NCERT Solution class 8 Science Chapter-2

NCERT Solution class 8 Science Chapter-2


  1. Fill in the blanks.

(a) Mircroorganisms can be seen with the help of a

—mgnificiant glass—.

(b) Blue green algae fix— nitragen— directly from air to enhance fertilityof soil.

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

(d) Cholera is caused by— bacteria.—



  1. Tick the correct answer.

(a)  Yeast is used in the production of

(i) suger     (ii) alcohol   (iii) hydrochloric acid   (iv)oxgen

Ans (ii)  alcohol

(b) The following is an antibiotic

(i) sodium bicarbonate   (ii) streptomycin  (iii) alcohol  (iv) yeast

Ans (ii) streptomycin

(c) Carrier of mamaria- protozan is

(i) female Anopheles mosquito   (ii) cockroach   (iii) housefly   (iv) butterfly

Ans (i) female Anopheles mosquito


The most common carrier of communicable

diseases is

(i) ant   (ii) housefly  (iii) dragonfly  (iv) spider

Ans (ii) housefly

(e) The bread or idli dough rises because of

(i) heat  (ii) grinding  (iii) growth of yeast cells

(iv) kneading

Ans (iii) growth of yeast cells

(f)  The process of conversion of sugar into alchol is


(i) nitrogen fixation  (ii) moulding

(iii) fermentation  (iv) infection

Ans (iii) fermentation


  1. Match the organisms in column A with their action

in column B.

A                                            B

(i) Bacteria                            (e) Caunsing cholera

(ii) Rhizobium                       (a) Fixing nitrogen

(iii) Lctobacillus                    (b) Setting of curd

(iv) Yeast                                (c) Banking of bread

(v) A protozoan                     (d) Causing malaria

(vi) A virus                              (f) Causing AIDS


Q4.  Can microorganisms be seen with the naked eye

if not, how can they be seen ?

Ans. No, mocroorganisms cannot be seen by naked

eye as they are very small and are called


Q5. What are the major groups of microorganisms ?

Ans. Microorganisms are classified into four major

group are bacteria, fungi, protozoa and some

algae. They vary in size and mode of nutrition.



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