The Abbasid Caliphate differed from others in that it did not have the same borders and extent as Islam. Particularly, in the west of the Caliphate, there were multiple smaller caliphates that existed in relative peace with them.
The major difference between the protist and the animal kingdom is protists are unicellular protozoans and unicellular & multicellular, but animals are multicellular animals.
The change from two to five kingdoms developed in the 1960s, when it became apparent that some organisms had characteristics of both plants and animals. Three major Domains of life - the first two are Prokaryotes (before the nucleus), while the Eukaryotes all have a true nucleus in each cell.