system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 the reason the brain and body ages faster in dogs than humans

What distinguishes any life form from aging at a different rate?
gpt
There are a few systems at play that seem to be in common between short lived and long lived species. 

The slower the heart rate, the longer they live. Whales and galapagos toirtoses can live a very long time, and have very low heart rates. A hummingbird has an incredibly high heart rate and they don't live long at all. 

Smaller things tend to live shorter lives than larger things. But a bacteria is really small, and it may never die under ideal conditions. A lobster starts out pretty small, but if allowed to live they just get larger and larger and nobody knows for sure how long one might survive if left alone. Perhaps longer than a human. 

The main factor for what causes aging in any animal is the limits placed on cellular reproduction by the DNA and RNA. Cells only divide a certain number of times before their internal clocks start to slow down, causing longer periods of time before splitting, and the cells get older. Usually cells are replaced fairly often, but as you grow older this slows down, so that when you're a kid the oldest cells in your body may only be a few years old, but by the time you're old it might take several years before a cell is replaced. 

Having an organism that gets old and dies, is bad for the individual, but good for the species as it forces the old to make way for the new and it prevents over population. When a species has few natural predators it tends to have few offspring and a longer life. When a species has many predators it tends to have many offspring and shorter lives. If predatory pressure were removed from a species, they would over populate, leading to lack of food and death.