12.1/12.2 Animal & plant pathogens/diseases

• Pathogens include:

  • bacteria
  • viruses
  • fungi
  • protists
• Bacteria

  • prokaryotes (no membrane)
  • classifies by shape and cell wall
  • e.g rod shaped (bacillus)

  bacterial by cell wall

  • cell wall made of peptidoglycan
  • gram positive and gram negative
  • gram positive - thin layer of peptodoglycan and outer layer of lipid membrane
  • gram negative - thin layer of peptodoglycan
• Viruses

  • non-living infectious agents
  • short section of DNA or RNA surrounded by protein
  • infects cells by Inserting its own DNA into the DNA of a cell
  • the infected cell will then begin to produce more viruses
  • all natural viruses are pathogens
  • affect all organisms (bacteriophage)
• Retroviruses

  • have RNA as genetic material
  • RNA reverse transcribed into DNA which is then inserted into the host DNA
  • e.g HIV
• Protista

  • eukaryotic cells
  • can exist as single celled organisms or cells grouped as colognes
  • do not affect genetic apparatus
  • disease causing protista are pathogens of other organisms
  • often requires a vector to transfer disease
  • may enter body directly e.g pollutes water
• Fungi

  • affect plants hugely
  • animal e.g athletes foot and thrush
  • eukaryotes
  • cannot carry out photosynthesis
  • produce millions of spores that rapidly affect other organisms
• Diseases cause by a virus

  • HIV
  • Influenza
  • Tobacco Mosaic Virus
• Diseases cause by a bacteria

  • Tuberculosis
  • Meningitus
  • Ringrot
• Diseases cause by a Fungi

  • Ring worm
  • Athletes foot
  • potato blight
  • black sigatoka
• Diseases cause by a protoctists

  • Malaria
• Tuberculosis - bacteria

  affects humans, cows, pigs and badgers

  affects respiratory system

  air borne droplets and contaminates foods

  treatment: antibiotics

  white blood cells called macrophages engulf bacteria by phagocytosis

  symptoms: coughing, fever and fatigue
• Meningitis - bacterial

  • young children and teenagers
  • using blood poising and rapid death.
  • damages membrane of the brain
  • blotchy red/purple rash
  • air borne droplets
• HIV/AIDS - virus

  • destroys immune system so open to other infections
  • passed from one person to another in bodily fluids
  • anti-retroviral drugs slow process
• Influenza (flu) - virus

  • infection of ciliate cells in gas exchange system, kills them leaving airways open to secondary Infection
  • 3 main strains - A, B & C
  • gives you some immunity
  • vulnerable groups given vaccine annually
• Malaria - protocists

  • spread by bites of mosquitos
  • invades rbc, liver and brain
  • no vaccine
  • vector destroyed by insecticides and remove standing water where they breed
• Ring worm - fungi

  • affects mammals
  • different fungi affect different species
  • causes grey/white crusty infectious circular areas of skin
  • not damaging but could be itchy
  • anti-fungal creams are an effective cue
• Athletes foot - fungi

  • form of human ring worm that grows on and digests warm, moist skin
  • causes cracking and scaling, which is itchy and may become sore
  • anti-fungal creams are an effective cue
• Ring rot - bacteria

  • affects potatoes, tomatoes and aubergines
  • damages leaves, tubers and fruits
• Tobacco Mosaic Virus - virus

  • damages leaves, flowers and fruit
  • stunts growth and reduces yields
  • no cure
  • resistance crop strains
• Potato Blight - fungi

  • destroys leaves, tubers and fruit
  • no cure but resistant strains
  • careful management and chemical treatments can reduce infection risk
• Black Sigatoka - fungi

  • banana disease
  • attacks and destroys bananas
  • can cause 50% reduction in yield
  • no cure
• pathogens can cause disease in two ways:

  damaging cells - e.g malarial parasites cause disease sysptoms by bursting red blood cells

  producing toxins - exotoxins and endotoxins

  exotoxins are secreted by a living pathogen

  endotoxins are released when the pathogen is damaged