Why do spiders, snakes, etc shed their entire skin at once instead of passively replacing skin cells like we do?

Question

Why do spiders, snakes, etc shed their entire skin at once instead of passively replacing skin cells like we do?

In: Biology

Answer 1

Spiders don’t have skin, they have an external skeleton. This hard material supports their body and cannot be continually replaced, it must be dumped and a new one formed.

Similarly snakes and lizards don’t have regular skin, they have scales. It doesn’t flake off in tiny pieces like skin, it is harder and sturdier so it is replaced all at once.