NCERT Solution class 8 Science Chapter-2
Science CIASS VIII CHAPTER-2
- 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.—
- 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
(d) 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
called
(i) nitrogen fixation (ii) moulding
(iii) fermentation (iv) infection
Ans (iii) fermentation
- 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
microscope.
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.