NCERT Class 8 Science Microorganisms Friend And Foe

Read and download NCERT Class 8 Science Microorganisms Friend And Foe in NCERT book for Class 8 Science. You can download latest NCERT eBooks chapter wise in PDF format free from Studiestoday.com. This Science textbook for Class 8 is designed by NCERT and is very useful for students. Please also refer to the NCERT solutions for Class 8 Science to understand the answers of the exercise questions given at the end of this chapter

NCERT Book for Class 8 Science Chapter 2 Microorganisms Friend or Foe

Class 8 Science students should refer to the following NCERT Book Chapter 2 Microorganisms Friend or Foe in Class 8. This NCERT Book for Class 8 Science will be very useful for exams and help you to score good marks

Chapter 2 Microorganisms Friend or Foe NCERT Book Class 8

MIICROORGANIISMS :: FRIIEND AND FOE

You have seen several kinds of plants and animals. However, there are other living organisms around us which we cannot see with eyes alone. These are called microorganisms or microbes. For example, you might have observed that during rainy season moist bread gets spoilt and its surface gets covered with greyish white patches. Observe these patches through a magnifying glass. You will see tiny, black rounded structures. Do you know what these structures are and where did these come from?

2.1 Microorganisms

These observations show that water and soil are full of tiny organisms, though not all of them fall into the category of microbes. Thes microorganisms or microbes are so small in size that they cannot be seen with the unaided eye. Some of these, such as the fungus that grows on bread, can be seen with a magnifying glass. Others cannot be seen without the help of a microscope. That is why these are called microorganisms or microbes. Microorganisms are classified into four major groups. These groups are bacteria, fungi, protozoa and some algae. Some of these common microorganisms are shown in Figs. 2.1 - 2.4. Viruses are also microscopic. They, however, reproduce only inside the cells of the host organism, which may be a bacterium, plant or animal. Some of the viruses are shown in Fig. 2.5. 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 whereas typhoid and tuberculosis (TB) are bacterial diseases. You have learnt about some of these microorganisms in Classes VI and VII.

Friendly Microorganisms Microorganisms are used for various purposes. They are used in thepreparation of curd, bread and cake. Curd contains several microorganisms. Of these, the bacterium Lactobacillus promotes the formation of curd. It multiplies in milk and converts it into curd. Bacteria are also involved in the making of cheese, pickles and many other food items. An important ingredient of rava (sooji ) idlis and bhaturas is curd. Can you guess why? Activity 2.3

Take ½ kg flour (atta or maida), add some sugar and mix with Fig. 2.5 : Viruses I saw that my mother added a little curd to warm milk to set curd for the next day. I wonder why! They are also used in cleaning up of the environment. For example, the organic wastes (vegetable peels, remains of animals, faeces, etc.) are broken down into harmless and usable substances by bacteria. Recall that bacteria are also used in the preparation of medicines. In agriculture they are used to increase soil fertility by fixing nitrogen. Making of Curd and Bread You have learnt in Class VII that milk is turned into curd by bacteria. 2.2 Where do Microorganisms Live?

Microorganisms may be single-celled like bacteria, some algae and protozoa, or multicellular, such as algae and fungi. They can survive under all types of environment, ranging from ice cold climate to hot springs and deserts to marshy lands. They are also found inside the bodies of animals including humans. Some microorganisms grow on other organisms while others exist freely. Microorganisms like amoeba can live alone, while fungi and bacteria may live in colonies.

2.3 Microorganisms and Us

Microorganisms play an important role in our lives. Some of them are beneficial in many ways whereas some others are harmful and cause diseases. Let us study about them in detail. Yeast reproduces rapidly and produces carbon dioxide during respiration. Bubbles of the gas fill the dough and increase its volume (Fig. 2.6). This is the basis of the use of yeast in the baking industry for making breads, pastries and cakes.

Commercial Use of Microorganisms Microorganisms are used for the large scale production of alcohol, wine and acetic acid (vinegar). Yeast is used for commercial production of alcohol and wine. For this purpose yeast is grown on natural sugars present in grains like barley, wheat, rice and crushed fruit juices, etc.

Exercises

1. Fill in the blanks:

(a) Microorganisms can be seen with the help of a ____________.

(b) Blue green algae fix __________ directly from air to enhance fertility of soil.

(c) Alcohol is produced with the help of __________.

(d) Cholera is caused by __________.

2. Tick the correct answer:

(a) Yeast is used in the production of

(i) sugar (ii) alcohol (iii) hydrochloric acid (iv) oxygen

(b) The following is an antibiotic

(i) Sodium bicarbonate (ii) Streptomycin (iii) Alcohol (iv) Yeast

(c) Carrier of malaria-causing protozoan is

(i) female Anopheles mosquito (ii) cockroach

(iii) housefly (iv) butterfly

(d) The most common carrier of communicable diseases is

(i) ant (ii) housefly (iii) dragonfly (iv) spider

(e) The bread or idli dough rises because of

(i) heat (ii) grinding (iii) growth of yeast cells (iv) kneading

(f) The process of conversion of sugar into alcohol is called

(i) nitrogen fixation (ii) moulding (iii) fermentation (iv) infection

3. Can microorganisms be seen with the naked eye? If not, how can they be seen?

4. What are the major groups of microorganisms?

5. Name the microorganisms which can fix atmospheric nitrogen in the soil.

6. Write 10 lines on the usefulness of microorganisms in our lives.

7. Write a short paragraph on the harms caused by microorganisms.

8. What are antibiotics? What precautions must be taken while taking antibiotics?


Please refer to attached file for NCERT Class 8 Science Microorganisms -Friend And Foe

Chapter 01 Crop Production and Management
NCERT Class 8 Science Crop Production And Management
Chapter 02 Microorganisms: Friend or Foe
NCERT Class 8 Science Microorganisms Friend And Foe
Chapter 03 Synthetic Fibres and Plastics
NCERT Class 8 Science Synthetic Fibres And Plastics
Chapter 04 Materials Metals and Non-Metals
NCERT Class 8 Science Materials Metals And Non Metals
Chapter 05 Coal and Petroleum
NCERT Class 8 Science Coal And Petroleum
Chapter 06 Combustion and Flame
NCERT Class 8 Science Combustion And Flame
Chapter 07 Conservation of Plants and Animals
NCERT Class 8 Science Conservation Of Plants And Animals
Chapter 08 Cell Structure and Functions
NCERT Class 8 Science Cell Structure And Functions
Chapter 09 Reproduction in Animals
NCERT Class 8 Science Reproduction In Animals
Chapter 10 Reaching the Age of Adolescence
NCERT Class 8 Science Reaching The Age Of Adolescence
Chapter 11 Force and Pressure
NCERT Class 8 Science Force And Pressure
Chapter 12 Friction
NCERT Class 8 Science Friction
Chapter 14 Chemical Effects of Electric Current
NCERT Class 8 Science Chemical Effects Of Electric Current
Chapter 15 Some Natural Phenomena
NCERT Class 8 Science Some Natural Phenomena
Chapter 17 Stars and the Solar System
NCERT Class 8 Science Stars And The Solar System
Chapter 18 Pollution of Air and Water
NCERT Class 8 Science Pollution Of Air And Water
Other Topics Class 8 Science
CBSE Class 8 Science Activity A Forseful Story
CBSE Class 8 Science Activity A Friend Indeed
CBSE Class 8 Science Activity A Mouldy Party
CBSE Class 8 Science Activity A Surprising Fact
CBSE Class 8 Science Activity A Tree Study
CBSE Class 8 Science Activity Back to the Earth
CBSE Class 8 Science Activity Bring Back The Shine
CBSE Class 8 Science Activity Delightful Daydreams
CBSE Class 8 Science Activity Egg Pops Into a Bottle
CBSE Class 8 Science Activity Growing Up
CBSE Class 8 Science Activity How Does Sound Travel
CBSE Class 8 Science Activity I Can See it
CBSE Class 8 Science Activity I Can See My Sound
CBSE Class 8 Science Activity Inside Story
CBSE Class 8 Science Activity Interview
CBSE Class 8 Science Activity Is The Moon Growing
CBSE Class 8 Science Activity Its CO2 Again
CBSE Class 8 Science Activity Just for Fun
CBSE Class 8 Science Activity Lets Make Music
CBSE Class 8 Science Activity Lighter or Heavier
CBSE Class 8 Science Activity Make A Periscope
CBSE Class 8 Science Activity Make Your Little Movie
CBSE Class 8 Science Activity Making a Solar System Model
CBSE Class 8 Science Activity Mysterious Forces
CBSE Class 8 Science Activity Pitcher Power
CBSE Class 8 Science Activity Please Hear
CBSE Class 8 Science Activity Spore Magic
CBSE Class 8 Science Activity Stages of Human Reproduction
CBSE Class 8 Science Activity Story of Granny
CBSE Class 8 Science Activity Suno Suno
CBSE Class 8 Science Activity The Ball Bearing
CBSE Class 8 Science Activity The Puzzling Letters
CBSE Class 8 Science Activity The Story of Magdeberg Hemisphere
CBSE Class 8 Science Activity The Tug of War
CBSE Class 8 Science Activity Want to be a Snake Charmer
CBSE Class 8 Science Activity What Makes Water
CBSE Class 8 Science Activity Wndow to our Rish BioDiversity
CBSE Class 8 Science Poster Making

Science NCERT Book Class 8 Chapter 2 Microorganisms Friend or Foe

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