CBSE Worksheet for Chapter - 2 Microorganisms: Friend and Foe class 8

Worksheets For class 8

Q1. Microorganisms are

  1. Both living and nonliving organisms we cannot see.
  2. Both living and non living which we can see with the help of microscope.
  3. Non living organisms that can only be seen through microscope.
  4. Living organisms that can only be seen through microscope.

Q2. Process by which Yeast produces CO2 during baking

  1. Fermentation
  2. Oxidation
  3. Preservation
  4. Vaccine

Q3. Pasteurisation is a method used for preserving

  1. Milk
  2. Jams
  3. Pickles
  4. Grains

Q4. Alcohol from sugar is produced by

  1. Rhizobium
  2. Plasmodium
  3. Lactobacillus
  4. Yeast

Q5. What are the major groups of microorganisms? Give two examples of each.

Q6. To which category of microorganisms does the given organism belongs – Mushroom and Yeast.

Q7. Name an antibiotic manufactured from fungi.

Q8. Which organism makes the bread soft and fluffy. Explain

Q9. Which bacterium is responsible for curdling of milk?

Q10. Write a note on the usefulness of microorganisms in our lives.


Q1. 2. Both living and non living we can see with the help of microscope

Q2. 1. Fermentation

Q3. 1. Milk

Q4. 4. Yeast

Q5. The major groups of micro-organisms are bacteria, fungi, protozoans, algae, and viruses.

Q6. Mushroom and Yeast belongs to the group of fungi.

Q7. Penicillin is an antibiotic produced from fungi Penicillium.

Q8. Yeast is a fungi that undergoes anaerobic respiration during which it releases CO2. This CO2 raises the dough and makes the bread soft and fluffy.

Q9. Lactobacillus is responsible for curdling of milk.

Q10. Microorganisms are an integral part of our life. They are useful to us in various ways such as-

  1. Fungi and bacteria are decomposers and natural scavengers. They help in converting dead and decaying complex organic matter into simpler ones which one useful for the growth of plants.
  2. Bacteria like Rhizobium and Azotobacter present in the root nodules of leguminous plants help in fixing atmospheric nitrogen into soluble nitrates and nitrites which are useful fertilizers for plants.
  3. In the food industry, Lactobacillus is used for the fermentation of milk into curd. Also, Acetobacter is used for the production of acetic acid. Yeast is used in distilleries for the fermentation of fruit juices, and molasses to make alcoholic drinks. In the bakery, Yeast is used to raising the dough for making bread.
  4. Antibiotics like penicillin and streptomycin are manufactured with the help of microbes like Penicillium and Streptococcus.
  5. Bacteria like Pseudomonas and Nitrosomonas are useful for sewage treatment and breaking down hydrocarbon in oil spills present in marine water.

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