Microorganisms Friend And Foe - Exemplar Solutions 3

CBSE Class 8 Science
NCERT Exemplar Solution
Microorganisms: Friend and Foe

8. Unscramble the jumbled words underlined in the following statements.
(a) Cells of our body produce santiidobe to fight pathogens.
(b) curbossulite is an air-borne disease caused by a bacterium.
(c) Xanrhat is a dangerous bacterial disease.
(d) Yeasts are used in the wine industry because of their property of meronettinaf.
Ans. (a) antibodies  (b) tuberculosis   (c) Anthrax    (d) fermentation

9. Suggest a suitable word for each of the following statements.
(a) Chemicals added to food to prevent growth of microorganisms.
(b) Nitrogen-fixing microorganism present in the root nodules of legumes.
(c) Agent which spreads pathogens from one place to another.
(d) Chemicals which kill or stop the growth of pathogens.
Ans. (a) Preservatives  (b) Rhizobium  (c) Carrier/vector  (d) Antibiotics

10. Match the names of scientists given in Column A with the discovery made by them given in Column B.
Column A
Column B
(a) Louis Pasteur
(i) Penicillin
(b) Robert Koch
(ii) anthrax bacterium
(c) Edward Jenner
(iii) Fermentation
(d) Alexander Fleming
(iv) small pox vaccine Typhoid
Ans. (a)-(iii); (b) (ii); (c)-(iv); (d)-(i)

11. Name one commercial use of yeast.
Ans. Making bread.

12. Name the process in yeast that converts sugars into alcohol.
Ans. Fermentation

13. In the soil, which nutrient is enriched by blue-green algae (cyanobacteria)?
Ans. Nitrogen

14. Why should we avoid standing close to a tuberculosis patient while he/she is coughing?
Ans. Tuberculosis is an air-borne disease which easily spreads when the infected person coughs.

15. Polio drops are not given to children suffering from diarrhoea. Why?
Ans. If the child is suffering from diarrhoea, the orally given vaccine may be excreted out because of frequent motions.   

16. Paheli watched her grandmother making mango pickle. After she bottled the pickle, her grandmother poured oil on top of the pickle before closing the lid. Paheli wanted to know why oil was poured? Can you help her understand why?
Ans. Oil prevents bacteria from attacking the pickle and spoiling it.