Microorganisms : Friend And Foe

Exercises 

1. Fill in the blanks.

(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       yeasts     .

(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

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

               

Ans:-

(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?

Ans:- 

No, microorganisms are so tiny in size that they cannot be seen with the naked eye. They can be seen using microscope.

5. What are the major groups of microorganisms?

Ans:- 

Microorganisms are classified mainly into four groups which are as follows :

1. Bacteria
2. Fungi
3. Protozoa
4. Algae

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

Ans:-

A bacterium called Rhizobium is involved in the fixation of nitrogen in the soil. It is present in the root nodules of leguminous plants such as - peas, beans etc.

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

Ans:-

Microorganisms play an important role in our lives because they can be beneficial to us in many ways. Below are some list of points which shows how they can be used for various purposes.

1. yeasts helps in making of bread, cake.
2. a bacterium called Lactobacillus promotes the formation of curd. It multiplies in milk and coverts it into curd.
3. bacteria are also involved in the making of cheese, pickles and many other food items.
4. microorganisms are used for the large scale production of alcohol,wine and acetic acid(vinegar)
5. used in medical purposes such as - producing antibodies, vaccines.
6. bacterium called Rhizobium increasing the soil fertility by fixing nitrogen
7. cleansing the environment by decomposing the bio-degradable wastes e.g. dead plant and animal bodies, vegetable peels etc to manure.

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

Ans:-

Microorganisms are harmful in many ways.Some of the microorganisms cause diseases in human beings, plants and animals as well. Such disease causing microorganisms are called pathogens. Some microorganisms spoil food, clothing and leather. Some harmful effects can be:

1. viruses can cause communicable diseases like - cough, cold, tuberculosis etc.
2. female Anopheles mosquito,which carries the parasite of malaria(Plasmodium).
3. female Aedes mosquito acts as carrier of dengue virus.
4. some bacteria can cause cholera, typhoid.
5. can spoil food, and having the consumption of such food results in food poisoning.
6. along with humans some microbes harm animals too, e.g. anthrax is a dangerous human and cattle disease caused by a bacterium.
7. some microbes also have a bad effect on plants like - wheat,rice, potato, sugarcane etc reduces the yield of crops. Some disease in plants are - Citrus canker (caused by bacteria), Rust of wheat (caused by fungi) etc.

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

Ans:-
The medicines that kill or stop the growth of the disease-causing microorganisms, such medicines are called antibiotics. These days a number of antibiotics are being produced from bacteria and fungi.
e.g. Streptomycin, Tetracycline and Erythromycin etc.

Also we need to take some precautions while taking antibodies such as :

1. it is important to remember that antibiotics should be taken only on the advice of a qualified doctor.
2. must complete the course prescribed by the doctor. 
3. antibodies taken in wrong dose, might make the drug less effective when needed in future. 
4. antibiotics taken unnecessarily may kill the beneficial bacteria in the body.