Using Monte Carlo simulations, we show that for a certain model of biologic
al evolution, which is driven by nonextremal dynamics, active and absorbing
phases are separated by a critical phase. In this phase both the density o
f active sites rho(t) and the survival probability of spreading P(t) decay
as t(-delta), where delta similar to 0.5. At the critical point that separa
tes the active and critical phases delta similar to 0.29, which suggests th
at this paint belongs to the so-called parity-conserving universality class
. Such a classification is also supported by finite-size analysis. The mode
l has infinitely many absorbing states and, except for a single point, has
no apparent conservation law.