Viral Diseases
Practise Viral Diseases for GCSE Biology with this free worksheet and full mark scheme — Foundation and Higher exam-style questions with worked answers for AQA, Edexcel and OCR. Learn measles, HIV and tobacco mosaic virus as your three named viral examples for the exam.
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These worksheets and mark schemes are original, written for Virtus Academy and checked against the current AQA, Edexcel and OCR specifications. Every worksheet comes with a full mark scheme.
Topic overview
Three viral diseases are required: measles, HIV and tobacco mosaic virus. Each has a distinct mode of spread and set of effects.
Measles spreads in droplets from sneezes and coughs. It causes fever and a red skin rash, and can be fatal if complications arise, which is why most young children are vaccinated against it.
HIV is spread by sexual contact or by exchange of body fluids such as blood when drug users share needles. It initially causes flu-like illness, then remains hidden before attacking the immune system. Late-stage HIV infection is called AIDS. Tobacco mosaic virus affects plants, giving a distinctive mosaic discolouration of leaves that reduces photosynthesis and therefore growth.
Revision notes
Measles
Spread by inhalation of droplets from sneezes and coughs.
Symptoms are fever and a red skin rash. It can be fatal if complications arise, so most young children are vaccinated against it.
HIV and AIDS
Spread by sexual contact or exchange of body fluids, such as sharing needles.
Initially causes a flu-like illness, then remains hidden. Unless controlled by antiretroviral drugs it attacks the immune cells. Late-stage HIV infection, or AIDS, occurs when the immune system is so badly damaged it cannot fight off other infections or cancers.
Tobacco mosaic virus
A widespread plant pathogen affecting many species including tomatoes.
It gives a distinctive mosaic pattern of discolouration on the leaves. Because the affected areas cannot photosynthesise properly, growth is reduced.
Key points
- Measles is spread by droplets from coughs and sneezes.
- Measles causes fever and a red skin rash.
- HIV is spread by sexual contact or exchange of body fluids.
- HIV attacks immune cells; late-stage infection is AIDS.
- Antiretroviral drugs control HIV.
- Tobacco mosaic virus discolours leaves and reduces growth.
Worked examples
Example 1
Describe how measles is spread and state two of its symptoms. [3 marks]
Model answer
Measles is spread by inhalation of droplets from sneezes and coughs (1 mark). Symptoms include a fever (1 mark) and a red skin rash (1 mark).
Example 2
Explain why a person with AIDS may die from an infection that would not normally be serious. [2 marks]
Model answer
HIV attacks and damages the body's immune cells (1 mark), so the immune system can no longer fight off other infections effectively (1 mark).
Example 3
Explain how tobacco mosaic virus reduces the growth of a plant. [2 marks]
Model answer
It causes a mosaic pattern of discolouration on the leaves (1 mark), so those areas cannot photosynthesise properly and less glucose is made for growth (1 mark).
Common mistakes
Saying HIV and AIDS are the same thing.
AIDS is the late stage of HIV infection, when the immune system is badly damaged.
Saying measles is treated with antibiotics.
Antibiotics do not work on viruses. Measles is prevented by vaccination.
Forgetting that tobacco mosaic virus affects plants.
It is the required plant example and is often overlooked.
Not linking discolouration to reduced photosynthesis.
That link is where the mark usually lies.
Exam tips
- Learn the mode of spread and the symptoms for each named disease.
- Distinguish HIV the virus from AIDS the late-stage condition.
- Remember tobacco mosaic virus as the plant example.
- Link plant symptoms to reduced photosynthesis and growth.
Key terms
- Virus
- A pathogen that reproduces inside host cells.
- AIDS
- The late stage of HIV infection when the immune system fails.
- Antiretroviral
- A drug used to control HIV infection.
- Mosaic pattern
- The distinctive leaf discolouration caused by tobacco mosaic virus.
Related topics
Written and reviewed against the current AQA, Edexcel and OCR specifications. Spotted an error? Let us know.