How many species have internal skeletons?

6.2 skeletons, there are 3 different types there is hydrostatic, endoskeletons and exoskeletons

The human skeleton is the internal framework of the body. It is composed of around 270 bones at birth – this total decreases to around 206 bones by adulthood after some bones get fused together

chemical weathering

explanation:

2%? i tried finding the exact sorry if it's not 100% correct ; -;