NCERT Solutions for Class 8 Science Ch 2 Microorganisms Friend and Foe

In this post we have covered NCERT class 8 science Microorganisms Friend and Foe chapter 2. We have highlighted some important concepts about Microorganisms and also listed important short question answers of this chapter. We hope these short notes will help students to learn the concepts quickly.

1. Introduction to Microorganisms

Microorganisms are the very tiny living organisms around us, normally we can't see with the naked eye. They are found everywhere, including in the air, water, soil, and inside our bodies. They are classified into different groups like bacteria, fungi, protozoa, algae, and viruses.

Microorganisms play a vital role in our lives, som of them are very beneficial and others are harmful and cause many diseases. Let's check it more about it.

2. Types of Microorganisms

• Bacteria: They are single-celled organisms, mostly free living organisms and found almost everywhere. Mostly they are not harmful but some bacteria can make you sick.

• Fungi: It occurs as molds, yeasts and mushrooms.

• Protozoa: They are one-celled organisms that often live in water.

• Algae: Simple plant like organisms.

• Viruses: Microscopic entities that reproduce only inside host cells.

3. Microorganisms as Friends

Microorganisms can be helpful in many ways. Some of the important benefits are mentioned below:

• Making Food: Some bacteria and fungi are used in the production of food items like curd, cheese, and bread. For example, the bacterium Lactobacillus helps in making curd from milk.

• Medicines: Antibiotics, like penicillin, are made from microorganisms. These medicines helps in treating infections by killing harmful bacteria.

• Decomposition: Microorganisms help in breaking down dead plants and animals into simpler inorganic materials. This process, called decomposition, helps in recycling nutrients in the environment.

• Nitrogen Fixation: Some bacteria, like Rhizobium, live in the roots of leguminous plants and help in fixing nitrogen from the air into the soil. This process increases soil productivity and fertility and helps in plant growth.

4. Microorganisms as Foes

While most of the microorganisms are beneficial, but they can also be harmful to our lives:

• Causing Diseases: Microorganisms can cause diseases in humans, animals, and plants. For example, bacteria cause diseases like tuberculosis, and viruses cause the common cold and flu. Fungi can cause infections like athlete’s foot.

• Food Spoilage: Microorganisms can grow on food and spoil it. Eating spoiled food can cause food poisoning.

• Biological Weapons: Some harmful microorganisms are used in biological weapons. They can spread diseases intentionally.

4. Food Preservation from Microorganisms

Various methods are used to preserve food from harmful microorganisms:

• Heat and Cold: Boiling and refrigeration kill or slow down the growth of microorganisms in food.

• Chemical Methods: Adding preservatives like salt, sugar, and vinegar can prevent the growth of microorganisms.

• Vacuum Packing: Removing air from food packaging also helps in preventing microbial growth.

Understand the Nitrogen Cycle

The nitrogen cycle is an important natural process involving microorganisms. In this cycle:

• Nitrogen Fixation: Bacteria convert atmospheric nitrogen into usable forms for plants.

• Nitrification: Ammonia in the soil is converted into nitrates by bacteria, and plants can easily absorb it.

• Denitrification: Some bacteria convert nitrates back into nitrogen gas, releasing it into the atmosphere.

Microorganisms Friend and Foe Class 8 Questions Answers

Q 1. Penicillin is obtained from? Ans. Fungi.

Q 2. What is yeast? Ans. Fungi.

Q 3. Most common mode of communicable disease is? Ans. Housefly.

Q 4. Which parasite caused malaria( plasmodium)? Ans. Female Anopheles Mosquito.

Q 5. First vaccine was discovered by? Ans. Edwardjenner.

Q 6. What is the mode of transmission of bacteria causing typhoid? Ans. Water.

Q 7. Measles disease is caused by? Ans. Virus.

Q 8. Foot and mouth disease of cattle is caused by which micro- organisms? Ans. Virus.

Q 9. Name the bacterium which promotes the formation of curd? Ans. Lactobacillus.

Q 10. Which type of microorganisms are bacteria and protozoa? Ans. Single-celled.

Q 11. Which gas is produced by yeast during fermentation? Ans. Carbon dioxide.

Q 12. Fungi is a? Ans. Multicellular micro organisms.

Q 13. Name the two types of fungi? Ans. Aspergillus and Penicillium.

Q 14. Amoeba and paramecium are? Ans. Protozoa.

Q 15. Name the process by which conversion of sugar into alcohol is known as? Ans. Fermentation.

Q 16. Dysentery and Malaria are caused by? Ans. Protozoa.

Q 17. How bread and idli dough rises? Ans. Because of growth of yeast cells.

Q 18. Disease like Typhoid and Tuberculosis are caused by? Ans. Bacteria.

Q 19. Name the preservative used in pickle and jams? Ans. Sodium benzoate.

Q 20. Examples of virus disease? Ans. Polio and chicken pox.