life

[nikk]

why does an organism die?

is it because it cannot divide further[i mean its cells] or does the gene 'pre- plan' its termination ?

i am a beginner in this and i dont know much.

[immortal]

Every organism on this earth in one or the other way is trying to reduce entropy and it is self-organizing itself, but in the process there are a few products which are produced that are harmful for the cells and increases the damage as time prolongs. Cells depend on ATP's to do most of the tasks like intercellular communication, cell division, cell motility, action potential transmission etc and the same process which produce ATP's also give up oxygen free radicals which cause much wear and tear in cells and eventually to cell death. This process is called aging.

 

The cells do pocess pre-programmed instructions to terminate themselves but they will not be activated unless there is some selection pressure acting on the genes. For example :- When prions attack the neurons they terminate themselves for small traces of prions in their protoplasm even before the concentration of prions increases there by preventing the spread of the prions to other brain cells.

 

There are other mechanisms as well, like at the end of the chromosomes we have some repeated redundant bits of information called teleomeres which will be chopped off one at a time every time the cell divides and it monitors the number of times a cell can divide, in some cases the teleomere ends of the chromosomes join together to become a fusion which may lead to cancer and other genetic abnormalities.

 

So all these factors which are internal and other external environmental factors cause the organism to die preventing them to proliferate again and again.