IGCSE Biology Diseases and immunity topical questions

Define each term.

1. (a)Pathogen[1]
2. (b)Transmissible disease[1]
3. (c)Antibody[1]

Name the body defence best matched to each entry route.

1. (a)Pathogens landing on the body surface.[1]
2. (b)Particles in inhaled air.[1]
3. (c)Pathogens in swallowed food.[1]
4. (d)Pathogens that reach the blood and tissues.[1]

For each situation, state whether transmission is direct or indirect and name the vehicle.

1. (a)Sharing a needle among drug users.[1]
2. (b)Eating reheated rice left uncovered overnight.[1]
3. (c)Being bitten by an infected mosquito.[1]
4. (d)Drinking stream water downstream of a sewage outflow.[1]

Match each public health measure to the route of disease spread it targets, then answer the question.

1. (a)A town’s cholera outbreak is traced to a broken sewer leaking into the river that supplies drinking water. Which two measures would target the routes involved?[2]
2. (b)A restaurant’s customers catch food poisoning from raw chicken. Which measure targets that route?[1]
3. (c)Explain how hand-washing reduces the spread of disease.[2]

Explain how two public health measures reduce the spread of transmissible disease.

1. (a)Name two measures.[1]
2. (b)Explain how each breaks a route of transmission.[3]

A person recovers from an infection with virus V and does not catch it again for many years.

1. (a)Explain how the body produced antibodies against virus V.[3]
2. (b)Explain why the antibody does not protect against a different virus, W.[2]

Outline the process of vaccination and its role in controlling disease.

1. (a)Outline what a vaccine contains and the immune response it triggers.[3]
2. (b)Explain why vaccination protects the population, not just the vaccinated person.[2]

A village has 1000 children. Health workers vaccinate 850 of them. A vaccination programme becomes fully effective at protecting the whole community once 90% of children are vaccinated.

1. (a)Calculate the percentage of children currently vaccinated.[2]
2. (b)How many more children must be vaccinated to reach 90%?[2]
3. (c)Explain how vaccinating most of the population protects even those who are not vaccinated.[2]

After a vaccination, a volunteer’s blood antibody level (in arbitrary units) was measured over four weeks.

1. (a)Calculate the percentage increase in antibody level between day 7 and day 14. Show your working.[2]
2. (b)Describe the trend shown by the data.[1]
3. (c)Explain the shape of the response between day 0 and day 21.[2]
4. (d)Predict, with a reason, what a second dose at day 28 would do to the antibody level.[1]

A patient with influenza (a viral disease) asks for antibiotics.

1. (a)Explain why the doctor should not prescribe antibiotics for this infection.[2]
2. (b)State what antibiotics do to bacteria.[1]
3. (c)Explain why vaccines are given before infection rather than after symptoms appear.[2]
4. (d)Name the cell responsible for long-term protection after vaccination.[1]

Compare active and passive immunity. (Supplement)

1. (a)State how antibodies are obtained in each type of immunity.[2]
2. (b)Explain why passive immunity is short-term but active immunity can be long-term.[3]
3. (c)Name one natural way a baby gains passive immunity.[1]

Cholera outbreaks often follow floods that mix sewage with drinking water. (Supplement)

1. (a)Name the pathogen and its transmission route.[2]
2. (b)Explain how the cholera toxin causes diarrhoea.[3]
3. (c)Explain one consequence of this fluid loss for the blood, and name a public health measure that would prevent the outbreak.[2]

A population is immune to virus W. Years later, virus W mutates so that its surface antigens change shape. (Supplement)

1. (a)Explain why people immune to the old strain can now catch the new strain.[3]
2. (b)Explain why antibodies do not attack the body’s own cells.[2]
3. (c)Name the type of biological molecule found in both antibodies and antigens.[1]

A bacterium enters the body through a cut and reaches the blood for the first time.

1. (a)Name the barrier defences the bacterium has already passed through.[1]
2. (b)Describe how phagocytes deal with the bacterium.[2]
3. (c)Describe how lymphocytes respond to the same bacterium.[2]
4. (d)Explain why a second infection by the same bacterium, months later, causes no illness.[2]