  We here discretize a predator-prey model by standard Euler forward method and
non-standard finite difference method and then compare their dynamic properties
with the corresponding continuous-time model. We show that NSFD model preserves
positivity of solutions and is completely consistent with the dynamics of the
corresponding continuous-time model. On the other hand, the discrete model
formulated by forward Euler method does not show dynamic consistency with its
continuous counterpart. Rather it shows scheme--dependent instability when
step--size restriction is violated.
