Page 13 - Ripples SCIENCE 7 - TEJPUR Edition 2024 Answer Key
P. 13

(b)   Parasitic  Nutrition:  In  this  type  of  nutrition,  organisms  (parasites)  derive

                            nutrients  from  another  living  organisms  (hosts),  often  harming  them.  For

                            example, cuscuta, mistletoe, etc.

                      (c)   Symbiotic  Nutrition:  In  this  type  of  nutrition,  two  different  types  of

                            organisms live together and benefit from each other. For example, lichens is a

                            symbiotic relationship between algae and fungi, where algae provide food via

                            photosynthesis and fungi provide protection and minerals.
                  3.  Discuss the significance of photosynthesis.

                  Ans.  Significance of photosynthesis:

                      I.    It is a primary source of energy for all organisms present on Earth.

                      II.     It  helps  in  purifying  air  and  maintaining  the  balance  of  carbon  dioxide  and

                            oxygen in nature.

                      III.   It helps in the synthesis of important nutrients present in food like carbohydrates,

                            fats and proteins.
                      IV.   It leads to the origin of life on Earth by conversion of anaerobic conditions on

                            the planet to aerobic conditions that occurred millions of years ago and made

                            the planet habitable.

                      V.      Fossil fuels found in nature have chemical energy stored in them which is the

                            solar  energy that was trapped and stored during photosynthesis millions  of

                            years ago.

                  4.  Write the difference between autotrophs and heterotrophs.
                  Ans.                          Autotrophs                        Heterotrophs

                        1.     These are organisms that can make  These are organisms that cannot make
                             their own food  with the  help of  their own food and  depend on other

                             sunlight, carbon dioxide and water.     for it.
                        2.       They cannot move from one place to  They can  move from  one  place  to

                             another in search of food.              another in search  for food.
                        3.     They are also  called   producers as  They are also called  consumers as they
                             they can produce food.                  consume the food made by autotrophs.

                        4.     They contain  chlorophyll  that helps  They do not contain chlorophyll, hence
                             them in preparing their food.           are dependent on producers for food.
                        5.     For  example,  green    plants,  algae,  For example,  humans, animals, etc.

                             etc.


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