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SAI International School
                                             Subject- Biology, Class-VIII
                                   Chapter- Reaching the age of adolescence
                              Subtopic- Role of hormones in completing the life
                                             history of insects and frog
                                                       Module- 24
                                                     Lesson Notes


               Metamorphosis


                     It  is  a  biological  process  by  which  an  animal  physically  develops  after  birth  or
                       hatching, involving  a  conspicuous  and relatively  abrupt  change in the  animal's
                       body structure through cell growth and differentiation.
                     The  conversion  of  larva  into  an  adult  by  undergoing  drastic  changes  is  called
                       metamorphosis.
                     The life cycle of a frog consists of three stages: egg, larva, and adult. As the frog
                       grows, it moves through these stages in a process known as metamorphosis.


                       Stage 1- Egg                   Stage 2-larvae (tadpole)                 Stage3-Adult (Frog)




















                     Metamorphosis  in  frog  is  controlled  by  thyroxine,  the  hormones  produced  by
                       thyroid gland.
                     Thyroxine  production  requires  the  presence  of  iodine  in  water.  If  the  water  in
                       which the tadpoles are growing does not contain sufficient iodine, the tadpoles
                       cannot become adults.
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