Define : (i) Juvenile phase, (ii) Reproductive phase, (iii) Senescent phase.

Explanation

(i) Juvenile phase . All organisms have to reach a certain stage of growth and maturity in their lige before they can repoduce sexually. This period of growth is called juvenile phase or vegetative phase ( term used in plants ).
(ii) Reproductive phase . Reproductive stage in plants is represented by appearance of flowers . In animals the end of juvenile phase is indicated by many of them showing morphological and physiological changes prior to active reproductive behaviour.
(iii) Senescent phase. The end of reproductive phase is one of the paramenters of senescence or old stage. At this stage body metabolism is slowed down and ultimately this stage leads to death .