NCERT Class VIII Science Solutions: Chapter 2-Microorganisms: Friend and Foe Part 3 (For CBSE, ICSE, IAS, NET, NRA 2022)

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Question 15:

Polio drops are not given to children suffering from diarrhoea. Why?


If the child is suffering from diarrhoea, the orally given vaccine may be excreted out because of frequent motions.

Question 16:

Paheli watched her grandmother making mango pickle. After she bottled the pickle, her grandmother poured oil on top of the pickle before closing the lid. Paheli wanted to know why oil was poured. Can you help her understand why?


Oil prevents bacteria from attacking the pickle and spoiling it.


Question 17:

Match the microorganisms given in the Column A to the group to which they belong in Column B.

Match the Microorganisms Given in the Column a and Column B. (Q)
Column AColumn B
  1. Paramecium
  • Bacteria
  • Spirogyra
  • Fungi
  • Aspergillus
  • Protozoa
  • Lactobacillus
  • Algae


Match the Microorganisms Given in the Column a and Column B. (A)
Column AColumn B
  1. Paramecium
iv Algae
  1. Spirogyra
iii Protozoa
  1. Aspergillus
i Bacteria
  1. Lactobacillus
ii Fungi

Question 18:

Classify the following into friendly and harmful microorganisms.

Yeast, malarial parasite, Lactobacillus, bread mould, Rhizobium, Bacillus anthracis

Friendly and Harmful (Q)


Friendly and Harmful (A)
YeastMalarial parasite
LactobacillusBread mould
RhizobiumBacillus anthracis

Question 19:

While returning from the school, Boojho ate cheat from a street hawker. When he reached home, he felt ill and complained of stomach ache and fell ill. What could be the reason?


The probable reason is that the chat was contaminated b pathogenic microbes due to unhygienic conditions near the shop or the utensil used for serving could have contaminated.

Question 20:

What will happen to ‘pooris’ and ‘unused kneaded flour’ if they are left in the open for a day or two?


The ‘unused kneaded flour’ , if left in warm conditions, gets infected by microbes which cause fermentation and spoils the flour. The pooris would remain in relatively good condition because they were deep fried in heated oil that kills microbes.

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