Explanation

The time period from birth till death is called life span. The life span is generally divided into four parts (i) Juvenility Period of life span from birth till the organism develops the capacity to reproduce (ii) Maturity Reproduction begins and flourished in this stage (iii) Senescence or ageing Progressive detoriation of the body is called ageing. Ageing ends in senescence (iv) Death It stopping of all vital activity of an organism at senescence leads to death