4.1 communicable diseases

Question 1

what bacterial disease affects plants

Answer 1

ring rot in potato

Question 2

what bacterial disease affects humans

Answer 2

tuberculosis

Question 4

what viral disease affects plants

Answer 4

tobacco mosaic virus causes discolouration and mottling of leaves

Question 5

what fungal disease affects plants

Answer 5

black sigatoka causes leaf spots and redcues yield in bananas

Question 6

what disease caused by prtoctists affects plants

Answer 6

tomato and potato blight - affects leaves and potatoes

Question 7

how are plant pathegeons spread

Answer 7

directly - via the roots or airborne in spores
indirectly - via insects
climate dwetermined eg wet seasons, warm seasons which might suit certain pathegeons

Question 8

list physical defences of plants

Answer 8

• Cellulose cell wall thickened with lignin
• Waxy cuticles to allow water (carrying fungi) to run off
• Callose - this blocks plasmodesmata or sieve tubes in phloem to prevent spread of pathogen through plant
• Bark which contains many chemicals that secrete chemicals

Question 9

list active defences of plants

Answer 9

• Necrosis - cell suicide. Infected leaves/ shoots are dropped (Often called dieback)
• Canker - deliberate death of branch by killing cambium
• Thickening of cell walls
• Producing more chemicals

Question 10

list chemical defences of plants

Answer 10

• Alkaloids - contain nitrogen eg cocaine, nicotine, caffeine, morphine. These often inhibit enzymes in animal predators
• Hydrolotic enzymes break down walls in fungi
• Phenols - these are antibiotic and antifungal and deactivate digestive enzymes preventing digestion in predators
• Tarpenoids - oils eg menthols that contain scent that are antibacterial or antifungal

Question 11

what is a disease

Answer 11

• an illness or disorder of the body or mind that leads to poor health
• Each disease is associated with a set of signs and symptoms

Question 12

what is a communicable disease

Answer 12

caused by pathogens and are transmissible (can be spread between individuals within a population)

Question 13

defien an infectious disease

Answer 13

Disease caused by a pathogen that passes from infected individuals to uninfected individuals

Question 14

define a non-infectious disease

Answer 14

Long-term diseases that are not caused by pathogens,

Question 15

what causes diseases

Answer 15

• bacteria
• viruses
• protoctists
• fungi

Question 16

info on bacteria

Answer 16

• Some bacteria are non-pathogenic (they do not cause any disease or damage) while others are pathogenic
• Pathogenic bacteria do not always infect the hosts of cells, they can remain within body cavities or spaces