can anyone provide me chapter 2 science notes of class 8.
no useless questions
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Answer:
CBSE Class 8 Science Chapter 2 Notes: Microorganisms
If you observe a drop of water from the pond through a microscope, you will see a lot of tiny rounded structures. These tiny creatures are known as microbes or microorganisms. They are all around us and are so small in size that they cannot be seen with bare human eyes. Microbes are classified into four groups as:
Protozoa
Bacteria
Fungi
Algae
Introduction
Microorganisms
Microorganisms are microscopic organisms that cannot be seen with the naked eye.
These organisms are usually unicellular in nature.
The Guys Who Are Everywhere – Bacteria
Bacteria
Bacteria are unicellular prokaryotic microorganisms.
Some bacteria are useful for humans while some can be harmful.
They are of four major types: Bacillus, Vibrio, Cocci and Spirilla
Probiotics
Probiotics are live bacteria and yeasts that are good for your health, especially the digestive system.
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.
Fermentation
Fermentation is a metabolic process that converts sugar to acids, gases or alcohol.
Fermentation is used in the preparation of curd and alcohol.
Creepy Protozoans
Protozoa
Protozoa are single-celled microscopic animals which include flagellates, ciliates, sporozoans, and many other forms.
Few examples are: amoeba, paramecium, euglena, plasmodium etc
Viruses – From Computers to Life
Viruses
Viruses are organisms that possess nucleic acid but lack the 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.
Few examples are: influenza virus, HIV, Rabies virus, poliovirus, tobacco mosaic virus etc
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.
Few examples are Salk vaccine for Polio, Influenza vaccine, Rabies vaccine etc
Antibiotics
Antibiotics is an inorganic or organic compound that inhibits and kills microorganisms.
Antibiotics usually target bacteria.
Thus most of the bacterial diseases are treated with antibiotics.
Pathogens
A pathogen is any organism that causes disease.
In this context, pathogens are microorganisms.
Bacteria, protozoa and viruses can be pathogenic.
Carrier
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
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 hosts to several pathogens.
Typhoid is the best example of 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
The absence of air prevents the growth of bacteria or fungi.
Explanation: