instruction:
Given a scientific question, generate a correct answer to it.
question:
How is a mammal developed if not inside of a placenta or a pouch?
answer:
hatched from eggs

question:
In vertebrates, a system of what structures attached to the endoskeleton enables movement?
answer:
muscles

question:
In vertebrates, a system of what structures attached to the endoskeleton enables movement?
answer:
muscles