8th Class Biology 3rd Lesson Story of Microorganisms 2 Textbook Questions and Answers

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Question 1.How do vaccines works in our body?

Answer: When a vaccine is given which contains weak microorganisms our body learn to fight them by producing antibodies whenever danger comes. When the disease causing microorganisms enter in our body, the already present antibodies fight and eliminate them. And the disease is controlled. The weakened disease causing microorganisms which are injected into our bodies are called as vaccine

Question 2.What are the differences between Antibiotic and Vaccine?


Antibiotic Vaccine
An antibiotic is a compound or a substance that inhibits or kills the growth of bacteria Vaccine is a preparation that improves the immunity to a particular disease
An antibiotic heals infection caused by small pox A vaccine prevents diseases like polio, bacteria
Antibiotics are available in different forms like tablets, capsules, drops or ointments Vaccines can be given orally or through injection
Antibiotics are taken after getting infected Vaccines are preventive method that is taken before getting infected
Question 3.Invention of pencillin protected the world from deaths during first world war, Explain?


  • Pencillin was invented by Dr. Alexander Flemming
  • He was an army doctor in First World War
  • In the First World War many injured soliders died because of bacterial infection of wounds
  • Pencillin killed many disease causing bacteria
  • So the invention of pencillin protect the world from deaths during the first World War
Question 4.Take three bowls and mark as A,B,C. Pour lukewarm milk in bowl A, hot milk in bowl B, cold milk in bowl C. Add one tea spoon of curd or butter milk in three bowls and stir them slightly. Cover the bowls with lids. Keep the bowls undisturbed for five to six hours. In which bowl milk turned into curd ? Give your reasons?

Answer: After six hours the milk in the bowl A converted into curd. This conversion is happened by fermentation. Fermentaion is one kind of enzy-matic action in anaerobic respiration. Fermentation needs the help of microbes like yeast or some other bacteria. This process occurs at a particular temperature. Be-cause of enzymes are inactive at low and high temperatures. Hence the milk in bowl A converted into curd by the bacterium Lactobacillus

Question 5.Collect more information about scientists who invented and discovered other facts related to Microorganisms. How these discoveries helped mankind ? Make a chart presentation and paste it on your classroom wall magazine?


Question 6.Make an album of scientists and their discoveries related to Microorganisms?


Question 7.Visit the veterinary hospital and prepare a list of cattle diseases by asking questions, to the doctor?


Disease Animal
1) African Horse Sickness Horses
2) Bovine Spongiform Encephalopathy Cattle
3) Contagious Equine Metritis Horses
4) Equine Infectious Anaemia Horses
5) Anthrax Cattle and other mammals
6) Brucellosis (Brucella abortus) Cattle
7) Brucellosis (Brucella melitensis) Sheep and Goats
8) Contagious agalactia Sheep and Goats
9) Contagious bovine pleuro - pneumonia Cattle
10) Dourine Horses
11) European Bat Lyssavirus (FBLV) Bats
12) Enzootic bovine leukosis Cattle
Question 8.What is pasteurisation? What is the use of it?


  • Pasteurisation is a process which helps in the preservation of the milk
  • It is discovered by "Louis Pasteur." Hence it is called as pasteurisation
  • In this process milk is heated up to 70° for 15 to 30 seconds and suddenly chilled and stored
  • This prevents the growth of the microorganisms
Question 9.How do you appreciate Edward Jenners experiment?

Answer: Edward Jenner was a man of the Enlightenment and believed in the intellectual and moral improvement of mankind. Possessing that spirit, he predicted in 1801 that "the annihilation of small pox-the most dreadful scourge of the human race-will be the final result of this practice" of vaccination. And he was right. Since the Enlightenment, the core branches of science and medicine have generally developed rationally. As a result, the World Health Organization was able to declare in 1980 that smallpox had been eradicated worldwide. Only two laboratory samples emained, one in Russia and one in the United States

Question 10.Visit a nearby milk chilling centre. Observe the process and make a report on it?

Answer: The Milk Collection Station is a specially designed, integrated unit, which combines the several functions of a milk collection centre. It measures the weight, fat content and gives the price of the milk brought in by the each producer. The equipment is particularly useful for the milk cooperatives / milk collection centres as it can also maintain a summary of milk supplied. This state of the art equipment operates both on battery and mains and is able to process and record 120-150 milk collection per hour. An Electronic Milk Weighing Unit, the Electronic Milk Tester and Data Processor Unit are main components of the system. The membership code of individual mem¬bers is entered automatically by member identity card / manually by an electronic key-board.

Question 11."Prevention is better than cure" comment?

Answer: We heard about "prevention is better than cure" since our childhood - brushing of teeth twice to prevent tooth decay, washing of hands before eating to prevent stomach upset, do not eat uncovered road side food items, get vaccine against polio to free from disability, get rid of stagnate water to prevent malaria like that follow the life skills to avoid dangerous AIDS. Its better to take care that a problem does not happen than to have to solve the problem afterwards. Its easier to stop something bad from happening in the first place than to fix the damage after it has happened

Question 12.Raheem tells to his neighbours, "stagnation of sewage in our surroundings is harmful to our health. " Do you support this? Why?

Answer: Stagnation of sewage in our surroundings is harmful to our health in different ways. Sewage consist different wastes of organic matters. Microbes decompose all organic wastes. Disease transmitting carriers prefer to grow on decomposing organic matters. Hence sewage provides good shelter to mosquitoes, houseflies and other insects which transmit life threatening diseases like encephalitis, malaria, cholera, typhoid and other epidemics. Therefore sewage stagnation is more harmful to our health.

Question 13.Jeevan said that "If there are no microorganisms earth will remain with wastes. " Will you agree this statement? Why?

Answer: Yes, I will agree this statement. Because of

  • Microorganisms present in the soil, air and water act upon wastes around us
  • They decomposes them
  • They are converted into simple substances
  • Thus microorganisms help us in cleaning the environment
  • So if there are no microorganisms earth will remain with wastes
Question 14.Pranavi is suffering from serious illness. Doctor prescribed antibiotics for five days. After three days of usage she stopped taking antibiotics. Is it right or not, discuss?

Answer: No, it is not right. Doctor prescribed anitbiotics for five days. Because the doctor knows that the correct days of the recovering of her illness. After three days of usage she stopped taking antibiotics. But her illness is not completely recovered. It is breaking out after some time. So it is not right

Question 15.What are the precautions taken to eradicate malaria?


  • Malaria is caused by the pathogen piasmodium, is transmitted by female Anopheles mosquito
  • Methods used to prevent malaria include medications, mosquito elimination and the prevention of bites
  • Using of indoor mosquito repellents, residual sprays, taking care not to store water
  • Providing awareness how to control mosquito population
Question 16.One medical store owner is giving antibiotics to his customer who is suffering from fever without doctors prescription? But the customers daughter Malathi is telling her father not to take antibiotics without doctors prescription. Whom do you support and why?

Answer: We must use antibiotics prescribed by qualified doctor only. If you use antibiotics without consulting a qualified doctor it may harm us. Unnecessary use of antibiotics affects blood cells which fight infections. Sometimes they may kill useful bacteria too in our intestine and this increases the resistance towards antibiotics

8th Class Biology 3rd Lesson Story of Microorganisms 2 InText Questions and Answers

Question 1.What diseases can be prevented if we control mosquitoes?

Answer: Malaria, Dengue, Chickungunya, Japanese Encephalitis

Question 2.Which diseases can we prevented by vaccination?

Answer: Tuberculosis, Chickenpox, Measles, Polio, Swineflu

Question 3.Name the diseases which are transmitted by contaminated water?

Answer: Cholera, Typhoid

Question 4.Can you name some diseases which are transmited by Air?

Answer: Tuberculosis, Chickenpox, Measles, Polio, Swineflu

8th Class Biology 3rd Lesson Story of Microorganisms 2 Activities

Activity - 1
Question 1.Take some lukewarm milk in two small bowls. Add a few drops of butter milk or little curd in one of the bowls. In the second bowl do not add anything. Keep the two bowls in a warm place and observe the milk in the bowls after 5 to 6 hours?
a) What changes did you observe?

Answer: In the first bowl milk changed into curd. There is no change in the second bowl

b) What is the reason for this?

Answer: We add curd or butter milk in the first bowl. Curd or buttermilk contain bacterium named lactobacillus. Lactobacillus converts the milk into curd

Activity - 2

Question 2.Take 100 grams of maida in a bowl, add one or two spoons of yeast powder, add some water and knead it to make dough. Keep the dough in a warm place. Observe the dough after 3 - 4 hours?
a) What changes do you observe in the dough ?

Answer: We observe that the dough rises and increase its volume

b) What might be the reason ? Discuss with your friends and write about it?

Answer: When yeast is added to the maida dough, the dough rises. This is due to the produc¬tion of carbondioxide gas during the process of fermentation. Bubbles of the gas fill the dough, increase its volume and make it spongy in nature

Activity - 3

Question 3.Commercial use of microorganisms?
Take some water in two separate beakers. Add 5 to 10 spoons of sugar to each beaker, then add 2 to 3 spoons of yeast to one of the bowls only. Close both of the bowls with lids and keep them in a warmplace. After 3 to 4 hours remove the lids and smell the contents.
a) What differences did you observe between the two bowls?

Answer: We feel a new variety of smell from one of the bowls. This is the characteristic smell of alcohol. There is no smell from another bowl

b) What will be the reason for the odour in yeast mixed bowl?

Answer: Sugars are converted into alcohol by yeast. This process of conversion of sugars into alcohol is known as fermentation

Activity - 4

Question 4.Visit nearby PHC and collect information about vaccination given to 0-15 years chil-dren. Meet a doctor or a health worker and ask what types of vaccines are there ? Which disease can be prevented ? When it should be taken? List them out?


Activity - 5

Question 5.Take two pots or dig two pits in the corner of the garden at home or at your school ground. Fill them up to half with loose soil. Put some biological wastes like fallen leaves, vegetable wastes, waste papers, etc., in one of them. Fill the second one with plastic wastes, polythene bags and with some empty glass bottles?

Answer: Now cover both the pits with soil and sprinkle water twice a day up to three weeks and observe the changes in both the pits and record. After three weeks the pit which consists organic wastes decomposed into inorganic matter. But the pit which is filled with polythene bags, plastics and glass bottles is remain same no change is observed. Because of plastics and polythene materials are non biodegradables

Activity - 6

Question 6.Meet a doctor of your locality and ask him about the different types of diseases, caused by different microorganisms. Note them down?
(OR) Read the following table and answer the following questions.
a) Name the viral diseases that can be prevented by controlling mosquito population?

Answer: Dengue, Chikungunya, Japanese encephalitis

b) Which bacterial disease / diseases cannot be controlled by vaccination ( above table) ?

Answer: Cholera, Typhoid

c) What would you do to control mosquito population ?

Answer: Use mosquito repellents, control breeding of mosquitoes by not allowing water stag¬nation in our surroundings

d) Name the viral disease that spreads through water?

Answer: Polio

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