Question.1: Fill in the blanks:
can be seen with the help of a
fix _________ directly from air to enhance
is produced with the help of ________.
is caused by _______.
microscope (b) atmospheric
oxygen (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
(b) The following is an antibiotic
Sodium bicarbonate (ii)
(iii) Alcohol (iv) Yeast
(c) Carrier of malaria-causing protozoan
(i) female Anopheles mosquito (ii)
(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
(i) heat (ii) grinding
(iii) growth of yeast cells (iv)
(f) The process of conversion of sugar
into alcohol is called
(i) nitrogen fixation (ii) moulding
(iii) fermentation (iv) infection
ii (b) ii (c) i (d) ii (e) iii (f) iii.
Question.3: Match the organisms in
column I with their actions in column
e (ii) a (iii) b (iv) c (v) d (vi) f.
Question.4: Can microorganisms be seen
with the naked eye? If not, how can they
microorganisms can not be seen with
naked eyes. They are so small that they
can not be seen with naked eyes. A
microscope is required to see these
Question.5: What are the major groups of
are mainly divided into five groups -
Bacteria, Fungi, Protozoa, Algae and
Question.6: Name the microorganisms
which can fix atmospheric nitrogen in
type of bacteria and blue
fix atmospheric nitrogen. For
like- Rhizobium, Azotobacter and blue
greenalgae like- Anabaena, Nostoc.
Question.7: Write ten lines on the
usefulness of microorganisms in our
are very useful to us. Some of their
usefulness is as follows:
1.They are used in the preparation of
curd, bread and cake. Lactobacillus
promotes the formation of curd and
Yeast in the baking industry.
2.Commercially microorganisms are used
for the large scale production of
alcohol, wine and vinegar.
3.Yeast is used for commercial
production of alcohol and wine while,
Acetobacter bacteria cause conversion of
alcohol to vinegar.
4.In medical industry antibiotics are
made from microorganisms like - some
fungi and bacteria.
5.Microorganisms are also used to
prepare vaccines for various diseases.
6.Microorganisms (bacteria) help us in
cleaning of our environment as they decomposethe
dead bodies of plants and animals and
other organic wastes.
7.In agriculture, microorganisms are
used to increase soil fertility by
8.Some bacteria like - Rhizobium and
are able to fix nitrogen from the
atmosphere to enrich soil and thus
increase its fertility.
9.It is due to the activities of
microorganisms because of which we are
able to prepare manure by decomposing organic
wastes and dead bodies of plants and
10.In food industry, they are used as
preservatives for food items. Further,
some fungi are eaten raw as food such
Question.8: Write a short paragraph on
the harms caused by microorganisms.
can be very harmful to us, as they cause
human and animal diseases. Diseases in
humans like common cold, tuberculosis,
measles, chicken pox, polio, cholera,
typhoid, hepatitis-B, malaria etc. all
are caused by microorganisms. Some
serious diseases like- Anthrax is a
dangerous human and cattle disease
caused by a bacterium. Microbes grow on
food products and render them unfit for
consumption. Consumption of such food
causes food poisoning. Microbes also
spoil clothes and leather products.
Microorganisms cause diseases of plants
like - blights in potatoes, sugarcanes,
oranges then, rust of wheat citrus,
canker etc. They also reduce the crop
Question.9: What are antibiotics? What
precautions must be taken while taking
Answer: Medicines taken
to kill or stop the growth of harmful or
disease causing microbes in human body
are called antibiotics. Antibiotics are
very useful as only antibiotics can save
us from many microbial infections and
diseases. Antibiotics are made from
fungi and bacteria. Alexander Fleming
discovered the first antibiotic called Penicillin in
1929. Now-a-days a number of
antibiotics are used to cure a variety
of human, animal and plant diseases.Streptomycin,
Erythromycin, Tetracycline etc
are some commonly used antibiotics.
Precautions for taking antibiotics:
Antibiotics should only be taken when
advised by a qualified physician.
Moreover it should only be taken when
needed otherwise; they became less
effective for future use. Also
antibiotics taken unnecessarily may kill
the beneficial bacteria in the body.