Chapter 2. Microorganisms : Freind and Foe

Extra Internal Question and Answer:

Question: What are microorganisms or microbes? Name the major groups of microorganisms

Answer: Microorganisms or microbes are very tiny living organisms that cannot be seen with the naked eye. We can observe them only with the help of a microscope. They are present almost everywhere, such as in air, water, soil and even inside living organisms.

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

Question: What is the role of bacteria in soil ?

Answer: Bacteria present in the soil play an important role in making it fertile. Some bacteria help in decomposing dead plants and animals into simple substances, which mix with the soil and increase its nutrients. Certain bacteria also help in fixing nitrogen from the air into the soil, which is essential for plant growth. In this way, bacteria improve soil fertility and support healthy plant growth.

Question: What are fungi? Give one example .

Answer: Fungi are a group of microorganisms that do not contain chlorophyll, so they cannot prepare their own food. They usually grow on dead and decaying organic matter and get their nutrition from it. Fungi help in decomposition. One common example of fungi is yeast.

Question: Where do microorganisms live?

Answer: Microorganisms are found almost everywhere on Earth. They live in air, water, soil, inside the bodies of plants and animals, and even in extreme places like hot springs and ice. Some are free-living, while others depend on living organisms for food and shelter.

Question: What is fermentation ?

Answer: Fermentation is a process in which sugar is converted into alcohol by yeast. This process produces a smell of alcohol.

Question: What are communicable diseases? Give an example.

Answer: Communicable diseases are diseases that spread from one person to another through air, water, food, or direct contact. They are caused by microorganisms like bacteria and viruses. For example, tuberculosis is a communicable disease that spreads through the air when an infected person coughs or sneezes.

Question: Why is influenza considered a communicable disease?

Answer: Influenza is considered a communicable disease because it spreads easily from one infected person to another. It mainly spreads through air when an infected person coughs or sneezes, releasing germs. It can also spread by touching contaminated surfaces and then touching the nose or mouth.

Question: How can proper hygiene help in preventing communicable diseases?

Answer: Proper hygiene helps prevent communicable diseases by stopping germs from spreading. Washing hands with soap, bathing regularly, drinking clean water, and keeping surroundings clean reduce the chances of infection. It breaks the chain of transmission and keeps us safe from diseases like cholera and diarrhoea.

Question: How do viruses differ from bacteria?

Answer: Viruses are non-living outside a host and need a living cell to reproduce, while bacteria are living organisms that can reproduce on their own. Viruses are much smaller than bacteria and cause diseases only inside host cells, whereas many bacteria can live freely in different environments.

Question: What are viruses and why are they called borderline between living and non-living things?

Answer: Viruses are very small infectious agents that can cause diseases. They are called borderline between living and non-living things because they show living characteristics only inside a host cell, where they reproduce, but outside the host, they remain inactive and non-living like particles.

Question: Why are viruses considered parasites?

Answer: Viruses are considered parasites because they cannot survive or reproduce on their own. They need to enter a living cell of a host organism to multiply. Inside the host, they use the cell’s machinery for their own reproduction and often harm or destroy the host cell in the process.

Question: What are viruses? Why are viruses called borderline between living and non-living?

Answer: Viruses are very small infectious particles that cause diseases and can only multiply inside a living cell. They are called borderline between living and non-living because they show living features like reproduction only inside a host, but outside a cell they remain inactive like non-living things.

Exercises :

1. Fill in the blanks.
(a) Microorganisms can be seen with the help of a ____________.
(b) Blue green algae fix __________ directly from air and enhance fertility of soil.
(c) Alcohol is produced with the help of __________.
(d) Cholera is caused by __________.

Answer : (a) Microorganisms can be seen with the help of a microscope.
(b) Blue green algae fix nitrogen directly from air and enhance fertility of soil.
(c) Alcohol is produced with the help of yeast.
(d) Cholera is caused by bacteria.
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) Yeast is used in the production of: (ii) alcohol

(b) The following is an antibiotic: (ii) Streptomycin

(c) Carrier of malaria-causing protozoan is: (i) female Anopheles mosquito

(d) The most common carrier of communicable diseases is: (ii) housefly

(e) The bread or idli dough rises because of: (iii) growth of yeast cells

(f) The process of conversion of sugar into alcohol is called: (iii) fermentation
3. Match the organisms in Column A with their action in Column B.
             A                                                  B
(i) Bacteria                              (a) Fixing nitrogen
(ii) Rhizobium                          (b) Setting of curd
(iii) Lactobacillus                      (c) Baking of bread
(iv) Yeast                                 (d) Causing malaria
(v) A protozoan                         (e) Causing cholera
(vi) A virus                                (f) Causing AIDS
                                               (g) Producing antibodies

Answer:  (i) Bacteria → (e) Causing cholera
(ii) Rhizobium → (a) Fixing nitrogen
(iii) Lactobacillus → (b) Setting of curd
(iv) Yeast → (c) Baking of bread
(v) A protozoan → (d) Causing malaria
(vi) A virus → (f) Causing AIDS
4. Can microorganisms be seen with the naked eye? If not, how can they be seen?

Answer: No, microorganisms cannot be seen with the naked eye because they are very small in size. They can be seen with the help of a microscope.

Some microorganisms like bread mould can be seen with naked eyes, but most of them need a microscope.

5. What are the major groups of microorganisms?

Answer: The major groups of microorganisms are Bacteria ,  Fungi , Protozoa , Algae and Viruses

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

Answer: The microorganisms which can fix atmospheric nitrogen in the soil are rhizobium and blue-green algae (like Nostoc and Anabaena)

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

Answer:  (i) Microorganisms are very useful in our daily life.

(ii) Yeast helps in making bread, cake and idli.

(iii) They are used to produce alcohol and wine.

(iv) Some microorganisms make curd from milk.

(v)  They are used in the production of antibiotics like penicillin.

(vi) Microorganisms help in decomposition of dead plants and animals.

(vii) They help in cleaning the environment.

(viii) Some bacteria fix nitrogen in the soil.

(ix) This increases soil fertility for crops.

(x)  Microorganisms are very important for humans and nature.

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

Answer: Microorganisms can also have harmful effects on human health and the environment. They can cause diseases such as bacterial infections, viral infections, and fungal infections. Pathogenic microorganisms can spread through contaminated food, water, or air. Additionally, certain microorganisms can cause spoilage of food, damage crops, and lead to the deterioration of materials like wood and fabric.

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

Answer: Antibiotics are medications used to treat bacterial infections by inhibiting or killing bacteria.

Precautions while taking antibiotics include following the prescribed dosage and duration, completing the full course of treatment, avoiding self-medication, not sharing antibiotics, and informing the healthcare provider about any allergies or adverse reactions experienced during previous antibiotic use.