So Snails naturally grow out of shells and go to find new ones. . . But Turtles have shells that grow with them. So why don't snails have shells that grow with them too? If they really need them, then why hasn't evolution, after all these years, gotten them to grow shells like turtles?

Different genus branch, I'd say

That's . . . a very thought-provoking question which I do not adequately know how to respond to!  It must be the components of the shell of both species that function and grow differently, though you have a very good point about the evolution theory.  I suppose maybe we aren't as evolutionary and adaptive as some might like to think!  There's so much mystery in the world, but I'll bet that someone has the 'scientific' answer that you're looking for. : P

I'm too busy to offer an elaborate answer so here's the short version: Turtle shells are actually an extension of their skeletons, so naturally it grows with the turtle as it ages. Snail shells are exoskeleton, so it forms and is permanently rigid.

 

I'm too busy to offer an elaborate answer so here's the short version: Turtle shells are actually an extension of their skeletons, so naturally it grows with the turtle as it ages. Snail shells are exoskeleton, so it forms and is permanently rigid.

 

AHH okay, and because Snails don't have bones on the inside of them, they couldn't really have anything to grow FROM if they grew with the snail. Makes sense. Thank yo u!