1. Fill in the blanks.
(a) Microorganisms can be seen with the help of a ____________.
Ans: Magnifying glass.
(b) Blue green algae fix __________ directly from air and enhance fertility
of soil.
Ans: Nitrogen
(c) Alcohol is produced with the help of __________.
Ans: Yeast.
(d) Cholera is caused by __________.
Ans: Vibrio cholerae.
2. Tick the correct answer.
(a) Yeast is used in the production of
(i) sugar (ii) alcohol (iii) hydrochloric acid (iv) oxygen
Ans: ii) alcohol
(b) The following is an antibiotic
(i) Sodium bicarbonate (ii) Streptomycin (iii) Alcohol (iv) Yeast
Ans: ii) Streptomycin.
(c) Carrier of malaria-causing protozoan 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 cell.
(f) The process of conversion of sugar into alcohol is called
(i) nitrogen fixation (ii) moulding (iii) fermentation (iv) infection
Ans: iii) fermentation.
3. Match the organisms in Column A with their action in
Column B.
A B
(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
Ans- A B
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
4. Can microorganisms be seen with the naked eye? If not, how can they be seen?
Ans- Microorganisms cannot be seen by naked eyes.
They can be seen be microscope.
5. What are the major groups of microorganisms?
Ans- The major groups of microorganisms are----
i) Fungi
ii) Bacteria
iii) Viruses
iv) Protozoa
v) Archaea
6. Name the microorganisms which can fix atmospheric nitrogen in the soil.
Ans- The microorganisms which can fix atmospheric nitrogen in the soil is----
i) Bacteria
ii) Cyanobacteria
7. Write 10 lines on the usefulness of microorganisms in our lives.
Ans- i) Bacteria and yeast are use to fermentation of rice idlis and dosa batter.
ii) Microorganism are used for the large scale production of alcohol, wine and vinegar.
iii) They are helpful in cleaning up the environment. For example, organic wastes vegetable peels, remains of animals etc. Are broken down into harmless and usable substances by bacteria
iv) Curd contains several microorganisms. Ex- the bacterium, Lactobacillus promotes the formation of curd. It multiplies in milk and converts it into curd.
v) Bacteria are also involved in the making of cheese, pickles and many other food items.
vi) Antibiotics are produced from bacteria and fungi.
vii) Microorganisms are helpful in producing vaccines against disease-causing agents.
viii) Some bacteria are able to fix nitrogen from the atmosphere to enrich the soil with nitrogen and increase its fertility.
ix) Microorganisms decompose dead organic waste of plants and animals to convert them into simple substances. These substances are again used by other plants and animals. Thus, microorganisms can be used to degrade harmful and smelly substances and thereby clean up the environment.
x) Yeast reproduces rapidly and produces carbon dioxide during respiration. Bubbles of gas fill up the dough and increase its volume. This is the basis of the use of yeast in the baking industry for making bread, pastries and cakes.
8. Write a short paragraph on the harmful effects of microorganisms.
Ans- While microorganisms play a main role in our world, some can cause harm. Pathogenic microbes, like bacteria and viruses can enter our bodies and cause illnesses ranging from the common cold to life-threatening diseases like pneumonia or malaria. Food spoilage by bacteria can lead to foodborne illnesses, and fungi can infect plants and animals, impacting agriculture and ecosystems. Despite these dangers, advancements in medicine, hygiene practices, and food preservation help us mitigate the harmful effects of microorganisms.
9. What are antibiotics? What precautions must be taken while taking
antibiotics?
Ans- These
medicines kill or stop the growth of the
disease-causing microorganisms. This are called antibiotics.
The precautions that must be taken while taking antibiotics are---
i) Antibiotics should be taken on the advice of qualified doctor.
ii) And also complete the course prescribed by the doctor.
