CLASS 8 Science Chapter 2 MICROORGANISMS: FRIEND AND FOE

 MICROORGANISMS: FRIEND AND FOE

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

Ans:  No, microorganisms cannot be seen with the naked eye as they are very small. Some of these,

such as the fungus that grows on bread, can be seen with a magnifying glass. Others can be seen using a microscope.

 

5. What are the major groups of microorganisms?

Ans: The major groups of microorganisms are bacteria, viruses, fungi, protozoa, and algae.

 

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

Ans: The microorganisms which can fix atmospheric nitrogen in the soil are Rhizobium bacteria and blue-green algae.

 

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

Ans: Microorganisms are very useful in our lives. They play an important role in various industries like food, medicine, and agriculture. Some of the usefulness of microorganisms are:

a.They help in the fermentation of food products like curd, bread, and cheese.

b.They are used to produce antibiotics, which are used to treat various diseases caused by bacteria.

c.They help in the production of vaccines which protect us from diseases.

d.They are used in the production of alcohol, vinegar, and other industrial chemicals.

e.They help in the decomposition of dead organic matter, which helps in the recycling of nutrients in the ecosystem.

f.They are used in the production of biofertilisers, which can improve soil fertility.

g.They play an important role in nitrogen fixation, which is essential for plant growth.

h.They are used in the treatment of wastewater, which helps in reducing water pollution.

i.They are used in the production of enzymes, which are used in various industries.

They are used in genetic engineering, which has revolutionized the field of biotechnology.

 

8. Write a short paragraph on the harmful effects of microorganisms.

Ans: Microorganisms can also cause harm to humans, animals, and plants. Some microorganisms are pathogenic and can cause diseases like cholera, tuberculosis, and malaria. They can also cause food spoilage and food-borne illnesses. Microorganisms can also cause plant diseases, which can lead to significant crop loss. They can also cause environmental damage by polluting water bodies and soil.

 

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

Ans: Antibiotics are medicines that are used to treat bacterial infections. They work by killing or inhibiting the growth of bacteria. Some precautions that must be taken while taking antibiotics are:

Antibiotics should only be taken when prescribed by a doctor.

The entire course of antibiotics should be completed, even if the symptoms of the infection have disappeared.

Antibiotics should not be taken unnecessarily, as this can lead to the development of antibiotic-resistant bacteria.

Alcohol should be avoided while taking antibiotics as it can reduce their effectiveness.