To be more clear, why do Humans live to be into their 100’s while canines rarely live past 15 years old. Or Certain Birds such as Parrots can outlive their owners.
There are a wide range of factors that go into the life expectancy of a organism, many of which we ourselves don’t entirely know. The rate of cellular division, genetic defects, evolutionary traits, and the overall environment can all be factors in a organisms life expectancy. Life only has one purpose, to reproduce, that’s doesn’t necessarily mean living long.
For example, many insects’ adult forms often don’t even have mouths or the physical makeup to last more than a week or so, but they produce a shit ton of offspring because their entire drive is now focused on mating. It doesn’t matter how long they live, they only need to be alive for a few minutes of action and egg laying. Octopuses are similar in that females and males pretty much die from the process of mating and protecting their eggs.
Another example is mice have a very fast rate of cellular division. Cells can only divide so much before their telomeres break down and their DNA breaks down with it. Because of this you can say mice age faster and die earlier.
Cellular division, this makes a lot of sense.
One interesting theory is that mammals live about 1.5 billion heartbeats. because of different metabolic rates, different mammals live different lengths. almost always, bigger animals have slower heart rates.
Not an expert but I have some basic knowledge on some factors that limit life span.
1.) Metabolism- many animals with higher metabolisms die pretty quick. I’ve seen some research that points at oxidants released during metabolism as a limiting factor when considering life span- tortoises vs hummingbirds.
2.) Evolution- depending on the species, some animals have evolved to require the death of the previous generation so that the next generation can live for example Praying Mantis, spiders, octopus, and of course, the mosquito.
3.) Genetics- cells are programmed to die(apoptosis). Everytime they reproduce the DNA cap (telomeres) at the end of every DNA strand gets shorter. When they get too short it starts messing with the essential instructions for your cells to continue multiplying into healthy cells. On the other side of the coin, cells with too much of the enzyme telomerase (protects the telomeres) can easily turn into cancer.
Tl;Dr Everything dies. There are a lot of reasons why. Sometimes death is programmed and purposeful. Sometimes it’s a mistake.