NCERT Class VIII Science Solutions: Chapter 2-Microorganisms: Friend and Foe Part 1

Download PDF of This Page (Size: 586K)

Question 1:

Fill in the blanks:

  1. Microorganisms can be seen with the help of a ____________.

  2. Blue green algae fix __________ directly from air to enhance fertility of soil.

  3. Alcohol is produced with the help of __________.

  4. Cholera is caused by __________.

Answer:

  1. Microorganisms can be seen with the help of a microscope.

  2. Blue green algae fix nitrogen directly from air to enhance fertility of soil.

  3. Alcohol is produced with the help of microorganisms.

  4. Cholera is caused by bacteria.

Question 2:

Tick the correct answer:

  1. Yeast is used in the production of

    1. Sugar

    2. Alcohol

    3. hydrochloric acid

    4. oxygen

  2. The following is an antibiotic

    1. Sodium bicarbonate

    2. Streptomycin

    3. Alcohol

    4. Yeast

  3. Carrier of malaria-causing protozoan is

    1. female Anopheles mosquito

    2. cockroach

    3. housefly

    4. butterfly

  4. The most common carrier of communicable diseases is

    1. Ant

    2. Housefly

    3. Dragonfly

    4. Spider

  5. The bread or idle dough rises because of

    1. Heat

    2. Grinding

    3. growth of yeast cells

    4. kneading

  6. The process of conversion of sugar into alcohol is called

  7. nitrogen fixation

  8. Eluding

  9. Fermentation

  10. infection

Answer:

  1. Alcohol

  2. Streptomycin

  3. Female Anopheles mosquito

  4. Housefly

  5. Growth of yeast cells

  6. Fermentation

Question 3:

Match the organisms in Column I with their action in Column II.

Match the Organisms in Column I with Their Action in Column II (Q)
Match the organisms in Column I with their action in Column II (Q)

Column I

Column II

Bacteria

Fixing Nitrogen

Rhizobium

Setting of curd

Lactobacillus

Baking of bread

Yeast

Causing Malaria

A protozoan

Causing Cholera

A Virus

Causing AIDS

Producing antibodies

Answer:

Match the Organisms in Column I with Their Action in Column II (A)
Match the organisms in Column I with their action in Column II (A)

Column I

Column II

Bacteria

Causing Cholera

Rhizobium

Fixing Nitrogen

Lactobacillus

Setting of curd

Yeast

Baking of bread

A protozoan

Causing Malaria

A Virus

Causing AIDS

Question 4:

Can microorganisms be seen with the naked eye? If not, how can they be seen?

Answer:

No, microorganisms cannot be seen by naked eye as they are very small and are called microbes. They can be seen with the help of microscope.

As showing in image is a result for microscope

Result for Microscope

As showing in image is a result for microscope

So, micro-organisms are very small organisms that cannot see with naked eye, but can be seen with the help of microscope.

Micro-organisms may be unicellular or multicellular; it may live alone or communities.

Question 5:

What are the major groups of microorganisms?

Answer:

Microorganisms are microscopic organisms that exist as unicellular, multicellular or cell clusters.

Microorganisms are widespread in nature and are beneficial to life, but some can cause serious harm. They can be divided into six major types: bacteria, archaic, fungi, protozoa, algae, and viruses.

This diagram shows types of microorganisms

Diagram Shows Types of Microorganisms

This diagram shows types of microorganisms