Question 1

Question 1Fill 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 ............... .

Accepted 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

Question 2(a)Yeast is used in the production ofsugaralcoholhydrochloric acidoxygen

Accepted Answer

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

Question 3

Question 2(b)The following is an antibioticSodium bicarbonateStreptomycinAlcoholYeast

Accepted Answer

StreptomycinReason — Streptomycin is an antibiotic made from streptomyces bacteria.

Question 4

Question 2(c)Carrier of malaria-causing protozoan isfemale Anopheles mosquitocockroachhouseflybutterfly

Accepted Answer

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

Question 5

Question 2(d)The most common carrier of communicable diseases isanthouseflydragonflyspider

Accepted Answer

houseflyReason — 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 6

Question 2(e)The bread or idli dough rises because ofheatgrindinggrowth of yeast cellskneading

Accepted Answer

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

Question 7

Question 2(f)The process of conversion of sugar into alcohol is callednitrogen fixationmouldingfermentationinfection

Accepted Answer

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

Question 8

Question 3Match the organisms in Column A with their action in Column B.AB1. Bacteria(a) Fixing nitrogen2. Rhizobium(b) Setting of curd3. Lactobacillus(c) Baking of bread4. Yeast(d) Causing malaria5. A protozoan(e) Causing cholera6. A virus(f) Causing AIDS (g) Producing antibodies

Accepted Answer

AB1. Bacteria(e) Causing cholera2. Rhizobium(a) Fixing nitrogen3. Lactobacillus(b) Setting of curd4. Yeast(c) Baking of bread5. A protozoan(d) Causing malaria6. A virus(f) Causing AIDS

Question 9

Question 4Can microorganisms be seen with the naked eye? If not, how can they be seen?

Accepted 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 10

Question 5What are the major groups of microorganisms?

Accepted Answer

Microorganisms are classified into four major groups. These groups are: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.Fungi — They are multicellular.Protozoa — They are single celled.Algae — They may be single celled or multi cellular.

Question 11

Question 6Name the microorganisms which can fix atmospheric nitrogen in the soil.

Accepted Answer

The microorganisms which can fix atmospheric nitrogen in the soil are:Rhizobium sp.Cyanobacteria or Blue green algae

Question 12

Question 7Write 10 lines on the usefulness of microorganisms in our lives.

Accepted Answer

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

Question 13

Question 8Write a short paragraph on the harmful effects of microorganisms.

Accepted 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 14

Question 9What are antibiotics? What precautions must be taken while taking antibiotics?

Accepted 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.

Microorganisms : Friend and Foe