Microorganisms : Friend and Foe

Exercises

Question 1

Fill in the blanks.

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

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

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

(d) Cholera is caused by bacteria .

Question 2(a)

Yeast is used in the production of

1. sugar
2. alcohol
3. hydrochloric acid
4. oxygen

Answer

alcohol

Reason — Yeast is grown on natural sugars present in grains like barley, wheat, rice and crushed fruit juices to produce alcohol.

Question 2(b)

The following is an antibiotic

1. Sodium bicarbonate
2. Streptomycin
3. Alcohol
4. Yeast

Answer

Streptomycin

Reason — Streptomycin is an antibiotic made from streptomyces bacteria.

Question 2(c)

Carrier of malaria-causing protozoan is

1. female Anopheles mosquito
2. cockroach
3. housefly
4. butterfly

Answer

female Anopheles mosquito

Reason — Female Anopheles mosquito carries the parasite of malaria i.e. Plasmodium.

Question 2(d)

The most common carrier of communicable diseases is

1. ant
2. housefly
3. dragonfly
4. spider

Answer

housefly

Reason — When houseflies sit on the garbage and animal excreta, pathogens stick to their bodies. When these flies sit on uncovered food they may transfer the pathogens which makes us sick.

Question 2(e)

The bread or idli dough rises because of

1. heat
2. grinding
3. growth of yeast cells
4. kneading

Answer

growth of yeast cells

Reason — Yeast reproduces rapidly and produces carbon dioxide during respiration. Bubbles of the gas fill the dough and increase its volume.

Question 2(f)

The process of conversion of sugar into alcohol is called

1. nitrogen fixation
2. moulding
3. fermentation
4. infection

Answer

fermentation

Reason — The process of conversion of sugar into alcohol is known as fermentation. It is done by yeast.

Question 3

Match the organisms in Column A with their action in Column B.

Answer

Question 4

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

Answer

Microorganisms cannot be seen with the naked eye because they are very small in size. Some of these, such as the fungus can be seen with a magnifying glass while others are seen with the help of a microscope.

Question 5

What are the major groups of microorganisms?

Answer

Microorganisms are classified into four major groups. These groups are:

1. Bacteria — They are single celled. They do not have true nucleus or membrane bound cell organelles. They may be spherical, rod shaped or comma shaped.
2. Fungi — They are multicellular.
3. Protozoa — They are single celled.
4. Algae — They may be single celled or multi cellular.

Question 6

Name the microorganisms which can fix atmospheric nitrogen in the soil.

Answer

The microorganisms which can fix atmospheric nitrogen in the soil are:

1. Rhizobium sp.
2. Cyanobacteria or Blue green algae

Question 7

Write 10 lines on the usefulness of microorganisms in our lives.

Answer

1. Microorganisms are extensively used for fermentation processes, producing products like bread, curd, alcohol, vinegar etc.
2. Microorganisms, such as bacteria in the human digestive system, contribute to the digestion process and help in nutrient absorption.
3. Soil bacteria such as Rhizobium sp enhance fertility by fixing nitrogen and breaking down complex organic compounds, supporting plant growth.
4. Microorganisms are used in wastewater treatment.
5. Microorganisms play a crucial role in medicine as they are essential for the production of antibiotics for treatment of bacterial infections.
6. Microorganisms are used in the production of biofuels such as biogas, providing a sustainable and renewable energy source for the future.
7. Microorganisms play a crucial role in waste decomposition, helping in the breakdown of organic matter and maintaining ecological balance.
8. Microorganisms are used in the production of vaccines helping us protect ourselves against deadly diseases.
9. Beneficial bacteria in the human body contribute to immune system function and protect against harmful pathogens.
10. Microorganisms are essential for the processing and ageing of cheese.

Question 8

Write a short paragraph on the harmful effects of microorganisms.

Answer

Microorganisms are harmful in many ways. Some of the microorganisms cause diseases in human beings, plants and animals. Such disease-causing microorganisms are called pathogens. Pathogenic microorganisms are responsible for a myriad of infectious diseases, ranging from common colds to severe illnesses. For example: Tuberculosis, Cholera, Malaria and Typhoid etc. In agriculture, certain microorganisms can cause crop diseases, affecting food production and quality. Some microorganisms spoil food and cause food poisoning or botulism. The microbes also destroy or decompose clothing and leather, deteriorating their quality.

Question 9

What are antibiotics? What precautions must be taken while taking antibiotics?

Answer

An antibiotic is a chemical substance produced by a living microorganism which can stop the growth of or kill some disease-producing bacteria and fungi.

Precautions that must be taken while taking antibiotics are:

• Antibiotics should be taken only on the advice of a qualified doctor.
• Patient must complete the course prescribed by the doctor. If antibiotics are taken when not needed or in wrong doses, it may make the drug less effective in subsequent infections.
• Also antibiotics taken unnecessarily may kill the beneficial bacteria in the body.
• Antibiotics should not be taken during cold and flu as they are not effective against it because these are caused by viruses and not bacteria.