2. Microorganisms : Friend And Foe Science class 8 in English Medium ncert book solutions Text Book Exercise

Text Book Exercise 

Que: Can microorganisms be seen with the naked eye? If not, how can they be seen?

Ans:  No, we cannot see microorganisms with unaided eyes. They can be seen with the help of a microscope.

Que: What are the major groups of microorganisms?

Ans: bacteria, protozoa, fungi and some algae are the major group of microorganism.

Que: Name the microorganisms which can fix atmospheric nitrogen in the soil.

Ans: These are Rhizobium, Azobacter, blue green algae.

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

Ans: Microorganisms are useful to us in many ways. For example:

• Bacteria like Lactobacillus convert milk into curd.
• Bacteria are also involved in the making of cheese.
• Acetobacter aceti is used for producing acetic acid from alcohol.
• Yeast is used in the commercial production of alcohol, wine and bakery products.
• Some specific microorganisms are helpful in manufacturing of antibiotics.
• Microorganisms act as cleansing agents and decompose the waste products into manure.
• Dead or weakened microbes are used in the preparation of vaccines.
• Some bacteria fix atmospheric nitrogen and increase soil fertility.
• Algae, yeast, fungi or bacteria may be used as an ingredient or a substitute for protein-rich foods that are suitable for human or animal consumption.
• Some microorganisms are taken as probiotics, that are believed to provide health benefits when consumed.

Que: Write a short paragraph on the harms caused by microorganisms.

Ans:        

(i) Many infectious or communicable disease like tuberculosis, cholera, plague, flue, chicken pox are caused by microorganism.

(ii) Many protozoa cause disease like malaria, filaria, amoebiasis etc.

(iii) Funguses are causative organisms of many skin diseases.

(iv) Dengue and polio like dangerous diseases are caused by virus like microorganisms.

(v) Several microorganisms harm crops like vegetables, fruits and grains.

Que: What are antibiotics? What precautions must be taken while taking antibiotics?

Ans: The medicines which kill or stop the growth of the disease-causing microorganisms. Such medicines are called antibiotics.

Precautions:

(i) It must be taken under advised of a qualified doctor.

(ii) Body may develop resistance when we take it unnecessary.

The course of antibiotic must be completed.