Final answer:
The end of the Abbasid Caliphate was marked by the overthrow of Baghdad in 1258, the invasion by the Mongols, and the decline of the Abbasid government due to corruption and rival states.
Step-by-step explanation:
The end of the Abbasid Caliphate was signaled by multiple factors. Firstly, the establishment and growing power of semi-autonomous dynasties weakened the Abbasid empire. This led to Baghdad being overthrown in 1258, which marked the end of the dynasty and the last time the Arab-Muslim empire would be united as one entity. Another factor was the invasion by the Mongols in 1258, who ended the Caliphate by murdering the last caliph and destroying much of the infrastructure built during Abbasid rule. Additionally, the Abbasid government's corruption, the incorporation of foreign cultures and ideas, and the rise of rival states and tribes further contributed to the decline and end of the Abbasid Caliphate.