Other pathogens: stem rust, influenza and malariaEdexcel A-Level Biology B: Subtopic test

1. 1
   A wheat farmer finds red-brown pustules on the stems and leaves of her crop. Hyphae of the fungus Puccinia graminis are seen growing through the leaf tissue under a microscope. Spores from the pustules are carried across neighbouring fields, and the infected plants produce small, shrivelled grains and a much lower yield.

   (a)

   To which group of organisms does Puccinia graminis belong?

   [1 mark]

   • ABacteria
   • BViruses
   • CFungi
   • DProtoctista

   (b)

   How are the spores of Puccinia graminis most commonly transmitted between wheat plants in different fields?

   [1 mark]

   • ACarried by the wind
   • BInjected by a mosquito vector
   • CIn droplets from coughs and sneezes
   • DCarried in blood

   (c)

   Explain why wheat plants infected with Puccinia graminis produce a lower yield of grain.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   Over three days, many pupils in a school develop fever, aching muscles and a dry cough. Swabs show influenza virus, an enveloped RNA virus, in the cells lining the nose and throat of the pupils. One pupil later develops a bacterial chest infection.

   (a)

   By which route is the influenza virus most likely to have spread between the pupils?

   [1 mark]

   • ABite of an infected insect
   • BContaminated soil
   • CWind-blown fungal spores
   • DAirborne droplets from coughs and sneezes

   (b)

   Which cells does the influenza virus infect first in the pupils?

   [1 mark]

   • ARed blood cells
   • BEpithelial cells lining the respiratory tract
   • CLiver cells
   • DNeurones

   (c)

   Explain why influenza makes a patient more likely to develop a bacterial chest infection.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A traveller returns from a region where malaria is endemic. Ten days later she develops a fever that returns every two to three days, and she feels weak and pale. A blood test shows a low haemoglobin concentration, and Plasmodium parasites are seen inside her red blood cells.

   (a)

   Describe how the traveller became infected with Plasmodium.

   [3 marks]

   (b)

   Explain why the traveller has a recurring fever and a low haemoglobin concentration.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A regional health and agriculture department is writing a briefing that compares three pathogens: the stem rust fungus Puccinia graminis in wheat, the influenza virus and the malarial parasite Plasmodium.

   (a)

   Describe the transmission, mode of infection and pathogenic effect of each of the three pathogens.

   [6 marks]

   (b)

   A trainee states that influenza and malaria both infect the human body, so they must damage the same cells and cause the same symptoms. Evaluate this statement.

   [6 marks]

   Total for question 4: 12 marks

End of questions