ty Brucia :P
well I want to know what do u think why do we age, diseases can make aging more rapid (destroy tissue, organs, or some other type of stress) but people who are healthy all the time, age as well, and die - why do u think is that - so I'm interested in internal reasons - some are on the cell level. some are on the level of the whole organism.
I can give u a hint because it will be pretty hard to google all
1. cells cannot go tru mitosis indefinitely, why?
2. one of the reasons why we age is not present in plants or insects (the upper one is)
3. the third reason is present in almost all organisms, and is one of the main principles why we exist at all