Module 4

• The genetic information is stored in the form of a circular strand of DNA in prokaryotes
• viruses consist of nucleic acid enclosed in a protein coat and their genetic material can take the form of DNA or RNA
• Bacteria do not require a host to survive whereas viruses require their host cells in order to survive
• Bacterial diseases: TB, Ring Rot and bacterial meningitis
• Viral diseases: HIV/AIDS, Influenza and Tobacco Mosaic Virus
• Protocista diseases: Malaria, Potato and tomato blight
• Fungal diseases: black sigatoka, ringworm and athlete's foot
• TB is caused by mycobacterium tuberculosis which infects phagocytes in the lungs.
• Symptoms of TB are coughing, weight loss, breathing problems and fever
• Bacterial meningitis can be caused by bacterial infection of the meninges - set of protective membranes in the brain
• HIV causes AIDS. The symptoms of this infection is fever, tiredness, headaches.
• Influenza is a viral disease where the virus infects the ciliated epithelial cells of the gas exchange system
• Athlete's foot in humans are caused by a fungus as it spreads by direct contact with the spores on the skin surface
• Malaria is a protoctista disease that is spread by indirect transmission via vector in the form of a female Anopheles mosquito.
• Tobacco mosaic virus infects tobacco plants by damaging the leaves to prevent plants from growing
• Potato blight is caused by phytophora as the hyphae enters the plant and causes damage to the leaves
• Black sigatoka is a fungal disease that damages the leaves due to the hyphae entering the plant. To prevent this, use fungicides to kill the fungus.
• Plants have physical and chemical defences
• Antimicrobial inhibits the growth of microorganisms
• Antiseptics inhibit the growth of germs that cause disease
• marine conservation zone is an example of a in situ conservation
• In Situ conservation takes place in the organism's natural ​habitat.
• Ex Situ takes place outside of the organism's natural habitat.
• Physical defences of plant are: stomata closing, additional cellulose in cell walls, callose between the membranes to block entry of pathogens, necrosis - cell suicide, areas where infected is killed to reduce spreading.
• Chemical defences in plants are: terpenoids are essential oils that have antibacterial and antifungal properties, phenols e.g. tannin has antifungal properties, alkaloids gives a bitter taste to inhibit herbivores feeding, defensins are proteins that inhibit ion transport, hydrolytic enzymes break down the cell walls of pathogens.
• Primary defences prevent the entry of pathogens into the body
• Secondary defences helps to remove the pathogen once it has entered the body.
• Primary defences are: skin, inflammation, and mucous membranes.
• Skin acts as a barrier to prevent the entry of pathogens
• Blood clotting reduces the loss of blood and makes a temporary seal to prevent access by pathogens.
• Blood clotting involves calcium ions and other clotting factors released by platelets or from the damaged tissues. These factors activate an enzyme cascade which produces insoluble fibres. Once a clot is formed, it forms a scab; over time the scab shrinks. Fibrous collagen is deposited under the scab and over time new cells are form by differentiation.
• Intraspecific variation occurs between members of the same species. These are observable features e.g. colour or sex
• Interspecific variation occurs in members of different species.
• The artery walls are made up of: an endothelial layer, a layer of connective tissue and a layer of elastic fibres
• What are the four types of pathogens that cause communicable diseases?

  Bacteria, viruses, Protoctista, fungi
• How do pathogens cause harm to the host?

  By damaging tissues or releasing toxins
• What diseases are caused by bacteria?

  • TB
  • Ring Rot
• What diseases are caused by viruses?

  • HIV/AIDS
  • Influenza
  • Tobacco Mosaic Virus
• What diseases are caused by Protoctista?

  • Malaria
  • Potato/Tomato blight
• What diseases are caused by fungi?

  • Black Sigatoka
  • Athlete’s Foot