Why do different animals have differing life spans???

Answer 1

it's based on metabolism and size

mice have a high metabolism, and can live up to three years.

galapagos tortoises have an incredibly slow metabgolism, and can live hundreds of years. scientists recently came up with evidence that a tortoise who is isolated from any threats to it's life (i.e. diseases and predators) will live forever.

Answer 2

It is a consequence of DNA evolution. Species are the result of mutations. A mutation may become very useful for an individual and this one will have higher chances of reproducing; thus, DNA will be passed to the next generation.
Some of those mutations have to do with the kinds of food or nutrients the individual can assimilate. Some are related to body mass and volume. This produces a remarkable difference in how long an animal can survive, since some elements are more or less damaging.
For instance, oxygen is a very dangerous element for a cell. Oxidation causes aging.
Therefore, if an animal has a rapid breathing frequency, more cell damage is expected.

Answer 3

Reptiles like turtles have very long lives because they have such a low metabolism which means they hardly ever need to eat and this decreases oxidative destruction of cells.
Humans have long life spans to help offspring as long as possible. Many grandparents raise grandkids for example.
Dogs have short lives because they atre a pack animal and old dogs arent needed and get in the way of pack survival.
Elephants have very long lives to help out in the survival of young and they have a slow metabolism.