Any office, department, commission, board or agency may be created, changed or abolished by ordinance, other than the offices, departments, commissions, boards and agencies established by this Charter. Additional duties or functions may be assigned by ordinance to offices, departments, commissions, boards and agencies established by this Charter, but may not discontinue or assign to any other office, department, commission, board or agency any function or duty assigned by this Charter to a particular office, department, commission, board or agency.