Disease (Cambridge O Level Biology)

Pathogens can be passed from one host to another in different ways.

State two examples of how this happens.

Hygienic food preparation methods are very important in preventing the spread of pathogens and disease.

Explain three examples of such methods.

Cholera is a bacterial disease.

State the name of the bacterium that causes cholera.

One of the symptoms of cholera is diarrhoea, which may become life-threatening if left untreated.

Suggest why persistent diarrhoea can be life threatening.

[4]

[1]

Eating food contaminated by bacteria can cause illness.

This type of illness is called food poisoning.

Fig. 1 shows the number of cases of food poisoning per 100 000 people in the population in one country.

Fig. 1

State the year with the highest number of cases of food poisoning in Fig. 1.

[1]

State the number of cases of food poisoning per 100 000 people in the population in the year 1996 in Fig. 1.

Describe the trend in the number of cases of food poisoning between 2003 and 2011 in Fig. 1.

Food poisoning is caused by different types of bacteria.

A common type of bacterium that causes food poisoning is Campylobacter jejuni.

State the genus of this species.

Food poisoning can result in vomiting and diarrhoea.

Outline the treatment of diarrhoea.

The body has several defence mechanisms against bacteria.

Table 1 shows three types of defence mechanism.

The word list gives examples of these defence mechanisms.

In Table 1 write the examples under the correct type of defence.

Use each word once only.

Table 1

State one type of blood cell that is involved in the defence against disease.

[1]

State two ways blood cells defend the body against disease.

HIV is a sexually transmitted infection (STI).

Define the term sexually transmitted infection.

[2]

Explain how the spread of HIV can be controlled.

[3]

Streptococcus pyogenes is a pathogenic bacteria that spreads through direct contact with discharges from the nose and throat, as well as through open wounds and sores on the skin of infected people.

In the 19th century, many women died shortly after childbirth due to a disease called puerperal fever, which is caused by an infection of S. pyogenes. At the time, it was common practice for doctors to dissect dead bodies in order to study human anatomy and then move straight on to delivering babies immediately after.

Suggest an explanation for the frequent deaths of women after childbirth due to puerperal fever.

Table 1 shows the number of births and deaths at a hospital between 1841 and 1846.

Table 1

Calculate the percentage change in the number of deaths between 1841 and 1846.

Show your working and give your answer to the nearest whole number.

In 1847 a handwashing policy was introduced at the hospital from part (b) which stated that doctors should wash their hands before delivering babies in the maternity ward. This policy was strictly enforced in 1848.

Fig. 1 shows the death rate of mothers from puerperal fever between 1846 and 1848.

Fig. 1

Describe and explain the data from January 1847 to July 1848.

Other than washing their hands, suggest two other hygiene practices that doctors in modern hospitals should follow in order to avoid the spread of pathogens to their patients.

Table 1 shows information about deaths from malaria in a particular area of Africa.

Table 1

Complete Fig. 1 using data from Table 1.

Fig. 1

Malaria is spread by the female Anopheles mosquito when they break through the skin of an uninfected person during a blood meal.

Explain how the skin acts as a mechanical barrier against disease.

Once the mechanical barrier formed by the skin is broken, the malaria pathogen enters the blood.

Outline the defence mechanism that will come into effect once a pathogen enters the blood.