Microorganisms: Friend and Foe quiz

The bacterium that helps in the formation of curd from milk is:

Yeast is used in baking because it releases:

Penicillin was discovered by:

Malaria is caused by a:

The nitrogen-fixing bacterium found in the root nodules of leguminous plants is:

Which of the following diseases is caused by a virus?

Anthrax is a dangerous disease of humans and cattle caused by a:

The carrier of the dengue virus is the:

Rust of wheat is caused by a:

Which of the following is a chemical preservative used for jams and squashes?

Name two microorganisms that are multicellular and two that are unicellular. (2 marks)

Why does bread or idli dough rise? (2 marks)

How do microorganisms help to clean the environment? (2 marks)

Name two antibiotics and state one precaution to be taken while using antibiotics. (2 marks)

Why do farmers grow leguminous crops between cereal crops? (2 marks)

How does a housefly carry germs to our food? (2 marks)

Name two plant diseases caused by microorganisms, with their causative agents. (2 marks)

What is food poisoning? How can it be prevented? (2 marks)

Why are salt and sugar effective in preserving foods? (2 marks)

Who discovered the bacterium that causes anthrax, and in which year? (2 marks)

A bacterial culture doubles every 30 minutes. If a sample contains 500 bacteria at 9:00 am, how many will it contain at 11:00 am? At what time will it first contain more than 10,000 bacteria? (3 marks)

In a school of 800 students, 120 students were absent with chicken pox during an outbreak. Find the percentage affected. If vaccination reduces the number of cases by 80% next year, how many students would be expected to fall ill? (3 marks)

A baker uses 10 g of yeast for every 1 kg of flour. How much yeast is needed for 7.5 kg of flour? If the dough must be left for 2 hours at about 30 degrees C to rise, explain why it rises more slowly on a cold day. (3 marks)

In a survey of 500 houses in a town, mosquito larvae were found in water stored in 125 houses. Find the percentage of houses with larvae. After a cleanliness drive, only 25 houses had larvae. Find the percentage reduction in the number of such houses. (3 marks)

A milk dairy pasteurises 6000 litres of milk a day in batches of 750 litres. How many batches are needed? If each batch is held at about 70 degrees C for 30 seconds, what is the total holding time for the day in minutes? (3 marks)

Read the passage and answer the questions. Rani's mother added a spoonful of old curd to a bowl of warm milk and kept it overnight in a warm place. In the morning, the milk had set into curd. On another day, when she added curd to cold milk and kept it in the refrigerator, the milk did not set. (i) Name the microorganism responsible for setting curd. (ii) Why did the milk set when kept warm? (iii) Why did the milk not set in the refrigerator? (5 marks)

Read the passage and answer the questions. In 1929, Alexander Fleming noticed that a mould growing on one of his culture plates had stopped the growth of bacteria around it. The substance produced by the mould was later purified and called penicillin. (i) What are antibiotics? (ii) Name two other antibiotics. (iii) Why should antibiotics be taken only on a doctor's advice? (5 marks)

Read the passage and answer the questions. After the monsoon, many people in a town fell ill with high fever. The health department found water collected in coolers, flower pots and old tyres, and found mosquito larvae in it. They advised people to empty and clean such containers every week. (i) Name two diseases that could be spreading. (ii) How does collected water help the spread of these diseases? (iii) Suggest three steps to prevent them. (5 marks)

Read the passage and answer the questions. A farmer noticed that his bean plants had small swollen structures on their roots. The agriculture officer told him that these structures help the plants and the soil. (i) What are these structures called? (ii) Name the microorganism living in them and its function. (iii) How does this help the farmer save money on fertilisers? (5 marks)

Read the passage and answer the questions. A family went on a picnic and ate sandwiches that had been packed in the morning and left in a hot car for many hours. Several members later had vomiting and stomach pain. (i) What could be the cause of their illness? (ii) Why did leaving the food in a hot car make it harmful? (iii) Suggest three ways of keeping food safe during a picnic. (5 marks)

Draw labelled diagrams of bacteria, fungi, protozoa and algae. Describe where microorganisms are found, and explain why viruses are different from the other groups. (6 marks)

Draw a flowchart showing how yeast is used in making bread and in the commercial production of alcohol. Explain fermentation, and describe three other uses of microorganisms in the food industry and medicine. (6 marks)

Draw a labelled diagram of the nitrogen cycle. Explain the role of microorganisms in fixing atmospheric nitrogen, and how nitrogen returns to the atmosphere. (6 marks)

Draw a labelled diagram of a mosquito as a carrier of disease. Describe four human diseases caused by microorganisms, giving the causative organism, mode of transmission and one preventive measure for each. (6 marks)

Draw a flowchart showing the steps of pasteurisation of milk. Explain six methods of food preservation, giving one example of a food preserved by each method and the reason why it works. (6 marks)