Frank Cce Everyday Science Solutions for Class 8 Science Chapter 2 Microorganisms are provided here with simple step-by-step explanations. These solutions for Microorganisms are extremely popular among Class 8 students for Science Microorganisms Solutions come handy for quickly completing your homework and preparing for exams. All questions and answers from the Frank Cce Everyday Science Book of Class 8 Science Chapter 2 are provided here for you for free. You will also love the ad-free experience on Meritnation’s Frank Cce Everyday Science Solutions. All Frank Cce Everyday Science Solutions for class Class 8 Science are prepared by experts and are 100% accurate.

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1. Euglena
2. Mycelium
3. Nostoc
4. Dehydration
5. Porphyra

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(a) salting
Salting is the method of preserving food by adding salt to it.

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(c) Rhizobium
Rhizobium is a bacterium that has the ability to fix nitrogen.

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(c) Euglena
Euglena is a protozoan that is photosynthetic.



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A vaccine is a serum prepared from either dead or live, attenuated (weakened) pathogens. When a vaccine is administered to a person, his body develops the immunity against the pathogen the vaccine was made from. Once gained, his body will always have this immunity. The next time the person's body encounters the pathogens of that specific disease, already having the immunity against the disease, it prevents the person from falling ill. 

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(a) Lactobacillus
Lactobacillus is a bacterium that turns milk into curd.

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(b) alcohol
Yeast is used in the production of alcohol by the process of fermentation.

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(a) bacteria
Bacteria are used to prepare vinegar from cane sugar.

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(a) Escherichia coli
Escherichia coli is a bacterium found in the human intestine, which helps in the digestion of food.

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(c) foot and mouth
The foot and mouth disease in animals is caused by viruses.

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(a) protozoa
Amoeba, euglena and giardia are examples of protozoa.

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(a) vacuum drying
Milk is converted into milk powder by vacuum drying.

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1. Microorganisms can be seen with the help of microscopes.
2. Bacillus bacteria are rod shaped.
3. Algae can make their own food because they possess chlorophyll.
4. Anaerobic bacteria can grow in the absence of oxygen.
5. The process of converting ammonia into nitrates is nitrification.

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Column A Column B
1. Bacteria (e) Tuberculosis
2. Algae (c) Kelp
3. Fungi (d) Ringworm
4. Protozoa (b) Diarrhoea
5. Virus (a) Polio

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1. (T) True. Rabies is a viral disease.
2. (F) False. Mumps is caused by a virus.
3. (F) False. The antibiotic, Penicillin is obtained from fungi.
4. (T) True. Euglena is known as a biological puzzle because it has the characteristics of both plants and animals.
5. (T) True. Some algae such as nostoc help in nitrogen fixation.



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Microorganisms have the ability of forming a cyst when conditions are unfavourable to them. This cyst is a hard outer covering around the body of these microorganisms. As the conditions become favourable, they emerge out of the cyst and start growing. Thus, they can survive in unfavourable conditions for a long period of time.

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During the course of a day, while we are engaged in different activities, harmful microorganisms might find their way into our bodies, especially through our hands. If we don't wash our hands before every meal, these microorganisms will enter our body along with the food. This might cause various diseases. Hence, it is important to wash our hands before every meal.

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Algae are a good food supplement because they are very rich in vitamins and proteins. They are also rich in minerals such as potassium, sodium, iodine etc. Some algae such as Chondrus, Chlorella etc., are consumed directly as food in many countries. Fishes consume green algae. When humans consume these fishes, they obtain the proteins and vitamins contained in the algae, indirectly.

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A sufficient amount of salt is added to pickles because salt acts as a preservative. It prevents pickles from getting spoilt by microbes. This method is known as salting.

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Microorganisms are those organisms that cannot be seen with the naked eye. They are visible only under a microscope. The people who study microorganisms are called microbiologists.

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(a) Rhizobium is an example of a bacterium.
(b) TMV (Tobacco Mosiac Virus) is an example of a virus.
(c) Yeast is an example of a fungus.
(d) Nostoc is an example of an alga.
(e) Euglena is an example of a protozoan.

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Fish and vegetables are preserved by sun drying.

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Rhizobium and nostoc are the microorganisms that can fix atmospheric nitrogen.

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Rhizobium lives in the root nodules of leguminous plants.

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Food preservation methods are based on the following two principles:
(a) Bactericidal preservation
(b) Bacteriostatic preservation

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In the bactericidal method, we apply suitable techniques to fully eliminate or kill the microorganisms that might spoil the food.

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The microorganisms that are useful in the nitrogen cycle are:

(a) Nitrogen-fixing bacteria: Examples: azotobacter and rhizobium
(b) Putrefying bacteria involved in ammonification
(c) Nitrifying bacteria: Examples: nitrosomonas and nitrobacter
(d) Denitrifying bacteria: Example: pseudomonas

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Deep freezing method is used for preserving leafy vegetables. This method involves keeping the food at very low temperatures. This temperature will be lower than that required by microbes to grow. Deep freezing helps the preserved food maintain its nutritional value.

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The process of fermentation is employed in making cheese and wine.

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Antibiotics are medicines that kill bacteria or inhibit their growth. They are widely used as a cure to many diseases because they kill the disease-causing bacteria. Examples: streptomycin and aureomycin.

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Following are the advantages of food preservation:

(a) It helps in protecting food from getting spoilt by microorganisms, for longer duration.
(b) It helps in creating a buffer stock of food material that can be used during an off season or an emergency.

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Fruits and vegetables remain fresh for a few days when kept in a refrigerator because the temperature in the refrigerator is too low for the growth of microorganisms. Thus, this low temperature prevents the food from being spoilt by microorganisms.



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Irradiation is a modern method of food preservation based on principle of bactericidal method in which the food is exposed to heavy energy radiation, usually gamma rays or X-rays. These kinds of radiation destroy the harmful microorganisms present in the food material so that it could be preserved for a longer period of time.

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Farmers cultivate the plants in the legume family to replenish nitrogen in the soil naturally. The roots of leguminous plants contain nitrogen fixing microorganisms that can fix the atmospheric nitrogen and convert it into the forms that plants can consume. This helps the farmers to increase the nitrogen content of the soil without adding any fertilisers.

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Following are five methods of food preservation:
(a) Dehydration
(b) Deep freezing
(c) Canning
(d) Vacuum drying
(e) Irradiation

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Algae are chlorophyll containing microorganisms that are classified as plants. They may be unicellular or multicellular. They can be found growing in both fresh water and seawater.

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Protozoa are unicellular microorganisms that have animal-like characteristics. They may be found in both, fresh and salt water. Some of them are also found in moist soil. They may be free living or may also be found as parasites in the body of other organisms. Examples: amoeba, euglena, giardia.

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The following are the economic importance of bacteria in agriculture:

(a) They help in recycling organic matter by decomposing the dead remains of plants and animals and their waste products.
(b) Some of them such as nitrosomonas and nitrobacter help in nitrification by converting ammonia into nitrates. This increases the soil fertility.
(c) Some of them help in atmospheric nitrogen fixation.

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Streptomycin, aureomycin and chloromycetin are three examples of antibiotics.

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Viruses are the smallest microorganisms which cannot be viewed even under a light microscope. They are studied under electron microscopes. They possess the characteristics of both living things and non-living things.

Viruses Other microbes
They cannot be viewed under a light microscope. They can be viewed under a light microscope.
They cannot reproduce by themselves. They need a host for reproduction. They can reproduce on their own.
They behave like non-living things, when outside the host body. They always possess the characteristics of living things.

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Economic importance of fungi in agriculture:
Fungi are either saprotrophic or parasitic. Saprotrophic fungi feed on the dead remains of plants and animals and decompose them. The products of these decomposed bodies escape into the air and soil. This adds important nutrients to the soil and makes it fertile.

Economic importance of fungi in industries:
(a) Yeast is extensively used in breweries and bakeries for making wine and bread, respectively. Alcohol and carbon dioxide are produced by the fermentation by yeast. Alcohol is used in breweries, whereas carbon dioxide is used in bakeries.
(b) Different species of penicillin are used in the preparation of cheese in cheese industry.
(c) Fermentation of several fungi is made use of in manufacturing several organic acids, such as oxalic acid.
(d) Fungi such as penicillin are used in manufacturing antibiotics.

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Algae     Fungi
They are autotrophic. They are either saprotrophic or parasitic.
They are found in both fresh water and seawater. They are found in dark, warm and moist places.
They do not act as decomposers.  Saprotrophic fungi act as decomposers.
They contain chlorophyll.     They lack chlorophyll.


 
   

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Nitrogen cycle:
It is the process that occurs in nature to maintain the nitrogen content of the atmosphere, soil and water.

Nitrogen cycle involves the following key steps:
(i) Nitrogen fixation:
Free atmospheric nitrogen is first converted into nitrates, which can be consumed by plants. This conversion is carried out by industrial nitrogen-fixation (by the manufacturing of ammonium salts or chemical fertilisers) or by nitrogen-fixing bacteria such as Azotobacter and Rhizobium. This conversion is called nitrogen-fixation. The nitrates are absorbed by plants and utilised by them for making organic matter such as proteins.

(ii) Ammonification:
Nitrogenous compounds present in plants and animals (through plants) are released back into the soil either in the form of nitrogenous waste like ammonia, urea or uric acid or by the decomposition of dead plants and animals. These nitrogenous compounds are then converted to ammonium ions by the process of ammonification that is carried out by certain putrefying bacteria and fungi.

(iii) Nitrification:
Microorganisms like Nitrobacter convert ammonia into nitrates by the process of nitrification.

(iv) Denitrification:
Decomposers such as Pseudomonas reduce nitrates back into nitrogen or some other oxide of nitrogen by the process of denitrification and release free nitrogen back into the atmospheric pool.

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There are two methods of food preservation:
(a) Bactericidal method:
In this method, we apply suitable techniques to fully eliminate or kill the microorganisms that may spoil food.
Example: canning, irradiation etc.

(b) Bacteriostatic method:
In this method, food is kept in conditions that are not suitable for the growth of microorganisms.
Example: deep freezing, salting etc.

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Algae have the following uses:
(a) Chlorella is a green alga used to make an antibiotic called chlorellin.
(b) Agar, obtained from red algae, is used in the preparation of food, medicines and cosmetics.

Fungi have the following uses:
(a) Penicillium notatum is a fungus used in making an antibiotic called penicillin.
(b) Yeast is used in making wine and to make bread soft and spongy.

Protozoa have the following uses:
(a) Some of them help in the degradation of sewage and waste.
(b) Some free-living forms of protozoa are eaten by algae, which, in turn, are eaten by bigger animals. Thus, they form important links in various ecosystems.

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Tuberculosis is caused by bacteria (Mycobacterium tuberculosis).
Polio is caused by a virus.
Athlete's foot is caused by fungi.
Dysentery is caused by protozoa.

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Several forms of bacteria are used in manufacturing antibiotics and vaccines. Hence, they have an important role in producing medicines.

The following points illustrate the role of bacteria in industries:
(a) Mycoderma aceti helps in producing vinegar (acetic acid).
(b) Lactobacillus is a bacteria responsible for the conversion of milk into curd and cheese.
(c) Some bacteria are used in the tanning of leather.
(d) Some bacteria are used in the retting of jute.

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Fungi grow in damp, warm and dark places. This can be shown by the following activity:

Take two slices of bread and moisten them with some water. Now place one of them on a plate and keep the plate in a warm and dark place. Keep the other slice in a cool place. Observe both the slices after a couple of days. The slice kept in the warm and dark place will have some small spots or there will be growth of bread mould on the slice. The slice kept in the cold place will not have any change because fungi do not grow at low temperatures. Repeat the same activity with a dried slice of bread. Keep it in a dark and warm place. The bread will show no sign of any change, which proves that moisture is also required for fungal growth.

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The following are the uses of protozoa:
(a) Some of them help in the degradation of sewage and waste.
(b) Some free-living forms of protozoa are eaten by algae, which, in turn, are eaten by bigger animals. Thus, they form an important link in various ecosystems.

The following are the harmful effects of protozoa:
Some protozoa cause diseases such as dysentery, malaria and dengue fever in humans. They also cause diseases in several animals.

Hence, protozoa are useful as well as harmful to us.



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