B5

Question 1

Equation for calculating bacteria growth?

Answer 1

Bacteria at end of growth period = bacteria at begging of period * 2 (to the power of number of divisions)

Question 2

D. Communicable diseases?

Answer 2

A disease caused by pathogens that can be passed from one organism to another.

Question 3

D. Non-communicable diseases?

Answer 3

A disease that isn’t infectious and can not be passed from one organism to another.

Question 4

Symptoms of disease in plants? (7)

Answer 4

• stunted growth (eg. Nitrate deficiency)
• spots on leaves (eg. Rose black spot)
• areas of decay or rotting (eg. Rose black spot on roses, blights in potatoes)
• growths (eg. Crown gall caused by bacterial infection)
• discolouration (eg. Yellowing it chlorides in magnesium deficiency, mosaic patterns from tobacco mosaic virus)
• presence of visible pests (eg. Aphids)
• malformed stems and leaves (eg. Due to aphid or nematode infestation)

Question 5

Plant defences?

Answer 5

• Physical barriers - bark, leaf fall, cellulose cell wall, waxy cuticle
• Chemical barriers - antibacterial chemicals, poisons