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   Distinguish between pests and parasites.
   Discuss the types of micro organisms that
    can cause disease
   Describe how our body responds to infection
   Explain how a vaccination works
   Explain how AIDS is caused and its dangers
           They are a nuisance.
            They affect us in a
            negative way.
           Common household
            pests include:
            - flies
            - rats
            - mosquitoes
            - cockroaches
   These are micro organisms that harm other
    living organisms.
   They live on or in that particular organism,
    also known as the host.

* Note: Unlike parasites, pests do not cause
  diseases; they can transmit organisms
  that do.
What types of micro
organisms cause disease?

Bacteria & Viruses
 Bacteria are unicellular organisms that
  multiply and release toxins.
 Not all are harmful- some exist naturally in
  the body.
*bacterial diseases- typhoid, cholera, TB

 Viruses are smaller than bacteria.
 They invade living cells and cause more
*viral diseases-AIDS, measles, influenza (flu)
How does the body respond to
being infected?
   We detect these foreign bodies and destroy
   These harmful micro organisms have a
    chemical marker on their surface called an
   An antigen is a substance that prompts the
    generation of antibodies and can cause an
    immune response.
   Immunity is the
    protection against
    diseases by antibodies.

   They are two types:
    - natural
Natural immunity
   Natural passive immunity involves antibodies
    passing directly from mother to the foetus,
    through the placenta and later in the breast

   Natural active immunity involves the white
    blood cells ( lymphocytes) producing
    antibodies that destroy the antigens.
Artificial immunity
   Artificial passive immunity occurs when the
    body is injects with antibodies produced by
    other organisms.

   Artificial active immunity occurs when the
    body is injected with weak strains of the
    pathogen. we make antibodies and memory
    cells against it so we can become immune to
    the actual disease. It is also known as a
Which type of immunity is seen here?
Acquired immune deficiency
   This is a disease caused by the Human
    Immunodeficiency Virus (HIV).
   This virus causes severe weakening of the
    body’s immune system.
   This results in the body not being able to
    produce antibodies and therefore becoming
    vulnerable to many diseases.
   Describe the conditions which promote the
    growth of micro organisms
   Discuss the principles of food preservation
   Discuss conditions that encourage the
    breeding of household pests
   Discuss the different types of waste
   Discuss the need for personal & community
Food spoilage
   When micro organisms
    feed on our food it spoils.

  This action is caused by:
-the micro organisms first
   breaking down food using
   digestive enzymes.
-then absorbing the soluble
Growth of micro organisms
The factors that influence this growth are:
 Temperature

 Moisture

 Oxygen

* Most micro organisms develop rapidly in
  moist conditions, because they need water to
  germinate and grow.
How can we preserve food?
   Canning
   Pickling
   Freezing
   Salting
   Drying
   Adding sugar
   Adding preservatives
   Refrigeration
Household pests
   Can you recall some of these pests?
   Household pests are a nuisance because of
    the economic damage they cause.
   They thrive best in dirty places filled with
    garbage; these conditions provide good
    breeding grounds.

Think about these conditions, how are pests
  encouraged to breed there??
How can they be controlled?
   Sanitary- keeping the surroundings clean

   Chemical- using pesticides

   Biological-using other animals to catch the

*Can you think of examples of each???
   Pollution results from waste
    substances of human activities.

   They are harmful to all living
    organisms & the environment.

   These waste substances can be:
   Micro organisms and pests, if given the right
    conditions to thrive can cause diseases
   Mosquitoes can cause malaria, dengue fever
   Rats can cause leptospirosis
   Other micro organisms can cause cholera,
    typhoid and food poisoning

   What are the symptoms of these diseases??
Personal hygiene
                 Can you make a list of
                  things that you can do to
                  prevent illness from micro
                  organisms and pests???
Community hygiene
   The members of your
    community can also
    play a role in the
    prevention of diseases.

   Can you think of some
    of the ways to dispose
    of this waste?

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