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Microorganisms: Friend And Foe Worksheet

Objective Type Questions

  1. Complete the table below by choosing the appropriate terms given in brackets.
    (fungi, air, citrus canker, foot and mouth, virus, insect)
  2. Name the following.
    (a) The scientist who discovered the vaccine for smallpox.
    (b) Microorganism used in making curd from milk.
    (c) Microorganism used in large scale production of alcohol.
    (d) Instrument required to see the microorganisms.
    (e) The insect which is the carrier of malarial parasite.

  3. Match the terms in column A with appropriate terms in column B.
  4. State whether the following statements are true or false. Correct and rewrite the false statements.
    (a) Meat and fish are covered with sugar to check the growth of bacteria.
    (b) Sugar reduces the moisture content which inhibits the growth of bacteria which spoil food.
    (c) Vegetables, fruits, fish, and meat can be preserved by the method of pasteurization.
    (d) High temperature inhibits the growth of microbes.
    (e) Pasteurised milk can be consumed without boiling as it is free from harmful microbes.

    Multiple Choice Questions

  5. Microorganisms are classified into
    (a) Four groups – Bacteria, Algae, Fungi and Protozoa
    (b) Four groups - Bacteria, Algae, Fungi and Virus
    (c) Three groups - Bacteria, Algae and Fungi
    (d) Three groups - Bacteria, Algae and Virus

  6. Padmashri saw some greenish cottony mass on the bread which she had left open in her kitchen for 2-3 days. Which group of microorganism is responsible for this growth?
    (a) Algae
    (b) Protozoa
    (c) Fungi
    (d) Bacteria

  7. Which of the following statements about viruses is true?
    (a) They are much bigger in size than bacteria.
    (b) They show most of the characteristics of living things.
    (c) They can reproduce and multiply only inside a host cell.
    (d) They do not cause diseases in plants, animals, and humans.

  8. Few statements about antibiotics are given below. Identify the true statements.

    (a) I and II
    (b) II and III
    (c) I and IV
    (d) II and IV

  9. Cyanobacteria are commonly called nitrogen fixers. They increase the fertility of the soil. How do these nitrogen fixers increase the soil fertility?
    (a) They produce nitrogen gas that is released into the atmosphere.
    (b) They convert nitrogen gas present in the atmosphere into compost.
    (c) They fix atmospheric nitrogen to make nitrogen compounds in the soil.
    (d) They decompose remains of plants and animals to produce nitrogen compounds.

  10. Which of the following correctly defines a pathogen?
    (a) Microbes which form curd
    (b) Microbes which decrease soil fertility
    (c) Microbes which cause diseases
    (d) Microbes which breakdown the remains of dead organisms

  11. Which statement associated with mosquito helps us understand that malaria is a communicable disease?
    (a) The causative agent of malaria is a protozoan.
    (b) The mosquito carries the parasite Plasmodium that causes malaria.
    (c) The mosquito lays its eggs in water collected in tyres, coolers, and open pits.
    (d) The parasite is transferred inside the body of a healthy person through mosquito bite.

  12. What is true about the communicable disease ‘dengue’?
    (a) It spreads due to female Aedes mosquitoes that act as carriers of dengue virus.
    (b) It spreads due to male Aedes mosquitoes that act as carriers of dengue virus.
    (c) It spreads due to male Anopheles mosquitoes that act as carriers of dengue virus.
    (d) It spreads due to female Anopheles mosquitoes that act as carriers of dengue virus.

  13. Which of the following shows the correct match of the disease with its causative agent?
      Disease Affects Caused by
    (a) Anthrax Plants Bacterium
    (b) Cholera Animals Fungus
    (c) Citrus canker Animals Bacterium
    (d) Rust of wheat Plants Fungus
  14. Riddhi observed that the fishes were coated with salt and kept in a tray in the fish market. What is the likely use of coating fish with salt?
    (a) It increases the moisture content of the fish allowing it to survive longer.
    (b) It stops the growth of bacteria by reducing the moisture content.
    (c) It increases the salt content of the fish that enhances its taste.
    (d) It reduces the weight of the fish making the transport easier.

    Subjective Questions

  15. Yash’s mother got him vaccinated with DTaP vaccine in his childhood.
    (a) Why is this vaccine given?
    (b) Explain how vaccines help to develop immunity against diseases.

  16. Manish took two pots X and Y. He placed fruit peels, tea leaves and vegetable waste in pot X and polythene bag, glass bottle and plastic toy in pot Y. He placed both the pots in an open area for 3- 4 weeks and observed the contents in both the pots.
    (a) What will Manish observe in pots X and Y?
    (b) What could be the reason for the above changes?
    (c) How can microorganisms be used to clean the environment?

  17. Why it is advisable to always keep the food covered?

  18. The given diagram depicts a nitrogen cycle in nature. Fill in the missing boxes by choosing the appropriate steps stated below.

    Case-Based Questions

  19. Shreeya mixed some maida flour with water and sugar and added a small amount of yeast powder in the mixture. She left the dough undisturbed for 4-5 hours.
    a) What will happen to the dough after 4-5 hours?
    (a) The dough will rise and increase in volume.
    (b) The dough will shrink and decrease in volume.
    (c) The dough will have no effect.
    (d) The dough will turn greenish and emit a foul smell.

    b) Which gas is produced by the yeast cells?
    (a) Nitrogen
    (b) Carbon dioxide
    (c) Oxygen
    (d) Carbon monoxide

    c) Why is yeast used in making bread, cakes, and pastries?

    d) To which group of microorganisms does yeast belong?
    (a) Fungi
    (b) Protozoa
    (c) Bacteria
    (d) Virus

  20. In 1929, Alexander Fleming was working on a culture of disease-causing bacteria. Suddenly he found the spores of a little green mould in one of his culture plates. He observed that the presence of mould prevented the growth of bacteria. In fact, it also killed many of these bacteria. This led to the discovery of an antibiotic.
    a) Define antibiotics.
    b) Which of the following correctly states the source organism and the antibiotic discovered by Fleming?
      Source organism Antibiotic
    (a) Fungus - Penicillium Penicillin
    (b) Bacteria - Penicillium Penicillin
    (c) Fungus - Streptomyces Streptomycin
    (d) Bacteria - Streptomyces Streptomycin

    c) Salina has cold and viral fever for the past 5 days. Her mother gave her antibiotics, but she is not recovering. What can be a likely reason for the same?
    (a) Antibiotics are not effective against viral infections.
    (b) Antibiotics are used against bacterial infections.
    (c) Antibiotics take time to cure the infection.
    (d) Antibiotics are used to prevent infections rather than cure them.

    Assertion-Reasoning Questions

    Below questions consist of two statements – Assertion (A) and Reason (R). Answer these questions selecting the appropriate option given below:
  21. Assertion (A): Preservatives are added to food to prevent the attack of microbes.
    Reason (R): Sodium benzoate and sodium metabisulphite are common preservatives.

  22. Assertion (A): Rhizobium bacterium lives in the root nodules of leguminous plants.
    Reason (R): Rhizobium and legumes share a parasitic relationship with each other.

  23. Assertion (A): We should not let water collect anywhere in the neighbourhood.
    Reason (R): Mosquitoes breed in stagnant water and spread diseases.

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