1[1 mark]
Which disease is caused by a protist?
- Cholera
- Malaria
- Tuberculosis
- Chalara ash dieback
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Answer: B B (1)
2[3 marks]
Cholera is caused by bacteria. Explain how cholera is spread and how its spread can be reduced.
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- bacteria are in water contaminated with sewage / faeces (1)
- people become infected by drinking the contaminated water (1)
- provide clean / treated drinking water or treat sewage (1) allow handwashing / thorough cooking of food
3
Triple only
[1 mark]Which disease is caused by a virus and spread by contact with infected body fluids?
- Ebola
- Stomach ulcers caused by Helicobacter
- Malaria
- Cholera
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Answer: A A (1)
4
Triple only
[3 marks]Describe what happens in the lysogenic pathway of a virus.
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- the viral genetic material enters the host cell (1)
- it becomes part of the host cell's DNA / is integrated into the host DNA (1)
- the virus is inactive / dormant, and is copied when the host cell divides (1) allow no new viruses are made until it is triggered
5[3 marks]
Chlamydia is a sexually transmitted infection (STI). Explain how its spread can be reduced.
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- use a condom (1)
- which acts as a barrier / stops the bacteria passing between partners (1)
- regular screening / testing and treating infected people with antibiotics (1)
- limit the number of sexual partners / inform partners so they can be tested (1) allow abstaining from sex
- Max 3
6[4 marks]
Chalara ash dieback is a disease of ash trees caused by a fungus. (a) State two effects of the disease on an ash tree. (2) (b) Describe how the disease spreads and give one way of reducing its spread. (2)
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- (a) leaf loss (1)
- bark lesions (1)
- (b) spores are carried in the air / by the wind (1)
- destroy infected trees / restrict the movement or import of ash plants (1)