Class 8 Micro-organisms Q-Answers

Class 8 Science Home Page

Previous       Next


Fill in the Blanks

  1. ___________ make up the largest living organisms in the planet.
  2. Round shaped bacteria are called ______.
  3. The shape of Vibrio cholera is ______.
  4. _______ contain chlorophyll and carry out the process of photosynthesis just like plants.
  5. _______ can reproduce and multiply only inside the cells of other organisms.

Multiple Choice Questions

  1. Which of the following microorganisms are autotrophs?
    1. HIV
    2. Plasmodium
    3. Mushroom
    4. Blue-green algae
  2. Microorganisms are found in
    1. Air
    2. Water
    3. Soil
    4. All of these
  3. Coli is a bacteria that has a
    1. Rod shape
    2. Comma shape
    3. Spherical shape
    4. All of these
  4. Algae can make their own food due to the presence of
    1. Haemoglobin
    2. Chlorophyll
    3. Microbes
    4. Preservatives
  5. An edible fungus is
    1. Mushroom
    2. Paramecium
    3. Amoeba
    4. Spirogyra

Short Answer Type Questions

  1. Name the device that produces enlarged images of very small objects.
  2. Who observed micro-organism for the first time using a microscope?
  3. Name a fungus that is microscopic and can not be seen through naked eyes.
  4. Name a fungus that can be easily seen through naked eyes.
  5. Name a freshwater alga.

Long Answer Type Questions

  1. Name the major groups of microorganisms? Give two examples of each.
  2. Classify bacteria, based on their shapes.


Fill in the Blanks

  1. Micro-organisms
  2. Cocci
  3. spiral
  4. Algae
  5. Virus

Answers: Multiple Choice Questions

  1. d
  2. d
  3. a
  4. b
  5. a

Short Answer Type Questions

  1. Microscope
  2. Leeuwenhoek
  3. Yeast
  4. Mushroom
  5. Spirogyra

Answers: Long Answer Type Questions

  1. The major groups of organisms are:
    1. Bacteria: E.g.
    2. Fungi: E.g.Yeast and Mushroom
    3. Protozoa: E.g. Amoeba and Paramecium
    4. Algae: E.g. Spirogyra, Chlamydomonas
    5. Virus: E.g. HIV, Rous sarcoma virus
    6. Based on the shape, they are classified into three groups:
    7. Rods: They are rod-shaped bacteria and are called bacilli. An example includes Coli, Salmonella typhi etc.
    8. Spherical: They are round in shape and are called cocci. An example includes Staphylococci, Diplococcus.
    9. Spirals: They are spiral in shape and are called spirilla. Example includes Vibrio cholera and Treponema pallidum

By now, you have learnt that there is a huge variety of microorganisms on earth. These organisms play an important role in our lives. Some of them are beneficial in many ways and some are harmful and cause diseases. Let us know discuss, how these microorganisms are beneficial to mankind and how they keep the planet earth running?


Micro-organisms are useful in following ways:


  1. Bacteria help us in making food.
    1. Making curd: Microorganisms play an important role in the formation of curd. Have you ever seen your mother or grandmother adding a teaspoonful of curd to lukewarm milk? Why does she so? She adds curd to the warm milk because curd contains a bacterium called Lactobacillus multiplies and converts the milk into curd.
    2. Making Cheese: Similarly, there is another bacterium called Rennin, which is used for making cheese from milk. Rennin ferments the milk sugar to produce lactic acid. This lactic acid separates the milk sugar producing lactic acid. This lactic acid separates the milk into solid curd and liquid called milk whey. Whey is the watery part of the milk that is separated from curd during cheese formation. Later, this separated curd from the milk is used to make cheese.
    3. In Baking of cake or bread: Yeast is commonly used in the baking of cake or bread, by the process of fermentation. Fermentation is the process of converting a complex organic substance into a simple substance with the action of bacteria or yeast.


Class 8 Science Home Page

Previous       Next