Question 2.
\nName the type of microorganism that is smaller than bacteria.
\nAnswer:
\nVirus<\/p>\n
Question 3.
\nWrite the name of a bacterium that helps in the formation of curd.
\nAnswer:
\nLactobacillus<\/p>\n
Question 4.
\nWrite a use of yeast.
\nAnswer:
\nYeast is used in the production of alcohol, wine, beer and other beverages.<\/p>\n
Question 5.
\nWhat does yeast produce during respiration?
\nAnswer:
\nYeast produces carbon dioxide gas during respiration.<\/p>\n
Question 6.
\nWhat are pathogens? Write another name of pathogens.
\nAnswer:
\nDisease-causing microorganisms are known as pathogens. They are also called germs.<\/p>\n
Question 7.
\nDefine food preservation.
\nAnswer:
\nFood preservation is the method of preserving food from being spoiled by the microbes.<\/p>\n
Question 8.
\nWrite the names of any two antibiotics.
\nAnswer:<\/p>\n
- \n
- Streptomycin<\/li>\n
- Erythromycin<\/li>\n<\/ul>\n
Question 9.
\nWho discovered the vaccine for small pox?
\nAnswer:
\nEdward Jenner<\/p>\nQuestion 10.
\nWhat is fermentation?
\nAnswer:
\nFermentation is the process of conversion of food into alcohol.<\/p>\nQuestion 11.
\nDefine refrigeration.
\nAnswer:
\nThe storing of food products at the temperature of 0\u00b0C to 5\u00b0C is known as refrigeration.<\/p>\nQuestion 12.
\nWhat is vaccine?
\nAnswer:
\nA substance which is used in the production of immunity against various diseases in the living body is termed as vaccine.<\/p>\nQuestion 13.
\nName any two human diseases caused by viruses.
\nAnswer:<\/p>\n- \n
- Measles<\/li>\n
- Polio<\/li>\n<\/ul>\n
Question 14.
\nName any three common plant diseases.
\nAnswer:
\nRust of wheat, citrus canker and wilt<\/p>\nQuestion 15.
\nName a microorganism which helps in nitrogen fixation.
\nAnswer:
\nRhizobium<\/p>\nQuestion 16.
\nName a disease caused by food poisoning.
\nAnswer:
\nBotulism<\/p>\nQuestion 17.
\nWhat is the difference between refrigeration and freezing?
\nAnswer:
\nIn refrigeration, the storing of the food is done at a temperature of 0\u00b0C to 5\u00b0C, whereas freezing is used to store food at -18\u00b0C of temperature.<\/p>\nQuestion 18.
\nWhat is decomposition?
\nAnswer:
\nDecomposition is the process in which organic materials are broken down into simple inorganic sub-stances by the microorganisms.<\/p>\nQuestion 19.
\nName the two microbes that are involved in the process of decomposition.
\nAnswer:
\nBacteria and fungi<\/p>\nQuestion 20.
\nName the first antibiotic discovered.
\nAnswer:
\nPenicillin<\/p>\nMicroorganisms: Friend and Foe Class 8 Extra Questions Short Answer Questions<\/h3>\n
Question 1.
\nWhat are microorganisms? Give four examples.
\nAnswer:
\nSmall organisms that cannot be seen through the naked eyes and can only be seen under a microscope are called microorganisms or microbes; e.g., Amoeba, Paramecium, Volvox, Spirogyra, etc.<\/p>\nQuestion 2.
\nClassify bacteria on the basis of their shapes.
\nAnswer:
\nOn the basis of their shapes, bacteria are classified into four categories:<\/p>\n- \n
- rod-shaped bacteria (bacilli)<\/li>\n
- spherical-shaped bacteria (cocci)<\/li>\n
- curved-shaped bacteria (vibrios)<\/li>\n
- spiral-shaped bacteria (spirilla)<\/li>\n<\/ul>\n
Question 3.
\nDefine communicable diseases. Give some examples.
\nAnswer:
\nCommunicable diseases are microbial diseases that can spread from an infected person to a healthy person through air, water, or other physical contacts; e.g., cholera, chicken pox, tuberculosis, common cold, etc.<\/p>\nQuestion 4.
\nDifferentiate between viruses and other microorganisms.
\nAnswer:<\/p>\n\n\n
\n Viruses<\/strong><\/td>\n Other microbes<\/strong><\/td>\n<\/tr>\n \n (i) They show the characteristics of living organ\u00adisms or reproduce only by entering the host or\u00adganisms.<\/td>\n (i) They do not need to enter any host organ\u00adism to reproduce or show any characteristics of life.<\/td>\n<\/tr>\n \n (ii) They are non-cellular microbes.<\/td>\n (ii) They are cellular microbes.<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n Question 5.
\nWhat do you mean by food spoilage?
\nAnswer:
\nThe process in which food is deteriorated to such extent that it does not remain fit for human consumption is known as food spoilage.<\/p>\nQuestion 6.
\nWhat role does sugar play in the preservation of food?
\nAnswer:
\nThe role of sugar in food preservation is significant. By adding sugar in the food item, we reduce its moisture content and hence, it stops the growth of the microorganisms.<\/p>\nQuestion 7.
\nHow are carriers harmful to us?
\nAnswer:
\nCarriers take with them many harmful microorganisms or pathogens. They play a great role in transferring these pathogens to a healthy person, by sitting on the food items, or directly transferring the pathogens inside the body of a person. Hence they are harmful to us.<\/p>\nQuestion 8.
\nWhat is vaccination?
\nAnswer:
\nThe process of putting a vaccine inside the body of a person in order to produce immunity against some disease is called vaccination.<\/p>\nQuestion 9.
\nWhat do you mean by immunity?
\nAnswer:
\nImmunity is the ability of a body to develop resistance against diseases.<\/p>\nQuestion 10.
\nGive two examples of each of the following types of microorganisms:
\n(a) Algae
\n(b) Fungi
\n(c) Protozoa
\nAnswer:
\n(a) Algae – Spirogyra, Chlamydomonas
\n(b) Fungi – Aspergillus, yeast
\n(c) Protozoa – Paramecium, Amoeba<\/p>\nQuestion 11.
\nWhat are antibodies?
\nAnswer:
\nWhenever any harmful disease-causing microorganism enters the human body, the body produces substances to fight with the entered microbe. These substances are called antibodies.<\/p>\nQuestion 12.
\nWhat is the role of bacteria in increasing the soil fertility?
\nAnswer:
\nSome bacteria, which are present in the root nodules of leguminous plants or free-living fix the atmospheric nitrogen in the soil which is ultimately used up by the plants. Hence they increase the fertility of the soil. For example, Rhizobium, Azotobacter, Azospirillum, etc.<\/p>\nQuestion 13.
\nDefine Ohmic heating.
\nAnswer:
\nOhmic heating is the process in which electric current of high voltage is passed through the food items to kill the microbes that cause the spoilage of food.<\/p>\nQuestion 14.
\nWhat is sterilisation?
\nAnswer:
\nThe process of killing all the microorganisms above the temperature of 100\u00b0C is known as sterilisation. It is one of the widely used methods to preserve food, and is often used for various food items.<\/p>\nQuestion 15.
\nWhat is pasteurisation?
\nAnswer:
\nPasteurisation can be defined as the partial sterilisation of foods at a temperature that destroys harmful microorganisms without major changes in the chemical property of the food.<\/p>\nMicroorganisms: Friend and Foe Class 8 Extra Questions Long Answer Questions<\/h3>\n
Question 1.
\nExplain why antibiotics do not work against flu or any infection caused by viruses.
\nAnswer:
\nViruses cannot be killed by using antibiotics as their cell pathways are different from that of bacteria. It means taking antibiotics to get rid of flu or any other viral infection is useless, because it does not re-duce the strength of the virus, nor does it reduce the duration of the infection. But, however, antibiotic will work if we get attacks of viral infection and bacterial disease at the same time. Even then, it will cure bacterial disease only but not the viral infection.<\/p>\nQuestion 2.
\nMention any three ways through which pathogens are transmitted.
\nAnswer:
\nThree ways because of which pathogens are transmitted are as follows:<\/p>\n- \n
- When a person sneezes or coughs, tiny droplets containing a number of disease-causing microorganisms come out of the mouth, and are released in the air. They are transmitted to a healthy person while breathing.<\/li>\n
- By making direct contacts with an infected person, pathogens are transferred to a healthy person.<\/li>\n
- Carriers of pathogens also help in their transmission. For instance, when a fly sits on animal excreta or garbage, harmful disease-causing microbes stick to its legs. And when this fly sits on the food items, pathogens get transferred to them. This contaminated food items cause serious diseases when it is eaten by a healthy person.<\/li>\n<\/ul>\n
Question 3.
\nExplain canning.
\nAnswer:
\nCanning is a process used for food preservation. Heat, at a certain temperature and for a limited period of time, is used to kill the harmful microorganisms as well as enzymes. This method also involves the removal of oxygen gas, and to avoid post-process contamination by airtight sealing of food items.<\/p>\nQuestion 4.
\nExplain how malaria is transmitted to humans.
\nAnswer:
\nA protozoan called Plasmodium is responsible for malaria. It lives in the liver and blood of the person who has been infected by this disease. A female Anopheles mosquito when sucks blood from the infected person, Plasmodium along with blood, is taken into its stomach. The Plasmodium, here, multiplies itself and reaches the salivary gland of the mosquito. Now, when this mosquito bites a healthy person, it injects Plasmodium along with saliva to him. The healthy person then gets an attack of malaria.
\nIn this way, malaria is transmitted to humans.<\/p>\nQuestion 5.
\nExplain various types of bacteria.
\nAnswer:
\nBacteria are classified on the basis of their shapes into the following categories:<\/p>\n- \n
- Rod-shaped bacteria (bacilli):
\nThese are aerobic rod-shaped, spore-producing bacteria. They are often occurring in chain-like formations, and they are found primarily in soil; e.g., Lactobacillus.<\/li>\n - Spherical-shaped bacteria (cocci):
\nThey are spherical or nearly spherical bacteria; e.g., Streptococcus.<\/li>\n - Curved-shaped bacteria (vibrios):
\nThey are curved-shaped bacteria; e.g., Vibrio.<\/li>\n - Spiral-shaped bacteria (spirilla):
\nThey are flagellated, aerobic bacteria, having a spirally twisted rod-like form; e.g., Treponema.<\/li>\n<\/ul>\nMicroorganisms: Friend and Foe Class 8 Extra Questions Higher Order Thinking Skills<\/h3>\n
Question 1.
\nUnscramble the jumbled words underlined in the following statements
\n(a) Curbossulite is an air-borne disease caused by a bacterium.
\n(b) Xanrhat is a dangerous bacterial disease.
\n(c) Yeasts are used in the wine industry because of their property of meronettinaf.
\n(d) Cells of our body produce santiidobe to fight pathogens.
\n(e) Aeeessrrwtip are added to food to prevent growth of microorganisms.
\nAnswer:
\n(a) Tuberculosis
\n(b) Anthrax
\n(c) Fermentation
\n(d) antibodies
\n(e) Preservatives<\/p>\nQuestion 2.
\nWhat is the difference between Rhizobium and cyanobacteria in the way of fixing nitrogen for the plants?
\nAnswer:
\nRhizobium lives in the root nodules of leguminous plants in a symbiotic relationship whereas cyanobacteria lives freely in the soil and fixes nitrogen.<\/p>\nQuestion 3.
\nIt is always suggested that not to eat anything from street hawkers. Why?
\nAnswer:
\nMost of street hawkers sells food items in an open area which always get contaminated with the dust and flies carrying germs with them. Such an unhygienic condition lead to spoilage of food which when consumed can lead to serious illness.<\/p>\nQuestion 4.
\nWhy oil is added while making pickle?
\nAnswer:
\nOil seals off the air from the item that is being pickled and thus inhibit the growth of most of the microorganisms.<\/p>\nQuestion 5.
\nRia thought of making curd. For this, she took lukewarm milk, mixed some curd into it and stir well. She kept the mixture in fridge. Next day she observed that curd was not set. Can you tell why the curd did not set?
\nAnswer:
\nCurd did not set because she kept the mixture in fridge. Lower temperature of fridge retarded the growth of Lactobacillus in the mixture.<\/p>\nQuestion 6.
\nWhy do idli and dosa maker add some yeast or old batter of pervious day to the newly-made batter and keep it for one day?
\nAnswer:
\nFor fermentation of idli and dosa yeast or old batter is added. Fermentation makes idli fluffy and dosa crispy, and change the flavour.<\/p>\nMicroorganisms: Friend and Foe Class 8 Extra Questions Value-Based Questions<\/h3>\n
Question 1.
\nSeema got cough and cold badly. Her teacher asked her to take rest at home and use handkerchief while sneezing and coughing. She obeyed her teacher.
\n(a) Why should we keep a handkerchief on nose and mouth while sneezing or coughing?
\n(b) What are the modes of transfer of diseases from infected to healthy person?
\n(c) Do you think Seema\u2019s teacher decision was right? Why?
\n(d) What value of Seema is shown here?
\nAnswer:
\n(a) We should keep a handkerchief on nose and mouth while sneezing or coughing because fine drop\u00aclets carrying thousands of viruses or bacteria spread in the air.
\n(b) Air, water, food, carriers and physical contact.
\n(c) Yes, because cough and cold spreads through air and there are chances that other students may also get infected.
\n(d) Seema is an obedient girl.<\/p>\nQuestion 2.
\nOn Rahul\u2019s birthday, his mother prepared many dishes for him. After having their meal, they found that many food items were left over. Rahul\u2019s mother kept these leftovers in a air-tight container and refrigerate them.
\n(a) What is food preservation?
\n(b) What will happen to the food if it is not refrigerated?
\n(c) What is the role of refrigeration in food preservation method?
\n(d) What value of Rahul\u2019s mother is shown here?
\nAnswer:
\n(a) The methods used for prevention of spoiling of food by the action of microbes is called food preservation.
\n(b) The food will get spoil and emit bad smell with changed colour or taste.
\n(c) Refrigeration retards or slow down the growth of microorganisms and enzyme activity on food. Thus, it prevents spoilage of food.
\n(d) Rahul\u2019s mother is intelligent, economical, have scientific aptitude towards preservation of food.<\/p>\nActivities and Projects<\/strong>
\nQuestion 1.
\nPull out a gram or bean plant from the field. Observe its roots. You will find round struc\u00actures called root nodules on the roots. Draw a diagram of the root and show the root nod\u00acules.
\nAnswer:
\n![\"Microorganisms](\"https:\/\/www.learncbse.in\/wp-content\/uploads\/2019\/10\/Microorganisms-Friend-and-Foe-Class-8-Extra-Questions-Science-Chapter-2-1.png\")
<\/p>\nQuestion 2.
\nCollect the labels from the bottles of jams and jellie on the labels.
\nAnswer:
\nDo it yourself.<\/p>\nQuestion 3.
\nVisit a dcotor. Find out why antibiotics should not be overused. Prepare a short report.
\nAnswer:
\nTo kill or stop the development of the disease-causing microbes, antibiotics are the medicines which are majorly used.
\nIt\u2019s very important to keep in mind that antibiotics must be taken only on the advice of a qualified doctor. Also, one should finish the prescribed course of antibiotics given by the doctor. If one takes an an\u00actibiotic when not required or overuse it, then it will help bacteria in one\u2019s body to develop resistance to the given antibiotic. Next time when one falls sick and needs that antibiotic, it will be less effective. Excess dose of antibiotics also kills friendly microbes inside our body and thus helps to flourish patho-genic microbes.<\/p>\nQuestion 4.
\nProject: Requirements 2 test tubes, marker pen, sugar, yeast powder, 2 balloons and lime water.
\nTake two test tubes and mark them A and B. Clamp these tubes in a stand and fill them with water leaving some space at the top. Put two spoonfuls of sugar in each of the test tubes. Add a spoonful of yeast in test tube B, Inflate the two balloons incompletely. Now tie the balloons on the mouths of each test tube. Keep them in a warm place, away from sunlight. Watch the setup every day for next 3-4 days. Record your observations and think of an explanation.
\nNow take another test tube filled 1\/4 with lime water. Remove the balloon from test tube B in such a manner that gas inside the balloon does not escape. Fit the balloon on the test tube and shake well. Observe and explain.
\n![\"Microorganisms](\"https:\/\/www.learncbse.in\/wp-content\/uploads\/2019\/10\/Microorganisms-Friend-and-Foe-Class-8-Extra-Questions-Science-Chapter-2-2.png\")
\nAnswer:
\nIt was observed that the balloon fitted on test tube B is completely inflated but balloon fitted on test tube A is not inflated. When the inflated balloon of test tube B is fitted on test tube filled with lime water, lime water turns milky. This is because yeast celj releases C02 during respiration which inflates the balloon and C02 present inside the balloon changes lime water milky.<\/p>\nI. Multiple Choice Questions (MCQs)<\/strong>
\nChoose the correct option.<\/strong>
\nQuestion 1.
\nTiny organisms which cannot be seen with the naked eyes are called
\n(a) microorganisms
\n(b) animals
\n(c) fungi
\n(d) bacteria<\/p>\nQuestion 2.
\nMicroorganisms are also known as
\n(a) yeast
\n(b) microbes
\n(c) viruses
\n(d) Amoeba<\/p>\nQuestion 3.
\nFungus can be seen with a
\n(a) microscope
\n(b) telescope
\n(c) magnifying glass
\n(d) both (a) and (c)<\/p>\nQuestion 4.
\nMicroorganisms that causes disease are also kn
\n(a) pathogens
\n(b) fungi
\n(c) antigen
\n(d) microbes<\/p>\nQuestion 5.
\nPathogens are also called
\n(a) germs
\n(b) antigen
\n(c) antibody
\n(d) carrier<\/p>\nQuestion 6.
\nBacteria are organisms.
\n(a) multicellular
\n(b) unicellular
\n(c) bicellular
\n(d) tricellular<\/p>\nQuestion 7.
\nBacilli are the bacteria that are
\n(a) rod-shaped
\n(b) comma-shaped
\n(c) curved-shaped
\n(d) spiral<\/p>\nQuestion 8.
\nSpherical-shaped bacteria are called
\n(a) bacilli
\n(b) vibrio
\n(c) spirilla
\n(d) cocci<\/p>\nQuestion 9.
\nSimple, plant-like microorganisms are called
\n(a) algae
\n(b) bacteria
\n(c) both (a) and (b)
\n(d) protozoa<\/p>\nQuestion 10.
\nMedium that transmits pathogens from an infected person to a healthy one is called
\n(a) fungi
\n(b) germs
\n(c) carrier
\n(d) none of these<\/p>\nQuestion 11.
\nMedicine that kills or stops the growth of harmful disease-causing microbes is known as
\n(a) antibiotic
\n(b) antibody
\n(c) antigen
\n(d) vaccine<\/p>\nQuestion 12.
\nThe process in which sugar in the food is transformed into alcohol and carbon dioxide by using microorganisms is known as
\n(a) transformation
\n(b) beverage
\n(c) fermentation
\n(d) respiration<\/p>\nQuestion 13.
\nThe fungus that is commonly used in bakery and beverage industries is
\n(a)Penicillium
\n(b) Yeast
\n(c) Agaricus
\n(d) Rhizopus<\/p>\nQuestion 14.
\nGiardia is listed under the category of
\n(a) fungi
\n(b) protozoa
\n(c) bacteria
\n(d) algae<\/p>\nQuestion 15.
\nSubstance used to produce immunity against diseases in the living body is called
\n(a) immune
\n(b) vaccine
\n(c) antibody
\n(d) antigen
\nAnswer:
\n1. (a)
\n2. (b)
\n3. (d)
\n4. (a)
\n5. (a)
\n6. (b)
\n7. (a)
\n8. (d)
\n9. (a)
\n10. (c)
\n11. (a)
\n12. (c)
\n13. (b)
\n14. (b)
\n15. (b)<\/p>\nII. Fill in the Blanks<\/strong>
\nFill in the blanks with suitable word\/s.<\/strong>
\n1. Bacteria, fungi, protozoa and _______ are the major four groups in which microorganisms are classified.
\n2. Two microorganisms which live in symbiotic association in lichens are _______ and _______.
\n3. We use a _______ to see the microorganisms.
\n4. _______ are considered different from other microorganisms because they can multiply only by entering the host organisms.
\n5. The gas released during the preparation of bread is _______.
\n6. The disease caused by a protozoan and spread by an insect is _______.
\n7. _______ are curved-shaped bacteria.
\n8. Saprophytes and _______ are the two main categories of fungi.
\n9. _______ are the threads of the multicellular fungi.
\n10. Yeast is a _______ fungus.
\n11. Protozoa are _______ in nature.
\n12. Flu, cough and cold are caused by _______.
\n13. The first antibiotic discovered was _______.
\n14. _______ are the microorganisms that help in the process of decomposition.
\n15. The process of formation of curd from milk is known as the _______ of milk.
\nAnswer:
\n1. algae
\n2. algae, fungus
\n3. microscope
\n4. Viruses
\n5. carbon dioxide
\n6. malaria
\n7. Vibrio
\n8. parasites
\n9. Hyphae
\n10. unicellular
\n11. heterotrophic
\n12. viruses
\n13. penicillin
\n14. Decomposers
\n15. curdling<\/p>\n
- Rod-shaped bacteria (bacilli):
![\"Microorganisms](\"https:\/\/www.learncbse.in\/wp-content\/uploads\/2019\/10\/Microorganisms-Friend-and-Foe-Class-8-Extra-Questions-Science-Chapter-2-3.png\")