenza virus that causes flu
  • Direct contact - e.g athletes foot