• NCERT Solutions
    • NCERT Library
  • RD Sharma
    • RD Sharma Class 12 Solutions
    • RD Sharma Class 11 Solutions Free PDF Download
    • RD Sharma Class 10 Solutions
    • RD Sharma Class 9 Solutions
    • RD Sharma Class 8 Solutions
    • RD Sharma Class 7 Solutions
    • RD Sharma Class 6 Solutions
  • Class 12
    • Class 12 Science
      • NCERT Solutions for Class 12 Maths
      • NCERT Solutions for Class 12 Physics
      • NCERT Solutions for Class 12 Chemistry
      • NCERT Solutions for Class 12 Biology
      • NCERT Solutions for Class 12 Economics
      • NCERT Solutions for Class 12 Computer Science (Python)
      • NCERT Solutions for Class 12 Computer Science (C++)
      • NCERT Solutions for Class 12 English
      • NCERT Solutions for Class 12 Hindi
    • Class 12 Commerce
      • NCERT Solutions for Class 12 Maths
      • NCERT Solutions for Class 12 Business Studies
      • NCERT Solutions for Class 12 Accountancy
      • NCERT Solutions for Class 12 Micro Economics
      • NCERT Solutions for Class 12 Macro Economics
      • NCERT Solutions for Class 12 Entrepreneurship
    • Class 12 Humanities
      • NCERT Solutions for Class 12 History
      • NCERT Solutions for Class 12 Political Science
      • NCERT Solutions for Class 12 Economics
      • NCERT Solutions for Class 12 Sociology
      • NCERT Solutions for Class 12 Psychology
  • Class 11
    • Class 11 Science
      • NCERT Solutions for Class 11 Maths
      • NCERT Solutions for Class 11 Physics
      • NCERT Solutions for Class 11 Chemistry
      • NCERT Solutions for Class 11 Biology
      • NCERT Solutions for Class 11 Economics
      • NCERT Solutions for Class 11 Computer Science (Python)
      • NCERT Solutions for Class 11 English
      • NCERT Solutions for Class 11 Hindi
    • Class 11 Commerce
      • NCERT Solutions for Class 11 Maths
      • NCERT Solutions for Class 11 Business Studies
      • NCERT Solutions for Class 11 Accountancy
      • NCERT Solutions for Class 11 Economics
      • NCERT Solutions for Class 11 Entrepreneurship
    • Class 11 Humanities
      • NCERT Solutions for Class 11 Psychology
      • NCERT Solutions for Class 11 Political Science
      • NCERT Solutions for Class 11 Economics
      • NCERT Solutions for Class 11 Indian Economic Development
  • Class 10
    • NCERT Solutions for Class 10 Maths
    • NCERT Solutions for Class 10 Science
    • NCERT Solutions for Class 10 Social Science
    • NCERT Solutions for Class 10 English
    • NCERT Solutions For Class 10 Hindi Sanchayan
    • NCERT Solutions For Class 10 Hindi Sparsh
    • NCERT Solutions For Class 10 Hindi Kshitiz
    • NCERT Solutions For Class 10 Hindi Kritika
    • NCERT Solutions for Class 10 Sanskrit
    • NCERT Solutions for Class 10 Foundation of Information Technology
  • Class 9
    • NCERT Solutions for Class 9 Maths
    • NCERT Solutions for Class 9 Science
    • NCERT Solutions for Class 9 Social Science
    • NCERT Solutions for Class 9 English
    • NCERT Solutions for Class 9 Hindi
    • NCERT Solutions for Class 9 Sanskrit
    • NCERT Solutions for Class 9 Foundation of IT
  • CBSE Sample Papers
    • Previous Year Question Papers
    • CBSE Topper Answer Sheet
    • CBSE Sample Papers for Class 12
    • CBSE Sample Papers for Class 11
    • CBSE Sample Papers for Class 10
    • Solved CBSE Sample Papers for Class 9 with Solutions 2024-2025
    • CBSE Sample Papers Class 8
    • CBSE Sample Papers Class 7
    • CBSE Sample Papers Class 6
  • Textbook Solutions
    • Lakhmir Singh
    • Lakhmir Singh Class 10 Physics
    • Lakhmir Singh Class 10 Chemistry
    • Lakhmir Singh Class 10 Biology
    • Lakhmir Singh Class 9 Physics
    • Lakhmir Singh Class 9 Chemistry
    • PS Verma and VK Agarwal Biology Class 9 Solutions
    • Lakhmir Singh Science Class 8 Solutions

Learn CBSE

NCERT Solutions for Class 6, 7, 8, 9, 10, 11 and 12

Microorganisms: Friend and Foe Class 8 Notes Science Chapter 2

August 12, 2024 by Sastry CBSE

CBSE Class 8 Science Notes Chapter 2 Microorganisms: Friend and Foe Pdf free download is part of Class 8 Science Notes for Quick Revision. Here we have given NCERT Class 8 Science Notes Chapter 2 Microorganisms: Friend and Foe.

CBSE Class 8 Science Notes Chapter 2 Microorganisms: Friend and Foe

Microorganisms are too small and are not visible with the naked eye.

They can live in all kinds of environment, ranging from ice cold climate to hot springs, deserts and marshy lands.

Microorganisms are found in air, water and in the bodies of plants and animals.

They may be unicellular or multicellular.

Microorganisms include bacteria, fungi, protozoa and some algae. Viruses though different from the above-mentioned living organisms are referred to as microbes.

Viruses are quite different from other microorganisms. They reproduce only inside the cells of the host organism: bacterium, plant or animal.

Bacteriophage Diagram Class 8

Friendly Microorganisms
The bacterium, Lactobacillus converts milk into curd.

Bacteria are also involved in the making of cheese, pickles and many other food items.

Acetobacter aceti bacteria is used for the production of acetic acid from alcohol.

Yeast is used for commercial production of alcohol and wine by growing them on natural sugars present in grains like barley, wheat, rice and crushed fruit juices etc.

Antibiotics are manufactured by growing specific microorganisms and are used to cure a variety of diseases.

Some microorganisms reside in the root nodules of leguminous plants. They can fix atmospheric nitrogen from the air into the soil and increase soil fertility.

Specialized bacteria convert nitrates and nitrites present in the soil into nitrogen gas which is released in the atmosphere.

Some microorganisms decompose organic wastes like dead plants and animals into simple substances and clean up the environment.

Harmful Microorganisms
The bacterium, Lactobacillus converts milk into curd.

Disease-causing microorganisms are called pathogens.

Common ailments like cold, influenza (flu) and most coughs are caused by viruses. Serious diseases like polio and chicken pox are also caused by viruses.

Diseases like dysentery and malaria are caused by protozoans.

Typhoid and tuberculosis (TB) are caused due to bacteria.

Some common diseases, their modes of transmission and preventive measures are given below.

Some Common Human Diseases Caused by Microorganisms
Microorganisms Friend and Foe Class 8 Notes Science Chapter 2 img-1
Foot and mouth disease of cattle is caused by a virus. Anthrax, a bacterial disease is very fatal for human and cattle.

Some common diseases caused by plants by microorganisms are given below.

Some of the Common Plant Diseases

Plant Diseases Microorganism Mode of Transmission
Citrus Canker Bacteria Air
Rust of wheat Fungi Insects and seeds
Yellow vein mosaic of bhindi (okra) Virus Insect

Food Poisoning: Microorganisms that grow on our food sometimes produce toxic substances. These make the food poisonous and result in serious illness and even death.

Food Preservation

Salts, sugar, edible oils and vinegar are the common chemicals generally used to check the growth of microorganisms. Therefore, they are called preservatives.

Heat and cold treatments also inhibit the growth of microbes.

Pasteurization of Milk: The milk is heated to 70°C for 15 seconds and then suddenly chilled and stored. Such milk is referred to as. pasteurized milk.

Symbiotic bacterium: Rhizobium helps in the fixation of nitrogen with the root of the leguminous plant. The action of lighting also helps into the fixation of nitrogen.

Nitrogen cycle: Nitrogen from the atmosphere is converted into nitrogen compounds by some bacteria like rhizobium and blue-green algae present in the soil and also by lightning. On the other hand, certain other bacteria present in the soil convert nitrogen compounds into nitrogen gas that is released to the atmosphere.

Nitrogen Cycle Diagram Class 8

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.

We hope the given CBSE Class 8 Science Notes Chapter 2 Microorganisms: Friend and Foe Pdf free download will help you. If you have any query regarding NCERT Class 8 Science Notes Chapter 2 Microorganisms: Friend and Foe, drop a comment below and we will get back to you at the earliest.

Filed Under: CBSE

LearnCBSE.in Student Education Loan
  • Student Nutrition - How Does This Effect Studies
  • Words by Length
  • NEET MCQ
  • Factoring Calculator
  • Rational Numbers
  • CGPA Calculator
  • TOP Universities in India
  • TOP Engineering Colleges in India
  • TOP Pharmacy Colleges in India
  • Coding for Kids
  • Math Riddles for Kids with Answers
  • General Knowledge for Kids
  • General Knowledge
  • Scholarships for Students
  • NSP - National Scholarip Portal
  • Class 12 Maths NCERT Solutions
  • Class 11 Maths NCERT Solutions
  • NCERT Solutions for Class 10 Maths
  • NCERT Solutions for Class 9 Maths
  • NCERT Solutions for Class 8 Maths
  • NCERT Solutions for Class 7 Maths
  • NCERT Solutions for Class 6 Maths
  • NCERT Solutions for Class 6 Science
  • NCERT Solutions for Class 7 Science
  • NCERT Solutions for Class 8 Science
  • NCERT Solutions for Class 9 Science
  • NCERT Solutions for Class 10 Science
  • NCERT Solutions for Class 11 Physics
  • NCERT Solutions for Class 11 Chemistry
  • NCERT Solutions for Class 12 Physics
  • NCERT Solutions for Class 12 Chemistry
  • NCERT Solutions for Class 10 Science Chapter 1
  • NCERT Solutions for Class 10 Science Chapter 2
  • Metals and Nonmetals Class 10
  • carbon and its compounds class 10
  • Periodic Classification of Elements Class 10
  • Life Process Class 10
  • NCERT Solutions for Class 10 Science Chapter 7
  • NCERT Solutions for Class 10 Science Chapter 8
  • NCERT Solutions for Class 10 Science Chapter 9
  • NCERT Solutions for Class 10 Science Chapter 10
  • NCERT Solutions for Class 10 Science Chapter 11
  • NCERT Solutions for Class 10 Science Chapter 12
  • NCERT Solutions for Class 10 Science Chapter 13
  • NCERT Solutions for Class 10 Science Chapter 14
  • NCERT Solutions for Class 10 Science Chapter 15
  • NCERT Solutions for Class 10 Science Chapter 16

Free Resources

RD Sharma Class 12 Solutions RD Sharma Class 11
RD Sharma Class 10 RD Sharma Class 9
RD Sharma Class 8 RD Sharma Class 7
CBSE Previous Year Question Papers Class 12 CBSE Previous Year Question Papers Class 10
NCERT Books Maths Formulas
CBSE Sample Papers Vedic Maths
NCERT Library

NCERT Solutions

NCERT Solutions for Class 10
NCERT Solutions for Class 9
NCERT Solutions for Class 8
NCERT Solutions for Class 7
NCERT Solutions for Class 6
NCERT Solutions for Class 5
NCERT Solutions for Class 4
NCERT Solutions for Class 3
NCERT Solutions for Class 2
NCERT Solutions for Class 1

Quick Resources

English Grammar Hindi Grammar
Textbook Solutions Maths NCERT Solutions
Science NCERT Solutions Social Science NCERT Solutions
English Solutions Hindi NCERT Solutions
NCERT Exemplar Problems Engineering Entrance Exams
Like us on Facebook Follow us on Twitter
Watch Youtube Videos NCERT Solutions App