Classical models for competition between two species usually predict exclusion or divergent evolution of resource exploitation. However, recent experimental data show that coexistence is possible for very similar species competing for the same resources \textit{without} niche partition. Motivated by this experimental challenge to classical competition theory, we propose an individual-based stochastic competition model, which is essentially a modification of a deterministic Lotka-Volterra type model. The proposed model of competition dynamics incorporates the effects of a discrete genotype, which determines the individual's adaptation to the environment, as well as its interaction with the other species.