Microorganisms Class 8 Notes

Probiotics

• Probiotics are live bacteria and yeasts that are good for your health, especially the digestive system.

For more information on Bacteria – The Guys Everywhere, watch the below video

They Love Death – Fungi

Fungi

• Fungi are saprophytic or parasitic organisms.
• They are mostly multicellular and not microscopic.
• However, yeast is a unicellular and microscopic organism.

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Fermentation

• Fermentation is a metabolic process that converts sugar to acids, gases or alcohol.
• Fermentation is used in the preparation of curd and alcohol.

For more information on Fungi – The Death Lovers, watch the below video

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Creepy Protozoans

Protozoa

• Protozoa are single-celled microscopic animals which include flagellates, ciliates, sporozoans and many other forms.
• A few examples of protozoa are amoeba, paramecium, euglena, plasmodium, etc.

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Viruses – From Computers to Life

Viruses

• Viruses are organisms that possess nucleic acid but lack replicating machinery.
• Thus, a virus cannot survive without a living cell.
• Viruses are also considered to be on the borderline between living and nonliving entities.
• A few examples of viruses are influenza virus, HIV, Rabies virus, poliovirus, tobacco mosaic virus, etc.

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Save Yourself – Vaccines and Antibiotics

Vaccines

A vaccine is a biological preparation that provides active acquired immunity to a disease.

• Vaccines are usually made for viral diseases.
• A few examples of vaccines are Salk vaccine for Polio, Influenza vaccine, Rabies vaccine, etc.

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Antibiotics

Antibiotics is an inorganic or organic compound that inhibits and kills microorganisms.

• Antibiotics usually target bacteria.
• Thus, most bacterial diseases are treated with antibiotics.

For more information on Microorganisms, Save Yourself with Vaccines and Antibiotics, watch the below video:

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Pathogens

• A pathogen is any organism that causes disease.
• In this context, pathogens are microorganisms.
• Bacteria, protozoa and viruses can be pathogenic.

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Carrier

• A carrier is a person or organism infected with an infectious disease agent but displays no symptoms of it.
• They can spread the infection since they already have the pathogen in their bodies.

Vector

• A vector is an organism, which is a biting insect or tick, that can transmit disease or parasite from one animal or plant to another.
• Common examples are mosquitoes.
• Aedes mosquito spreads dengue virus, Anopheles mosquito spreads the malarial parasite.

Airborne diseases

• Certain diseases can spread by air.
• These diseases are called airborne diseases.
• Influenza is the best example of this type of disease.

Waterborne diseases

• The diseases that spread through water are called waterborne diseases.
• Contaminated water is host to several pathogens.
• Typhoid is the best example of a waterborne disease.

Examples of Diseases

Human diseases	Causative Organism	Mode of Transmission
Tuberculosis	Bacteria	Air
Measles	Virus	Air
Chickenpox	Virus	Air/Contact
Polio	Virus	Air/Contact
Cholera	Bacteria	Water/Food
Typhoid	Bacteria	Water
Hepatitis B	Virus	Water
Malaria	Protozoa	Mosquito bite
Sleeping sickness	Protozoa	Tsetse fly

Plant diseases

• Certain pathogens can cause diseases in plants. Just like humans, plants can be attacked by bacteria or viruses.
• Several micro-organisms cause diseases in plants like rice, potato, wheat, sugarcane, orange, apple and others.

Disease	Pathogen	Mode of Transmission
Citrus canker	Bacteria	Air
Rust of Wheat	Fungi	Air/Seed
Yellow vein mosaic of bhindi	Virus	Insect

Watch What You Eat! – Food Poisoning and Preservation

Food poisoning

• When food contaminated with pathogens or toxins is consumed, it causes food poisoning.
• The most common symptom is a pain in the stomach.
• In severe cases, food poisoning can also cause death.

Food preservation

• Food preservation is the most vital part of the food industry.
• Certain chemicals inhibit the growth of bacteria and increase the life of the cooked food.
• Certain simple preservation methods can be carried out at our home.

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Chemical methods

• Chemical preservatives are used in food preservation by major food industries as they are harmless to humans.
• Sodium meta-bisulphate and sodium benzoate are commonly used chemical preservatives.

Uses of common salt

• Common salt also known as sodium chloride,  is used as a preservative at home.
• Vegetables are pickled using salt as the salt removes water and kills bacteria and fungus cells.

Preservation by Sugar

• Sugar is used for the preservation of jams, jellies and squashes.
• The growth of microbes is restricted by the use of sugar as it reduces the moisture content.

Preservation by oil and Vinegar

• Many food preparations, like pickles,  are preserved by adding either oil or vinegar to them.
• Bacteria cannot grow in such medium.

Pasteurization

• Pasteurization is a process of superheating and cooling beverages to kill pathogenic microbes.
• Pasteurization ensures the taste of the beverage, such as milk does not get destroyed.

Storage and Packing

• Dry fruits and many vegetables are preserved in airtight/air-sealed containers.
• The absence of air prevents the growth of bacteria or fungi.

For more information on Food Poisoning and Preservation, watch the below video

Nitrogen Cycle

The nitrogen cycle is a biogeochemical cycle by which nitrogen is converted into various chemical forms as it circulates among the atmosphere and terrestrial and marine ecosystems.

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Also Access

NCERT Solutions for class 8 Science Chapter 2

NCERT Exemplar for class 8 Science Chapter 2

Learn more about Microorganisms living around us and other related topics, including CBSE class 8 Science notes, at BYJU’S.

Also Read:-

Microbes

Useful and Harmful Microorganisms