Final answer:
The cells in the mucosal surface of the gastrointestinal tract capable of cell division and differentiation are stem cells, specifically, most likely multipotent stem cells tailored for that tissue.
Step-by-step explanation:
The cells in the mucosal surface of the gastrointestinal tract that serve as a reserve source for specialized cells are known as stem cells. These cells are capable of continued cell division and can differentiate into the various specialized cells necessary for tissue function and repair. In the hierarchy of stem cell potentiality, totipotent stem cells come from the zygote and can differentiate into any cell type. As they specialize further, they become pluripotent stem cells, which can differentiate into nearly any cell but cannot develop into a whole organism. Beneath pluripotent stem cells are multipotent stem cells, which can only become a certain family of cells.
When discussing tissues like the gastrointestinal tract's mucosal surface, the stem cells relevant here are most likely to be multipotent, as they are specialized enough to produce the range of cells necessary for that particular tissue but not the entire organism.