  We have performed angle-resolved photoemission and core-level x-ray
photoemission studies of the single-layer cuprate
Bi$_2$Sr$_{2-x}$La$_x$CuO$_{6+\delta}$ (Bi2201) and revealed the doping
evolution of the electronic structure from the lightly-doped to optimally-doped
regions. We have observed the formation of the dispersive quasi-particle band,
evolution of the Fermi ``arc'' into the Fermi surface and the shift of the
chemical potential with hole doping as in other cuprates. The doping evolution
in Bi2201 is similar to that in Ca$_{2-x}$Na$_{x}$CuO$_{2}$Cl$_2$ (Na-CCOC),
where a rapid chemical potential shift toward the lower Hubbard band of the
parent insulator has been observed, but is quite different from that in
La$_{2-x}$Sr$_{x}$CuO$_{4}$ (LSCO), where the chemical potential does not
shift, yet the dispersive band and the Fermi arc/surface are formed around the
Fermi level already in the lightly-doped region. The (underlying) Fermi surface
shape and band dispersions are quantitatively analyzed using tight-binding fit,
and the deduced next-nearest-neighbor hopping integral $t'$ also confirm the
similarity to Na-CCOC and the difference from LSCO.
