{"id":3645,"date":"2022-12-30T05:37:34","date_gmt":"2022-12-30T05:37:34","guid":{"rendered":"https:\/\/theexampillar.com\/ncert\/?p=3645"},"modified":"2023-01-31T07:01:57","modified_gmt":"2023-01-31T07:01:57","slug":"ncert-solutions-class-8-science-chapter-2-microorganisms-friend-and-foe","status":"publish","type":"post","link":"https:\/\/theexampillar.com\/ncert\/ncert-solutions-class-8-science-chapter-2-microorganisms-friend-and-foe\/","title":{"rendered":"NCERT Solutions Class 8 Science Chapter 2 Microorganisms : Friend and Foe"},"content":{"rendered":"

NCERT Solutions Class 8 Science\u00a0<\/span><\/h2>\n

The NCERT Solutions in English Language for Class 8 Science Chapter – 2 (Microorganisms: Friend and Foe) <\/strong>has been provided here to help the students in solving the questions from this exercise.<\/span><\/p>\n

Chapter – 2 (Microorganisms : Friend and Foe)<\/span><\/h2>\n

1. Fill in the blanks.
\n<\/strong>(a)<\/strong> Microorganisms can be seen with the help of a ____________.
\n(b)<\/strong> Blue-green algae fix __________ directly from the air and enhance the fertility of the soil.
\n(c)<\/strong> Alcohol is produced with the help of __________.
\n(d)<\/strong> Cholera is caused by __________.<\/span><\/p>\n

Answer – <\/strong><\/span><\/p>\n

(a)<\/strong> Microorganisms can be seen with the help of a Microscope<\/strong><\/span>.
\n(b)<\/strong> Blue-green algae fix Nitrogen<\/strong><\/span> directly from the air and enhance the fertility of the soil.
\n(c)<\/strong> Alcohol is produced with the help of Yeast<\/strong><\/span>.
\n(d)<\/strong> Cholera is caused by Bacteria- Vibrio cholera<\/strong><\/span>.<\/span><\/p>\n

2. Tick the correct answer.
\n<\/strong>(a) Yeast is used in the production of
\n<\/strong>(i) sugar
\n(ii) alcohol
\n(iii) hydrochloric acid
\n(iv) oxygen
\nAnswer – <\/strong>(ii)<\/strong> alcohol<\/span><\/p>\n

(b) The following is an antibiotic
\n<\/strong>(i) Sodium bicarbonate
\n(ii) Streptomycin
\n(iii) Alcohol
\n(iv) Yeast
\nAnswer – (ii)<\/strong> Streptomycin
\n<\/span><\/p>\n

(c) Carrier of malaria-causing protozoan is
\n<\/strong>(i) female Anopheles mosquito
\n(ii) cockroach
\n(iii) housefly
\n(iv) butterfly
\nAnswer – (i)<\/strong> female Anopheles mosquito
\n<\/span><\/p>\n

(d) The most common carrier of communicable diseases is
\n<\/strong>(i) ant
\n(ii) housefly
\n(iii) dragonfly
\n(iv) spider
\nAnswer – (ii)<\/strong> housefly
\n<\/span><\/p>\n

(e) The bread or idli dough rises because of
\n<\/strong>(i) heat
\n(ii) grinding
\n(iii) growth of yeast cells
\n(iv) kneading
\nAnswer – (iii)<\/strong> growth of yeast cells
\n<\/span><\/p>\n

(f) The process of conversion of sugar into alcohol is called
\n<\/strong>(i) nitrogen fixation
\n(ii) moulding
\n(iii) fermentation
\n(iv) infection
\nAnswer – (iii)<\/strong> fermentation<\/span><\/p>\n

3. Match the organisms in Column A with their action in Column B.<\/strong><\/span><\/p>\n

\n\n\n\n\n\n\n\n\n\n\n
A<\/strong><\/span><\/td>\nB<\/strong><\/span><\/td>\n<\/tr>\n
(i) Bacteria<\/span><\/td>\n(a) Fixing nitrogen<\/span><\/td>\n<\/tr>\n
(ii) Rhizobium<\/span><\/td>\n(b) Setting of curd<\/span><\/td>\n<\/tr>\n
(iii) Lactobacillus<\/span><\/td>\n(c) Baking of bread<\/span><\/td>\n<\/tr>\n
(iv) Yeast<\/span><\/td>\n(d) Causing malaria<\/span><\/td>\n<\/tr>\n
(v) A protozoan<\/span><\/td>\n(e) Causing cholera<\/span><\/td>\n<\/tr>\n
(vi) A virus<\/span><\/td>\n(f) Causing AIDS<\/span><\/td>\n<\/tr>\n
<\/td>\n(g) Producing antibodies<\/span><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n

Answer –<\/strong><\/span><\/p>\n

\n\n\n\n\n\n\n\n\n\n
A<\/strong><\/span><\/td>\nB<\/strong><\/span><\/td>\n<\/tr>\n
(i) Bacteria<\/span><\/td>\n(e) Causing cholera<\/span><\/td>\n<\/tr>\n
(ii) Rhizobium<\/span><\/td>\n(a) Fixing nitrogen<\/span><\/td>\n<\/tr>\n
(iii) Lactobacillus<\/span><\/td>\n(b) Setting of curd<\/span><\/td>\n<\/tr>\n
(iv) Yeast<\/span><\/td>\n(c) Baking of bread<\/span><\/td>\n<\/tr>\n
(v) A protozoan<\/span><\/td>\n(d) Causing malaria<\/span><\/td>\n<\/tr>\n
(vi) A virus<\/span><\/td>\n(f) Causing AIDS<\/span><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n

4. Can microorganisms be seen with the naked eye? If not, how can they be seen?<\/strong><\/span><\/p>\n

Answer –\u00a0 <\/strong>Microorganisms cannot be seen by the naked eye because they are very small. They can be seen by using a microscope.<\/span><\/p>\n

5. What are the major groups of microorganisms?<\/strong><\/span><\/p>\n

Answer –\u00a0 <\/strong>The major groups of microorganisms are as follows:<\/span><\/p>\n

    \n
  1. Bacteria<\/span><\/li>\n
  2. Fungi<\/span><\/li>\n
  3. Protozoans<\/span><\/li>\n
  4. Algae<\/span><\/li>\n
  5. Viruses<\/span><\/li>\n<\/ol>\n

    6. Name the microorganisms which can fix atmospheric nitrogen in the soil.<\/strong><\/span><\/p>\n

    Answer –\u00a0<\/strong>Bacteria like Rhizobium, Azotobacter and blue green algae like Anabaena and Nostoc can fix atmospheric nitrogen in the soil in form of nitrogenous compounds.<\/span><\/p>\n

    7. Write 10 lines on the usefulness of microorganisms in our lives.<\/strong><\/span><\/p>\n

    Answer –\u00a0 <\/strong>Microorganisms are very useful to us. They help us in following ways: <\/span><\/p>\n

      \n
    1. Microorganisms help us in food sector. They are used for curdling of milk, preparation of bread, cake, etc. <\/span><\/li>\n
    2. Microorganisms are used to produce alcohol at large scale. <\/span><\/li>\n
    3. They are also used to produce wine. <\/span><\/li>\n
    4. Yeast is used in bakeries. <\/span><\/li>\n
    5. They are also used as preservatives for food items. <\/span><\/li>\n
    6. They are used to make different medicines, especially the antibiotics. <\/span><\/li>\n
    7. Microorganisms are used to prepare vaccines for various diseases. <\/span><\/li>\n
    8. They are useful for agriculture sector, as they enhance the fertility of soil by fixing nitrogen. <\/span><\/li>\n
    9. They work as natural cleaners, as they decompose the dead bodies of plants and animals. <\/span><\/li>\n
    10. Microorganisms prepare manures by decomposing dead bodies of plants and animals.\u00a0\u00a0<\/span><\/li>\n<\/ol>\n

      8. Write a short paragraph on the harmful effects of microorganisms.<\/strong><\/span><\/p>\n

      Answer –\u00a0 <\/strong>Microorganisms are useful as well as harmful also, in fact, some microbes are very helpful but most of them are harmful to living beings.\u00a0\u00a0<\/span><\/p>\n