biology revision


communicable diseases

communicable diseases - diseases thaat can be passed on to people and are infectious

they can be caused by a large number of causes (pathogens) e.g. bacteria, fungi ect.

  • Bacteria – reproduce rapidly and can affect the host by releasing toxins, these damage tissues and make us feel unwell, (see Bacterial Diseases
  • Viruses – need a host to survive and reproduce, (see Viral Diseases)
  • Fungi – grow on living tissue, some are single-celled and others have a body made of hyphae, see (Fungal Diseases)
  • Protists – eukaryotic organisms some of them are parasitic, that live on or inside the host organism. They are often transferred by vectors, (see Protists)

lets look at some of these diseases in more detail


  • viruses do not class as living orgaisms as they dont fulfil the 7 life processes
  • viruses reproduce rapidly ( examples of viruses are measles, HIV and the flu)
  • they reproduce rapidly by inserting their genetic material into host cells and creating new protein capsules to build new viral particles, eventually causing the host cell to burst open due to to much pressure which releases the viral particles which go on to infect other cells

Ways viral diseases spread and their cures (E.G. HIV)

one example of a viral disease is HIV (human immunodeficiency virus). this is an example of an STD as it is transferred with the exchange of bodily fluids which usually occurs during direct sexual contact. although there is no cure for HIV there are drugs called antiretroviral drugs which if used early enoigh can slow/ halt the progress to AIDS. e.g.


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