Microorganisms: Friend Or Foe, Class 8th Notes

THESE NOTES ARE PREPARED ACCORDING TO JKBOSE SYLLABI IN SIMPLIFIED AND CONCISE PATTERN

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                                Exercise

Q. Fill in the blanks

i. Microorganisms can be seen with the help of the MICROSCOPE

ii. Blue green algae fix ..NITROGEN. directly from air to enhance fertility of soil

iii. Alcohol is produced with help of .YEAST.

iv. Cholera is caused by ...BACTERIA

Q. Tick the correct answer:

a. Yeast is used in production of ......
A. Sugar     B. Alcohol   C. HCl    D. Oxygen

ANS: B. ALCOHOL

b. The following is an antibiotic
A. Sodium bicarbonate    B. Streptomycin
C. Alcohol           D. Yeast

ANS: STREPTOMYCIN

c. Carrier of malaria causing protozoan is
A. Anopheles Mosquito     B. Cockroach   C. Housefly D. Butterfly

ANS: ANOPHELES MOSQUITO

d. Most common carrier of communicable diseases is
A. Ant     B. Housefly    C. Dragonfly   D. Spider

ANS: HOUSEFLY


e. The bread or idli dough rises because of
A. Heat   B. Grinding   C. Yeast cells  D. Kneading

Ans: YEAST CELLS

f. The process of conversion of sugar into alcohol is called
A. Nitogen fixation   B. Moulding   C. Fermentation    D. Infection

Ans:   FERMENTATION




Q. Match the following

Ans:

Bacteria  :    Causing cholera
Rhizobium :  Fixing nitrogen
Lactobacillus: Setting of Curd
Yeast:                Baking of bread
Protozoan:        Causing Malaria
Virus:      Causing AIDS

Q. Can microorganisms be seen with naked eye? If not how can they be seen?

Ans: No, the microorganisms cannot be seen with Naked eye.
We can see microorganisms with the help of Microscope.

Q. What are the major groups of microorganisms?

Ans: The major groups of microorganisms are:
a. Virus,
b. Bacteria,
c. Protozoan,
d. Fungi,
e. Algae.

Q. Name the microorganisms which can fix atmospheric nitrogen in the soil?

Ans: The microorganisms which can fix atmospheric nitrogen in the soil are species of Rhizobium, some bluegreen algae, azobacter etc.

Q. Write ten lines of usefulness of microorganisms in our lives?

Ans: Microorganisms are useful to us in many ways.
1. Microorganisms help in decomposition of waste
2. They help to increase fertility of soil.
3. They are used to prepare curd, bread.
4. They are used to produce antibiotics.
5. They are used to produce vaccines
6. They are used to produce alcohol
7. They are used to clean industrial wastage.
8. They are now also used to clean plastics and petrol
9. They are used to prepare pickles, cheese etc. 
10. They are used in research.

Q. Write a short paragraph on harms caused by microorganisms?

Ans: Few microorganisms are harmful to humans, plants and animals.
They cause diseases like small pox, cholera, tuberculosis, malaria in humans. 
They cause decay of food and make it unfit for consumption.
They spoil products like leather, cotton, wood etc.

Q. What are antibiotics? What precautions must be taken while taking antibiotics?

Ans:  Antibiotics are the chemical substances produced by microorganisms that kill other microorganisms.
The antibiotics are used as medicine.
They were first discovered by Alexander Fleming.

Precautions:
1. Antibiotics should be taken only when doctor advises.

2. Full course of antibiotics should be taken. 

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