Class 8 Science Lesson 2 Inside Question

Class 8 Science Lesson 2 Inside Question and Answer NCERT & CBSE Board Here in this post. NCERT Class 8 Science Textbook Lesson 2 Inside Questions.

  • Grade: VIII
  • Lesson 2 Microorganisms : Friend and Foe

Que .1) Fill in the blanks.

(1) Microorganism are classified into bacteria, fungi, —— and ——-

Ans –  Protozoa and Fungi

(2) The process of conversion of sugar into alcohol is known as —–

Ans- fermentation

(3) Cholera is caused by——-


(4) The most common carrier of communicable diseases is ——-


(5) Yeast is used in the production of——


Que .2) Answers the followings questions.

(1) What is microorgansm? Give examples.

Ans- the microorgainsm are the living organism which can not seen by naked eyes. They are also called microbes. Eg. Bacteria, protozoa, fungi etc.

(2) Who discovered vaccine for small pox?

Ans- Edward Jenner discovered the vaccine for small pox.

(3) Give example of nitrogen fixing bacteria?

Ans- Cyanobacterium ( blue green algae )

(4) Which are communicable diseases?

Ans-   cholera , common cold, chicken pox and tuberculosis are communicable diseases.

(5) Name of dengue carrier virus.

Ans- Female Aedes mosquito acts as carrier of dengue virus.

(6) What are preservatives?

Ans- Salts and edible oils are the common chemicals generally called preservatives.

(7) Who discovered pasteurisation?

Ans- Louis Pasteur discovered pasteurisation process.

Que. 3) Explain the following.

(1) Discuss about harmful microorganism.

Ans-There are many microorganisms are harmful for human beings, plants and animals. Because of them many disease causes like cholera, chicken pox etc. disease causing microorganism are called Pathogens. Some microorganism spoil food, clothing and leather. Pathogens are entered in our body through the air we breathe, the water we drink or the food we eat. They can also get transmitted by direct contact with an infected person to normal person they spread diseases called communicable diseases. Example – cholera, chicken pox, tuberculosis.

There are some insects and animals which act as carriers of disease causing microbes. For example – female Anopheles mosquito which carries of the parasite of malaria (Plasmodium). Female mosquito Aedes carrier of dengue virus. This are the some examples of harmful microorganism.

(2) Give prevention measures for tuberculosis, cholera and malaria.

Ans- a) prevention measure for tuberculosis- keep the patient in complete isolation. Keep the personal belongings of the patient away from those of the other. Vaccination to be given.

b) Prevention measure for cholera- maintain personal hygiene and good sanitary habits. Consume property cooked food and boiled drinking water. Vaccination.

c) Prevention measure for malaria- use mosquito net and repellents. Spary insecticides and control breeding of mosquitoes by not allowing water to collect in the surrounding.

(3) Which disease causing microorganism in plant?

Ans- several microorganism causes diseases in plants like wheat ,rice, potato, sugarcane, orange, apple and others. The disease reduce the yield of crops the can be control by certain chemicals which kills the microbes. Some common diseases caused by microorganism in plants are below-

Plant diseases

microorganism Mode of transmission
Citrus canker Bacteria


Rust of wheat

Fungi Air ,seeds
Yellow vein mosaic of bhindi Virus


(4) Discuss food preservation and it’s method.

Ans- food preservation is the technique of store the food material for long time or a particular time. There are various methods for preserving food like chemicals methods, preservation by sal and sugar etc. out of them some are discuss below-

(a) Chemical methods- salts and ediable oil are the common chemicals generally used to check the growth of microorganism therefore they are called as preservatives. Add salt into pickles for preservation. Sodium benzoate and sodium metasulphite are common preservatives and are used for preservation of jams.

(b) Preservation by common salt– it is used to preserve meat and fish for ages. Salting is used to preserve amla, raw mangoes, tamarind etc.

(c) Preservation by sugar- jams ,jellies and squashes are preserved by sugar. Sugar reduces the moisture content which inhibits the growth of bacteria which inhibits the growth of bacteria which spoil food.

(d) Preservation by oil and vinegar- vegetables, fruits , fish and meat are preserved by this.

(e) Heat and cold treatments – boiling kills microorganism , for the preservation of milk this is used. Low temperature is also inhibits the growth of microorganism so refrigerator is used.

Updated: December 16, 2020 — 1:56 pm

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