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1) Write a note on Microorganisms.
     The living organisms which are very minute and cannot be seen by naked (unaided) eyes are known as microorganisms or microbes.
Some of the microorganisms are unicellular (consisting of a single cell), for example, bacteria. Some have a well-organised multicellular body, for example, moulds like Mucor. Microorganisms include virus, bacteria, fungi like yeast and moulds, algae like chlamydomonas and spirogyra, and protozoan like amoeba and paramecium. Some multicellular microorganisms, such as fungi which grows on bread can be seen with a magnifying glass, others such as bacteria, cannot be seen without the help of a microscope.

2) Define bacteria.
     Bacteria are single celled microorganisms. They are put under plant kingdom because they have rigid definite cell wall like plant cells. Bacteria can be seen under microscope which enlarges their image from a hundred to thousand times.
3) What is Fungi?
     Fungi are non-green plants. They cannot synthesize their own food. They have to depend for their food on others. Most fungi take their food from dead organic matter. Some live on other organisms as parasites. Some fungi like yeast are unicellular; other like Penicillium, Mucor, Aspergillus, etc. are multicellular .
4) Write a note on algae.
     Algae are green substances floating on the surface of pond, lake, river, stagnant water, moist soil, stones etc. They tend to grow on wet surfaces. Therefore, they can synthesize their own food. They are found in water or in very moist places.Some of the algae are unicellular like chlamydomonas but some algae are multicellular. Some multicellular algae are a few metres long, for example kelps, which are found in sea.

5) Write a note on Protozoa.
     Protozoa are unicellular animals. Some are free-living, others are parasites. Several parasitic protozoans cause diseases in human beings, domestic animals and plants. For example, Plasmodium, a protozoan, causes malaria. Entamoeba causes amoebic dysentery. Some free living protozoa eat unicellular algae and are, in turn, eaten by bigger animals in the food chain.

6) Can microorganisms be seen with the naked eye? If not how can they be seen.
     Microorganisms cannot be seen with our naked eyes. They can be seen with the help of a microscope.

7) What are the major groups of microorganism?
     There are four major groups of microorganisms:
     i) Bacteria                     (ii) Fungi                      (iii) Protozoa                (iv)Algae

8) Name the microorganisms which can fix atmospheric nitrogen in the soil.
    Bacteria like Rhizobium and Azotobacter and blue green algae can fix atmospheric nitrogen in soil.

9) Write 10 uses of microorganisms in our lives.
     (i) Microorganisms help in the preparation of curd, bread, cake etc.
     (ii) They are used to produce alcohol at large scale.
     (iii) Yeast is used to prepare vinegar.
     (iv) Microorganisms are used to make wines.
     (v) They act as cleaning agent and decompose the waste products into manure.
     (vi) They destroy the plant and animal dead bodies by decomposing them.
     (vii) They increase soil fertility by fixing the nitrogen in the atmosphere.
     (viii) They are used in making medicines like antibiotics and vaccines.
     (ix) They are used as preservatives for food items.
     (x) They help in various metabolic activities in our body.

10) Write a short paragraph on the diseases caused by microorganisms.
        Microorganisms are also very harmful to us. They cause a number of diseases in humans as well as in other animals. Common cold, Tuberculosis, Measles, Chicken Pox, Polio, Cholera, Typhoid, Hepatitis B, Malaria, are some common human diseases caused by microorganisms. Anthrax is a serious disease in animals caused by microbes. They also make food items unfit for use by food poisoning. They also spoil clothes and leather products. They cause diseases in plants like blights in potatoes, sugarcanes, oranges etc and reduce the production.

11) What are antibiotics? What precautions must be taken while taking antibiotics?
       The medicines which kill or stop the growth of microorganisms in our body are called antibiotics. These are very useful to us as they prevent us from the effects of microorganisms. Antibiotics are made from bacteria and fungi. The penicillin is the first antibiotic

s which is discovered by Alexander Fleming in 1929. These days a number of antibiotics are used to cure various human and animal diseases. Streptomycin, Tetracycline, Erythromycin etc. are some common antibiotics.
Precautions: We should take antibiotics only under the advice of a doctor. Antibiotics should only be taken when needed. Otherwise, they may be harmful and become less effective in future.

12) What are viruses?
       Very tiny microscopic organisms which reproduce only inside the cells of host organisms are called virus.

13) Write the names of some diseases caused by virus.
       Influenza (Flu), Polio and Chicken Pox are some diseases caused by viruses.

14) Name some diseases caused by Protozoans.
      Dysentery and Malaria.

15) Mention some diseases caused by bacteria.
       Typhoid and Tuberculosis (TB) are the bacterial diseases.

16) What are the two types of microorganisms on the basis of their functions?
       (i) Useful Microorganisms                         (ii) Harmful Microorganisms.

17) Name the Microorganisms which promotes the formation of curd.
       Bacterium Lactobacillus promotes the formation of curd.

18) What is fermentation?
      The process of conversion of sugar into alcohol is known as fermentation.

19) Name the scientist who discovered fermentation.
      Louis Pasteur discovered fermentation in 1957.

20) Name some antibiotics.
       Streptomycin, Tetracycline and Erythromycin are some antibiotics.

21) What do you mean by antibodies?
       When a disease carrying microbe enters in the body, the body produces a substance to fight the invader, these are called antibodies.

22) What is vaccine?
        The medicine used to protect children from several diseases is called vaccine.

23) What do you mean by vaccination?
       The process of providing vaccine is called vaccination.

24) Name a most popular vaccination programme. Who discovered the vaccine for Small Pox?
       Pulse Polio Programme. Edward Jenner in 1798.

25) What is meant by nitrogen fixation?
       The process by which atmospheric nitrogen is converted into nitrates by the action of microorganisms is called nitrogen fixation.

26) What are pathogens? How do pathogens enter in our body?
       The disease causing microorganisms are called pathogens. The pathogens enter in our body through air, water and food.

27) Name two communicable diseases.
       Cholera and Chicken Pox.

28) What are carriers of disease causing microbes?
       The insects and animals which help in the transmission of the pathogens from source to the persons are called carriers of disease causing microbes.

29) Who is the carrier of dengue virus?
        Female Aedes mosquito.

30) Why we should not let water collect anywhere?
       All mosquitoes breed in fresh water or stagnant pools.  Hence we should not let water collect anywhere.

31) What do you mean by food preservation?
       Process to prevent food material from spoilage of food by the action of microbes is called preservation.

32) What are preservatives?
        The chemicals which are used to check the growth of microorganisms are called preservatives.

33) Name some preservatives.
       Sugar, salt, oils and vinegar are some common preservatives.

34) What do you mean by symbiotic relationship?
       The relationship between two organisms in which both the organisms are benefitted is called symbiotic relationship.

35) What are viruses? Name some common diseases in human caused by virus.
        Viruses are microscopic. They however reproduce only inside the cells of host organism, which may be a bacterium plant or animal. Some diseases like cold, influenza (flu), polio and chicken pox are caused by viruses.

36) How do microorganisms survive under adverse conditions?
      Under unfavourable conditions of temperature and water, they generally form a hard and tough covering called cyst.  It  protects them. When favourable conditions come they emerge from their shell, multiply and go through their different life cycles.

37) How do microorganisms act as a cleaning agent of nature?
      Microorganisms are also used in cleaning up of the environment. The organic wastes like vegetable peels and remains of animals are broken down into harmless and usable substances by the action of microorganisms. In agriculture they are used to increase soil fertility by fixing nitrogen and by making manure.

38) Explain the formation of curd from  milk.
       Curd contains several microorganism of these the Lactobacillus bacterium promotes the formation of curd. It multiplies in milk and converts it into curd. Curd is an important ingredient of rava idlis and bhaturas.

39) What is the role of yeast in baking industry?
       Yeast plays an important role in the baking industry. Yeast reproduces rapidly and produces carbon dioxide during respiration. Bubbles of the gas fill the dough and increase its volume. This is why yeast is used in the baking industry for making breads, pastries and cakes.

40) Explain the commercial use of microorganisms.
       Microorganisms are used for 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 sugar present in grains. Yeast converts sugar into alcohol. This process is called fermentation. Microorganisms, are also used to prepare medicine like antibiotics.

41) Mention some beneficial effects of bacteria.
       Beneficial effects of bacteria:
      (i) They help in fixation of nitrogen to increase soil fertility.
     (ii) They are used to make vinegar, curd and alcohol etc.
    (iii) They help in the cleaning of environment by the decomposition of organic wastes.
    (iv) They are also used in making medicines like antibiotics.

42) Explain the various types of bacteria.
       The bacteria are classified into three types on the basis of their shape:
     (i) Rod shaped (Bacillus): These are long and rod shaped bacteria like Lactobacillus.
    (ii) Round shaped (Coccus): They are round shaped like Streptococcus.
   (iii) Spiral: These are comma shaped bacteria like Triponema.

43) Explain the discovery of Penicillin.
      In 1929, Alexander Fleming was working on a culture of disease causing bacteria. Suddenly he found the spores of little green mould in one of his culture plates. He observed that the presence of mould kill and stop the growth of bacteria. From this mould penicillin was prepared.

44) Explain how does a vaccine work.
     When a disease carrying microbe enter in our body, the body produces antibodies to fight the invader. The body also remembers how to fight the microbe if it enters again. The body fights and kills the microbes by producing suitable antibodies. The antibodies remain in the body and we are protected thus from disease causing microbes. This is how a vaccine works.

45) Describe the role of blue green algae and bacteria in fertility of soil.
        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. In this way bacteria and blue green algae increase the soil fertility.

                 Blue green algae

46) What are communicable diseases? Explain with examples. 
       The 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.

47) What do you mean by food poisoning?
          Some microorganisms get settled on the food stuff. They release the toxic substances in the food stuff. This makes the food contaminated and unfit for use. This is called food poisoning. If any one consumes this food it can produce fatal results. Serious illness is caused and patient get frequent vomiting and loose motion. This physical condition can lead even to death. So it is very important that we preserve food to prevent it from being spoilt.

48) What is pasteurization of milk?
       Pasteurised milk can be consumed without boiling as it is free from harmful microbes. The milk is heated to about 70°C for 15 to 30 seconds and then suddenly chilled and stored.  By doing so the milk is prevented by the growth microbes. This process was discovered by Louis Pasteur so it is called Pasteurization.

49) Explain causative microorganisms, mode of transmission and preventive measure of the human diseases like Tuberculosis, Measles, Chicken pox, Polio, Cholera, Typhoid, Hepatitis B and Malaria etc.
          Some of the common diseases affecting humans, their mode of transmission and few general methods of prevention are given in the following table:

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