GSEB Solutions Class 8 Science Chapter 2 Microorganisms: Friend and Foe

   

Gujarat Board GSEB Textbook Solutions Class 8 Science Chapter 2 Microorganisms: Friend and Foe Textbook Questions and Answers,Notes Pdf.

Gujarat Board Textbook Solutions Class 8 Science Chapter 2 Microorganisms: Friend and Foe

Gujarat Board Class 8 Science Microorganisms: Friend and Foe Textbook Questions and Answers

GSEB Solutions Class 8 Science Chapter 2 Microorganisms: Friend and Foe

Question 1.
Fill in the blanks:
(a) Microorganisms can be seen with the help of a ________ .
(b) Some bacteria fix ________ directly from air and enhance fertility of soil.
(c) Alcohol is produced with the help of ________.
(d) Cholera is caused by ________.
Answer:
(a) microscope
(b) nitrogen
(c) yeast
(d) bacteria.

Question 2.
Tick (/) the correct answer:
(a) Yeast is used in the production of –
(i) sugar
(ii) alcohol
(iii) hydrochloric acid
(iv) oxygen.
Answer:
(ii) alcohol

(b) The following is an antibiotic –
(i) sodium bicarbonate
(ii) streptomycin
(iii) alcohol
(iv) yeast.
Answer:
(ii) streptomycin

GSEB Solutions Class 8 Science Chapter 2 Microorganisms: Friend and Foe

(c) Carrier of malaria-causing protozoan is –
(i) female Anopheles mosquito
(ii) cockroach
(iii) housefly
(iv) butterfly.
Answer:
(i) female Anopheles mosquito

(d) The most common carrier of communicable diseases is –
(i) ant
(ii) housefly
(iii) dragonfly
(iv) spider.
Answer:
(ii) housefly

(e) The bread or idli dough rises because of –
(i) heat
(ii) grinding
(iii) growth of yeast cells
(iv) kneading.
Answer:
(iii) growth of yeast cells

(f) The process of conversion of sugar into alcohol is called –
(i) nitrogen fixation
(ii) moulding
(iii) fermentation
(iv) infection
Answer:
(iii) fermentation.

Question 3.
Match the organisms in Column A with their action in Column B.
GSEB Solutions Class 8 Science Chapter 2 Microorganisms Friend and Foe
Answer:
GSEB Solutions Class 8 Science Chapter 2 Microorganisms Friend and Foe

Question 4.
Can microorganisms be seen with the naked eyes? If not, how can they be seen?
Answer:
Microorganisms cannot be seen with the naked eyes. They can be seen with the help of a microscope.

GSEB Solutions Class 8 Science Chapter 2 Microorganisms: Friend and Foe

Question 5.
What are the major groups of micro-organisms?
Answer:
There are following four major groups of microorganisms:

  • Bacteria
  • Fungi
  • Protozoa
  • Algae

Question 6.
Name the microorganisms which can fix atmospheric nitrogen in the soil.
Answer:
Bacteria, like rhizobium and blue green algae can fix atmospheric nitrogen in soil.

Question 7.
Write 10 lines on the usefulness of microorganisms in our lives.
Answer:
Uses of microorganisms:

  • Microorganisms help in the preparation of curd, bread, cake, etc.
  • Yeasts are used for commercial pro-duction of wine and alcohol.
  • They are used to control many plant diseases.
  • They are used in making vinegar.
  • They act as cleaning agent and decom-pose the waste products into manure.
  • They destroy the plant and animal dead bodies by decomposing them.
  • They increase soil fertility by fixing nitrogen of atmosphere.
  • They are used in making medicines like antibiotics and vaccines.
  • They are used as preservatives for food items.
  • They help in various metabolic activities in our body.

GSEB Solutions Class 8 Science Chapter 2 Microorganisms: Friend and Foe

Question 8.
Write a short paragraph on the harmful effects of microorganisms.
Answer:
Microorganisms are also very harmful to us. They cause a number of diseases in human as well as in other animals. Common cold, Tuberculosis, Measles, Chicken Pox, Polio, Cholera, Typhoid, Hepatitis B, Malaria, are some common human diseases caused by microorganisms. Anthrax is a serious disease in animals caused by microbes.

They also make food items unfit for use by food poisoning. They also spoil clothes and leather products. They also cause diseases in plants like blights in potatoes, sugarcanes, oranges etc. They also reduce the crop production.

Question 9.
What are antibiotics? What precautions must be taken while taking antibiotics?
Answer:
The medicines which kill or stop the growth of microorganisms in our body are called antibiotics. These are very useful to us, as they protect us from the harmful affect of microorganisms. Antibiotics are made from bacteria and fungi. The penicillin is the first antibiotic, discovered by Alexander Fleming in 1929.

These days a number of antibiotics are used to cure various human and animal diseases. Streptomycin, Tetracycline, Erythromycin etc. are some common antibiotics. Precautions: We should take antibiotics only by the advice of a qualified doctor. Antibiotics should only be taken when needed. Otherwise, they may be harmful and become less effective in future.

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