Question

Why do some animals have a thick coat of hair

Answer 1

wool comes from sheep, goat, yak,and some other animals. these wool yielding animals bear hair on their body because hair keeps these animals warm and wool is derived from these hairy fibres....... some breeds of sheeppossess only fine under hair......
hope this answer will helps you.

Answer 2

All the animals have a thick coat of hair, especially the animals who live in extreme regions. 

This hair helps them as it keeps them protected from the extreme cold.  

The hair growth is more in goats, sheep etc due to some genetic variations, including mostly proteins.

HOPE THIS ANSWER HELPS!!