B5 infection & response

• viruses CANNOT be killed by antibiotics
• Measles (viral disease)

  • symptoms: fever & red skin rash
  • spread by inhalation of droplets from sneezes and coughs
  • Most young children are vaccinated against measles
• HIV (viral disease)

  • Flu-like illness
  • the virus attacks the body’s immune cells , late stage HIV infection (AIDS) occurs when the body’s immune system is so badly damaged it can no longer deal with other infections
  • spread by sexual contact (STD) or exchange of body fluids
  • treated with ANTIRETROVIRAL drugs
• Tobacco mosaic virus (viral disease)

  • affects plants only
  • it gives a distinctive ‘mosaic’ pattern of discolouration on the leaves which affects the growth of the plant due to a lack of photosynthesis
• Salmonella (bacterial disease)

  • symptoms: fever, abdominal cramps, vomiting and diarrhoea
  • food poisoning caused by ingesting dead animals that had disease or food prepared in unhygienic conditions
  • spread by bacteria ingested in food
  • To control the spread poultry are vaccinated against salmonella
• Gonorrhoea (bacterial disease)

  • symptoms: thick yellow or green discharge from the vagina or penis, pain when urinating
  • Sexually transmitted disease (STD)
  • easily treated with the antibiotic penicillin until many resistant strains appeared
  • spread can be controlled by treatment with antibiotics or contraception
• Rose black spot (fungal disease)

  • purple or black spots develop on leaves turning yellow and drop early
  • affects the growth of plant as photosynthesis is reduced
  • spread by water or wind
  • can be treated by using FUNGICIDES or removing and destroying affected leaves
• Malaria (protist disease)

  • Malaria causes fever and can be fatal
  • often transferred by a vector (mosquito)
  • the spread is controlled by preventing mosquitoes from breeding and using mosquito nets
• Binary fission - the process of bacteria dividing and reproduce
• Binary fission

  1. genetic material replicate
  2. bacteria cell grows
  3. Large circular DNA moves to opposite ends of cells
  4. cell membrane forms around new cell

  CONDITIONS: warm environment + lots of nutrients
• The job of the non-specific defence system is to prevent pathogens from entering the body
• Humans have two lines of defence:

  1st line - using physical & chemical barriers

  2nd line - immune system which targets pathogens
• 1st line of the human defence system:

  • skin - outer layer consists of dead cells which makes it difficult for pathogens to penetrate , produces sebum which kills bacteria
  • Nose - contains hair and mucus to trap pathogens
  • trachea & bronchi - covered with cilia which are covered in mucus to trap pathogens
  • stomach - produces hydrochloric acid which kills pathogens
• 2nd line of the human defence system:

  • Phagocytes - ingest and destroy pathogens
  • Lymphocytes - produce antibodies
  • anti toxin producing white blood cell
• Antigens - proteins unique to a cell
• • lymphocytes can learn to recognise antigens and produce antibodies
  • The shape of the antibody matches the antigen
  • then they are able to make antibody rapidly the second time and develop immunity
  • rapid production of antibodies kills pathogens before they can reproduce
• common signs of plant disease

  • stunted growth
  • spots on leaves
  • areas of decay
  • Abnormal growths
  • malformed stems or leaves
  • discolouration
  • the presence of pests
• Plants can be attacked by insects (aphids) which extract nutrients stunting growth. Aphids can act as vectors
• Mineral deficiency in plants non-communicable
• NITRATES are needed to make proteins (via protein synthesis) for growth. A lack of nitrates causes STUNTED GROWTH
• MAGNESIUM IONS are needed for making chlorophyll. A deficiency in magnesium causes plants to loose their colour and develop chlorosis
• Identification of plant disease:

  • reference to a gardening manual or website
  • taking infected plant to a laboratory to identify the pathogen
  • using testing kits
• some plant diseases can be treated with pesticides or fungicides
• Mineral deficiency can be treated by using fertilisers
• Physical plant defence

  • tough waxy cuticle on leaves
  • cellulose cell walls
  • Layers of dead cells around stems (bark on trees)
• Chemical plant defence

  • antibacterial chemicals
  • poisons to deter herbivores
• Mechanical plant defence

  • Thorns and hairs
  • leaves which droop or curl when touched
  • mimicry to trick animals