NCERT Solutions for Class 8 Science Microorganism Chapter 2
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In this article, we will discuss the topic of Class 8 Science. We have already discussed microorganism and its types. We will now discuss ‘the uses of microorganism’.
Microorganisms benefit us in a number of ways. Their uses can be divided into four categories: commercial, medicinal, agricultural, and environmental.
Commercial uses are listed as below :-
- Making curd and cheese – A protein called casein present in milk coagulates to form a curd. For casein to coagulate the milk has to be made acidic. A bacterium called Lactobacillus, present in the spoonful of curd added to the milk converts the lactose sugar present in milk to lactic acid.The process of conversion of a sugar into an acid or an alcohol by the action of microorganism is called fermentation.
- Making alcoholic beverages – Production of alcoholic beverages such as beer and wine involves fermentation of sugar present in barley, grapes, etc. by a microscopic fungus called yeast.
- Making bread – The process of making bread involves kneading a mixture of flour, salt,sugar, yeast cells, and water into the dough. Yeast converts sugar to an alcohol and carbon dioxide as more and more carbon dioxide is produced, the dough rises in volume.
- Making Vinegar,coffee, and tobacco – Bacteria are used in the production of vinegar. It is also used in the processing of tea,coffee, and tobacco.
- Making toothpaste – Shells of diatoms are used in toothpaste to give it a gritty texture that helps in cleaning teeth.
- Making antibiotics – Certain bacteria and fungi are used in the production of medicines called antibiotics that destroy certain disease-causing microbes. Antibiotics are used to control microbial disease in animals and plants.
- Making Vaccines – When a disease causing microbe entersintothe body,our body produces substances called antibodies.A vaccine is a preparation of killed or weakened disease causing microbe. Vaccines help in preventing disease caused by microbes.
- Making food supplements
- In human body – They help to digest food and destroy disease causing microbes.
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Nitrogen fixation is the process by which free atmospheric nitrogen is converted into nitrogen compounds. Leguminous plants such as peas and soybeans have nitrogen fixing bacteria Rhizobium present in their root nodules. The cycling of nitrogen between the atmosphere, soil, and organisms is called a nitrogen cycle.
The Nitrogen cycle is a usual process in which atmospheric nitrogen enters the soil and becomes a part of living organisms before returning to the atmosphere.
A microbe, such as bacteria and fungi act on dead bodies of dead plants and animals, converts them into simple substances. Removal of dead bodies keeps our planets clean. Bacteria are also used in sewage treatment where they help in the decay of waste organic matter.
For objective and subjective question bank on Microorganism, click on NCERT Solutions for Class 8 science.
Harmful effects of microorganisms can be divided into the following two categories:
- Causing disease in human beings,animals, and plants
- Food spoilage
Disease causing microorganisms
A microorganism that causes diseases in human beings, animals, and plants are called pathogens.
- In human beings – Pathogens can enter the body of a healthy person through the air, water, and food. Pathogens can also spread from an infected person to a healthy one. Diseases that can spread from one person to another are called communicable diseases. E.g :- Malaria, Cholera, etc.
- In animal – Eg:- foot and mouth disease, rinderpest, fin rot.
Microorganism and food spoilage
The main conditions required for the growth of these microorganisms are a moderately warm temperature, air, and moisture. Few things that can help us detect food that has become unfit for consumption
- Foul odour
- Slimy surface
- Surface discoloration
- Sour taste
- Gas formation
The process of treating and controlling food with an aim to stop or slow down its spoilage while maintaining its nutritional value, texture, and flavor is called Food preservation.
Methods of food preservation
- Refrigeration and freezing
- Using chemical preservatives
- Using salt, sugar, oil, or vinegar
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