Topic outline

    • Microorganisms: Friend and Foe

      Q24. What causes food poisoning?

      Ans. Food poisoning could be due to the consumption of food spoilt by some microorganisms.


      Q25. How do we preserve pickles?

      Ans. We add salt or acid preservatives to pickles to prevent the attack of microbes.


      Q26. What are preservatives?

      Ans. Chemicals (Salts, edible oils etc.) used to check the growths of microorganisms are called preservatives.

      Q27. Why pasteurized milk can be consumed without boiling?

      Ans. Pasteurized milk can be consumed without boiling as it is free from harmful microbes.


      Q28. Name some unicellular and multicellular organisms.

      Ans. Unicellular organisms- bacteria, some algae and protozoa

      Multicellular organisms- algae and fungi


      Q29. How can we prevent the spread of communicable diseases?

      Ans. We prevent the spread of communicable diseases:

                              i.        By keeping handkerchief on the nose and mouth while sneezing.

                             ii.        By keeping distance from infected persons.


      Q30. How are viruses different from other microorganisms?

      Ans. Viruses are quite different from other microorganisms. They reproduce only inside the host organism; bacterium, plant or animal cell.


      Q31. How do microorganisms clean the environment?

      Ans. Some microorganisms decompose the organic waste and dead plants and animals into simple substances and clean up the environment.

      Q32. How are jams and squashes preserved?

      Ans. Sodium benzoate and sodium metabisulphite are used in the jams and squashes to check their spoilage.


      Q33. What are the major groups of microorganisms?

      Ans. Microorganisms are classified into four major groups. These groups are bacteria, fungi, protozoa and some algae.


      Q34. What are microorganisms?

      Ans. Microorganisms or microbes are the living organisms around us which cannot be seen with naked eye.


      Q35. What diseases are prevented through vaccination?

      Ans. Several diseases, including cholera, tuberculosis, smallpox and hepatitis can be prevented by vaccination.


      Q36. Why do we keep food in refrigerator?

      Ans. We keep food in the refrigerator because low temperature inhibits the growth of microbes and keep the food fresh.

      Q37. Why dry fruits and even vegetables are sold in sealed air tight packets?

      Ans. Dry fruits and even vegetables are sold in sealed air tight packets to prevent the attack of microbes.


      Q38. Why is it important to vaccinate small children?

      Ans. It is important to vaccinate small children in order to protect them against several diseases.


      Q39. Who discovered the bacterium which causes anthrax disease?

      Ans. Robert Köch (1876) discovered the bacterium (Bacillus anthracis) which causes anthrax disease.


      Q40. How are cholera and typhoid transmitted?

      Ans. Cholera is transmitted through water or food.

      Typhoid is transmitted through water.


      Q41. Write any two common cattle diseases and its cause.

      Ans. Anthrax is a dangerous cattle disease caused by a bacterium.

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