Class 8 Microorganisms: Friend and Foe Short Notes Science Chapter 2
- Protozoa
- Bacteria
- Fungi
- Algae
Microorganisms
Microorganisms are microscopic organisms that cannot be seen with the naked eye.
There are Four groups :
Bacteria
Probiotics are live bacteria and yeasts that are good for your health, especially the digestive system.
Fungi
Fungi are parasitic organisms. They are mostly multicellular and not microscopic. However, yeast is a unicellular and microscopic organism.Fermentation is a metabolic process that converts sugar to acids, gases or alcohol.
Fermentation is used in the preparation of curd and alcohol.
Protozoa
Protozoa are single-celled microscopic animals which include flagellates, ciliates, sporozoans and many other forms. Few examples are: amoeba, paramecium, euglena, plasmodium, etc.Algae
Viruses
Viruses are also microscopic but are different from other microorganisms. They, however, reproduce only inside the cells of the host organism, which may be a bacterium, plant or animalSave From Virus
Vaccines
Vaccines are usually made for viral diseases.
A few examples are Salk vaccine for Polio, Influenza vaccine, Rabies vaccine, etc.
Antibiotics
Where do Microorganisms Live?
Some Disease by Microorganisms
Pathogens
A pathogen is any organism that causes disease.In this context, pathogens are microorganisms. Bacteria, protozoa and viruses can be pathogenic.Vector
Vector is an organism, which is a biting insect or tick, that can transmit a 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 waterborne disease.| 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 virus.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 |
| Chickenpox | Virus | insect |
What's you eats ?? See at once
Food poisoning
- When food contaminated with pathogens or toxins are 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.
Chemical methods
- Chemical preservatives are used in food preservations 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 the 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.
Nitrogen Cycle
Some important keyword
Algae: A group of plants which is mostly aquatic. They are autotrophs (i.e., have chlorophyll). Their body is not divided into root, stem and leaf.
Antibiotics: The medicines that kill or stop the growth of disease-causing microorganisms are called antibiotics.
Bacteria: Bacteria are single-celled microorganism. They can be seen only under a microscope. Their cells are prokaryotic (primitive type).
Carrier: The organisms which carry the pathogen from a diseased person to a healthy person are called carriers. For example, female Anopheles mosquito.
Communicable Diseases: Microbial diseases that can be spread from an infected person to a healthy person through the air, water, food or physical contact are called communicable diseases.
Fermentation: The process of conversion of sugar into alcohol by yeast is called fermentation.
Fungi: Fungi are non-green plants. They cannot synthesize their own food. They may be unicellular or multicellular.
Lactobacillus: Lactobacillus is the bacteria responsible for the formation of curd from milk.
Microorganisms: These are organisms that are too small and are not visible to the naked eye. These include a virus, bacteria, fungi, protozoa and some algae.
Nitrogen Cycle: A process (cycle) by which the amount of nitrogen remains constant in the atmosphere is known as the nitrogen cycle.
Nitrogen Fixation: The process of conversion of atmospheric nitrogen into its usable forms is called nitrogen fixation.
Pasteurisation: The process in which milk is heated to about 70°C for 15 to 30 seconds and then suddenly cooled.
Pathogen: Disease-causing microorganisms are called pathogens.
Preservation: Prevention of spoiling of food from the action of microorganisms is called food preservation.
Protozoa: Protozoa are unicellular animals
Rhizobium: Rhizobium is a bacterium which lives in the root nodules of leguminous plants. This helps in the fixation of nitrogen.
Vaccine: The substance which is injected to trigger the body to develop its own defence (by producing antibodies) is called vaccine.
Virus: Viruses are living only inside other living cells. They are considered as connecting link between living and non-living.
Yeast: Yeast is a unicellular fungus.
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