2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/22531We study the time evolution of two ecosystems in the presence of external noise and climatic periodical forcing by a generalized Lotka-Volterra (LV) model. In the first ecosystem, composed by two competing species, we find noise induced phenomena such as: (i) quasi deterministic oscillations, (ii) stochastic resonance, (iii) noise delayed extinction and (iv) spatial patterns. In the second ecosystem, composed by three interacting species (one predator and two preys), using a discrete model of the LV equations we find that the time evolution of the spatial patterns is strongly dependent on the initial conditions of the three species.9 pages, 6 figures, 23 panels. Appeared in Fluctuation and Noise Letters (2003)Statistical MechanicsPopulations and Evolutiontext