Biology Module 4 - Disease

• What is a pathogen

  A microorganism that causes disease
• communicable disease


  Can be spread from organism. to organism by a pathogen
• non-communicable disease


  a disease that is not transmitted by another person, a vector, or the environment
• Example of communicable disease in humans

  Flu, TB, influenza, malaria, athletes foot
• Example of communicable disease in plants.

  Ringrot, mosaic ( tobacco), late blight , black sigatoka (bannana).
• 4 types of pathogen

  bacteria, viruses, fungi, and protists
• What is a parasite?

  an organism that lives in or on another organism (its host) and benefits by deriving nutrients at the host's expense.
• Is bacteria prokaryotic or eukaryotic?

  Prokaryotic (no nucleus or membrane bound organelles)
• How is bacteria classified?

  Cell walls structure[ By their gram (+) (-) ] and their shape
• Is a virus living or non-living?.


  Viruses are non-living particles.
• How does a virus reproduce?

  Invades living cells ( takes over biochemistry of cells to make more )
• What does a virus do?

  Causes disease in every other type of organism
• Is a protist a prokaryote or a eukaryote?

  Eukaryote ( contains chloroplasts )
• Are protists unicellular or multicellular?


  Most are unicellular but some are multicellular
• How does a protist enter a host

  Often require a vector ( eg. Mosquitoes = malaria ) or waterborn
• Is fungi prokaryotic or eukaryotic?

  Eukaryotic ( have cell wall+ vacuole )
• Are fungi unicellular or multicellular?

  both often multicalluar ( mushroom) but can be unicelluar ( yeast )
• Is fungi more damaging to plants or animals?


  Much more damaging to plants than animals
• How do fungi reproduce?

  reproduce by spores ( can spread quickly over huge amounts of distances
• Ways of direct spread of disease

  Physical contact, inoculation, ingestion
• How does disease spread through physical contact?

  Kissing, bodily fluids, skin to skin
• How does disease spread via inoculation?

  Sex ( breaks in the skin), animal biles, sharing needles
• How does disease spread through ingestion?

  Contaminated food / drink,microorganisms from faeces on hand
• Ways of indirect spread of disease

  Fomite, droplet infection, vectors
• How does disease spread via fomite?

  Inanimate objects - furniture, clothing, utensils
• How does disease spread via droplet infections?

  Pathogens contained within minute droplets of saliva + mucus
• How does disease spread via vectors

  Mosquitoes = malaria, rat fleas =bubonic plague, dogs / raccoons = rabies
• Direct factors that affect increasing chance of communicable diseases being spread

  Population density, human behavior, public health measures, international travel, microbial adaptation change
• Indirect factors that affect increasing chance of communicable diseases being spread

  Population density, vector population, economic development, public health measures, climate / weather
• Non specific Defences against pathogens

  Skin, mucous membrane, Expulsive reflexes, Chemical secretion
• How does skin provide as a defence against pathogens

  Provides a protective layer

  Covered in oily sebum (acidic layer)

  Skin flora
• How does the mucous membrane defend against pathogens?

  Secrete mucous which trap microorganisms (which allow phagocytes to destroy pathogen )

  
  

  Contains lysozymes which destroys bacteria by digesting cell wall
• How do expulsive reflexes defend against pathogens?

  Expels the pathogen via sneezing coughing vomiting and diarrhoea
• How do chemical reactions defend against pathogens?

  Lysozyme in tears and HCL (hydrochloric acid) kill pathogens
• Plants physical barriers against pathogens

  Waxy cuticle, bark on trees, cellulose cell wall
• What is abcission?


  When plants seal of an infected part of a plant and sacrifice it
• Plants chemical defences


  Tamins - create bitter taste

  Insect repellent - pine resin or lemon grass

  Insecticides - caffeine acting as neurotoxin

  Antibacterial compounds - disrupt cell wall/membrane of bacteria

  Anti fungal compounds

  General Toxins
• Non specific responses


  Inflammatory response, phagocytosis, Blood clotting
• What is the purpose of blood clotting

  - Preventing excess blood loss

  - Preventing the entry of pathogens

  through wounds
• What are platelets?


  Small fragments of cells