microorganisms: friend and foe class 8(vishakha)

microorganisms: friend and foe

1. MICROORGANISMs: FRIENDS AND FOE

2. Microorganisms are present all around us but they are too small to be seen with naked eye. They are present everywhere in the atmosphere(air, water and soil) INTRODUCTION

3. MICROORGANISMS (MICROBES) :- Microorganisms are very small organisms which cannot be seen with the unaided eye. They can be seen only with a microscope. Microorganisms may be unicellular or multicellular. Microorganisms may exist alone or in colonies. for example , you mighty observed that during the rainy seasons moist bread gets spoilt and its surface gets covered with greenish-white patches.

4. TYPES OF MICROORGANISMS :- There are four main types of microorganisms. They are :- bacteria, fungi, algae and protozoans . for example:- Bacteria – lactobaccilus , E.Coli etc. Algae – Chlamydomonas , Spirogyra etc. Fungi – Bread mould, Penicillium , Aspergilles etc. Protozoans – Amoeba, Paramaecium etc. Viruses are also considered as microorganisms. They are different from other microorganisms because they reproduce only in the body of host organisms like bacteria, plants or animals. Common ailments like cold, influenza(flu) and most coughs are caused by viruses. Serious diseases like polio and chicken pox are also caused by viruses.

5. Bacteria Spiral bacteria Rod-shaped bacteria Algae Chlamydomonas Spirogyra Protozoa Amoeba Paramecium Fungi Bread Mould Penicillium Aspergillus

6. VIRUS

7. Microorganisms play an important role in our lives. Some of them are beneficial in many ways whereas some others are harmful and cause diseases. Microorganisms are used for making curd from milk, for making cheese, pickles, bread, cakes, pastries, alcohol, wine, vinegar (acetic acid) etc. a) Making curd from milk :- The bacterium called Lactobacillus reproduces in milk and helps to convert milk into curd. b) Making bread :- The fungus called yeast reproduces in flour dough and produces carbon dioxide during respiration which makes the dough soft and helps in making bread, cakes, biscuits, pastries etc. FRIEND AND FOE?

8. Commercial Use of Microorganisms Microorganisms are used for the large scale production of alcohol, wine and acetic acid (vinegar). Yeast is used for commercial production of alcohol and wine. For this purpose yeast is grown on natural sugars present in grains like barley, wheat, rice and crushed fruit juices, etc. The process of conversion of sugar into alcohol is known as fermentation. Louis Pasteur discovered fermentation in 1857.

9. Whenever you fall ill the doctor may give you some antibiotic tablets, capsules or injections such as of penicillin. The source of these medicines is microorganisms. Such medicines are called antibiotics. These days a number of antibiotics are being produced from bacteria and fungi. Streptomycin, tetracycline and erythromycin are some of the commonly known antibiotics. These medicines kill or stop the growth of the disease-causing microorganisms. Medicinal Use of Microorganisms

10. It is important to remember that antibiotics should be taken only on the advice of a qualified doctor. Also you must finish the course prescribed by the doctor. If you take antibiotics when not needed or in wrong doses, it may make the drug less effective when you might need it in future. Also antibiotics taken unnecessarily may kill the beneficial bacteria in the body. Antibiotics, however, are not effective against cold and flu as these are caused by viruses. Precautions while Administering Antibiotics

11. In 1929, Alexander Fleming was working on a culture of disease causing bacteria. Suddenly he found the spores of a little green mould in one of his culture plates. He observed that the presence of mould prevented the growth of bacteria. In fact, it also killed many of these bacteria. From this the mould penicillin was prepared. Penicillin

12. When a disease-carrying microbe enters our body, the body produces antibodies to fight the invader. The body also remembers how to fight the microbe if it enters again. So, if dead or weakened microbes are introduced in a healthy body, the body fights and kills them by producing suitable antibodies. The antibodies remain in the body and we are protected from the disease causing microbes. This is how a vaccine works. Several diseases, including cholera, tuberculosis, smallpox and hepatitis can be prevented by vaccination. Children are given injections to protect themselves against several diseases. Necessary vaccines are available in hospitals. Vaccinations are given to children for protection against polio under Pulse Polio Program. Polio drops given to children are actually a vaccine. This is called Oral vaccination. These days vaccines are made on a large scale from microorganisms to protect humans and other animals from several diseases. VACCINE

13. Some bacteria and blue green algae are able to fix nitrogen from the atmosphere to enrich soil with nitrogen and increase its fertility. These microbes are commonly called biological nitrogen fixers . Increasing Soil Fertility

14. You often see large amounts of dead organic matter in the form of decaying plants and sometimes dead animals on the ground. You find that they disappear after some time. This is because the microorganisms decompose dead organic waste of plants and animals converting them into simple substances. These substances are again used by other plants and animals. Thus, microorganisms can be used to degrade the harmful and smelly substances and thereby clean up the environment. Cleaning the Environment

15. 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. Pathogens enter our body through the air we breathe, the water we drink or the food we eat. They can also get transmitted by direct contact with an infected person or carried through an animal. Microbial diseases that can spread from an infected person to a healthy person through air, water, food or physical contact are called communicable diseases. Examples of such diseases include cholera, common cold, chicken pox and tuberculosis. When a person suffering from common cold sneezes, fine droplets of moisture carrying thousands of viruses are spread in the air. The virus may enter the body of a healthy person while breathing. Harmful Microorganisms

16. There are some insects and animals which act as carriers of disease-causing microbes. Housefly is one such carrier. The flies sit on the garbage and animal excreta. Pathogens stick to their bodies. When these flies sit on uncovered food they may transfer the pathogens. Whoever eats the contaminated food is likely to get sick. Mosquito is another carrier. Examples of carriers are: the female Anopheles mosquito which carries the parasite of malaria; Female Aedes mosquito acts as carrier of dengue virus. Harmful Microorganisms All mosquitoes breed in water. Hence, one should not let water collect anywhere, in coolers, tyres , flower pot etc. By keeping the surroundings clean and dry we can prevent mosquitoes from breeding.

17. Human Disease Causative Microorganisms Mode of Transmission Preventive Measures (General) Tuberculosis Measles Chicken Pox Polio Bacteria Virus Virus Virus Air Air Air/Contact Air/Water Keep the patient in complete isolation. Keep the personal belongings of the patient away from those of others. Vaccinations to be given at suitable age Cholera Typhoid Bacteria Bacteria Water/Food Water Maintain personal hygiene and good sanitary habits. Consume properly cooked food and boiled drinking water. Vaccination Hepatitis A Virus Water Drink boiled drinking water. Vaccination. Malaria Protozoa Mosquito Use mosquito net and repellents. Spray insecticides and control breeding of mosquitoes by not allowing water to collect in the surroundings. Some Common Human Diseases caused by Microorganisms

18. Several microorganisms not only cause diseases in humans and plants, but also in other animals. For example, anthrax is a dangerous human and cattle disease caused by a bacterium. Foot and mouth disease of cattle is caused by a virus. Robert Köch (1876) discovered the bacterium ( Bacillus anthracis ) which causes anthrax disease. Disease-causing Microorganisms in Animals

19. Disease-causing Microorganism in Plants Several microorganisms cause diseases in plants like wheat, rice, potato, sugarcane, orange, apple and others. The diseases reduce the yield of crops. They can be controlled by the use of certain chemicals which kill the microbes.

20. Some Common Plant Diseases caused by Microorganisms Plant Disease Microorganism Mode of Transmission Figure Citrus canker Bacteria Air Rust of wheat Fungi Air, seeds Yellow vein mosaic of bhindi (Okra) Virus Insect

21. Food preservation Food is spoilt by microorganisms. Spoilt food has bad smell and bad taste and causes food poisoning. Food can be preserved by protecting it from microorganisms. Food can be preserved by different methods. They are :- i ) Chemical method :- Food like pickles can be preserved by using chemicals like salts and edible oils. Jams and squashes can be preserved by using sodium benzoate, sodium metabisulphite . These chemicals are called preservatives. ii) By using common salt :- Food items like fish, meat, amla , raw mangoes, tamarind etc can be preserved by using common salt. It prevents the growth of microbes. iii) By using sugar :- Food items like jams, jellies, squashes etc. can be preserved by using sugar solution. It prevents the growth of microbes. iv) By using oil and vinegar :- Food items like pickles, vegetables, fish, meat etc. are preserved by using oil and vinegar. It prevents the growth of microbes. v) By heat and cold treatments :- Heating food items kills microbes. Similarly storing food items at low temperatures prevents growth of microbes.

22. Pasteurization :- The process of heating milk to about 70 o C for 15 to 30 seconds and then suddenly chilling it to prevent the growth of microbes is called pasteurization. This process was discovered by Louis Pasteur. vi) By storage and packing :- Many food items are stored in air tight containers to protect them from microbes.

23. Nitrogen cycle ATMOSPHERIC NITROGEN LIGHTNING FIXES NITROGEN NITROGEN FIXING BACTERIA AND BLUE GREEN ALGAE FIX ATMOSPHERIC NITROGEN COMPOUNDS OF NITROGEN IN THE SOIL UPTAKE BY PLANTS ANIMAL EATS PLANTS NITROGENOUS WASTE FROM EXCRETION AND DEATH BACTERIA TURN COMPOUNDS OF NITROGEN INTO GASEOUS NITROGEN

24. Nitrogen cycle The nitrogen in the atmosphere is converted into nitrogen compounds in the soil by nitrogen fixing bacteria and blue green algae. Lightning also converted into nitrogen compounds in the soil. The nitrogen compounds in the soil is used by plants for the synthesis of proteins and other compounds. Animals feeding on plants get these proteins and other compounds. When plants and animals die, bacteria and fungi in the soil converts the nitrogenous waste into nitrogen compounds in the soil which are again use by plants. Some other bacteria converts some nitrogen compounds in the soil into nitrogen gas which goes back into the atmosphere. Hence the nitrogen in the atmosphere almost remains constant.

25. ACTIVITY 1 Take some soil in a glass container. Fill it with tap water. Keep it exposed to sunlight. After few days, you will see growth of green layer on the surface of the container. Observe it using magnifying glass. a) what do you see? b)Name the microorganism.

26. ACTIVITY 2 Take ½ kg flour ( atta   or  maida   ),add some sugar and mix with warm water. Add a small amount of yeast powder and knead to make a soft dough. a) What do you observe after two hours? b)Did you find the dough rising?

27. ACTIVITY 3   Take a 500 ml beaker filled up to ¾ with water. Dissolve 2-3 tea spoons of sugar in it. Add half a spoon of yeast powder to the sugar solution. Keep it covered in a warm place for 4-5 hours. Now smell the solution. Could you get a smell? What type of smell it is?

28. ACTIVITY 4 Take two pots and fill each pot half  with soil. Mark them A and B. Put plant waste in pot A and things like polythene bags, empty glass bottles and broken plastic toys in pot B. Put the pots aside. Observe them after 3-4 weeks. Do you find any difference in the contents of the two pots? If so, what is the difference?

29. HOTS 1. Why do you think? i ) Curd sets faster in summer than in winters? ii) Curd turns sour faster in summer than in winter? 2. The sealed packets in which food items such as chips are sold are usually filled with nitrogen. How do you think that helps? 3. Why should you always wash your hands before handling food and after going to the toilet? 4. Evolution i.e. changes in an organisms to adjust to the environment, as suggested by Charles Darwin, is a very slow process that takes place over tens of thousands of generations, taking millions of years. However, in bacteria, developing resistance to antibiotics, which is a type of evolution, takes place within our own lifetime. Can you say why it occurs so quickly in bacteria? 5. Why are protozoa known as an important link for aquatic food chains? 6. Most of the preservatives are chemicals still we use them in our food to preserve. Why? 7. After consuming a dish of mutton, a person complained of nausea, vomiting, diarrhea and pain in the abdomen. ( i ) What type of disease is he suffering from? (ii) What causes this disease. 8. Why do dry food items such as biscuits not spoil easily?

30. ANSWER THE FOLLOWING QUESTIONS 1. GIVE REASON FOR THE FOLLOWING: a) Antibiotics are not useful in treatment of viral infections. b) Milk is stored in refrigerator during summers. c) Are all microorganisms harmful? d) Algae are plant-like while protozoa are animal-like microorganisms. e) Yeast is used in bakeries and breweries.   2. Differentiate between communicable and non- communicable diseases   3. SHORT ANSWER TYPE QUESTIONS: a) How are viruses different from other microbes? b) Mention the role of nitrogen- fixing bacteria in soil. c) How do microorganisms help in cleaning the environment? d) What are antibiotics? What precautions must be taken while taking antibiotics?   4. LONG ANSWER TYPE QUESTION: a)Why bacteria are regarded as our foes and friend? b) Mention the ways in which the following micro- organisms are harmful to mankind: Bacteria, protozoa and viruses. c) What is fermentation? Discuss its uses in making alcoholic beverages.

31. COMPLETE THE TABLE DISEASE CAUSE SYMPTOMS PREVENTION Malaria Amoebic dysentery Measles TB Hepatitis B

32. THANK YOU !