The Scrum Team should have all the skills needed to turn Product Backlog items into a valuable, useful Increment, as this is the primary goal of each Sprint. The Scrum Guide states that "The Scrum Team consists of one Scrum Master, one Product Owner, and Developers. Within a Scrum Team, there are no sub-teams or hierarchies. It is a cohesive unit of professionals focused on one objective at a time, the Product Goal."1 The Scrum Team should be cross-functional, which means that the Developers have all the skills necessary to create a product Increment.1 The Scrum Team should also be self-managing, which means that they decide how best to accomplish their work, rather than being directed by others outside the Scrum Team.1

References:

1: The Scrum Guide2, page 6

2: The Scrum Guide