  Using exact diagonalization for non-interacting systems and density matrix
renormalization group for interacting systems we show that Li and Haldane's
conjecture on the correspondence between the low-lying many-particle excitation
spectrum and the entanglement spectrum holds for disordered ballistic
one-dimensional many-particle systems. In order to demonstrate the
correspondence we develop a computational efficient way to calculate the ES of
low-excitation of non-interacting systems. We observe and explain the presence
of an unexpected shell structure in the excitation structure. The low-lying
shell are robust and survive even for strong electron-electron interactions.
