NCERT Solutions for Class 8 Science Chapter 2 Microorganisms: Friend and Foe

NCERT Solutions for Class 8 Science Chapter 2

Class 8 Science Chapter 2 – Microorganisms: Friend and Foe is an important chapter that helps students understand the role of microorganisms in our daily life. This chapter explains different types of microorganisms such as bacteria, fungi, protozoa, algae, and viruses, and how they can be both useful and harmful. Students often search for science ch 2 class 8 to revise concepts like food preservation, nitrogen fixation, vaccines, and diseases caused by microbes.

To prepare well for exams, students should practice class 8 science chapter 2 question answer, as it helps in building clear concepts and improving answer-writing skills. The chapter also highlights useful microbes used in making curd, bread, medicines, and antibiotics, along with harmful microbes that cause diseases like malaria and tuberculosis. Many learners look for microorganisms friend and foe class 8 questions answers to revise important topics before tests.

For easy and accurate preparation, NCERT solutions for class 8 science microorganisms friend and foe are highly recommended. These solutions explain answers in simple language and follow the latest CBSE guidelines. Using NCERT solutions for class 8 science chapter 2 helps students score better by understanding key concepts clearly and revising efficiently.

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

Get the Science Class 8 Chapter 2 Solutions below:-

1. Fill in the blanks.

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

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

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

(d) Cholera is caused by __________.

Answer:

a) Microscope

b) Nitrogen

c) Yeast

d) Bacteria- Vibrio cholera

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

Answer:

a) (ii) alcohol

b) (ii) Streptomycin

c) (i) female Anopheles mosquito

d) (ii) housefly

e) (iii) growth of yeast cells

f) (iii) fermentation

3. Match the organisms in Column A with their action in Column B.

Sol:-

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

Answer:-  Microorganisms are generally not visible to the naked eye due to their minuscule size. These tiny organisms, including bacteria, viruses, fungi, and protozoa, are often only a few micrometres or nanometers in length. For comparison, a micrometre is one-millionth of a meter, and a nanometer is one-billionth.

To view microorganisms, specialized instruments known as microscopes are used. Microscopes can magnify objects many times their actual size, allowing us to see details that are otherwise invisible. 

5. What are the major groups of microorganisms?

Answer:- The major groups of microorganisms are as follows:

• Bacteria

• Fungi

• Protozoans

• Algae

• Viruses

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

Answer:- Rhizobium

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

1. Answer:- Microorganisms play a crucial role in decomposing dead organic matter from plants and animals, breaking it down into simple substances that are then reused by other organisms. This process helps in cleaning up the environment by degrading harmful and smelly substances.

2. In the production of food items, microorganisms are essential. For instance, curd is made by the bacterium Lactobacillus, which ferments milk into curd. Similarly, bacteria and yeast are involved in making cheese, and pickles, and in the fermentation of rice idlis and dosa batter.

3. Yeast is particularly useful in the baking industry. It reproduces quickly and produces carbon dioxide during respiration, which makes dough rise and increases its volume. This process is used to make bread, pastries, and cakes.

4. Microorganisms are also employed in the large-scale production of alcohol, wine, and vinegar (acetic acid).

5. Antibiotics, which are critical for treating bacterial infections, are derived from bacteria and fungi.

6. Some bacteria can fix atmospheric nitrogen, enriching soil fertility and supporting plant growth.

7. Microorganisms are used in producing vaccines to protect against various diseases.

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

Answer:- Microorganisms can have several harmful effects on plants, animals, and humans. They can cause diseases, such as cholera in humans, which is caused by the bacterium Vibrio cholerae, and foot-and-mouth disease in animals, caused by a virus. Additionally, microorganisms can spoil food by decomposing it, leading to foodborne illnesses and food poisoning. They can also damage materials like leather and clothes, causing further problems. Overall, while microorganisms play many beneficial roles, they can also pose significant threats to health and property.

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

Answer:- Chemical agents that kill or inhibit the growth of disease-causing microorganisms are known as antibiotics. It is important to use antibiotics only under the guidance of a qualified doctor and to complete the full course of treatment as prescribed.

Mastering Class 8 Science Chapter 2 Question Answer for Better Grades

Because there are so many different kinds of microscopic life, it can be hard to find the appropriate class 8 science chapter 2 question answer. Microbes are all around us, even in the air we breathe and the dirt in your garden. Some of them cause diseases like malaria and tuberculosis, but others are necessary for generating curd, bread, and even medicines that save lives. This guide breaks down these interactions so that you can do well on your tests and learn a lot about microbiology.

Classifying the Microscopic World

For your class 8 science chapter 2 question answer curiosity questions, you need to know that microorganisms are divided into four main kinds.

• Bacteria: Single-celled creatures that can be formed like rods or spirals.

• Fungi: They are living things that can be made up of more than one cell or only one cell. Examples are bread mould, mushrooms, and yeast.

• Protozoa: These are living things like amoebas and paramecia that usually dwell in water.

• Algae: They are plant-like organisms like Spirogyra and Chlamydomonas.

Viruses are likewise quite little, however they are not like the other four types. They can only multiply inside the cells of a host organism, like a plant, animal, or bacteria. Most textbooks have class 8 science chapter 2 question answer.

Read More: Components of Environment

Friendly Microorganisms: Our Tiny Allies

We don't usually think of bacteria as buddies, but we need them to stay alive. In the kitchen, the bacterium Lactobacillus helps make curd by growing in milk. Yeast, which is a type of fungus, is very important in baking. It reproduces quickly and creates carbon dioxide when it breathes, which makes dough rise and gives bread its fluffy texture.

Microbes are important for the environment outside of the kitchen. They break down organic trash into simple parts, which cleans up the area around us. In farming, certain bacteria and blue-green algae take nitrogen from the air and put it into the soil to make it richer and more fertile. This is a key part of the class 8 science chapter 2 question answer curriculum.

Medicinal Uses and Vaccines

When you fall ill, doctors might give you antibiotics. These are medicines made from fungi and bacteria that kill or stop the growth of disease-causing microbes. Penicillin, discovered by Alexander Fleming, is a classic example.

Vaccines work on a similar principle of "learning." When a dead or weakened microbe enters the body, our immune system produces antibodies to fight it. The body "remembers" how to fight the microbe if it ever attacks again. This is how we've managed to protect children from diseases like polio, smallpox, and hepatitis.

Harmful Microorganisms and Pathogens

Not all microbes are helpful. Pathogens are disease-causing microorganisms that enter our bodies through air, water, or food. Some diseases are communicable, meaning they spread from an infected person to a healthy one through physical contact or insects.

• Carriers: The female Anopheles mosquito carries the parasite for malaria. The Aedes mosquito acts as a carrier for the dengue virus.

• Human Diseases: Tuberculosis (bacteria), Measles (virus), and Cholera (bacteria) are common examples found in the class 8 science chapter 2 question answer sets.

• Plant Diseases: Microbes also reduce crop yields. Citrus canker is caused by bacteria, while rust of wheat is a fungal infection.

Food Preservation Techniques

Food poisoning occurs when we consume food spoilt by certain microorganisms. To prevent this, we use various preservation methods:

1. Chemical Method: Salts and edible oils are common preservatives.

2. Heat and Cold Treatments: Boiling kills many microbes, while refrigeration inhibits their growth.

3. Pasteurization: Milk is heated to about $70^\circ\text{C}$ for 15 to 30 seconds and then suddenly chilled.

4. Storage and Packing: Dry fruits and vegetables are sealed in airtight packets to prevent microbial attack.

The Nitrogen Cycle

Plants and animals can't use nitrogen gas directly, even though it makes up 78% of the air. Rhizobium bacteria, which live in the root nodules of leguminous plants, turn nitrogen from the air into chemicals that plants may use. Bacteria and fungi in the soil turn the nitrogenous waste from dead plants and animals back into nitrogen molecules that can be used again. Some bacteria even turn it back into nitrogen gas, which keeps the amount of nitrogen in the air the same.

Read More: Ecosystem

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