8th std science microorganisms chapter question paper in english version 2020-21

Information's | Sunday, 2 May 2021

 1.   Fill in the blanks:

(a)  Microorganisms can be seen with the help of a             . (b)  Blue green algae fix             directly from air to enhance

fertility of soil.

(c)  Alcohol is produced with the help of                    . (d)  Cholera is caused by                   .

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 


(i) Nitrogen fixation             (ii) Moulding


(iii) Fermentation                (iv) Infection


3.   Match the organisms in Column I with their action in Column II.


Column I                          Column II


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


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

5.   What are the major groups of microorganisms?


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

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


8.   Write a short paragraph on the harms caused by microorganisms.


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




1.


(a)  Microorganisms can be seen with the help of a  microscope. (b)  Blue green algae fix  nitrogen directly from air to enhance

fertility of soil.


(c)  Alcohol is produced with the help of  yeast. (d)  Cholera is caused by  bacteria.

2.


(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) Nitrogen fixation                     (ii) Moulding


(iii) Fermentation                         (iv) Infection


3.


Column I                          Column II


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. Microorganisms are extremely tiny living beings which are not visible  through  our  naked  eyes.  To  observe  these microorganisms, we need to use Microscope.

5.   There are five major groups of micro-organisms:


i. Bacteria − A single celled organism mainly responsible for diseases. They can be Spiral, rod shaped, spherical shaped, comma shaped.

ii.   Fungi − Fungi are mostly multicellular and responsible for


diseases too. Moulds on bread is a type of fungi.


iii. Protozoa − Protozoa can be unicellular or multicellular. And they are harmful to humans and other organisms Eg: Amoeba and Plasmodium are protozoa. 


iv.   Virus − Viruses are disease causing microorganisms which can only divide inside a host organism/cell. It can affect plants as well as animals. Eg: HIV virus for humans and TMV virus for plants.

v. Algae  −  Algae  are  the  only  microorganism  which  are multicellular and has photosynthetic pigments. Algae are also known as precursor of plants Eg: Spirogyra, Chlamydomonas etc.

6. Bacteria like Rhizobium can fix atmospheric nitrogen in the soil and make it to such nitrogenous compound which can be taken up by the plants. Plants use these nitrogenous compounds to make proteins and other important compounds. Eg: Rhizobacteria

and Blue green algae have capacity to fix nitrogen.


7.


1. Microorganisms are used in making of wine, break, pickels and other food products

2. Lactobacillus bacteria is mainly used at homes to make curd from milk

3. Yeast is a microorganism which is used at home to make batter for fermented food.

4. Various fungi are the one responsible for decaying the waste in the nature, they obtain nutrients from the dead and decompose the waste. 


8. Microorganisms are responsible for various diseases in humans and  plants.  Diseases  caused  by  bacteria  are  tuberculosis, cholera, typhoid, etc. Various viruses are responsible for foot and mouth  disease  in  cattle.  In  plants  productivity  of  wheat,  rice, apple, sugarcane etc can all be reduced because of the microorganisms. Microbes present in our body produces harmful substances which will harm the body cells. Microbes also spoil our food and other materials.

9. Antibiotics are the drugs or medicine which we take to kill disease causing microorganisms. Antibiotics are produced from the microorganisms. There are separate antibiotics which kills bacteria, fungus and other organisms.

Eg: penicillin, Tetracycline, Streptomycin and so on. Precautions:

1. Antibiotics should be consumed under the supervision of a qualified doctor

2. The course of antibiotics should be completed as described in the prescription.

3. Correct dosage of antibiotics is important. High dosage or low dosage of antibiotic can cause harm to th


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