Which social scientist primarily studies how people change resources into goods and services

The social scientist that primarily studies how people change resources into goods and services is called: economist

Basically, Economist study how people will utilize the resource that they have at their disposal to fulfill their needs. (for example, you can't use words directly as your clothing and paper)
A lot of  Resources that people found around the environment often couldn't directly fulfill their needs. So, they transform those resources in a form of goods and services so it can fulfill it.

The one that most represents the earths mantle would be the skin since the mantle is the upper part of the earths depths which is just like the skin of an apple.