Lifespan Comparison of Animals

. If life spans of different kinds of organisms are to be compared, it is essential that these variations be accounted for. The end of an organism’s existence results when irreversible changes have occurred to such an extent that the individual no longer actively retains its organization. There is thus a brief period during which it is impossible to say whether the organism is still alive, but this time is so short relative to the total length of life that it creates no great problem in determining life span.