diseases

• communicable disease


  a disease caused by a pathogen which can be passed between animals or plants e.g. the flu
• a pathogen


  a disease-causing microorganism e.g. bacteria
• how do bacteria cause disease?

  once inside the body, they divide rapidly. they produce harmful toxins which kill cells
• how do viruses cause disease?

  they invade rapidly and reproduce inside living body cells, leading to cell damage
• how can pathogens be spread? (3)

  • by air - through droplet infection
  • by water - fungal spores in water spread plant diseases
  • by direct contact - common in plant diseases and sexually transmitted infections
• measles


  a viral disease that can cause blindness and brain damage. the main symptoms are a fever and a red skin rash
• what is HIV/AIDS?

  a virus which attacks and damages the immune system until it can no longer function properly

  -AIDS is the condition resulting from long-term HIV infection - there is no cure or vaccine
• TMV


  a plant pathogen which causes leaf discolouration when cells are damaged

  affected areas cannot photosynthesise, reducing crop yield

  as there is no treatment, farmers grow TMV-resistant crop strains to avoid infection
• salmonella


  a type of bacteria found in raw meat and poultry

  it can enter the body via food poisoning, they can affect natural gut bacteria
• symptoms of salmonella:

  • fever
  • abdominal cramping
  • vomiting
  • diarrhoea
• gonorrhoea


  a sexually transmitted bacterial infection caused by unprotected sex

  -early symptoms include a yellow/green discharge from genitals and painful urination

  -the spread can be controlled through the us of antibiotics and using condoms
• rose black spot


  a fungal disease which causes black discolouration to develop on rose leaves

  -it reduces the area of the leaf which is available for photosynthesis and causes leaves to turn yellow or drop prematurely
• malaria


  a disease caused by protist pathogens, which is carried from host to host by mosquitoes and the is transmitted to human through the bloodstream on which they feed

  symptoms include fever and shaking