  Dynamical features of tagged particles are studied in a one dimensional $A+A
\rightarrow kA$ system for $k=0$ and 1, where the particles $A$ have a bias
$\epsilon$ $(0 \leq \epsilon \leq 0.5)$ to hop one step in the direction of
their nearest neighboring particle. $\epsilon=0$ represents purely diffusive
motion and $\epsilon=0.5$ represents purely deterministic motion of the
particles. We show that for any $\epsilon$, there is a time scale $t^*$ which
demarcates the dynamics of the particles. Below $t^*$, the dynamics are
governed by the annihilation of the particles, and the particle motions are
highly correlated, while for $t \gg t^*$, the particles move as independent
biased walkers. $t^*$ diverges as $(\epsilon_c-\epsilon)^{-\gamma}$, where
$\gamma=1$ and $\epsilon_c =0.5$. $\epsilon_c$ is a critical point of the
dynamics. At $\epsilon_c$, the probability $S(t)$, that a walker changes
direction of its path at time $t$, decays as $S(t) \sim t^{-1}$ and the
distribution $D(\tau)$ of the time interval $\tau$ between consecutive changes
in the direction of a typical walker decays with a power law as $D(\tau) \sim
\tau^{-2}$.
