@Transactional method calling another method without @Transactional anotation?

I've seen a method in a Service class that was marked as @Transactional, but it was also calling some other methods in that same class which were not marked as @Transactional.

Does it mean that the call to separate methods are causing the application to open separate connections to DB or suspend the parent transaction, etc?

What's the default behavior for a method without any annotations which is called by another method with @Transactional annotation?