4.1.1 Communicable diseases, disease prevention and immune system

4.1.1 Communicable diseases, disease prevention and immune system

1. (a) the different types of pathogen that can cause communicable diseases in plants and animals

   • •bacteria – tuberculosis (TB), bacterial meningitis, ring rot (potatoes, tomatoes)
   • •virus – HIV/AIDS (human), influenza (animals), Tobacco Mosaic Virus (plants)
   • •protoctista – malaria, potato/tomato late blight
   • fungi – black sigatoka (bananas), ring worm (cattle), athlete’s foot (humans)

2. (d) the primary non-specific defences against pathogens in animals

   • skin, mucous membrane, blood clotting, inflammation,, wound repair, empulsive reflexes

3. (e) (i) the structure and mode of action of phagocytes (ii) examination and drawing of cells observed in blood smears

4. (f) the structure, different roles and modes of action of B and T lymphocytes in the specific immune response

   • T helper cells
   • T killer cells
   • T regulatory cells
   • B plasma cells
   • memory cells

5. (b) the means of transmission of animal and plant communicable pathogens

   • Direct transmission
     • droplet infection
       • coughing and sneezing
     • sexual intercourse
       • e.g HIV
     • touching an infected organism
       • e.g Athlete's foot
   • Indirect transmission
     • air
     • water
     • food
     • vector
       • e.g malaria- mosquitoes are vectors that spread plasmodium

6. (c) plant defences against pathogens

   • waxy cuticle provides a physical barrier
   • plant cells are surrounded by cell walls
   • produce a polysaccharide called callose which makes it harder for pathogens to enter cells. At the plasmodesmata it limits the spread of viiruses between cells

7. (g) the primary and secondary immune responses

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