·        The period from birth to the natural death of an organism is called is LIFE SPAN. The life span of an organism may be from few minutes to several hundred years, for example life span of May Fly is one day, while giant tortoise is considered to be the longest living animal with a life span of about 200 years.

·        Life Span of an organism usually includes four stages.

·        STAGE ONE- JUVENILITY—During this stage organism develops the capacity to reproduce.

·        STAGE TWO- MATURITY—Reproduction begins during this stage.

·        AGEING AND SENESCENCE—Aging is progressive deterioration n he body of the organism. The terminal irreversible stage of aging is called senescence.

·        DEATH—Senescence finally leads to death. During this stage there is final permanent cessation of all vial activities of an organism.

·        The change over from one stage to another is determined by genetic as well as environmental factors.

·        It is not essential that life span of an organism should be correlated with their sizes. For example a mango tree has a much shorter life span as compared to a Peepal tree. Whatever be the life span, death of every organism is a must. It means no individual is immortal except some single –celled amoeba organisms.

1. Some microorganisms Few minutes to few hours.
2. May Fly  1 Day
3. Butterfly 1-2 Weeks
4. Rice Plant  3-4 Months
5. Rat  4 Years
6. Banana Tree  25 Years
7. Whale  37 years
8. Elephant  60-90 Years
9. Man  100 Years
10. Tortoise  200 Years
11. Banyan Tree 200-300 years