  Fractional quantum Hall states in bilayer system at total filling fraction
$\nu=1/2$ are examined numerically under some ranges of the layer separation
and interlayer tunneling. It is shown that the ground state changes
continuously from two-component state to one-component state as the interlayer
tunneling rate is increased, while the lowest excited state changes
discontinuously. This fact explains observed unusual behavior of the activation
energy which reveals upward cusp as a function of interlayer tunneling. Some
trial wave functions for the ground state and quasihole states are inspected.
