Generally cells get cancer after having processed a certain amount of energy. That means that some fly species will reach obvious senescence in a matter of double-digit hours whereas for humans it takes 60 years or so. But cell-for cell, the cells in those bodies do "about" the same in terms of watts that go through them (nanowatts in reality, of course).
This is related to age and cell count, but it's not the only factor. For instance when an animal becomes larger, the size of the animal goes up with the third power, while energy use only goes up with the second power. So the bigger an animal, the less individual cells can do.
The way to arrive at this insight is to imagine animals are balls. To about a factor 2 this is accurate. The energy use is limited by energy exchange with the outside world, ie, it's limited by the amount of skin they have, which is the surface of the ball. The amount of cells is related to the volume the animal occupies.
The net effect of this is that bigger animals live longer. Some details are different too. For instance, larger animals tend to have larger cells. So the cell count goes up, but not by as much you'd think (If humans had mouse-sized cells in their tissues we'd be on average 54cm).
This is related to age and cell count, but it's not the only factor. For instance when an animal becomes larger, the size of the animal goes up with the third power, while energy use only goes up with the second power. So the bigger an animal, the less individual cells can do.
The way to arrive at this insight is to imagine animals are balls. To about a factor 2 this is accurate. The energy use is limited by energy exchange with the outside world, ie, it's limited by the amount of skin they have, which is the surface of the ball. The amount of cells is related to the volume the animal occupies.
The net effect of this is that bigger animals live longer. Some details are different too. For instance, larger animals tend to have larger cells. So the cell count goes up, but not by as much you'd think (If humans had mouse-sized cells in their tissues we'd be on average 54cm).