Topic outline

    • Microorganisms: Friend and Foe

      Q1. Fill in the blanks.

                                i.        Microorganisms can be seen with the help of a microscope.

                               ii.        Blue green algae fix nitrogen directly from air to enhance fertility of soil.

                              iii.        Alcohol is produced with the help of yeast.

                              iv.        Cholera is caused by bacteria.

                               v.        Carrier of malaria-causing protozoan is female Anopheles mosquito.

                              vi.        The bread or idli dough rises because of growth of yeast cells.


      Q2. True/False

                                i.        Housefly is the common carrier of communicable diseases. True

                               ii.        Amoeba lives in colonies. False

                              iii.        Bacteria are also involved in the making of cheese, pickles and many other food items. True

                              iv.        Polio drops given to children are actually a vaccine. True

      Q3. What causes malaria?

      Ans. Malaria is caused by protozoa.


      Q4. Which mosquito act as carrier of dengue virus?

      Ans. Aedes mosquito acts as carrier of dengue virus.


      Q5. Name any two diseases that can be prevented by vaccination.

      Ans. Polio and smallpox


      Q6. Give two examples of algae.

      Ans. Chlamydomonas and Spirogyra


      Q7. Give two examples of protozoa.

      Ans. Amoeba and Paramecium


      Q8. How are cholera and typhoid caused?

      Ans. Cholera and typhoid are caused by bacteria.

      Q9. Give few of examples of fungi.

      Ans. Bread mould, Penicillium and Aspergillus


      Q10. Who discovered penicillin?

      Ans. In 1929, Alexander Fleming discovered penicillin.


      Q11. Name any two diseases caused by bacteria.

      Ans. Typhoid and tuberculosis (TB)


      Q12. What causes foot and mouth disease of cattle?

      Ans. Foot and mouth disease of cattle is caused by a virus.


      Q13. Who discovered the vaccine for smallpox?

      Ans. Edward Jenner discovered the vaccine for smallpox in 1798.


      Q14. Name any two diseases caused by protozoa.

      Ans. Diseases like dysentery and malaria are caused by protozoans.

      Q15. Name some antibiotics.

      Ans. Streptomycin, tetracycline and erythromycin


      Q16. How are meat and fish preserved?

      Ans. Meat and fish are covered with dry salt to check the growth of bacteria.


      Q17. What is fermentation?

      Ans. The process of conversion of sugar into alcohol is called fermentation.


      Q18. Why do we boil milk before storing?

      Ans. We boil milk before storing because boiling kills many microorganisms.


      Q19. Name one plant disease caused by bacteria and its mode of transmission.

      Ans. Citrus canker is caused by bacteria and transmitted through air.


      Q20. Why are the antibiotics not effective against colds and the flu?

      Ans. Antibiotics are not effective against cold and flu as these are caused by viruses.


      Q21. Name one plant disease caused by virus and its mode of transmission.

      Ans. Yellow vein mosaic of bhindi (Okra) is caused by virus and transmitted through insect.

      Q22. How can we control plant diseases?

      Ans. They can be controlled by the use of certain chemicals which kill the microbes.


      Q23. Name one plant disease caused by fungi and its mode of transmission.

      Ans. Rust of wheat is caused by fungi and transmitted through air and seeds.