Salhi Tayeb2026-06-012026-05-14https://dspace.univ-bba.dz/handle/123456789/1460This lesson is presented for first-year Master’s students in Dynamical Systems. It introduces the basic principles of modeling via differential equations and develops three major biological applications: infectious disease models, predator–prey systems, and competition between species. The emphasis is on assumptions, model construction, equilibrium analysis, qualitative interpretation, and mathematical reasoningenThesis