4.1.1 organisms that cause disease

Question 1

communicable diseases

Answer 1

illnesses that spread from:
- 1 person to another
- animal to person
- surface or food

Question 2

what are involved in the spread of disease
- give examples

Answer 2

vectors
- eg. water/insects

Question 3

what are communicable diseases caused by

Answer 3

infective organisms called pathogens

Question 4

name the 4 main pathogens (which are eukaryotic/prokaryotic/neither)

Answer 4

• bacteria (prokarytic)
• fungi (eukaryotic)
• viruses (-)
• protoctista (eukaryotic)

Question 5

describe how pathogens (overall) may cause infection

Answer 5

may damage host tissue directly/produce toxins which damage it

Question 6

what causes the symptoms of disease

Answer 6

damage to tissue comvined with how your body responds

Question 7

explain how viruses cause infection

Answer 7

• invade cells & take over genetic machinery/cell metabolism alongside other organelles
• insert genetical material into host DNA & produce new viruses
• these burst out of cell (damage)
• these infect more healthy cells

Question 8

explain how protoctistas cause infection

Answer 8

• take over cells & break them open (don’t take over genetic material)
• digest & use cell contents as they reproduce

Question 9

explain how bacteria cause infection

Answer 9

• produce toxins that poison the host cell by:
  
  • breaking down cell membranes
  • damage/inactivate enzymes
  • intefere with genetic material so cell
    cannot divide
• toxins are a by-product of the normal functioning bacteria
• in plants: often live in vascular tissue & cause blackening/death of these tissues

Question 10

explain how fungi cause infection

Answer 10

• digest living cells & destroy them
• some produce toxins that affect the host cell
• some live in skin of animals where the hyphae (form mycelium) grow under surface & sends out specialised reproductive hyphae to grow to surface & release spores
• plants: often lives in vascular tissue & gains nutrients —> hyphae releases extracellular enzymes (eg. cellulase) to digest surrounding tissue causing decay

Question 11

name 3 modern technologies used to identify pathogens - incl. examples

Answer 11

1. culture based eg. gram staining
2. antigen detection eg. use of monoclonal antibodies
3. nucleic acid detection eg. DNA sequencing, PCR (polymerase chain reaction - find DNA/RNA of pathogen)

Question 12

outline, pathogen, transmission, symptoms, organisms affected & prevention/treatment of athletes foot

Answer 12

• fungus (trichophyton rubum)
• direct physical contact
• growth under skin of feet esp. between toes
• humans
• treat: medicine provided, prevent: keep feet dry & avoid using swimming pools, public showers or foot baths

Question 13

outline, pathogen, transmission, symptoms, organisms affected & prevention/treatment of bacterial meningitis

Answer 13

• bacteria (nelsseria meningitis/streptococcus pneumonia)
• direct physical contact
• infection of meninges (membranes surrounding brain/spinal cord) —> become swollen & may cause damage to brains/nerves
• humans
• treat: antibiotics, prevent: vaccination

Question 14

outline, pathogen, transmission, symptoms, organisms affected & prevention/treatment of black sigatoka

Answer 14

• fungus (mycosphaerella fijiensis)
• rain splash & windborne spores
• leaf spots on banana plants & reduces yield
• bananas
• treat: frequent applications of fungicides & cultural practices, prevent: use resistant cultivars & remove/burn infected leaves & use under canopy drip irrigation

Question 15

outline, pathogen, transmission, symptoms, organisms affected & prevention/treatment of HIV/AIDS

Answer 15

• virus (human immunodeficiency virus)
• direct physical contact
• attacks cells in immune system & comprimises immune response
• humans.. (?)
• prevent: abstinence, never sharing needles, using condoms, treat: medicine to manage HIV

Question 16

outline, pathogen, transmission, symptoms, organisms affected & prevention/treatment of influenza (flu)

Answer 16

• virus (from family orthomyxoviridae - ‘flu’ viruses)
• droplet infection
• attacks respiratory system & causes muscle pain/headaches
• humans.. (?)
• treat: antiviral drugs, prevent: annual flu vaccine

Question 17

outline, pathogen, transmission, symptoms, organisms affected & prevention/treatment of malaria

Answer 17

• protoctistan (plasmodium falciparum, p. vivax, p. ovale, p. malariae)
• vector
• parasite in blood that causes headache & fever & may progress to coma/death
• humans.. (?)
• treat: antimalarial medicine, prevent: mosquito nets (eg. when sleeping) & insect repellent

Question 18

outline, pathogen, transmission, symptoms, organisms affected & prevention/treatment of potato/tomato blight

Answer 18

• protoctistan (phytophthora infestans)
• from spores produced from infected plants
• affects leaves/potato tubers
• tomatoes/potatoes
• treat: remove infected leaves & burn, prevent: spray crops with protective fungicide

Question 19

outline, pathogen, transmission, symptoms, organisms affected & prevention/treatment of ring rot

Answer 19

• bacterium (clavibacter michiganensis subsp. sepedonicus)
• infected tubers & micro-propogated plantlets
• ring of decay in vascular tissue of potato tuber/tomato, accompanied by leaf wilting
• plants
• prevent/treat: keep disease/pathogen off farm & use certified seeds tested in lab but if found, incinerate or deeply bury infected material