Class -08,
Chapter-02,
Microorganism friend and foe
Science
Microorganism :- Microorganisms are to small in size and are not visible to the unaided eye. It cannot be seen without the help of microscope. So that it is called microorganism.
** Microorganism are found in air, water and in the bodies of plants and animals.
** They can live all kind of environment.
Microorganism are classified into four major groups.
1- Bacteria
2- Fungi
3- Protozoa
4- Algae
Virus :- it is also microscopic but are different from other microorganisms. They reproduce only inside the cells of the host organisms. Which may be bacteria, plants and animal.
Disease caused by virus :-
* Polio
* Corona
* Chicken pox
* Cold
* Influenza etc.
Disease caused by bacteria :-
* Tuberculosis
* Typhoid
* Leprosy
Disease caused by protozoa :-
* Dysentery
* Malaria
Microorganism live :-
> It may be single side like bacteria, Some algae.
> Some are multi cellular like fungi and algae.
> They live in all types of environment.
> Also found inside the bodies of animals including humans.
Microorganism and us :- It play an important role in our lives. Some of them are beneficial in many ways where is some other are very harmful and cause disease.
Friendly microorganism :- They are used for various purposes. example preparation of card bread and cake.
* They are cleaning up the environment. example organic waste are broken down into harmless and usable substance by bacteria.
* They increase soil fertility by fixing nitrogen.
Making of card and bread :- Curd contain several microorganism like lactobacillus. It promotes the formation of curd and converts milk into curd.
* Bacteria are also involved formation of cheese, cake pickle and food items.
* East used for commercial production of alcohol and wine and making breads, pastries, cakes etc.
Commercial use of microorganism :- Microorganisms are used for the large scale production of alcohol, wine and acetic acid.
Fermentation :- the process of conversion of sugar into alcohol is known as fermentation.
Lui pasure discovered fermentation in 1857.
Medicinal use of microorganism :- We use microorganism in the form of antibiotics and vaccines in medicine.
Antibiotics :- the medicine which kill or stop the growth of disease causing microorganism are called antibiotics.
Ex. Penicillin, streptomycin, tetracycline and erythromycin.
** Antibiotics are made from bacteria and fungi.
** If antibiotics taken unnecessarily may kill the beneficial bacteria in the body.
Vaccine :- 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 enters again. If dead or we can't microbes are introduce into the healthy body, the body fights and kills the invading bacteria by producing suitable antibodies.
Ex. Cholera, tuberculosis small pox and hepatitis etc.
** Edward Jenner discovered the vaccine for smallpox in 1798.
Increasing soil fertility :- some bacteria 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.
Ex. Blue green algae, rhizobium etc.
Cleaning the environment :- Microorganism decompose dead organic waste of plants and animals converting them into simple substances. The substance are again used by other plants and animals. These microorganisms can be used to degrade the harmful and smiley substance and their by clean up the environment.
Harmful microorganism :- some of microorganism cause disease in human beings, plants and animals. Such disease causing microorganism are called pathogens.
Disease causing microorganisms in humans :- pathogens inter our body through the air we breathe, the water we drink for the food we eat. They can also get transmitted by direct contact with an infected person or carried by an animal.
Communicable disease :- microbial disease that can spread from an infected person to a healthy person through air water or physical contact are called communicable disease.
Carriers :- some insect and animals which act as carries of disease causing microbes.
Ex. Housefly, mosquito etc.
** Anopheles mosquito carries the parasite of malaria (plasmodium).
** Female ladies mosquito act as carries dengue virus.
** All mosquitoes breed in water. Hence one should not let water collect anywhere, in coolers, tyres, flower pot etc.
Some common human disease caused by microorganism. :-
Disease causing microorganism in animals :- Anthrax is a dangerous human and cattle disease caused by a bacterium.
Food and mouth disease of cattle caused by a virus.
Disease causing microorganism in plants :-several microorganisms cause disease in plants like wheat, rice, potato, sugarcane, Orange, Apple and others. The disease reduce the yield of crops.
Food poisoning :- It could be due to the consumption of food spoiled by some microorganisms. Which grow on our food sometimes produce toxic substances. These make the food poisonous causing serious illness even death.
Food preservation :- Some common methods of preserving food in our homes are -
(1) Chemical method :- shorts and edible oils are the common chemicals generally used to check the growth of microorganism. Therefore they are called preservative.
Ex. Sodium benzoate and sodium metabisulphite.
(2) preservation by common salt:- Meat and fish are covered with dry salt to check the growth of bacteria. It also preserve Amla from mangoes and tamarind.
(3) preservation by sugar :- Jams, jellies and squashes are preserved by sugar.
(4) preservation by oil and vinegar :- it prevents spoilage of pickle because bacteria can not leave in such environment. It also preserved vegetables, fruits, fish and meat.
(5) heat and cold treatment :- boiling kills many microorganisms.
Low temperature in beat the growth of microbes.
Pasteurization :- When the milk is heated to about 70 degree Celsius for 15 to 30 seconds and then suddenly chilled and stored. It prevent the growth of microbes. This process is called posturization.
(6) storage and packing :- these days dry fruits and even vegetables are sold infield a tide packet to prevent the attack of microbes.
Nitrogen fixation :- Rhizobium involved the fixation of nitrogen in leguminous plants. It leaves in the root nodules of leguminous plants (pulses) such as beans and peace, with which it has a symbiotic relationship.
Nitrogen cycle :- our atmosphere has 78% nitrogen gas. Which is one of the essential constituents of all living organisms as part of proteins, chlorophyll, nucleic acid and vitamins.
** The atmospheric nitrogen can not be taken directly by plants and animals.
** Certain bacteria and blue green algae present in the soil fix nitrogen from the atmosphere and convert it into compound of nitrogen.
** When plants and animals die, bacteria and fungi present in the soil convert the nitrogenous wastes into nitrogenous compound to be used by plant again.
Ex.
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