Test students' ability to apply linear stability analysis to determine whether a homogeneous steady state in two-species reaction–diffusion models can undergo a diffusion-driven (Turing) instability. Scope: linearization about the steady state, construction of the Jacobian, inclusion of diffusion terms, derivation and analysis of the dispersion relation, identification of parameter ranges and critical wavenumbers where eigenvalues acquire positive real parts, and interpretation of how parameter changes promote or suppress spatial pattern formation.