Multiplicity of species in some replicative systems

In an attempt to explain the uniqueness of the coding mechanism of living c ells as contrasted with the multispecies structure of ecosystems we examine two models of individuals with some replicative properties. In the first m odel the system generically remains in a multispecies state. Even though fo r some of these species the replicative probability is very high, they are unable to invade the system. In the second model, in which the death rate d epends on the type of the species, the system relatively quickly reaches a single-species state and fluctuations might at most bring it to yet another single-species state.