2. Microorganisms : Friend and Foe

CBSE 2. Microorganisms : Friend and Foe

Chapter 2 . MICROORGANISMS : FRIEND AND FOE

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.

(d) Cholera is caused by the bacterium Vibrio cholerae .

2. Tick the correct answer.
(a) Yeast is used in the production of
(i) sugar (ii) alcohol

(iii) hydrochloric acid (iv) oxygen

Answer : (a) Yeast is used in the production of: (ii) alcohol

(b) The following is an antibiotic
(i) Sodium bicarbonate (ii) Streptomycin

(iii) Alcohol (iv) Yeast

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

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

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

(iii) dragonfly (iv) spider

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

(e) The bread or idli dough rises because of
(i) heat (ii) grinding

(iii) growth of yeast cells (iv) kneading

Answer : (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
(i) nitrogen fixation (ii) moulding

(iii) fermentation (iv) infection

Answer : (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 - (a) Fixing nitrogen

(ii) Rhizobium - (b) Setting of curd

(iii) Lactobacillus - (c) Baking of bread

(iv) Yeast - (g) Producing antibodies

(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 due to their small size. They require the use of a microscope to be visible. Microscopes magnify the image of microorganisms, enabling their observation and study.

5. What are the major groups of microorganisms?

Answer : The major groups of microorganisms include bacteria, viruses, fungi, protozoa, and some algae .

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

Answer : The microorganisms that can fix atmospheric nitrogen in the soil include certain bacteria, such as Rhizobium and Azotobacter, and cyanobacteria (blue-green algae).

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

Answer : Microorganisms play a significant role in our lives and have various beneficial applications:

Medicine: Microorganisms are used in the production of antibiotics, vaccines, and other pharmaceutical products that help treat and prevent diseases.

Food production: Microorganisms are involved in processes like fermentation, which is crucial for producing bread, cheese, yogurt, and other fermented food products.

Agriculture: Certain microorganisms, like Rhizobium and mycorrhizal fungi, form symbiotic relationships with plants, aiding in nutrient uptake and improving soil fertility.

Environmental cleanup: Some microorganisms have the ability to break down pollutants and contaminants, contributing to the bioremediation of soil and water.

Waste management: Microorganisms are used in sewage treatment plants to break down organic waste, purify water, and produce biogas.

Industrial processes: Microorganisms are utilized in various industrial processes such as biofuel production, enzyme production, and biodegradable plastics.

Research and development: Microorganisms serve as model organisms in scientific research, providing insights into genetics, cell biology, and biochemistry.

Nutrient recycling: Microorganisms play a vital role in decomposing organic matter and recycling nutrients, returning them to the ecosystem.

Production of chemicals: Microorganisms are used in the production of enzymes, organic acids, and other chemicals used in various industries.

Environmental balance: Microorganisms contribute to maintaining ecological balance by participating in nutrient cycling, soil formation, and the breakdown of organic matter.

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.