Dynamical features of tagged particles are studied in a one dimensional A + A → kA system for k = 0 and 1, where the particles A have a bias ǫ (0 ≤ ǫ ≤ 0.5) to hop one step in the direction of their nearest neighboring particle. ǫ = 0 represents purely diffusive motion and ǫ = 0.5 represents purely deterministic motion of the particles. We show that for any ǫ, 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 ≫ t * , the particles move as independent biased walkers. t * diverges as (ǫc − ǫ) −γ , where γ = 1 and ǫc = 0.5. ǫc is a critical point of the dynamics. At ǫc, the probability S(t), that a walker changes direction of its path at time t, decays as S(t) ∼ t −1 and the distribution D(τ ) of the time interval τ between consecutive changes in the direction of a typical walker decays with a power law as D(τ ) ∼ τ −2 .