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INTRODUCTION - Chapter 2 Microorganisms Friend & Foe class 8 ncert solutions Science - SaraNextGen [2024]


Question 1:

Fill in the blanks:

(a) Microorganisms can be seen with the help of a _________.

(b) Blue green algae fix _________ directly from air to enhance fertility of soil.

(c) Alcohol is produced with the help of _________.

(d) Cholera is caused by _________.

Answer:

(a) Microorganisms can be seen with the help of a _ microscope _.

(b) Blue green algae fix __ nitrogen _ directly from air to enhance fertility of soil.

(c) Alcohol is produced with the help of _ yeast _.

(d) Cholera is caused by _ bacteria _.

Question 2:

Tick the correct Answer:

(a) Yeast is used in the production of

(i) sugar (ii) alcohol

(iii) hydrochloric acid (iv) oxygen

(b) The following is an antibiotic

(i) Sodium bicarbonate (ii) Streptomycin

(iii) Alcohol (iv) Yeast

(c) Carrier of malaria-causing protozoan is

(i) female Anopheles mosquito (ii) cockroach

(iii) housefly (iv) butterfly

(d) The most common carrier of communicable diseases is

(i) ant (ii) housefly

(iii) dragonfly (iv) spider

(e) The bread or idli dough rises because of

(i) heat (ii) grinding

(iii) growth of yeast cells (iv) kneading

(f) The process of conversion of sugar into alcohol is called

(i) nitrogen fixation (ii) moulding

(iii) fermentation (iv) infection

Answer:

(a) Yeast is used in the production of

(i) sugar (ii) alcohol&mnTick;

(iii) hydrochloric acid (iv) oxygen

(b) The following is an antibiotic

(i) sodium bicarbonate (ii) streptomycin&mnTick;

(iii) alcohol (iv) yeast

(c) Carrier of malaria-causing protozoan is

(i) female Anopheles mosquito&mnTick; (ii) cockroach

(iii) housefly (iv) butterfly

(d)The most common carrier of communicable diseases is

(i) ant (ii) housefly&mnTick;

(iii) dragonfly (iv) spider

(e)The bread or idli dough rises because of

(i) heat (ii) grinding

(iii) growth of yeast cells&mnTick; (iv) kneading

(f) The process of conversion of sugar into alcohol is called

(i) nitrogen fixation (ii) moulding

(iii) fermentation&mnTick; (iv) infection

Question 3:

Match the organisms in Column I with their action in Column II.

Column I

Column II

(i)

Bacteria

(a)

Fixing nitrogen

(ii)

Rhizobium

(b)

Setting of curd

(iii)

Lactobacillus

(c)

Baking of bread

(iv)

Yeast

(d)

Causing malaria

(v)

A protozoan

(e)

Causing cholera

(vi)

A virus

(f)

Causing AIDS

 

(g)

Producing antibodies

Answer:

 

Column I

Column II

(i)

Bacteria

(e)

Causing cholera

(ii)

Rhizobium

(a)

Fixing nitrogen

(iii)

Lactobacillus

(b)

Setting of curd

(iv)

Yeast

(c)

Baking of bread

(v)

A protozoan

(d)

Causing malaria

(vi)

A virus

(f)

Causing AIDS

 

Can microorganisms be seen with the naked eye? If not, how can they be seen?Question 4:

Answer:

Micro-organisms are too small to be seen through naked eyes. They can be seen with the help of a magnifying glass or microscope.

For example, fungus that grows on bread is so small that it can be seen only with the help of a magnifying glass or microscope.

Also Read : Page-No-30:-Chapter-2-Microorganisms-Friend-&-Foe-class-8-ncert-solutions-Science

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