Biology B3

• Pathogens are microorganisms that cause infectious disease
• Communicable diseases are infectious so they can be spread between animals and plants
• Types of pathogens


  • Bacteria
  • Viruses
  • Fungi
  • Protists
• Bacterial pathogens


  May reproduce quickly in the body and produce toxins that damage tissue
• Viral pathogens


  Infect and reproduce themselves inside body cells- causing damage to body cells
• Non-specific human defence systems


  • Nose contains hair which traps mucus and microbes
  • Stomach contains stomach acid which kills microbes, - skin as a physical barrier and the -trachea and bronchi containing mucus which trap microbes and cilia move microbes up
• White blood cell defence against pathogens


  1. Phagocytosis- engulf and destroy bacteria, virus

  2. Antibody production- Antibodies stick to pathogens triggers pathogen to be destroyed.

  3. Antitoxin production-neutralise toxins
• Vaccination


  Injection of dead or weakened pathogens to stimulate antibody production against pathogen. Memory cells stay in body therefore when reinfection antibodies are produced quickly in large numbers.
• Pathogens and diseases

  • Salmonella (bacteria)
  • Gonorrhea (bacteria)
  • Measles (viral)
  • HIV (viral)
  • Tobacco mosaic virus (viral)
  • Rose black spot (fungal)
  • Malaria (protist)
• (B)Salmonella- spread by eating food cooked in unhygienic conditions.

  Symptoms-Fever, Diarrhoea, Vomiting, Abdominal cramps.

  Treatment- Vaccinating poultry, disinfecting surfaces
• (B)Gonorrhoeae- spread through sexual contact. Symptoms- Painful urination, thick yellow or green Discharge from penis/ vagina. Treatment- Antibiotics
• (V)Measles- spread via droplets when coughing/ sneezing. Symptoms- Fever, Cough, Runny nose, Rash. Treatment- Vaccine
• (V)HIV- sexual contact or through bodily fluids

  Symptoms-Flu, late stage body’s immune system becomes so badly damaged can no longer deal with infections or cancer

  treatment- antiretroviral drugs, not sharing needles
• (V)Tobacco mosaic virus- contact between plants

  symptoms- mosaic pattern of discolouration on leaves, less photosynthesis

  Treatment-remove and destroy infected plant
• (F) Rose black spot is spread by wind or water.

  Symptoms- purple black spots on leaves, turn yellow and drop

  Treatment-use fungicides
• (P)Malaria- spread by vectors. Symptom—recurring fever, can be fatal.

  Treatment- use mosquito nets, prevent breeding of mosquitoes