Why in so many cases does it seem like the larger an animal is, the older is average lifespan is? Some bugs can live for days or weeks, but humans and sea turtles can be over 100 years old?
In: Biology
Not a specialist, but it depends. But, basically, if the animal is simple (not many types of cells), then it survives because… It’s simple. Examples: sponges and some jellyfish. If it is complex, then the smaller the animal, the easier it loses heat, and therefore, the higher its metabolism. Higher metabolism means more oxidation, which means more cell and DNA damage, which causes age (or cancer) and eventually leads to death. The opposite works for bigger animals, which basically have slower metabolism, but as they have huge number of cells, one would expect them to be infested with cancer: more cells, more replication, more cancer, then death. I think it’s not well understood how, but it’s generally agreed that they have mechanisms to prevent cancer and so they live longer, because they have slower metabolism and less cancer.
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