the spread of diseases- paper 1

• Methods to control the spread of disease

  • Hygiene (hand washing, disinfecting surfaces/machinery, keeping raw meat separate, covering mouth when coughing or sneezing)
  • Isolation (isolating infected individuals - people, animals and plants)
  • Controlling vectors (destroying or controlling the population of the vector)
  • Vaccination (to protect large numbers of individuals against disease)
• Hygiene measures can help control the spread of disease
• Isolating infected individuals can stop the spread of diseases
• Controlling vectors that spread a disease can limit the spread of disease
• Vaccination can protect large numbers of individuals against disease
• Bacteria

  • Reproduce rapidly, inside organisms
  • May produce toxins that damage tissues and cause illness
• salmonella is spread by bacteria that is in or on food that is then ingested
• Salmonella

  • Bacteria that can cause typhoid fever
  • Spread through contaminated food that is ingested
  • Symptoms include vomiting, diarrhoea, fever, abdominal cramps
  • Prevented by poultry being vaccinated against salmonella
• Gonorrhoea

  • Sexually transmitted disease
  • Causes thick, yellow-green discharge from the vagina or penis
  • Painful urination
• Protists

  • Pathogen that causes malaria
  • Spread by mosquitoes that feed on infected people
  • Causes recurrent fever that can be fatal
  • Prevented by stopping/preventing mosquito from breeding by using mosquito nets, and taking anti-malarial medication
• Virus

  Live and produce rapidly inside an organism's cell, this destroys/damages the cell
• Spread of diseases by viruses

  1. Inhalation of droplets produced by infected people when sneezing or coughing

  2. Exchange of bodily fluids (e.g. sharing needles)

  3. Direct contact of contaminated objects with virus
• Prevention of fungal diseases

  1. Removal of affected leaves

  2. Use of fungicides
• examples of viruses

  • measles
  • HIV
  • TMV
• examples of fungi

  • rose black spot
• rose spot disease is spread through water and wind
• symptoms of rose black spot disease

  • purple or black spots on the leaf that turn yellow and then infected leaf fall off
  • chlorophyll is destroyed which reduces plants ability to photosynthesise - affects plant growth
• prevention of rose black spot disease

  • fungicides
  • remove the affected leaves and destroy them
• TMV is spread by:

  • direct contact of plants with the infected material
  • animal and plant vectors
  • soil: the pathogen can remain in soil for days
• TMV symptoms:

  • flu like symptoms at first
  • attacks the body’s immune cells which can lead to AIDS - the immune system becomes so damaged that it cannot fight infections or cancers
• virus symptoms:

  • fever
  • red skin rash
• measles can be fatal - young children are vaccinated for immunity
• Signs that a plant is diseased

  • Stunted growth
  • Spots on leaves
  • Areas of rotting
  • Abnormal growths
  • Malformed stems or leaves
  • Discolouration
  • Pest infestation
• Aphids

  Insects that secrete sap from stems of plants, resulting in reduced growth rate, wilting, discoloration of leaves
• Ladybirds

  • Can control aphid infestation as ladybird larvae eat aphids
• Plant defences

  • Physical barriers (cellulose cell wall, tough waxy cuticle, bark on trees)
  • Chemical barriers (anti-bacterial chemicals, poison production)
  • Mechanical barriers (thorns/hairs, leaves that droop or curl, mimicry of poisonous plants)