Sunday 30 August 2020

Lecture: 8 :CLASS VIII : SCIENCE : Chapter 2: GOOD MICRO-ORGANISMS

Friendly microorganisms/ beneficial microorganism:

Not all microorganisms are bad for human. Some of them are useful too. Beneficial effects of microorganisms are as follows:

1. In the making of card, bread and cake microorganisms are used.
2. In the production of alcohol, wine, acetic acid or vinegar microorganisms are used.
3. Microorganisms are used to produce antibiotics.
4. Microorganisms are used to increase the fertility of the soil by nitrogen fixation.
5. Microorganisms are used to decompose the organic waste matter.

a. Process to make curd:

Milk is is turned into curd by using the bacteria Lactobacillus
Milk contains sugar called lactose. Lactobacilli bacteria convert the lactose sugar into lactic acid. This lactic acid then converts milk into curd.

b. Process to make bread:

Yeast is used in the baking industry for making bread. When Yeast is mixed in dough, it reproduces quickly and produces carbon dioxide during respiration. The bubbles of carbon dioxide gas filled the dough and increases volume. This is the secret of increasing the volume of bread. It makes the bread light, soft and spongy.

c. Commercial use of microorganisms:

Microorganism are used for the large scale production of alcohol and acetic acid. Yeast is the microorganism used for the large scale production of alcohol.

The process of conversion of sugar into alcohol by the action of yeast is called fermentation. 

Bacteria can turn alcohol into acetic acid. A dilute solution of acetic acid is called vinegar.
The bacteria which convert alcohol into acetic acid is called Acetobacter.

d. Medicinal use of microorganism:

A medicine which stops the growth of, or kills the disease causing microorganisms is called antibiotic. Antibiotics medicine are made from microorganisms. 
Example: some of the common antibiotics which are made from fungi and bacteria are: penicillin, streptomycin, erythromycin, tetracycline.

Antibiotics are effective for bacteria causing diseases but they are ineffective against the diseases caused by virus.

Precautions that to be observed in the use of antibiotics:

1. Antibiotics should be taken only on the advice of a qualified doctor.
2. A person must complete the full course of antibiotics prescribed by the doctor.
3. The antibiotics should be taken in proper doses as advised by the doctor.
4. Antibiotics should not be taken unnecessarily, if taken unnecessarily it may kill the useful bacteria in the body and harm us.

Vaccine:

A vaccine is a special kind of preparation or medicine which provides immunity or protection against a particular disease.

A vaccine contains the dead or weakened but alive microorganisms of a disease. Find the vaccine containing dead or alive microorganisms introduced into the body of a healthy person either orally or by injection the body of that person responds by producing some substances called antibodies in the blood. These antibodies kill the disease causing microorganism in the body. Thus a vaccine developes the immunity from a disease.

Vaccination: 
Vaccination is the process of giving a vaccine orally or by injection which provides protection against a particular disease.

The diseases which can be prevented by vaccination of children at proper age are: polio, smallpox, cholera, typhoid, hepatitis, tuberculosis, tetanus, measles, rabies, diphtheria and whooping cough.

Polio in India is prevented by giving oral polio vaccine or OPV under the pulse polio programmes of government of India.

e. Increasing soil fertility by microorganisms:

Some bacteria and blue green algae are able to fix nitrogen gas from the atmosphere to enrich the soil with nitrogen compounds and increase its fertility. The nitrogen fixing bacteria and blue green algae are called biological nitrogen fixers. One of the nitrogen fixing bacteria is rhizobium. Rhizobium bacteria present in the root nodules of leguminous plant (like peace, beans etc) also fix atmospheric nitrogen and increase soil fertility.

f. Cleaning the environment by microorganisms:

Some microorganisms decompose the harmful and smelly dead remains of plants and animals and animal wastes (like faeces, urine etc) into harmless materials and thus they clean the environment. In addition to the cleaning the environment, the microorganisms also help in recycling the nutrients present in dead plants, dead animals and animal wastes in nature which can then bi used as food by Green plants.









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