Class 8 science chapter 2 extra questions and Answers

In this page we have Class 8 science chapter 2 extra questions and Answers . Hope you like them and do not forget to like , social share and comment at the end of the page.

Very Short Answer type

(a) Name the types of bacteria?


Bacteria are classified regarding their shape and they are as follows:- i. Spirilla:- spiral-shaped bacteria ii. Cocci:- sphere-shaped bacteria iii. Bacilli:- rod-shaped bacteria iv. Vibrios:- curved-shaped bacteria

(b) What is fermentation?


The process in which the microorganisms are converted into alcohol or sugar is called fermentation.

(c) What is vaccination?


A technique that is used to increase the immunity of the body to fight against disease-causing microorganisms is called vaccination or immunization.

(d) What is pasteurization?


A technique that is used to preserve milk is called pasteurization.

(e) What is an electron microscope?


A special type of microscope that can detect organisms of much smaller size like viruses.

2. Complete the table

Complete the following table by using the correct option:

a. Virus
b. Air
c. Vaccination
d. Contaminated food or water

Class 8 science chapter 2 extra questions and Answers


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

3. Short answer type questions (HOTS)

(i) What are microorganisms ?


Living organisms that are too tiny to be seen with the unaided human eyes. They only can be seen through Microscope.

(ii) Describe algae in brief with examples?


Algae are plant like organisms & have cell wall around them. They are autotrophs as they contain chlorophyll.

Ex: Spirogyra, volvox

(iii) Difference between algae & protozoa ?


§ Have cell wall
§ Possesses chlorophyll
§ Unicellular or Multicellular
§ No cell wall
§ Heterotrophic
§ Unicellular

(iv) How viruses behave inside the host?


Viruses when enters hosts body they start behaving like a living organisms. It reproduces & carries out other life processes inside host body.

(v) What is the official name of Coronavirus?


Official name of Coronavirus is Covid 19 or SARS-COV-2.

(vi) Write any two uses of microorganisms?


  • Microorgansim Lactobacillus converts milk into curd.
  • Fungus penicillium used as antibiotics in medicinal field

(vii) Describe Fermentation?


Process by which the microorganisms converts a sugar into an acid or an alcohol is called fermentation.

(viii) Define Pathogens? And give some examples of air borne diseases?


Microorganisms that cause diseases are called pathogens.

Ex: Common cold , Tuberculosis

4. Long Answer type Question

(i) Describe Bacteria & it’s types with diagrams?


Bacteria are unicellular organisms. They live together in colonies of millions.Most of them are harmless but few of them are disease causing bacterias such as Cholera & Tuberculosis.

Based on their shapes bacteria are classified into four types-

Spirilla- Spiral bacteria

Cocci- Sphere Shaped Bacteria

Bacilli- Rod Shaped Bacteria

Vibrios- Comma Shaped Bacteria

(ii) What do you mean by food preservation? Explain any four food preservation methods.


Our food can be contaminated by microorganisms. Food preservation is the process of making sure our food doesn't get contaminated by microorganisms. Food can be preserved in a number of ways. Some of food preservation methods are:

  1. Drying: It reduces the moisture in food, which stops the growth of microorganisms.
  2. Refrigeration and freezing: This growth of microorganisms is slowed by low temperatures. As a result, it is suitable for human consumption.
  3. By oil and vinegar : Using oil and vinegar to preserve pickles minimizes spoiling since bacteria cannot survive in such an environment.
  4. Using common salt and sugar: Dry salt is applied to meat and fish to prevent microbial growth. Sugar lowers moisture content, preventing the formation of microorganisms that ruin food.

(iii) What exactly are antibiotics? What precautions should be taken when using antibiotics?


Antibiotics are medications that are preferred during illness. They are used to treat bacterial infections in humans and animals. They either kill the bacteria or make it hard for the bacteria to grow and multiply. Precautions to take while using antibiotics include:
(i) They should only be used with the advice of a trained doctor.
(ii) The doctor-recommended course must be completed.
(iii) They should only be taken in the recommended doses.
(iv) Do not take these medications when they are unnecessary or in the incorrect dosage. It may make the drug less effective if you need it in the future.
(v) Unnecessary antibiotic use can kill beneficial microorganisms in the body.

(iv) Explain through a brief note Can microorganisms be harmful to humans?


Microorganisms can be harmful in a number of ways. Some microorganisms, for example, cause diseases in humans, other animals, and plants. Pathogens are microorganisms that cause disease. Pathogens can be bacteria, viruses, protozoa, or fungi, among other things.

Diseases caused by microorganisms include tuberculosis (TB), tetanus, diphtheria, whooping cough, cholera, typhoid, AIDS, food poisoning, malaria, smallpox, and chickenpox, etc..

Apart from causing disases some microorganisms contaminate food, clothing, and leather items.

5. Multiple Choice Questions (MCQ)

(1) Branch of science that involves the study of microorganisms is called
(I) Biology
(II) Microbiology
(III) Zoology
(IV) None of these

(2) Algae are
(I) Unicellular
(II) Multicellular
(III) Unicellular or Multicellular
(IV) None of these

(3) Which one of them is not an algae
(I) Volvox
(II) Chlamydomonas
(III) Trypnosoma
(IV) Spirogyra

(4) The Bread Mould
(I) Rhizopus
(II) Agaricus
(III) Yeast
(IV) Penicillium

(5) Viruses that can infect bacteria
(I) Influenza virus
(II) Hepatitis virus
(III) Poliovirus
(IV) Bacteriophages

(6) Microorganisms which are used for medicines
(I) Penicillium
(II) Streptomycin
(III) Oxytetracycline
(IV) All of them

(7) Which one of them is an example of viral disease
(I) Cholera
(II) Common cold
(III) Malaria
(IV) Typhoid

(8) Which one of them is not an example of communicable disease
(I) Ringworm
(II) Tuberculosis
(III) Asthma
(IV) Anthrax

(9) Which one of them is an example of plant disease
(I) Citrus canker
(II) Malaria
(III) Cholera
(IV) Typhoid

(10) The micro-organism which is capable of converting sugar into alcohol and carbon dioxide is :
(I) bacterium
(II) fungus
(III) alga
(IV) protozoan


(1) Microbiology

(2) Unicellular or Multicellular

(3) Trypnosoma

(4) Rhizopus

(5) Bacteriophages

(6) All of them

(7) Common cold

(8) Asthma

(9) Citrus canker

(10) fungus


This Class 8 science chapter 2 extra questions and Answers sheet is prepared keeping in mind the latest syllabus of CBSE . This has been designed in a way to improve the academic performance of the students. If you find mistakes , please do provide the feedback on the mail.

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