DIFFERENT PHASES IN SEXUAL REPRODUCTION:

 

1. JUVENILE PHASE

   It is a period of growth and maturity of an organism before it can reproduce sexually.

 

 2. REPRODUCTIVE PHASE

   Period in which organism is capable of reproducing sexually

•             Easily seen in higher plants when they come to flower.

•             Some plants flower seasonally & some through out the year

•             Few plants exhibit unusual flowering phenomenon

 For e.g.. 1. Bamboo species flower only once in their lifetime. 2. Srobilanthus kunthiana (neelakurinji) found in hilly areas of Kerala, Karnataka & Tamil Nadu flower once in 12 years the latest being in September 2006.

•             In animals sexual reproduction is usually seasonal

•             In placental mammals there is occurrence of cyclical changes in the activities of ovaries & accessory ducts as well as hormones.

•             In non primate mammals like dogs, rats etc these cyclical changes during reproduction is called oestrus cycle – no bleeding occurs.

•             In primate mammals like apes & humans, these cycles are called menstrual cycles.

3. SENESCENT PHASE

•             It is the end of reproductive phase.

•             Old age ultimately leads to death