Biology (T3U1)

• A pathogen is a disease-causing organism.
• A host is the organism that is infected by a pathogen.
• Transmissible Disease:

  A disease caused by pathogens that can be passed from one host to another

  • Once inside the body, some pathogens damage our cells by living in them and using their resources
  • Others cause harm to cells and body systems by producing waste products, called toxins, which spread around the body and cause symptoms like high fever, rashes and make you ill.
• Direct contact: some pathogens pass from one person to another when there is direct contact between an infected person and an uninfected one

  • Into blood, (ex: from a scratch)
  • Body fluids during intercourse
• Indirect contact: some pathogens are transmitted indirectly. This can happen through:

  • Breathing in droplets with pathogens
  • Touching a contaminated surface, substance or food
  • Eating food or drinking containing pathogens
  • Contact with animals carrying pathogens
• Natural Defences:

  • Skin: prevents pathogens from entering the body. If the skin is broken, a blood clot forms to seal the wound and stop pathogens getting in.
  • Stomach: has hydrochloric acid, which kills a lot of bacteria in our food.
  • Hair in nose: filters out particles from air which could have pathogens
  • Smelling or tasting food that's bad: makes us not want to eat it, or it might get us sick.
  • Mucus in airways: traps bacteria and are swept up to the back of the throat and swallowed instead of getting into the lungs.
• Controlling the spread of diseases: Clean water supply

  • Availability of water that is safe for drinking, cooking food and washing.
  • Water from dirty containers from a river or lake can contain many different pathogens
  • People who don’t have access to clean water or have to rely on polluted water sources are prone to water-borne diseases.
• Controlling the spread of diseases: Hygienic food preparation

  • Makes it less likely that someone eating the food prepared will get ill. 
  • Most food poisoning is caused by bacteria, so knowing the conditions bacteria need for growth and reproduction can help us control them.

  
  

  Simple rules to prevent food poisoning:

  • Keep your own bacteria and viruses away from food.
  • Keep animals away from food.
  • Do not keep foods at room temperature for long periods.
  • Keep raw meat away from other foods.
• Controlling the spread of diseases: Good personal hygiene

  • keeping your body clean to reduce the risk of getting or passing transmissible diseases
  • Not washing hands or bodies regularly can cause building up of oil, sweat and dirt, providing a breeding ground for bacteria.
  • Brushing teeth regularly can keep harmful bacteria in the mouth controlled.
• Controlling the spread of diseases: Waste disposal

  • Food waste, human waste and other waste materials are attractive food sources for many insects. They may act as vectors for transmissible diseases.

  To prevent transmission of disease:

  • Place food waste in a covered container.
  • Dispose the waste away from human habitation
• Controlling the spread of diseases: Sewage treatment

  • Waste liquid from houses, industries and other parts of villages, towns and cities. It is mostly water, but can also contain many other substances (urine, faeces, chemical among others)
  • Human waste should be collected in sewage systems and kept separate from drinking water supplies until treated. 
  • This treatment kills the pathogens so that the water can be released into the environment safely.
• Process of vaccination:

  1. Weakened pathogens or their antigens are introduced to the body.
  2. They get recognised by lymphocytes that can make antibodies with complementary shape to their antigens
  3. Lymphocytes multiply and produce antibodies
  4. They make memory cells as antibodies target the antigen to attach themselves to it
  5. The memory cells lasting for years stay in the blood. If an antigen is encountered again, antibodies produce much faster to give us long-term immunity.