B7 The spread of diseases

• Mosquitos


  Organisms that spread disease by carrying pathogens between people
• Spread of malaria


  1. Mosquitos feed on the blood of infected people

  2. Spread the protist pathogen when they feed on another person
• Plant disease identification


  • Gardening manuals and websites
  • Laboratory testing of infected plants
  • Testing kits containing monoclonal antibodies
• Plant defences - Physical barriers


  • Cellulose cell walls provide a barrier to infection
  • Tough waxy cuticle on leaves
  • Bark on trees - a layer of dead cells that can fall off
• Plant defences - Chemical barriers


  • Many plants produce antibacterial chemicals
  • Poison production stops animals eating plants
• Plant defences - Mechanical adaptations


  • Thorns and hairs stop animals eating plants
  • Leaves that droop or curl when touched to scare herbivores or dislodge insects
  • Some plants mimic the appearance of unhealthy or poisonous plants to deter insects or herbivores
• Plant diseases can also be directly caused by insects
• Aphids


  Insects that suck sap from the stems of plants, resulting in reduced rate of growth, wilting, and discolouration of leaves
• Ladybirds can be used to control aphid infestations as ladybird larvae eat aphids
• Rose black spot is a fungal disease that causes purple or black spots on leaves, which turn yellow and drop early, reducing the plant's ability to photosynthesise
• Malaria is caused by a protist pathogen spread by mosquito vectors
• Salmonella bacteria and the toxins they produce cause fever, abdominal cramps, vomiting, and diarrhoea
• Gonorrhoea is a sexually transmitted disease caused by bacteria that can lead to a thick yellow or green discharge and pain when urinating
• There are several ways to help prevent the spread of communicable diseases, including hygiene, isolation, controlling vectors, and vaccination
• Viruses live and reproduce rapidly inside an organism's cells, which can damage or destroy the cells
• Bacteria reproduce rapidly inside organisms and may produce toxins that damage tissues and cause illness
• Fungi, protists, and viruses can also cause plant diseases
• Signs that a plant is diseased include stunted growth, spots on leaves, areas of rot or decay, growths, malformed stems or leaves, and discolouration
• Ways of identifying plant diseases include using gardening manuals and websites, laboratory testing, and testing kits containing monoclonal antibodies