Page 80 - Biology - XII
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Q4.  How do plants benefi t from having mycorrhizal symbiotic association?
          Ans.  Mycorrhizal fungi allow plants to draw more nutrients and water from the soil. They also increase
                 plant tolerance to diff erent environmental stresses, soil aggregation process, and stimulate microbial
                 activity.
           Q5.  Give two examples of mutualism.
          Ans.  (i) Coral and algae
                 (ii) Oxpecker (a kind of bird) and the rhinoceros or zebra

           Q6.  Give an example of a symbiotic relationship involving humans.
          Ans.  For  example,  humans  have  a  mutualistic  relationship  with  the  bacterium  Bacteroides
                 thetaiotetraiotamicron, which lives in the intestinal tract.
           Q7.  Mention a symbiotic relationship involving plants and insects.
          Ans.  An association between fl owering plants and insects such as pollination. Pollination is a mutualism
                 in which two interactors reciprocally benefi t: the host plant receives the service of insect pollination
                 in return for a reward of nectar provided by the fl owers.
           Q8.  Mention the role of fungus in Lichen.
          Ans.  (i)  To provide water and minerals.                     (ii)  To give support or shelter to alga cells.

           Q9.  What is Rhizobium?
          Ans. Rhizobium is a bacterium.

          Q10.  If you want to see/observe Rhizobium, where should you look?
          Ans.  A section of root nodules of a leguminous plant.
          Q11.  Mention the role of symbiotic Rhizobium in a leguminous plant.
          Ans.  Nitrogen fi xation into ammonia.

          Q12.  What is the benefi t to Rhizobium in symbiotic association?
          Ans.  It gets nutrients to survive and shelter.
          Q13.  How do you identify Cuscuta on the host plant?
          Ans.  It is golden yellow coloured wire-like structure around the host.

          Q14.  Mention the components of Lichen.
          Ans.  (i) Fungus                         (ii)  Algae
          Q15.  What is the role of alga in Lichen?
          Ans.  To provide food to fungus.
          Q16.  What are the three types of symbiotic relationships?
          Ans.  There are three main symbiotic relationships: mutualism, commensalism, parasitism.





                                           COMPETENCY BASED QUESTIONS


          Multiple Choice Questions

           Q1.  Identify the ectoparasite.
                 (a)  Cuscuta             (b)  Alga               (c)  Rhizobium          (d)  Fungi




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